BACKGROUND: Mechanical ventilation is mandatory in patients undergoing general anaesthesia for major surgery. Tidal volumes higher than 10 mL/kg of predicted body weight have been advocated for intraoperative ventilation, but recent evidence suggests that low tidal volumes may benefit surgical patients. To date, the impact of low tidal volume compared with conventional tidal volume during surgery has only been assessed in clinical trials that also combine different levels of positive end-expiratory pressure (PEEP) in each arm. We aimed to assess the impact of low tidal volume compared with conventional tidal volume during general anaesthesia for surgery on the incidence of postoperative respiratory complications in adult patients receiving moderate levels of PEEP.. STUDY DESIGN AND METHODS: Single-centre, two-arm, randomised clinical trial. In total, 1240 adult patients older than 40 years scheduled for at least 2 hours of surgery under general anaesthesia and routinely monitored with an ...
This study by the Acute Respiratory Distress Syndrome Network supports the use of low tidal volumes in acute lung injury and ARDS, and is consistent with a previous trial.1 It differs from 3 previous negative trials2-4 by having a larger difference in tidal volumes between groups, and by having a more aggressive approach to correcting acidosis. This study provides important information about tidal volume size; however, further research is still needed to determine the importance of concurrent strategies such as positive end expiratory pressure (PEEP).. In this study, an equation based on sex and height was used to calculate a predicted body weight, which was then used to set tidal volumes. Obesity is a common problem; the use of measured body weight can inadvertently lead to the use of high tidal volume ventilation. Tidal volumes should be based on ideal versus measured body weight.. This information is relevant to nurses who care for mechanically ventilated patients. Through continuous ...
The Waters lab focuses on mechanobiology and acute lung injury. Patients with acute respiratory distress syndrome (ARDS) are placed on mechanical ventilators to improve oxygenation, