Airway Resistance: Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow.Airway Obstruction: Any hindrance to the passage of air into and out of the lungs.Plethysmography, Whole Body: Measurement of the volume of gas in the lungs, including that which is trapped in poorly communicating air spaces. It is of particular use in chronic obstructive pulmonary disease and emphysema. (Segen, Dictionary of Modern Medicine, 1992)Lung Compliance: The capability of the LUNGS to distend under pressure as measured by pulmonary volume change per unit pressure change. While not a complete description of the pressure-volume properties of the lung, it is nevertheless useful in practice as a measure of the comparative stiffness of the lung. (From Best & Taylor's Physiological Basis of Medical Practice, 12th ed, p562)Bronchoconstriction: Narrowing of the caliber of the BRONCHI, physiologically or as a result of pharmacological intervention.Airway Remodeling: The structural changes in the number, mass, size and/or composition of the airway tissues.Respiratory Mechanics: The physical or mechanical action of the LUNGS; DIAPHRAGM; RIBS; and CHEST WALL during respiration. It includes airflow, lung volume, neural and reflex controls, mechanoreceptors, breathing patterns, etc.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Lung Volume Measurements: Measurement of the amount of air that the lungs may contain at various points in the respiratory cycle.Drug Resistance: Diminished or failed response of an organism, disease or tissue to the intended effectiveness of a chemical or drug. It should be differentiated from DRUG TOLERANCE which is the progressive diminution of the susceptibility of a human or animal to the effects of a drug, as a result of continued administration.Respiratory Function Tests: Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc.Bronchoconstrictor Agents: Agents causing the narrowing of the lumen of a bronchus or bronchiole.Methacholine Chloride: A quaternary ammonium parasympathomimetic agent with the muscarinic actions of ACETYLCHOLINE. It is hydrolyzed by ACETYLCHOLINESTERASE at a considerably slower rate than ACETYLCHOLINE and is more resistant to hydrolysis by nonspecific CHOLINESTERASES so that its actions are more prolonged. It is used as a parasympathomimetic bronchoconstrictor agent and as a diagnostic aid for bronchial asthma. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1116)Bronchial Hyperreactivity: Tendency of the smooth muscle of the tracheobronchial tree to contract more intensely in response to a given stimulus than it does in the response seen in normal individuals. This condition is present in virtually all symptomatic patients with asthma. The most prominent manifestation of this smooth muscle contraction is a decrease in airway caliber that can be readily measured in the pulmonary function laboratory.Asthma: A form of bronchial disorder with three distinct components: airway hyper-responsiveness (RESPIRATORY HYPERSENSITIVITY), airway INFLAMMATION, and intermittent AIRWAY OBSTRUCTION. It is characterized by spasmodic contraction of airway smooth muscle, WHEEZING, and dyspnea (DYSPNEA, PAROXYSMAL).Bronchi: The larger air passages of the lungs arising from the terminal bifurcation of the TRACHEA. They include the largest two primary bronchi which branch out into secondary bronchi, and tertiary bronchi which extend into BRONCHIOLES and PULMONARY ALVEOLI.Respiratory System: The tubular and cavernous organs and structures, by means of which pulmonary ventilation and gas exchange between ambient air and the blood are brought about.Drug Resistance, Microbial: The ability of microorganisms, especially bacteria, to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Drug Resistance, Bacterial: The ability of bacteria to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Pulmonary Ventilation: The total volume of gas inspired or expired per unit of time, usually measured in liters per minute.Inhalation: The act of BREATHING in.Bronchial Provocation Tests: Tests involving inhalation of allergens (nebulized or in dust form), nebulized pharmacologically active solutions (e.g., histamine, methacholine), or control solutions, followed by assessment of respiratory function. These tests are used in the diagnosis of asthma.Rhinomanometry: Technique for measuring air pressure and the rate of airflow in the nasal cavity during respiration.Drug Resistance, Neoplasm: Resistance or diminished response of a neoplasm to an antineoplastic agent in humans, animals, or cell or tissue cultures.Nasal Obstruction: Any hindrance to the passage of air into and out of the nose. The obstruction may be unilateral or bilateral, and may involve any part of the NASAL CAVITY.Plethysmography: Recording of change in the size of a part as modified by the circulation in it.Functional Residual Capacity: The volume of air remaining in the LUNGS at the end of a normal, quiet expiration. It is the sum of the RESIDUAL VOLUME and the EXPIRATORY RESERVE VOLUME. Common abbreviation is FRC.Air Pressure: The force per unit area that the air exerts on any surface in contact with it. Primarily used for articles pertaining to air pressure within a closed environment.Histamine: An amine derived by enzymatic decarboxylation of HISTIDINE. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter.Spirometry: Measurement of volume of air inhaled or exhaled by the lung.Bronchodilator Agents: Agents that cause an increase in the expansion of a bronchus or bronchial tubes.Drug Resistance, Multiple: Simultaneous resistance to several structurally and functionally distinct drugs.Respiratory Physiological Phenomena: Physiological processes and properties of the RESPIRATORY SYSTEM as a whole or of any of its parts.Rhinometry, Acoustic: Diagnostic measurement of the nose and its cavity through acoustic reflections. Used to measure nasal anatomical landmarks, nasal septal deviation, and nasal airway changes in response to allergen provocation tests (NASAL PROVOCATION TESTS).Nasal Decongestants: Drugs designed to treat inflammation of the nasal passages, generally the result of an infection (more often than not the common cold) or an allergy related condition, e.g., hay fever. The inflammation involves swelling of the mucous membrane that lines the nasal passages and results in inordinate mucus production. The primary class of nasal decongestants are vasoconstrictor agents. (From PharmAssist, The Family Guide to Health and Medicine, 1993)Disease Resistance: The capacity of an organism to defend itself against pathological processes or the agents of those processes. This most often involves innate immunity whereby the organism responds to pathogens in a generic way. The term disease resistance is used most frequently when referring to plants.Respiration: The act of breathing with the LUNGS, consisting of INHALATION, or the taking into the lungs of the ambient air, and of EXHALATION, or the expelling of the modified air which contains more CARBON DIOXIDE than the air taken in (Blakiston's Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= OXYGEN CONSUMPTION) or cell respiration (= CELL RESPIRATION).Bronchoalveolar Lavage Fluid: Washing liquid obtained from irrigation of the lung, including the BRONCHI and the PULMONARY ALVEOLI. It is generally used to assess biochemical, inflammatory, or infection status of the lung.Vascular Resistance: The force that opposes the flow of BLOOD through a vascular bed. It is equal to the difference in BLOOD PRESSURE across the vascular bed divided by the CARDIAC OUTPUT.Nose: A part of the upper respiratory tract. It contains the organ of SMELL. The term includes the external nose, the nasal cavity, and the PARANASAL SINUSES.Administration, Inhalation: The administration of drugs by the respiratory route. It includes insufflation into the respiratory tract.Tidal Volume: The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are TV or V with subscript T.Oscillometry: The measurement of frequency or oscillation changes.Forced Expiratory Volume: Measure of the maximum amount of air that can be expelled in a given number of seconds during a FORCED VITAL CAPACITY determination . It is usually given as FEV followed by a subscript indicating the number of seconds over which the measurement is made, although it is sometimes given as a percentage of forced vital capacity.Ipratropium: A muscarinic antagonist structurally related to ATROPINE but often considered safer and more effective for inhalation use. It is used for various bronchial disorders, in rhinitis, and as an antiarrhythmic.Albuterol: A short-acting beta-2 adrenergic agonist that is primarily used as a bronchodilator agent to treat ASTHMA. Albuterol is prepared as a racemic mixture of R(-) and S(+) stereoisomers. The stereospecific preparation of R(-) isomer of albuterol is referred to as levalbuterol.Drug Resistance, Viral: The ability of viruses to resist or to become tolerant to chemotherapeutic agents or antiviral agents. This resistance is acquired through gene mutation.Drug Resistance, Multiple, Bacterial: The ability of bacteria to resist or to become tolerant to several structurally and functionally distinct drugs simultaneously. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Respiratory Hypersensitivity: A form of hypersensitivity affecting the respiratory tract. It includes ASTHMA and RHINITIS, ALLERGIC, SEASONAL.Epiglottis: A thin leaf-shaped cartilage that is covered with LARYNGEAL MUCOSA and situated posterior to the root of the tongue and HYOID BONE. During swallowing, the epiglottis folds back over the larynx inlet thus prevents foods from entering the airway.Nasal Provocation Tests: Application of allergens to the nasal mucosa. Interpretation includes observation of nasal symptoms, rhinoscopy, and rhinomanometry. Nasal provocation tests are used in the diagnosis of nasal hypersensitivity, including RHINITIS, ALLERGIC, SEASONAL.Aerosols: Colloids with a gaseous dispersing phase and either liquid (fog) or solid (smoke) dispersed phase; used in fumigation or in inhalation therapy; may contain propellant agents.Nasal Cavity: The proximal portion of the respiratory passages on either side of the NASAL SEPTUM. Nasal cavities, extending from the nares to the NASOPHARYNX, are lined with ciliated NASAL MUCOSA.Intubation, Intratracheal: A procedure involving placement of a tube into the trachea through the mouth or nose in order to provide a patient with oxygen and anesthesia.Bronchial Spasm: Spasmodic contraction of the smooth muscle of the bronchi.Positive-Pressure Respiration: A method of mechanical ventilation in which pressure is maintained to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange.Respiratory Muscles: These include the muscles of the DIAPHRAGM and the INTERCOSTAL MUSCLES.Clemastine: A histamine H1 antagonist used as the hydrogen fumarate in hay fever, rhinitis, allergic skin conditions, and pruritus. It causes drowsiness.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Maximal Expiratory Flow-Volume Curves: Curves depicting MAXIMAL EXPIRATORY FLOW RATE, in liters/second, versus lung inflation, in liters or percentage of lung capacity, during a FORCED VITAL CAPACITY determination. Common abbreviation is MEFV.Mouth Breathing: Abnormal breathing through the mouth, usually associated with obstructive disorders of the nasal passages.Work of Breathing: RESPIRATORY MUSCLE contraction during INHALATION. The work is accomplished in three phases: LUNG COMPLIANCE work, that required to expand the LUNGS against its elastic forces; tissue resistance work, that required to overcome the viscosity of the lung and chest wall structures; and AIRWAY RESISTANCE work, that required to overcome airway resistance during the movement of air into the lungs. Work of breathing does not refer to expiration, which is entirely a passive process caused by elastic recoil of the lung and chest cage. (Guyton, Textbook of Medical Physiology, 8th ed, p406)Airway Management: Evaluation, planning, and use of a range of procedures and airway devices for the maintenance or restoration of a patient's ventilation.Pharynx: A funnel-shaped fibromuscular tube that conducts food to the ESOPHAGUS, and air to the LARYNX and LUNGS. It is located posterior to the NASAL CAVITY; ORAL CAVITY; and LARYNX, and extends from the SKULL BASE to the inferior border of the CRICOID CARTILAGE anteriorly and to the inferior border of the C6 vertebra posteriorly. It is divided into the NASOPHARYNX; OROPHARYNX; and HYPOPHARYNX (laryngopharynx).Respiratory Mucosa: The mucous membrane lining the RESPIRATORY TRACT, including the NASAL CAVITY; the LARYNX; the TRACHEA; and the BRONCHI tree. The respiratory mucosa consists of various types of epithelial cells ranging from ciliated columnar to simple squamous, mucous GOBLET CELLS, and glands containing both mucous and serous cells.Thyroid Cartilage: The largest cartilage of the larynx consisting of two laminae fusing anteriorly at an acute angle in the midline of the neck. The point of fusion forms a subcutaneous projection known as the Adam's apple.Muscle, Smooth: Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)Snoring: Rough, noisy breathing during sleep, due to vibration of the uvula and soft palate.Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).Total Lung Capacity: The volume of air contained in the lungs at the end of a maximal inspiration. It is the equivalent to each of the following sums: VITAL CAPACITY plus RESIDUAL VOLUME; INSPIRATORY CAPACITY plus FUNCTIONAL RESIDUAL CAPACITY; TIDAL VOLUME plus INSPIRATORY RESERVE VOLUME plus functional residual capacity; or tidal volume plus inspiratory reserve volume plus EXPIRATORY RESERVE VOLUME plus residual volume.Lung Diseases, Obstructive: Any disorder marked by obstruction of conducting airways of the lung. AIRWAY OBSTRUCTION may be acute, chronic, intermittent, or persistent.Forced Expiratory Flow Rates: The rate of airflow measured during a FORCED VITAL CAPACITY determination.Sleep Apnea Syndromes: Disorders characterized by multiple cessations of respirations during sleep that induce partial arousals and interfere with the maintenance of sleep. Sleep apnea syndromes are divided into central (see SLEEP APNEA, CENTRAL), obstructive (see SLEEP APNEA, OBSTRUCTIVE), and mixed central-obstructive types.Sleep Apnea, Obstructive: A disorder characterized by recurrent apneas during sleep despite persistent respiratory efforts. It is due to upper airway obstruction. The respiratory pauses may induce HYPERCAPNIA or HYPOXIA. Cardiac arrhythmias and elevation of systemic and pulmonary arterial pressures may occur. Frequent partial arousals occur throughout sleep, resulting in relative SLEEP DEPRIVATION and daytime tiredness. Associated conditions include OBESITY; ACROMEGALY; MYXEDEMA; micrognathia; MYOTONIC DYSTROPHY; adenotonsilar dystrophy; and NEUROMUSCULAR DISEASES. (From Adams et al., Principles of Neurology, 6th ed, p395)Vital Capacity: The volume of air that is exhaled by a maximal expiration following a maximal inspiration.Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Mucus: The viscous secretion of mucous membranes. It contains mucin, white blood cells, water, inorganic salts, and exfoliated cells.Nasal Mucosa: The mucous lining of the NASAL CAVITY, including lining of the nostril (vestibule) and the OLFACTORY MUCOSA. Nasal mucosa consists of ciliated cells, GOBLET CELLS, brush cells, small granule cells, basal cells (STEM CELLS) and glands containing both mucous and serous cells.Helium: Helium. A noble gas with the atomic symbol He, atomic number 2, and atomic weight 4.003. It is a colorless, odorless, tasteless gas that is not combustible and does not support combustion. It was first detected in the sun and is now obtained from natural gas. Medically it is used as a diluent for other gases, being especially useful with oxygen in the treatment of certain cases of respiratory obstruction, and as a vehicle for general anesthetics. (Dorland, 27th ed)Respiratory Sounds: Noises, normal and abnormal, heard on auscultation over any part of the RESPIRATORY TRACT.Methacholine Compounds: A group of compounds that are derivatives of beta-methylacetylcholine (methacholine).Cromolyn Sodium: A chromone complex that acts by inhibiting the release of chemical mediators from sensitized mast cells. It is used in the prophylactic treatment of both allergic and exercise-induced asthma, but does not affect an established asthmatic attack.Sleep: A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility.Pulmonary Gas Exchange: The exchange of OXYGEN and CARBON DIOXIDE between alveolar air and pulmonary capillary blood that occurs across the BLOOD-AIR BARRIER.Cough: A sudden, audible expulsion of air from the lungs through a partially closed glottis, preceded by inhalation. It is a protective response that serves to clear the trachea, bronchi, and/or lungs of irritants and secretions, or to prevent aspiration of foreign materials into the lungs.Hypersensitivity: Altered reactivity to an antigen, which can result in pathologic reactions upon subsequent exposure to that particular antigen.Eosinophils: Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin.Respiration, Artificial: Any method of artificial breathing that employs mechanical or non-mechanical means to force the air into and out of the lungs. Artificial respiration or ventilation is used in individuals who have stopped breathing or have RESPIRATORY INSUFFICIENCY to increase their intake of oxygen (O2) and excretion of carbon dioxide (CO2).Sneezing: The sudden, forceful, involuntary expulsion of air from the NOSE and MOUTH caused by irritation to the MUCOUS MEMBRANES of the upper RESPIRATORY TRACT.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Pulmonary Emphysema: Enlargement of air spaces distal to the TERMINAL BRONCHIOLES where gas-exchange normally takes place. This is usually due to destruction of the alveolar wall. Pulmonary emphysema can be classified by the location and distribution of the lesions.Tetracycline Resistance: Nonsusceptibility of bacteria to the action of TETRACYCLINE which inhibits aminoacyl-tRNA binding to the 30S ribosomal subunit during protein synthesis.Mice, Inbred BALB CAtropine Derivatives: Analogs and derivatives of atropine.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Bronchitis: Inflammation of the large airways in the lung including any part of the BRONCHI, from the PRIMARY BRONCHI to the TERTIARY BRONCHI.Trachea: The cartilaginous and membranous tube descending from the larynx and branching into the right and left main bronchi.Pressure: A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Wakefulness: A state in which there is an enhanced potential for sensitivity and an efficient responsiveness to external stimuli.Exhalation: The act of BREATHING out.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Lung Diseases: Pathological processes involving any part of the LUNG.Pneumonia: Infection of the lung often accompanied by inflammation.Plant Diseases: Diseases of plants.Ascaris suum: A species of parasitic nematode usually found in domestic pigs and a few other animals. Human infection can also occur, presumably as result of handling pig manure, and can lead to intestinal obstruction.Penicillin Resistance: Nonsusceptibility of an organism to the action of penicillins.Mice, Inbred C57BLPulmonary Disease, Chronic Obstructive: A disease of chronic diffuse irreversible airflow obstruction. Subcategories of COPD include CHRONIC BRONCHITIS and PULMONARY EMPHYSEMA.Respiratory System Agents: Drugs used for their effects on the respiratory system.Maximal Expiratory Flow Rate: The airflow rate measured during the first liter expired after the first 200 ml have been exhausted during a FORCED VITAL CAPACITY determination. Common abbreviations are MEFR, FEF 200-1200, and FEF 0.2-1.2.Residual Volume: The volume of air remaining in the LUNGS at the end of a maximal expiration. Common abbreviation is RV.Tongue: A muscular organ in the mouth that is covered with pink tissue called mucosa, tiny bumps called papillae, and thousands of taste buds. The tongue is anchored to the mouth and is vital for chewing, swallowing, and for speech.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Inflammation: A pathological process characterized by injury or destruction of tissues caused by a variety of cytologic and chemical reactions. It is usually manifested by typical signs of pain, heat, redness, swelling, and loss of function.Elasticity: Resistance and recovery from distortion of shape.Ovalbumin: An albumin obtained from the white of eggs. It is a member of the serpin superfamily.Polysomnography: Simultaneous and continuous monitoring of several parameters during sleep to study normal and abnormal sleep. The study includes monitoring of brain waves, to assess sleep stages, and other physiological variables such as breathing, eye movements, and blood oxygen levels which exhibit a disrupted pattern with sleep disturbances.Drug Resistance, Fungal: The ability of fungi to resist or to become tolerant to chemotherapeutic agents, antifungal agents, or antibiotics. This resistance may be acquired through gene mutation.Vocal Cord Paralysis: Congenital or acquired paralysis of one or both VOCAL CORDS. This condition is caused by defects in the CENTRAL NERVOUS SYSTEM, the VAGUS NERVE and branches of LARYNGEAL NERVES. Common symptoms are VOICE DISORDERS including HOARSENESS or APHONIA.Atropine: An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.Ventilators, Mechanical: Mechanical devices used to produce or assist pulmonary ventilation.Hyperventilation: A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Pulmonary Alveoli: Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place.Pulmonary Circulation: The circulation of the BLOOD through the LUNGS.Allergens: Antigen-type substances that produce immediate hypersensitivity (HYPERSENSITIVITY, IMMEDIATE).Humidity: A measure of the amount of WATER VAPOR in the air.Sleep Stages: Periods of sleep manifested by changes in EEG activity and certain behavioral correlates; includes Stage 1: sleep onset, drowsy sleep; Stage 2: light sleep; Stages 3 and 4: delta sleep, light sleep, deep sleep, telencephalic sleep.Pulmonary Edema: Excessive accumulation of extravascular fluid in the lung, an indication of a serious underlying disease or disorder. Pulmonary edema prevents efficient PULMONARY GAS EXCHANGE in the PULMONARY ALVEOLI, and can be life-threatening.Mandibular Advancement: Moving a retruded mandible forward to a normal position. It is commonly performed for malocclusion and retrognathia. (From Jablonski's Dictionary of Dentistry, 1992)Thorax: The upper part of the trunk between the NECK and the ABDOMEN. It contains the chief organs of the circulatory and respiratory systems. (From Stedman, 25th ed)Bacterial Proteins: Proteins found in any species of bacterium.Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.beta-Lactam Resistance: Nonsusceptibility of bacteria to the action of the beta-lactam antibiotics. Mechanisms responsible for beta-lactam resistance may be degradation of antibiotics by BETA-LACTAMASES, failure of antibiotics to penetrate, or low-affinity binding of antibiotics to targets.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Laryngeal Masks: A type of oropharyngeal airway that provides an alternative to endotracheal intubation and standard mask anesthesia in certain patients. It is introduced into the hypopharynx to form a seal around the larynx thus permitting spontaneous or positive pressure ventilation without penetration of the larynx or esophagus. It is used in place of a facemask in routine anesthesia. The advantages over standard mask anesthesia are better airway control, minimal anesthetic gas leakage, a secure airway during patient transport to the recovery area, and minimal postoperative problems.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Positive-Pressure Respiration, Intrinsic: Non-therapeutic positive end-expiratory pressure occurring frequently in patients with severe airway obstruction. It can appear with or without the administration of external positive end-expiratory pressure (POSITIVE-PRESSURE RESPIRATION). It presents an important load on the inspiratory muscles which are operating at a mechanical disadvantage due to hyperinflation. Auto-PEEP may cause profound hypotension that should be treated by intravascular volume expansion, increasing the time for expiration, and/or changing from assist mode to intermittent mandatory ventilation mode. (From Harrison's Principles of Internal Medicine, 12th ed, p1127)Immunity, Innate: The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring ANTI-INFECTIVE AGENTS, constitutional factors such as BODY TEMPERATURE and immediate acting immune cells such as NATURAL KILLER CELLS.Continuous Positive Airway Pressure: A technique of respiratory therapy, in either spontaneously breathing or mechanically ventilated patients, in which airway pressure is maintained above atmospheric pressure throughout the respiratory cycle by pressurization of the ventilatory circuit. (On-Line Medical Dictionary [Internet]. Newcastle upon Tyne(UK): The University Dept. of Medical Oncology: The CancerWEB Project; c1997-2003 [cited 2003 Apr 17]. Available from: http://cancerweb.ncl.ac.uk/omd/)Resistance Training: A type of strength-building exercise program that requires the body muscle to exert a force against some form of resistance, such as weight, stretch bands, water, or immovable objects. Resistance exercise is a combination of static and dynamic contractions involving shortening and lengthening of skeletal muscles.Sympatholytics: Drugs that inhibit the actions of the sympathetic nervous system by any mechanism. The most common of these are the ADRENERGIC ANTAGONISTS and drugs that deplete norepinephrine or reduce the release of transmitters from adrenergic postganglionic terminals (see ADRENERGIC AGENTS). Drugs that act in the central nervous system to reduce sympathetic activity (e.g., centrally acting alpha-2 adrenergic agonists, see ADRENERGIC ALPHA-AGONISTS) are included here.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.R Factors: A class of plasmids that transfer antibiotic resistance from one bacterium to another by conjugation.Anesthesia, General: Procedure in which patients are induced into an unconscious state through use of various medications so that they do not feel pain during surgery.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.Cytokines: Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Acetanilides: Compounds based on N-phenylacetamide, that are similar in structure to 2-PHENYLACETAMIDES. They are precursors of many other compounds. They were formerly used as ANALGESICS and ANTIPYRETICS, but often caused lethal METHEMOGLOBINEMIA.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Cross-Over Studies: Studies comparing two or more treatments or interventions in which the subjects or patients, upon completion of the course of one treatment, are switched to another. In the case of two treatments, A and B, half the subjects are randomly allocated to receive these in the order A, B and half to receive them in the order B, A. A criticism of this design is that effects of the first treatment may carry over into the period when the second is given. (Last, A Dictionary of Epidemiology, 2d ed)P-Glycoprotein: A 170-kDa transmembrane glycoprotein from the superfamily of ATP-BINDING CASSETTE TRANSPORTERS. It serves as an ATP-dependent efflux pump for a variety of chemicals, including many ANTINEOPLASTIC AGENTS. Overexpression of this glycoprotein is associated with multidrug resistance (see DRUG RESISTANCE, MULTIPLE).Ampicillin Resistance: Nonsusceptibility of a microbe to the action of ampicillin, a penicillin derivative that interferes with cell wall synthesis.Chloramphenicol Resistance: Nonsusceptibility of bacteria to the action of CHLORAMPHENICOL, a potent inhibitor of protein synthesis in the 50S ribosomal subunit where amino acids are added to nascent bacterial polypeptides.Blood Gas Analysis: Measurement of oxygen and carbon dioxide in the blood.Hemodynamics: The movement and the forces involved in the movement of the blood through the CARDIOVASCULAR SYSTEM.Oxygen: An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.Reflex: An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.Plasmids: Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.Vagus Nerve: The 10th cranial nerve. The vagus is a mixed nerve which contains somatic afferents (from skin in back of the ear and the external auditory meatus), visceral afferents (from the pharynx, larynx, thorax, and abdomen), parasympathetic efferents (to the thorax and abdomen), and efferents to striated muscle (of the larynx and pharynx).Blood Pressure: PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.Tetracycline: A naphthacene antibiotic that inhibits AMINO ACYL TRNA binding during protein synthesis.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Paralysis: A general term most often used to describe severe or complete loss of muscle strength due to motor system disease from the level of the cerebral cortex to the muscle fiber. This term may also occasionally refer to a loss of sensory function. (From Adams et al., Principles of Neurology, 6th ed, p45)Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Cystic Fibrosis: An autosomal recessive genetic disease of the EXOCRINE GLANDS. It is caused by mutations in the gene encoding the CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR expressed in several organs including the LUNG, the PANCREAS, the BILIARY SYSTEM, and the SWEAT GLANDS. Cystic fibrosis is characterized by epithelial secretory dysfunction associated with ductal obstruction resulting in AIRWAY OBSTRUCTION; chronic RESPIRATORY INFECTIONS; PANCREATIC INSUFFICIENCY; maldigestion; salt depletion; and HEAT PROSTRATION.Genes, Bacterial: The functional hereditary units of BACTERIA.Acetylcholine: A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Genotype: The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Conjugation, Genetic: A parasexual process in BACTERIA; ALGAE; FUNGI; and ciliate EUKARYOTA for achieving exchange of chromosome material during fusion of two cells. In bacteria, this is a uni-directional transfer of genetic material; in protozoa it is a bi-directional exchange. In algae and fungi, it is a form of sexual reproduction, with the union of male and female gametes.Methicillin Resistance: Non-susceptibility of a microbe to the action of METHICILLIN, a semi-synthetic penicillin derivative.Erythromycin: A bacteriostatic antibiotic macrolide produced by Streptomyces erythreus. Erythromycin A is considered its major active component. In sensitive organisms, it inhibits protein synthesis by binding to 50S ribosomal subunits. This binding process inhibits peptidyl transferase activity and interferes with translocation of amino acids during translation and assembly of proteins.Insulin: A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Electromyography: Recording of the changes in electric potential of muscle by means of surface or needle electrodes.Cell Line, Tumor: A cell line derived from cultured tumor cells.Treatment Outcome: Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.Cephalosporin Resistance: Non-susceptibility of an organism to the action of the cephalosporins.Dyspnea: Difficult or labored breathing.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Propranolol: A widely used non-cardioselective beta-adrenergic antagonist. Propranolol has been used for MYOCARDIAL INFARCTION; ARRHYTHMIA; ANGINA PECTORIS; HYPERTENSION; HYPERTHYROIDISM; MIGRAINE; PHEOCHROMOCYTOMA; and ANXIETY but adverse effects instigate replacement by newer drugs.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Posture: The position or attitude of the body.Infant, Newborn: An infant during the first month after birth.

Nitric oxide limits the eicosanoid-dependent bronchoconstriction and hypotension induced by endothelin-1 in the guinea-pig. (1/1568)

1. This study attempts to investigate if endogenous nitric oxide (NO) can modulate the eicosanoid-releasing properties of intravenously administered endothelin-1 (ET-1) in the pulmonary and circulatory systems in the guinea-pig. 2. The nitric oxide synthase blocker N(omega)-nitro-L-arginine methyl ester (L-NAME; 300 microM; 30 min infusion) potentiated, in an L-arginine sensitive fashion, the release of thromboxane A2 (TxA2) stimulated by ET-1, the selective ET(B) receptor agonist IRL 1620 (Suc-[Glu9,Ala11,15]-ET-1(8-21)) or bradykinin (BK) (5, 50 and 50 nM, respectively, 3 min infusion) in guinea-pig isolated and perfused lungs. 3. In anaesthetized and ventilated guinea-pigs intravenous injection of ET-1 (0.1-1.0 nmol kg(-1)), IRL 1620 (0.2-1.6 nmol kg(-1)), BK (1.0-10.0 nmol kg(-1)) or U 46619 (0.2-5.7 nmol kg(-1)) each induced dose-dependent increases in pulmonary insufflation pressure (PIP). Pretreatment with L-NAME (5 mg kg(-1)) did not change basal PIP, but increased, in L-arginine sensitive manner, the magnitude of the PIP increases (in both amplitude and duration) triggered by each of the peptides (at 0.25, 0.4 and 1.0 nmol kg(-1), respectively), without modifying bronchoconstriction caused by U 46619 (0.57 nmol kg(-1)). 4. The increases in PIP induced by ET-1, IRL 1620 (0.25 and 0.4 nmol kg(-1), respectively) or U 46619 (0.57 nmol kg(-1)) were accompanied by rapid and transient increases of mean arterial blood pressure (MAP). Pretreatment with L-NAME (5 mg kg(-1); i.v. raised basal MAP persistently and, under this condition, subsequent administration of ET-1 or IRL 1620, but not of U-46619, induced hypotensive responses which were prevented by pretreatment with the cyclo-oxygenase inhibitor indomethacin. 5. Thus, endogenous NO appears to modulate ET-1-induced bronchoconstriction and pressor effects in the guinea-pig by limiting the peptide's ability to induce, possibly via ET(B) receptors, the release of TxA2 in the lungs and of vasodilatory prostanoids in the systemic circulation. Furthermore, it would seem that these eicosanoid-dependent actions of ET-1 in the pulmonary system and on systemic arterial resistance in this species are physiologically dissociated.  (+info)

Dose-response slope of forced oscillation and forced expiratory parameters in bronchial challenge testing. (2/1568)

In population studies, the provocative dose (PD) of bronchoconstrictor causing a significant decrement in lung function cannot be calculated for most subjects. Dose-response curves for carbachol were examined to determine whether this relationship can be summarized by means of a continuous index likely to be calculable for all subjects, namely the two-point dose response slope (DRS) of mean resistance (Rm) and resistance at 10 Hz (R10) measured by the forced oscillation technique (FOT). Five doses of carbachol (320 microg each) were inhaled by 71 patients referred for investigation of asthma (n=16), chronic cough (n=15), nasal polyposis (n=8), chronic rhinitis (n=8), dyspnoea (n=8), urticaria (n=5), post-anaphylactic shock (n=4) and miscellaneous conditions (n=7). FOT resistance and forced expiratory volume in one second (FEV1) were measured in close succession. The PD of carbachol leading to a fall in FEV1 > or = 20% (PD20) or a rise in Rm or R10 > or = 47% (PD47,Rm and PD47,R10) were calculated by interpolation. DRS for FEV1 (DRSFEV1), Rm (DRSRm) and R10 (DRSR10) were obtained as the percentage change at last dose divided by the total dose of carbachol. The sensitivity (Se) and specificity (Sp) of DRSRm, DRS10 delta%Rm and delta%R10 in detecting spirometric bronchial hyperresponsiveness (BHR, fall in FEV1 > or = 20%) were assessed by receiver operating characteristic (ROC) curves. There were 23 (32%) "spirometric" reactors. PD20 correlated strongly with DRSFEV1 (r=-0.962; p=0.0001); PD47,Rm correlated significantly with DRSRm (r=-0.648; p=0.0001) and PD47,R10 with DRSR10 (r=-0.552; p=0.0001). DRSFEV1 correlated significantly with both DRSRm (r=0.700; p=0.0001) and DRSR10 (r=0.784; p=0.0001). The Se and Sp of the various FOT indices to correctly detect spirometric BHR were as follows: DRSRm: Se=91.3%, Sp=81.2%; DRSR10: Se=91.3%, Sp=95.8%; delta%Rm: Se=86.9%, Sp=52.1%; and delta%R10: Se=91.3%, Sp=58.3%. Dose-response slopes of indices of forced oscillation technique resistance, especially the dose-response slope of resistance at 10Hz are proposed as simple quantitative indices of bronchial responsiveness which can be calculated for all subjects and that may be useful in occupational epidemiology.  (+info)

Bradykinin-induced bronchospasm in the rat in vivo: a role for nitric oxide modulation. (3/1568)

Bradykinin has an important role in asthma pathogenesis, but its site of action is unclear. It was previously reported by the authors that bradykinin causes a dose-dependent reduction in dynamic compliance but little change in total lung resistance. This suggested that bradykinin may have a preferential effect in the distant lung. The purpose of the current investigation was to better characterize the effects of bradykinin on pulmonary resistance in rodents and explore the role of nitric oxide release in modulating the effect of bradykinin. Airway constriction was induced in the rats by aerosol administration of bradykinin with or without treatments with the inhaled bradykinin-2 receptor antagonist, Hoe 140 or the nitric oxide synthase inhibitors N(G)-nitro-L-arginine methylester or N(G)-monomethyl-L-arginine. Total lung resistance was partitioned into tissue and airway resistance by using the alveolar capsule method. Bradykinin induced a significant increase in both resistances. Hoe 140 abolished the response to bradykinin. The nitric oxide synthase inhibitors enhanced the bronchoconstricting response. In conclusion, the bradykinin response in the rats was not only localized to conducting airways but also involved a relatively selective tissue reaction. Bradykinin-induced bronchospasm in the rat is solely due to activation of bradykinin-2 receptor. Further, it was shown that nitric oxide significantly modulates the bronchospasm caused by bradykinin, suggesting that nitric oxide is an important modulator of airways responsiveness to bradykinin.  (+info)

Acinar flow irreversibility caused by perturbations in reversible alveolar wall motion. (4/1568)

Mixing associated with "stretch-and-fold" convective flow patterns has recently been demonstrated to play a potentially important role in aerosol transport and deposition deep in the lung (J. P. Butler and A. Tsuda. J. Appl. Physiol. 83: 800-809, 1997), but the origin of this potent mechanism is not well characterized. In this study we hypothesized that even a small degree of asynchrony in otherwise reversible alveolar wall motion is sufficient to cause flow irreversibility and stretch-and-fold convective mixing. We tested this hypothesis using a large-scale acinar model consisting of a T-shaped junction of three short, straight, square ducts. The model was filled with silicone oil, and alveolar wall motion was simulated by pistons in two of the ducts. The pistons were driven to generate a low-Reynolds-number cyclic flow with a small amount of asynchrony in boundary motion adjusted to match the degree of geometric (as distinguished from pressure-volume) hysteresis found in rabbit lungs (H. Miki, J. P. Butler, R. A. Rogers, and J. Lehr. J. Appl. Physiol. 75: 1630-1636, 1993). Tracer dye was introduced into the system, and its motion was monitored. The results showed that even a slight asynchrony in boundary motion leads to flow irreversibility with complicated swirling tracer patterns. Importantly, the kinematic irreversibility resulted in stretching of the tracer with narrowing of the separation between adjacent tracer lines, and when the cycle-by-cycle narrowing of lateral distance reached the slowly growing diffusion distance of the tracer, mixing abruptly took place. This coupling of evolving convective flow patterns with diffusion is the essence of the stretch-and-fold mechanism. We conclude that even a small degree of boundary asynchrony can give rise to stretch-and-fold convective mixing, thereby leading to transport and deposition of fine and ultrafine aerosol particles deep in the lung.  (+info)

A genome-wide screen for asthma-associated quantitative trait loci in a mouse model of allergic asthma. (5/1568)

Asthma is the most common illness of childhood, affecting one child in seven in the UK. Asthma has a genetic basis, but genetic studies of asthma in humans are confounded by uncontrolled environmental factors, varying penetrance and phenotypic pleiotropy. An animal model of asthma would offer controlled exposure, limited and consistent genetic variation, and unlimited size of sibships. Following immunization and subsequent challenge with ovalbumin, the Biozzi BP2 mouse shows features of asthma, including airway inflammation, eosinophil infiltration and non-specific bronchial responsiveness. In order to identify genetic loci influencing these traits, a cross was made between BP2 and BALB/c mice, and a genome-wide screen carried out in the F2progeny of the F1intercross. Five potentially linked loci were identified, four of which corresponded to human regions of syntenic homology that previously have shown linkage to asthma-associated traits.  (+info)

Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities, and eotaxin production. (6/1568)

Interleukin (IL)-13 is a pleiotropic cytokine produced in large quantities by activated CD4(+) Th2 lymphocytes. To define further its potential in vivo effector functions, the Clara cell 10-kDa protein promoter was used to express IL-13 selectively in the lung, and the phenotype of the resulting transgenic mice was characterized. In contrast to transgene-negative littermates, the lungs of transgene-positive mice contained an inflammatory response around small and large airways and in the surrounding parenchyma. It was mononuclear in nature and contained significant numbers of eosinophils and enlarged and occasionally multinucleated macrophages. Airway epithelial cell hypertrophy, mucus cell metaplasia, the hyperproduction of neutral and acidic mucus, the deposition of Charcot-Leyden-like crystals, and subepithelial airway fibrosis were also prominently noted. Eotaxin protein and mRNA were also present in large quantities in the lungs of the transgene-positive, but not the transgene-negative, mice. IL-4, IL-5, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-5 were not similarly detected. Physiological evaluations revealed significant increases in baseline airways resistance and airways hyperresponsiveness (AHR) to methacholine in transgene-positive animals. Thus, the targeted pulmonary expression of IL-13 causes a mononuclear and eosinophilic inflammatory response, mucus cell metaplasia, the deposition of Charcot-Leyden-like crystals, airway fibrosis, eotaxin production, airways obstruction, and nonspecific AHR. IL-13 may play an important role in the pathogenesis of similar responses in asthma or other Th2-polarized tissue responses.  (+info)

Respiratory mechanics in airways obstruction associated with inspiratory dyspnoea. (7/1568)

Inspiratory muscle strength and the flow and elastic pressure opposing inspiration were measured in seven patients with severe airways obstruction who found inspiration difficult at rest. A comparison was made of measurements obtained from seven normal subjects and five patients with airways obstruction not experiencing inspiratory dyspnoea at rest. Measurements were also obtained when inspiratory dyspnoea was induced in the normal subjects by adding an inspiratory resistance or by voluntarily increasing lung volume. Compared with the controls the inspiratory muscle strength of the patients was reduced but was not significantly less than that of the patients without inspiratory dyspnoea. The pressure required to produce inspiratory flow was significantly greater when inspiratory dyspnoea was present (P = 0-01). However, there was considerable overlap in the pressures of those with and without inspiratory dyspnoea. A better relationship was obtained when muscle strength was considered. The ratio of inspiratory muscle strength to the pressure required to produce flow was 0-24 +/- 0-07 (mean +/- SD) in patient with inspiratory dyspnoea, 0-10 +/- 0-03 in patients without inspiratory dyspnoea, and 0-033 +/- 0-019 in normal subjects. There was no overlap between the two patient groups. The ratios of the normal subjects were increased when inspiratory dyspnoea was induced and, with the exception of two cases, were all above those obtained when inspiratory dyspnoea was absent. Inspiratory dyspnoea was experienced with lower ratios in the normals than in the patients with airways obstruction.  (+info)

Physiologic basis and interpretation of common indices of respiratory mechanical function. (8/1568)

Tests of pulmonary mechanical function may be used in determining the prominent site of pulmonary reaction to intervention. Responses may be localized from a knowledge of changes in lung resistance and compliance. A peripheral airway or parenchymal response is characterized by a decrease in lung compliance. A central airway reaction is characterized by an increase in pulmonary resistance. In mixed reactions both parameters may change. In this communication some of the physiologic determinants of pulmonary resistance and compliance are discussed and examples of localized responses given.  (+info)

While sRaw captures information on airflow resistance, it is important to realize that it is not a true measurement of airway resistance. Its units are cmH2O.s while typical airway resistance units would be cmH2O.s/mL. sRaw rather denotes work of breathing as it is defined by the product of airway resistance and the lung volume at the end of inspiration, the functional residual capacity or FRC. Since both factors can influence the outcome of sRaw and that there is an inverse relationship between them, best practice would be to complement measurements of sRaw with direct measurements of both upper and lower airway resistance. This would not only provide more insight in interpreting the results but also a refined and comprehensive assessment leading to a deeper understanding. The flexiVent system offers detailed lung function measurements which can prove helpful in identifying the response site within the lower airway segment while also providing direct upper airway resistance measurements. Both ...
Research reports on pulmonary function measurements often mention caffeine abstinence as a condition for testing subjects. Yet, the effects of caffeine on respiration are not well documented. This study was intended to investigate the physiological effects of caffeine on respiratory resistance measurements and the necessity of caffeine avoidance in such testing. Thirty-one subjects were administered caffeine in pill form for dosages in the range of 3 - 4.5 mg/kg body weight. Respiratory resistance was measured with the Airflow Perturbation Device every 15 minutes after caffeine ingestion until a full hour of elapsed time. No changes were noted in inhalation, exhalation, and average respiratory resistances during the times of measurements. The conclusion is that for low dosages of caffeine, respiratory resistance measurements are not affected by caffeine ingestion prior to testing.
How is Expiratory Upper Airway Resistance abbreviated? eUAR stands for Expiratory Upper Airway Resistance. eUAR is defined as Expiratory Upper Airway Resistance very rarely.
C522-03(2016) Standard Test Method for Airflow Resistance of Acoustical Materials airflow resistance~ airflow velocity~ acoustical absorption~ sound~
TY - JOUR. T1 - Low frequency forced oscillation technique in infants. AU - Hall, Graham L.. AU - Hantos, Z.. AU - Pelak, Ferenc. AU - Wildhaber, Johannes. AU - Sly, Peter D.. PY - 1999. Y1 - 1999. N2 - The respiratory system in infants undergoes profound changes in the first few years of life. We applied two adaptions of the FOT to characterise 1 ) changes in airway and parenchymal mechanics with growth in the first two years of life; 2) contribution of the nose to total respiratory impedance (Zrs); and 3) the influence of the chest wall to Zrs. Methods: For studies 1 (n=34, 1 -24 months) & 2 (n=20, 3-21 months) a pseudo-random forcing signal (0.5-21 Hz) was applied to sedated infants via a face mask & Zrs was determined at a transrespiratory pressure of 20cm HzO. A model containing an airway compartment [airway resistance (R) & inertance (I)] & a frequency dependant constant-phase tissue compartment [tissue damping (G) & tissue elastance (H)] was fitted to Zrs. In the second study, Zrs was ...
Respiratory resistance was measured by the isovolume method [7] at 500 ml above functional residual capacity. Before each study, a Datex Ultima Capnomac spirometer (Datex Instrumentation, Helsinki, Finland) was calibrated for volume using a 1-1 syringe (Hans Rudolph, Kansas City, Mo). The ventilatory flow and pressure curves were sampled at 10-ms intervals, output to a personal computer, and the volume curve then determined by integration of the flow curve. The pressure drop across the endotracheal tube was excluded by first constructing a pressure-flow curve for both the 7.5-mm and 8-mm endotracheal tubes. For each measurement, the pressure drop across the tube for the flow noted was subtracted from the pressure measurements used during calculation, resulting in a value for R sub rs exclusive of the endotracheal tube. The isovolume method of resistance measurement is a technique applicable to mechanically ventilated patients and is based on measuring airway pressure and flow at identical ...
Ruhle and colleagues suggested in a recent review that upper airway impedance measurements using the forced oscillation technique may be useful as a surrogate of Pes in the diagnosis of UARS. With this technique, an airflow of 2 L/min is applied to a conventional nCPAP mask at an oscillatory frequency of 20 Hz. The researchers studied 25 nono-bese patients with EDS and a mean RDI of 3.4, Although the majority of arousals could not be explained on the basis of standard polysomnographic measurements, this technique showed IUAR in over half of these unexplained events. These authors also suggested that the pulse transit time (the time between the ECG R wave and the fingertip pulse shock wave) correlated with subtle changes in both the Pes and the arousals Reading here asthma medications inhalers. They also discussed changes in BP as a marker of IUAR because more negative intrathoracic pressure would decrease BP and arousal would increase BP. ...
We have studied 26 asthmatic patients in whom deep inspiration induced a transient but marked bronchodilatation when carbachol-induced bronchoconstriction was present. Changes in bronchial tone were assessed by specific airway resistance measurements. Bronchodilatation after a slow inspiration (eight subjects) or a 10-second breath-hold at total lung capacity (13 subjects) was significantly less than that observed after either a fast inspiration or no breath-holding period. The magnitude of the bronchodilatation induced by a fast inspiration without breath-holding was directly and significantly related to the magnitude of the carbachol-induced bronchoconstriction in five subjects.. ...
doctorstevenpark.com, The Truth About Prescription and OTC Sleep Aids [Podcast 71] In this episode, Kathy and I are going to be talking about another controversial topic that many of you have probably had some experience with at one time or another…and thats the issue of sleeping pills and OTC sleep aids. In particular, we will… ...
Airway resistance is the resistance to the flow of air through the respiratory tract during inhalation and expiration. The level of resistance depends on many things, particularly the diameter of the airway and whether flow is laminar or turbulent. In this article we shall consider how these factors affect the air flow, and consider some clinical conditions in which airway resistance is affected.
1. The forced expiratory volume (FEV0·75) was measured at increasing mouth pressures in twenty-seven patients with obstructive airways disease. Attempts were made to divide the patients on clinical grounds into emphysematous, bronchitic or asthmatic categories; there was no evidence from the (FEV/mouth pressure) plots that their airways functioned differently during forced expiration.. 2. Static elastic recoil was measured in twelve patients. There was no evidence that this factor alone caused the loss of FEV in any patient.. 3. It is suggested that the use of the FEV as a test of respiratory function during the natural history of obstructive airways disease should be considered in three stages. There is an initial phase when peripheral airways disease develops with little or no alteration of the FEV. In the second phase the FEV decreases from normal values to below 1·0 litre, and at this stage is considered a sensitive indicator of peripheral airways resistance. In stage 3 the FEV is low and ...
The OASYS Oral/Nasal Airway System™ is the first dental device for Snoring, Obstructive Sleep Apnea (OSA) and Upper Airway Resistance Syndrome (UARS) that treats the two major causes of sleep disordered breathing by addressing upper airway resistance in the nasal region and blockage in the throat region. The OASYS is FDA approved as a medical device in two separate classifications (1) As a mandibular repositioner for treatment of snoring and sleep apnea and (2) As a nasal dilator for improved ease of breathing.. The OASYS treats both vulnerable areas of the upper airway with one patented system while strengthening the throat area by pulling the lower jaw and tongue forward to prevent the tongue from blocking the airflow and strengthening the throat against collapse. ...
Airway resistance (RL) and dynamic compliance (Cdyn) as measures of lung function and airway reactivity. Basal values of RL (A) and Cdyn (B), and MCh challenge-
Specific Conductance (Sp C). Most substances dissolved in water dissociate into ions that can conduct an electrical current. Specific conductance measures electrical conductivity, and therefore is an indicator of the amount of material dissolved in water. The larger the conductance, the more mineralized the water. In general terms, the more mineralized the water, the lower its quality. Specific conductance values are reported in micromhos per centimeter at 25° C. Specific conductance measurements can be used to estimate total dissolved solids (TDS) content if the general characteristics of the water sample are known. For example, in the Flint Hills, most of the ground water contains some calcite or dolomite that has been derived from the limestone bedrock. In the absence of evaporite minerals or contaminants, the water chemistry is generally a calcium-bicarbonate type. If gypsum or anhydrite are present, calcium-sulfate waters are generated. Contamination of the ground water with brine produces ...
P. Fontanari, M-C. Zattera-Hartmann, H. Burnet, Y. Jammes. Nasal eupnoeic inhalation of cold, dry a airway increases airway resistance in asthmatic patients. European Respiratory Journal, European Respiratory Society, 1997, 10 (10), pp.2250 - 2254. ⟨10.1183/09031936.97.10102250⟩. ⟨hal-01802744⟩ ...
An electrical circuit for extensive testing of a ground fault interrupter. Means to create a current differential between the hot and neutral conductors of a ground fault interrupter device, and thereby test the circuit interrupt features of said device, are disclosed. Means are also provided for determining the sensitivity of the device being tested to an accidental grounding of the neutral conductor. The invention also can be used to check the wiring connections between the ground fault interrupter and the electrical system to which it is attached. A further advantage of the invention is that it provides an indirect test of said electrical system. Modifications to the circuitry will provide similar testing devices for two and three phase ground fault interrupters.
The results of the comparative analysis among the AUC of FOT and spirometric parameters are described in Figure 5. In general, R0 (Figure 5A), Rm (Figure 5C), and Crs,dyn (Figure 5E) presented significantly higher AUC in smoking subjects with , 20 pack-years, and AUC similar to that presented by spirometric parameters as the amount of tobacco smoked increased. Spirometric parameters presented significantly higher AUC than S (Figure 5B), fr (Figure 5D), and Xm (Figure 5F) considering groups of smoking subjects with 20-39 pack-years and 40-59 pack-years.. DISCUSSION. This study documented a significantly deleterious effect of smoking on the impedance of the respiratory system. Although many other published reports have used the FOT to compare control groups with ex-smokers and/or smoking subjects, to the best of our knowledge, this study is the first study to investigate respiratory impedance in groups with different degrees of tobacco consumption. Earlier studies have found deleterious ...
5.3 Airway Resistance - Shock Losses for Bends and Area Changes - Free download as PDF File (.pdf), Text File (.txt) or read online for free.
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High-power packages show a characteristic three-dimensional heat flow resulting in large lateral changes in chip and case surface temperature. This paper p
P.H. Howarth, J.S. Mann, S.T. Holgate; The Influence of Resting Airway Calibre on Non-Specific and Specific Airway Reactivity in Asthma. Clin Sci (Lond) 1 January 1984; 67 (s9): 5P-6P. doi: https://doi.org/10.1042/cs067005Pb. Download citation file:. ...
TY - THES. T1 - Measurement of lung function using broadband forced oscillations /Cindy Thamrin. AU - Thamrin, Cindy. PY - 2006. Y1 - 2006. N2 - [Truncated abstract] Respiratory system impedance (Zrs) is commonly measured at low to medium frequencies (0.5 - 40 Hz) to infer structural and physiological information about the respiratory system. Coupled with the use of mathematical models of the lungs, Zrs has been used to partition the behaviour of the conductive airways and the respiratory tissues. High-frequency (HF) Zrs beyond 100 Hz has been comparatively less studied and understood. Past work has revealed spectral features at high frequencies termed antiresonances, marked by peaks in the real part of Zrs, often coinciding with zero-crossings in the imaginary part. It has been shown that the first occurrence of antiresonance in humans primarily reflects the contribution of the airways, and is a property of sound wave propagation in the airways. Also, the first antiresonance is altered in ...
A temperature responsive current interrupter in which two conductors are connected by electrically conductive, low-melting-point fusible elements respectively mounted on the conductors and a connector element interconnecting the fusible elements and urged against an electrically non-conductive high-melting-point fusible element, the connector element being moved into a position separate from at least one of the conductors when the high-melting-point fusible element is melted by heat.
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Oscillatory Resistance measurement answers the central question for the degree of obstruction immediately and practically without the patients cooperation
This paper discusses the techniques utilized during automated testing of Z-technology modules for mosaic focal planes. The testing includes continuity and isolation resistance measurements on both layers and modules, and functional tests of the Signal Processing Chips as they are wirebonded to the modules. The criteria for layer selection, empirically derived, is presented. Test results are presented and their impact on product development are described ...
Grading the severity of obstruction in mixed -obstructive-restrictive lung disease. Chest 140:598-603, 2011. 7. Krowka MJ, Enright PL, Rodarte JR, Hyatt RE. Effect of effort on measurement of forced -expiratory volume in one second. Am Rev Respir Dis 136:829-833, 1987. indd 34 30/01/14 10:36 AM 4 Diffusing Capacity of the Lungs An important step in the transfer of oxygen from ambient air to the arterial blood is the process of diffusion, that is, the transfer of oxygen from the alveolar gas to the hemoglobin within the red cell. 1 gives: PB VF = (PB + ∆P)(VF − ∆V) Piston and: Simplifies to: VF = ∆V (PB + ∆P) ∆P VF = ∆V (PB) ∆P FIG. 3-6. The subject is seated in an airtight plethysmograph and the pressure in the plethysmograph (Ppleth) changes with changes in lung volume. When the subject stops breathing, alveolar pressure equals barometric pressure (Pb). Consider what happens if the valve at the mouth is closed at the end of a quiet expiration, that is, FRC, and the subject makes ...
EXTREMES FOR PERIOD OF DAILY RECORD - SPECIFIC CONDUCTANCE: Maximum, 2,040 microsiemens, Oct. 2, 1994; minimum, 85 microsiemens, August 17, 1996.pH: Maximum, 9.4 units, September 28, 1989; minimum, 6.4 units, June 19, 2013 and April 22-23, 2014.WATER TEMPERATURE: Maximum, 39.0°C, July 2, 1990; minimum, -0.6°C, January 10-11, 2011 DISSOLVED OXYGEN: Maximum, 20.7 mg/l, July 19, 2006; minimum, 0.7 mg/l, August 28, 2014 ...
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Looking for online definition of Resistance measurement in the Medical Dictionary? Resistance measurement explanation free. What is Resistance measurement? Meaning of Resistance measurement medical term. What does Resistance measurement mean?
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TY - JOUR. T1 - Comparative respiratory system mechanics in rodents. AU - Gomes, R. F.M.. AU - Shen, X.. AU - Ramchandani, R.. AU - Tepper, R. S.. AU - Bates, J. H.T.. PY - 2000/12/1. Y1 - 2000/12/1. N2 - Because of the wide utilization of rodents as animal models in respiratory research and the limited data on measurements of respiratory input impedance (Zrs) in small animals, we measured Zrs between 0.25 and 9.125 Hz at different levels (0-7 hPa) of positive end-expiratory pressure (PEEP) in mice, rats, guinea pigs, and rabbits using a computer-controlled small-animal ventilator (Schuessler TF and Bates JHT, IEEE Trans Biomed Eng 42: 860-866, 1995). Zrs was fitted with a model, including a Newtonian resistance (R) and inertance in series with a constant-phase tissue compartment characterized by tissue damping (Gti) and elastance (Hti) parameters. Inertance was negligible in all cases. R, Gti, and Hti were normalized to body weight, yielding normalized R, Gti, and Hti (NHti), respectively. ...
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Introduction. Overweight contributes to the development of significant cardiorespiratory impairments, including the increase in airway and respiratory system resistance, limited ventilatory capacity, and changes in the cardiovascular autonomic function. As these changes are proportional to the body mass index (BMI), they are more pronounced in patients with morbid obesity.1,2. The respiratory system resistance and its components can be determined using the Forced Oscillation Technique (FOT), described by Dubois et al. in 1956 as a non-invasive method for the evaluation of mechanical properties of the respiratory system in different frequencies.3 Morbidly obese patients also present increased cardiovascular sympathetic discharge and reduced parasympathetic activity.4 Because heart rate variability is influenced by the autonomic control, the time and frequency-domain analysis of RR intervals has been recognized as an effective and non-invasive method of evaluating the cardiovascular autonomic ...
Download PULMONARY AIRWAY RESISTANCE by profisy4CHRIST for physiology students University of Ilorin [PULMONARY AIRWAY RESISTANCE - 1102]
PURPOSE: ALI and ARDS are associated with lung volume derecruitment, usually counteracted by PEEP and recruitment maneuvers (RM), which should be accurately tailored to the patients needs. The aim of this study was to investigate the possibility of monitoring the amount of derecruited lung by the forced oscillation technique (FOT). METHODS: We studied six piglets (26 +/- 2.5 kg) ventilated by a mechanical ventilator connected to a FOT device that produced sinusoidal pressure forcing at 5 Hz. The percentage of non-aerated lung tissue (V (tiss)NA%) was measured by whole-body CT scans at end-expiration with zero end-expiratory pressure. Respiratory system oscillatory input reactance (X (rs)) was measured simultaneously to CT and used to derive oscillatory compliance (C (X5)), which we used as an index of recruited lung. Measurements were performed at baseline and after several interventions in the following sequence: mono-lateral reabsorption atelectasis, RM, bi-lateral derecruitment induced by ...
A prospective respiratory health survey of the general population in Busselton, Western Australia, was conducted between 2005 and 2007. Subjects had measures of spirometry, and resistance and reactance at 6, 11, 19 Hz. Eligible subjects were never smokers, with no history of respiratory disease, no symptoms of cough, shortness of breath or chest tightness in the previous 12 months, and no respiratory tract infections in the previous 4 weeks.. ...
Background: It is unclear why obesity is associated with worse asthma control. We hypothesized that(1) obesity affects asthma control independent of spirometry, airway inflammation, and airway hyperresponsiveness (AHR) and (2) residual symptoms after resolution of inflammation are due to obesity-related changes in lung mechanics. Methods: Forty-nine subjects with asthma underwent the following tests, before and after 3 months of high-dose inhaled corticosteroid (ICS) treatment: five-item asthma control questionnaire (ACQ-5), spirometry, fraction of exhaled nitric oxide (FENO), methacholine challenge, and the forced oscillation technique, which allows for the calculation of respiratory system resistance (Rrs) and respiratory system reactance (Xrs) as indicators of airway caliber and elastic load, respectively. The effects of treatment were assessed by BMI group (18.5-24.9, 25-29.9, and ≥30 kg/m 2 ) using analysis of variance. Multiple regression analyses determined the independent predictors of ACQ-5
Respiratory resistance at 20 Hz (R20) by impulse oscillometry (IO) characterizes airways resistance with inextensible walls. Airways resistance (Rtot) by body plethysmography reflects the total resistance of the first 8 - 10 bronchi generations. These indicators by different methods are close physiologically. The airways in patients with an emphysema are deprived of elastic support, so a lung compliance (CL) considerably increases. We have assumed that shunting of R20 increases with loss of lung elastic recoil.. Aim of the study is evaluation loss of respiratory resistance by IO with increasing of compliance and decreasing of lung elastic recoil.. Materials and methods: We compared Rtot and R20 in 67 healthy volunteers (32F/35M, 47±1 yrs) and in the patients with obstructive disorders - 41 patients with COPD (0F/41M, 56±1 yrs) and 52 patients with bronchial asthma (34F/18M, 47±2 yrs). We have used the relation Rtot/R20. All patients were performed investigation of lung elasticity using ...
Inflation of the leg compartments of pneumatic trousers increases thoracic blood volume. The resultant response in respiratory impedence was investigated in nine normal volunteers, and compared with the response to increasing doses of inhaled carbachol. Respiratory impedance was measured by the forced oscillation technique (4-32 Hz), and respiratory resistance at zero frequency (R0) was extrapolated from linear regression analysis of resistive impedance versus frequency. The mean increase in R0 was 31% after inhalation of 125 micrograms carbachol, and 21% after inflation of pneumatic trousers. The percentage changes in R0 following pneumatic trouser inflation highly correlated those induced by inhalation of 125 micrograms carbachol (r = 0.98) Our data demonstrate that, even in normal subjects, pneumatic trouser inflation causes an increase in respiratory resistance, which can be predicted by the response to a low dose of carbachol. These results support the assumption that cholinergic agents ...
To determine the sensitivity of pulmonary resistance (RL) to changes in breathing frequency and tidal volume, we measured RL in intact anesthetized dogs over a range of breathing frequencies and tidal volumes centering around those encountered during quiet breathing. To investigate mechanisms responsible for changes in RL, the relative contribution of airway resistance (Raw) and tissue resistance (Rti) to RL at similar breathing frequencies and tidal volumes was studied in six excised, exsanguinated canine left lungs. Lung volume was sinusoidally varied, with tidal volumes of 10, 20, and 40% of vital capacity. Pressures were measured at three alveolar sites (PA) with alveolar capsules and at the airway opening (Pao). Measurements were made during oscillation at five frequencies between 5 and 45 min-1 at each tidal volume. Resistances were calculated by assuming a linear equation of motion and submitting lung volume, flow, Pao, and PA to a multiple linear regression. RL decreased with increasing
We tested the hypothesis that different strategies are used to alter tracheal pressure (Pt) during sustained and transient increases in intensity. It has been suggested that the respiratory system plays the primary role in Pt changes associated with alteration in overall intensity, whereas laryngeal adjustment is primary for transient change in Pt related to emphasis. Tracheal pressure, obtained via tracheal puncture, airflow (U), and laryngeal electromyography from the thyroarytenoid muscle (TA EMG) were collected from 6 subjects during sentence production at different intensity levels and with various stress patterns. Using a technique described in a previous study, we computed lower airway resistance (Rlaw) from measures of Pt and U obtained during a sudden change in upper airway resistance. We used this resistance value, together with direct measures of Pt and U during speech, to derive a time-varying measure of alveolar pressure (Pa), the pressure created by respiratory muscle activity and ...
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This was an interesting study, because it showed what sRAW can and cannot do when compared to RAW and JPEG files. If your intention is to be able to recover white balance, the sRAW format has a definite advantage over JPEG as demonstrated in the first part of the article. Although there is definite loss of colors, you can recover most of the data when altering white balance, which is good news. Hence, if you want to have smaller RAW files and have the flexibility to change white balance, the sRAW format seems to be a viable option.. However, when it comes to recovering information from shadows and highlights, the sRAW format must be used with caution. First, you should not be using Adobe Camera RAW (Photoshop and Lightroom) for sRAW file conversion, since the Adobe RAW engine ends up heavily under-exposing images and losing more data in highlights, as demonstrated above. Capture NX-D clearly does a better job, but the software is very buggy and has its own set of problems (for example, ...
In this second posting on this topic, I will attempt to bring together some of the latest research that I have found regarding a very controversial topic of respiratory system weakness. In other words, there is something about your respiratory system that is limiting performance. How does this happen?. I propose, here, a different type of "zoning". Most people talk about fat burning zones, or carb burning zones, or threshold power. I propose here zoning based on respiratory mechanics, and, especially if your primary weakness is based on respiratory mechanics.. You say what???. Many, many coaches have shot me down for making such a comment. They say that the respiratory muscles are sometimes insignificant in the overall production of a PB performance. Many of these traditional coaches also think that to succeed, you must be training hard or long all the time, and you must have a winning attitude. I dont disagree with the psychological aspect of a PB performance, but instead of training hard or ...
0047]To test the transparent conductor 120 of the touch panel 200, the bottom panel 101 is connected to a voltage testing supply 203 that supplies a supply voltage V0. In the present embodiment, the supply voltage is set at five volts, but may be any suitable testing voltage that will not harm the underlying circuitry and touch panel materials but will allow for adequate testing of the touch panel 200. The top panel 105 is preferably set at a zero voltage level. Also, connected to the bottom panel 101 and the voltage testing supply 203, there is a resistor RT. There is also a sense terminal 204 at which a sensing voltage Vsense can be detected. The sensing voltage is used to measure a voltage caused by the bottom panel 101 and the top panel 105 coming into electrical contact at a point 201. The sensing voltage Vsense is used to calculate the contact resistances for each point of contact made between the bottom panel 101 and the top panel 105. For example, electrical contact is made at the point ...
Also parallel bar instruments are intended to measure flat, regular material surfaces and are intended to measure the effect of many parallel paths across the material between the two bars. Using these instruments for Point to Point measurements are different than area measurements and will provide different measurement results. In this case they are simply indicators and not specification measurements.. For example, the ESD Check ESI-870 is probably just fine. You can check it by placing it on surfaces of various resistance characteristics e.g., on an insulated surface and a clean metal surface. The problem is when comparing two different measurement fixtures on an undefined surface - Soft Rubber vs Machined Metal contact fixtures - and expect to get the same answer. This is not always possible. This is the reason Prostat provides REMOVABLE conductive boots & ...
They had them breathe in through a machine that could vary the temperature and humidity of the air. They would have the patients pant afterwards, and they would measure airway resistance. For those that had mild asthma, they showed airway resistance to hot, humid air. (That means they were having a hard time breathing) The "normal people" showed very little or now problems. Figures. Once again our asthma bodies over-react to normal every day things. Here are the results of the study ...
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Upper airway resistance[edit]. Airway resistance increases by about 230% during NREM sleep. Elastic and flow resistive ... Upper airway function[edit]. Upper airway resistance is expected to be highest during REM sleep because of atonia of the ... Upper airway resistance syndrome[edit]. This section needs expansion. You can help by adding to it. (December 2010) ... Main article: Upper airway resistance syndrome. Obstructive sleep apnea (including hypopnea) syndrome[edit]. Main article: ...
The upper airway resistance syndrome". Chest. 104 (3): 781-7. doi:10.1378/chest.104.3.781. PMID 8365289. Attribution of the ... Following this work, he went on to describe the presence of elevated upper airway resistance in children in 1982, emphasizing ... "upper airway resistance syndrome" (UARS) in adults. Finally, working in collaboration with Dr. William C. Dement, Guilleminault ... "Sleep-induced apnea syndrome, a surgical procedure to establish patency of the upper airway during sleep". "Sleep-induced apnea ...
... increases with any airway resistance. Things that may increase PIP could be increased secretions, ...
Upper airway resistance syndrome may also be implicated. Treatment may involve investigation, reassurance and explanation, and ... "Functional somatic syndromes, anxiety disorders and the upper airway: A matter of paradigms". Sleep Medicine Reviews. 15 (6). ...
... in 2014 granted pre-market approval for an upper airway stimulation system that senses respiration and delivers mild electrical ... Automatic positive airway pressure, or automatic positive airway pressure, also known as "Auto CPAP", incorporates pressure ... Surgical treatments to modify airway anatomy, known as sleep surgery, are varied and must be tailored to the specific airway ... Continuous positive airway pressure (CPAP) is effective for both moderate and severe disease.[29] It is the most common ...
... increasing airway resistance. The bronchoconstriction is also caused by left ventricular dysfunction, caused by the SRTXs. Left ... it was found that there was a marked increase in airway resistance. This was likely caused by bronchoconstriction. ... "Resistance of the egyptian mongoose to sarafotoxins". Toxicon. 35 (8): 1251-1261. doi:10.1016/s0041-0101(97)00019-6. Lüscher, ... Bronchoconstriction occurred due to constriction of smooth muscle and airway wall thickening due to peribronchial edema. This ...
... of the total resistance originating at the nasal passages. Decreased resistance reduces the airway forces across the pulmonary ... In the case where no blood is visible in the trachea, EIPH in the small airways may still be present and can be confirmed by a ... Ramzan, Peter H.L. (2014). "Respiratory conditions: lower airway disease". The racehorse: a veterinary manual. pp. 222-234. ... Bronchoalveolar lavage (BAL) is a procedure whereby a small volume of fluid is put into the airways in order sample the cells ...
Upper Airway Resistance Syndrome, or Obstructive Sleep Apnea Syndrome". The Laryngoscope. 107 (6): 726-734 "Clinical Program - ... Upper Airway Resistance Syndrome, or Obstructive Sleep Apnea Syndrome". The Laryngoscope. 107 (6): 726-734. doi:10.1097/ ... "Recognition and Surgical Management of the Upper Airway Resistance Syndrome". The Laryngoscope. 106 (9): 1089-1093 Terris, D. J ... "Recognition and Surgical Management of the Upper Airway Resistance Syndrome". The Laryngoscope. 106 (9): 1089-1093. doi:10.1097 ...
Airway resistance is typically increased by bronchospasm and airway secretions. Chest wall compliance can be decreased by fixed ... which eliminates the effects of airway resistance. Pplat is never > PIP and is typically < 3-5 cmH2O lower than PIP when airway ... Alterations in airway resistance, lung compliance and chest wall compliance influence Cdyn. C s t a t = V T P p l a t − P E E P ... Lung compliance Chest wall compliance Airway resistance Lung compliance is influenced by a variety of primary abnormalities of ...
Partitioning airway and lung tissue resistances in humans: effects of bronchoconstriction. J Appl Physiol 82: 1531-1541, 1997. ... Airway caliber in healthy and asthmatic subjects: effects of bronchial challenge and deep inspirations. J Appl Physiol 91: 506- ... Tissue resistance and the contractile state of lung parenchyma. J Appl Physiol 74: 1387-1397, 1993. Fredberg JJ, Jones KA, ... Friction in airway smooth muscle: mechanism, latch, and implications in asthma. J Appl Physiol 81: 2703-2712, 1996. Bursac P, ...
Suction airway secretions with variable airway resistance. *Palpable pulse. *Responds to needle thoracentesis and chest tube ... Airway trauma features: upper airway obstruction, laryngospasm and bronchial occlusion for intubation ... Responds to airway trauma or obstruction: esophageal, nasal and oral intubation, and BVM ventilation and laryngoscopic ...
The Inspire Upper Airway Stimulation system senses respiration and applies mild electrical stimulation during inspiration, ... continuous positive airway pressure improves insulin resistance in patients with sleep apnea without diabetes". Annals of the ... or automatic positive airway pressure (APAP) device.[46][47] These splint the person's airway open during sleep by means of ... "Inspire Upper Airway Stimulation - P130008". FDA.gov. Food and Drug Administration. 11 January 2016. Archived from the original ...
The increased airway resistance that is associated with obstructive sleep apnea may also lead to nocturnal polyuria. ...
... lung volumes and airway resistance in normal children ages 5 to 18". Br J Dis Chest. 64 (1): 15-24. doi:10.1016/S0007-0971(70) ... It measures the airflow through the bronchi and thus the degree of obstruction in the airways. Peak flow readings are higher ... The Airways Journal. 2 (2): 80. Retrieved 2006-06-06. Nunn A, Gregg I (1989). "New regression equations for predicting peak ... when patients are well, and lower when the airways are constricted. From changes in recorded values, patients and doctors may ...
Unilateral measurements are performed to detect any asymmetry or abnormality in nasal airway resistance. When the measurements ... Increased resistance on rhinomanometry after allergen application is an objective mean in proving allergy to airborne allergens ... Nasal obstruction leads to increased values of nasal resistance. Rhinomanometry may be used to measure only one nostril at a ... Increased pressure during respiration is a result of increased resistance to airflow through nasal passages (nasal blockage), ...
"Enlargement of the lateral pharyngeal fat pad space in pigs increases upper airway resistance". Journal of Applied Physiology. ...
... decreasing resistance in the respiratory airway and increasing airflow to the lungs. Bronchodilators may be endogenous ( ... From among 6000 compounds that relax the smooth muscle cells of the lungs' airways and open up the airways in asthmatic lung ... agonist that relaxes airway smooth muscle cells and reduces asthmatic pulmonary resistance. The authors claim that "TSG12 is ... These medications may take longer to begin working, but relieve airway constriction for up to 12 hours. Commonly taken twice a ...
This narrows the upper airway during sleep, increasing resistance and making airflow through the upper airway turbulent and ... The upper airway becomes more floppy.. *The rhythmic innervation results in weaker muscle contractions because the ... This problem is exacerbated in overweight people when sleeping on the back, as extra fat tissue may weigh down on the airway, ... During non-REM sleep, the tonic drive to most respiratory muscles of the upper airway is inhibited. This has two consequences: ...
The increased fluid in the lungs leads to increased airway resistance and reduced lung compliance. It is thought this could be ...
With only a thoracic signal, all parameters can be obtained except for specific airway resistance (SRaw) and specific airway ... Another important parameter, which can be calculated with a body plethysmograph is the airway resistance. During inhalation the ... While observing the so-called resistance loop (cabin pressure and flow), diseases can easily be recognized. If the resistance ... including airway resistance and conductance. Different sizes of plethysmograph exist to study mice, rats or guinea pigs. The ...
Pplat is never bigger than PIP and is typically < 3-5 cm H2O lower than PIP when airway resistance is not elevated. PEEP is ... During this maneuver, airflow is transiently (~0.5 sec) discontinued, which eliminates the effects of airway resistance. ... Alterations in airway resistance, lung compliance and chest wall compliance influence Cdyn. Lung compliance is an important ...
A 2013 review found an instant increase in airway resistance after using a single e-cigarette. Any reported harmful effects to ... The short-term toxicity of e-cigarette use appears to be low, with the exception for some people with reactive airways. The ... A 2015 PHE report concluded that the risks of fire from e-cigarettes "appear to be comparable to similar electrical goods". ... A 2014 review found "disposable e-cigarettes might cause an electrical waste problem." Since the majority of e-cigarettes are ...
Increased airways resistance (chronic obstructive pulmonary disease, asthma, suffocation). *Reduced breathing effort (drug ... continuous positive airway pressure can be useful when started before conveying to hospital.[3] ... "Continuous positive airway pressure and noninvasive ventilation in prehospital treatment of patients with acute respiratory ...
FEV1 is diminished because of increased airway resistance to expiratory flow; the FVC may be decreased as well, due to the ... but the former is more affected because of the increased airway resistance). This generates a reduced value (,80%, often ~45 ... It is sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway ... Actual volume of the lung including the volume of the conducting airway. ...
Laminar flow tends to generate less resistance than turbulent flow. In the small airways where flow is laminar, resistance is ... The Hagen-Poiseuille equation describes laminar resistance. In the large airways where flow is turbulent, resistance is ... The mixture generates less resistance than atmospheric air when passing through the airways of the lungs, and thus requires ... Currently, heliox is mainly used in conditions of large airway narrowing (upper airway obstruction from tumors or foreign ...
Drug resistance is increasingly more common and presents a serious problem in persons who are immunocompromised. Prophylactic ... CS1 maint: Extra text: authors list (link) Inhaled steroids in asthma optimizing effects in the airways. [S.l.]: Marcel Dekker ...
The buildup of fat leads to a decrease in chest well compliance and increase in airway resistance, both of which are ...
... of total airway resistance.{ref6} The nasal cavity has been modeled as 2 resistors in parallel.{ref1}{ref9} The 3 components of ... Nasal airway resistance accounts for more than 50% of total airway resistance. [6] The nasal cavity has been modeled as 2 ... Its overall contribution to total airway resistance is small. The component of nasal cavum resistance is determined by degree ... Nasal resistance increases markedly in the first 2-3 cm of the nasal airway. [1] ...
The effect of rapid maxillary expansion on nasal airway resistance.. Hartgerink DV1, Vig PS, Abbott DW. ... Nasal resistance measurements, assessed in four modes (natural state, anterior nares dilation with Tygon tubing, following ... Individual variation in nasal resistance values was considerable and hence the median response for the group was not a reliable ... The purpose of this study was to evaluate changes in nasal resistance to airflow in persons undergoing rapid maxillary ...
Apparently, according to the paper work I have a diagnosis of upper airway resistance syndrome (23 arousals an hour). No one ... Treatment for Upper Airway Resistance Syndrome nipsic987 Hello, I just reviewed my medical records which included a sleep study ... Apparently, according to the paper work I have a diagnosis of upper airway resistance syndrome (23 arousals an hour). No one ... Create an account to receive updates on: Treatment for Upper Airway Resistance Syndrome ...
... eUAR stands for Expiratory Upper Airway Resistance. eUAR is defined as Expiratory Upper Airway Resistance very rarely. ... www.acronymfinder.com/Expiratory-Upper-Airway-Resistance-(eUAR).html. *Chicago style: Acronym Finder. S.v. "eUAR." Retrieved ... www.acronymfinder.com/Expiratory-Upper-Airway-Resistance-(eUAR).html,eUAR,/a,. ... www.acronymfinder.com/Expiratory-Upper-Airway-Resistance-(eUAR).html ...
... airway resistance is the resistance of the respiratory tract to airflow during inhalation and expiration. Airway resistance can ... these airways may collapse causing increased airway resistance. This is simply the mathematical inverse of airway resistance. G ... in asthma during an attack the airways constrict causing an increase in airway resistance. Airway resistance can also vary ... An individual small airway has much greater resistance than a large airway, however there are many more small airways than ...
Upper airway resistance syndrome or UARS is a common sleep disorder characterized by the narrowing of the airway that can cause ... Upper airway resistance syndrome is caused when the upper airway narrows without closing. Consequently, airflow is either ... "Upper airway resistance syndrome in children". Seminars in Pediatric Neurology: 207-215 - via Elsevier. "Upper Airway ... Medicine portal Airway resistance Sleep apnea Shneerson, John M., ed. (2005). Sleep Medicine (Second ed.). New York: Blackwell ...
... surgical intervention did not change structural shape or resistance during normal breathing; however, researchers found ... Rhinoplasty has little effect on airway, resistance for external nasal valve dysfunction. Source/Disclosures Source: Palesy T, ... According to the researchers, a relationship between nasal airway resistance and minimum cross-sectional area may exist, where ... However, no significant changes were observed for median nasal airway resistance or the minimum cross-sectional area. ...
Monitoring of airway resistance (Raw) in exacerbation of asthma Message Subject (Your Name) has sent you a message from ... Monitoring of airway resistance (Raw) in exacerbation of asthma. Tajana Jalusic Gluncic, Latinka Basara Toromanovic ...
Browse by Outcome: Airway Resistance (2 articles). % of records by year: 1965 2017 ...
AIRWAY RESISTANCE You will receive an email whenever this article is corrected, updated, or cited in the literature. You can ... J. A. Nadel, J. G. Widdicombe; AIRWAY RESISTANCE. Anesthesiology 1963;24(2):266. ... Effects of Changes in Blood Gas Tension and Carotid Sinus Pressure on Airway calibre of Dogs.) ...
AIRWAY RESISTANCE You will receive an email whenever this article is corrected, updated, or cited in the literature. You can ...
Cartilaginous airway wall dimensions and airway resistance in cystic fibrosis lungs. HA Tiddens, LP Koopman, RK Lambert, WM ... Cartilaginous airway wall dimensions and airway resistance in cystic fibrosis lungs. HA Tiddens, LP Koopman, RK Lambert, WM ... Cartilaginous airway wall dimensions and airway resistance in cystic fibrosis lungs. HA Tiddens, LP Koopman, RK Lambert, WM ... Cartilaginous airway wall dimensions and airway resistance in cystic fibrosis lungs Message Subject (Your Name) has sent you a ...
1. The inverse relationship between airway resistance and lung volume contributes to variation in measurement of resistance, as ... of airway resistance was compared with conventional volume-standardized variables such as specific airway resistance, specific ... A Method for Standardizing Airway Resistance for Variations in Lung Volume. T. Higenbottam, T. J. H. Clark ... A Method for Standardizing Airway Resistance for Variations in Lung Volume Message Subject (Your Name) has forwarded a page to ...
... airway caliber, lung volumes and their combination, specific resistance) and that resistance parameters of the two techniques ... while Rrsmean and Raw0.5 explored more central airways. Only specific resistances taking into account the specific resistance ... resistance extrapolated at 0 Hz [Rrs0 Hz], mean resistance [Rrsmean], and resistance/frequency slope [Rrsslope]) and (2) to ... to compare numerical parameters of specific airway resistance (total, sRawtot, effective, sRaweff and at 0.5 L • s-1, sRaw0.5) ...
But airways resistance continues to increase and could be a more sensitive measurement of further airways disease. ... Peripheral Airways Resistance, Static Recoil and the Forced Expiratory Volume Ruth M. Cayton Ruth M. Cayton ... Ruth M. Cayton, P. Howard; Peripheral Airways Resistance, Static Recoil and the Forced Expiratory Volume. Clin Sci 1 April 1972 ... and at this stage is considered a sensitive indicator of peripheral airways resistance. In stage 3 the FEV is low and further ...
5.3 Airway Resistance - Shock Losses for Bends and Area Changes - Free download as PDF File (.pdf), Text File (.txt) or read ... not exist in physical form in the airways at all. Hence, we can say that the airway. first contract from Aa to Ao and then ... saveSave 5.3 Airway Resistance - Shock Losses for Bends and... For Later. ... saveSave 5.3 Airway Resistance - Shock Losses for Bends and... For Later. ...
Glucocorticosteroid effects on cytokine production: studies in a glucocorticosteroid resistance model and in allergic airway ... produced during allergic airway inflammation have been proposed to induce the resistance to GCS. IL-2 and IL-4 also induce GCS ... produced during allergic airway inflammation have been proposed to induce the resistance to GCS. IL-2 and IL-4 also induce GCS ... produced during allergic airway inflammation have been proposed to induce the resistance to GCS. IL-2 and IL-4 also induce GCS ...
Influence on airway resistance and functional residual capacity. Together they form a unique fingerprint. * Sort by ...
We assessed associations of long-term air pollution exposure with airway resistance. Methods: We measured airway resistance at ... Air pollution and airway resistance at age 8 years - The PIAMA birth cohort study. Publication. Publication. Environmental ... Air pollution and airway resistance at age 8 years - The PIAMA birth cohort study. Environmental Health: A Global Access ... but measurements of airway resistance may provide additional information. ...
... upper airway resistance syndrome (UARS), and obstructive sleep apnea (OSA) ... Sleep disordered breathing can be severe to the point of complete airway collapse where your airway gets sucked closed.. Those ... These appliances allow maximum airway capacity. It gently holds your jaw in the correct position to maintain proper airway flow ... upper airway resistance syndrome (UARS), and obstructive sleep apnea (OSA).. Obstructive Sleep Apnea (OSA) is defined by the ...
Multiday Exposure of Men to High Nitrogen Pressure and Increased Airway Resistance at Natural Expired Oxygen Tension: A 14-day ... Multiday Exposure of Men to High Nitrogen Pressure and Increased Airway Resistance at Natural Expired Oxygen Tension: A 14-day ... Multiday Exposure of Men to High Nitrogen Pressure and Increased Airway Resistance at Natural Expired Oxygen Tension: A 14-day ...
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  • Due to the elastic nature of the tissue that supports the small airways airway resistance changes with lung volume. (wikipedia.org)
  • Airway dimensions were measured in lungs obtained from CF patients who had undergone lung transplantation (n=12), lobectomy (n=1), or autopsy (n=4). (ersjournals.com)
  • 1. The inverse relationship between airway resistance and lung volume contributes to variation in measurement of resistance, as it is difficult to control precisely the lung volume at which resistance is determined each time. (clinsci.org)
  • A correction for variation in lung volume was applied to measurement of airway resistance by using analysis of covariance with lung volume as a covariate. (clinsci.org)
  • This method provides an assessment in each subject of degree of association between airway resistance and lung volume and uses the individual's unique slope, relating resistance to volume in order to correct resistance to a single lung volume. (clinsci.org)
  • 2. Eight normal male subjects had airway resistance and lung volume measured in a body plethysmograph, a mean of seven measurements being made. (clinsci.org)
  • 3. Airway resistance showed only a limited association with lung volume and the slopes relating the two measurements varied between subjects. (clinsci.org)
  • 4. Analysis of covariance adequately corrects airway resistance for variations in lung volume but further studies are required to validate its precision and sensitivity. (clinsci.org)
  • In forced expiration the lung compresses and the small airways are narrowed, causing the resistance to increase further. (teachmephysiology.com)
  • Airway resistance (RL) and dynamic compliance (Cdyn) as measures of lung function and airway reactivity. (nih.gov)
  • Its units are cmH 2 O.s while typical airway resistance units would be cmH 2 O.s/mL. sR aw rather denotes work of breathing as it is defined by the product of airway resistance and the lung volume at the end of inspiration, the functional residual capacity or FRC. (scireq.com)
  • The flexiVent system offers detailed lung function measurements which can prove helpful in identifying the response site within the lower airway segment while also providing direct upper airway resistance measurements. (scireq.com)
  • The majority of these pathologic features of human airway inflammation have also been observed in experimental lung injury models. (jimmunol.org)
  • Systemic LPS administration induces neutrophil sequestration into the pulmonary microvasculature without passage into the lung tissues and bronchoalveolar space ( 12 ), whereas neutrophil recruitment upon aerogenic LPS exposure occurs in all airway compartments ( 8 ). (jimmunol.org)
  • However, pulmonary resistance (R(L)) is the sum of airway resistance (R(aw)), which changes with airway caliber, and of tissue resistance (R(ti)), which depends on the pressure-volume hysteresis of the lung. (elsevier.com)
  • The authors conclude that changes in R(L) during halothane administration are caused not only by changes in airway caliber, as previously assumed, but also reflect a significant effect of halothane on lung tissue pressure-volume hysteresis. (elsevier.com)
  • To learn about your lung health, your doctor may want you to have several pulmonary function tests done including spirometry , lung volumes , diffusing capacity , and airway resistance. (getasthmahelp.org)
  • Forced expiratory volume in 1 s and forced vital capacity from spirometry have been studied most frequently, but measurements of airway resistance may provide additional information. (eur.nl)
  • Using human airway epithelial cells as a proper in vitro model, we show that prior exposure to physiological nanomolar serum concentrations of simvastatin (ranging from 10-1,000 nM) confers significant cellular resistance to the cytotoxicity of pneumolysin, a pore-forming toxin and the main virulence factor of Streptococcus pneumoniae. (ewha.ac.kr)
  • Inspiratory loss in bifurcations is greatly increased by the onset of flow separation: irreversibility is minimal in central airways, where separation either is absent or else is much less pronounced. (asme.org)
  • Following dermal exposure 7 days a week for 35 days, animals exposed to up to 25% AMT demonstrated a dose-dependent elevation in total serum IgE and an increase in airway hyperreactivity upon methacholine challenge. (cdc.gov)
  • The airway dimensions of the CF and COPD patients were introduced into a computational model to study their effect on airway resistance. (ersjournals.com)
  • While sR aw captures information on airflow resistance, it is important to realize that it is not a true measurement of airway resistance. (scireq.com)
  • The inner wall and smooth muscle areas of peripheral CF airways were increased 3.3- and 4.3-fold respectively compared to those of COPD airways. (ersjournals.com)
  • The sensitivity and maximal plateau resistance of the computed dose/response curves were substantially increased in the CF patients compared to COPD patients. (ersjournals.com)
  • The aim of the present study was to evaluate the associations between airway resistance with TGF-β1 G/A and TNF-α 308 G/A gene polymorphisms in COPD patients. (cdc.gov)
  • These results can suggest the lack of association between TNF-α 308 G/A and TGF-β1 800 G/A gene polymorphisms with COPD development and airway resistance in Turkish population. (cdc.gov)
  • Nasal resistance measurements, assessed in four modes (natural state, anterior nares dilation with Tygon tubing, following administration of decongestant, and nares dilation with tubing and decongestant), were taken on a group of 38 patients receiving rapid maxillary expansion and compared with a control group not receiving expansion. (nih.gov)
  • Moreover, since air flow limitations are partly caused by increased airway resistance, direct measurements of airway resistance may provide additional information [ 10 ]. (biomedcentral.com)
  • [ 15 ] Active dilation of the dilator naris occurs during exercise, reducing airway resistance. (medscape.com)
  • A major area of resistance occurs at the anterior tip of the inferior turbinate at the entrance to the piriform aperture. (medscape.com)
  • A neomycin resistance cassette replaced the entire coding sequence and part of the 5' noncoding region. (jax.org)
  • The four coding exons were replaced by a neomycin resistance cassette using the (129X1/SvJ x 129S1/Sv)F1- Kitl + -derived R1 embryonic stem (ES) cell line. (jax.org)
  • Rebreathing has been shown to increase arterial carbon dioxide levels, causing nasal vasoconstriction and a reduction in nasal resistance. (medscape.com)
  • There was a significant median reduction in nasal resistance following rapid maxillary expansion, measured in the natural state only, and this appeared to be stable up to 1 year after maximum expansion was obtained. (nih.gov)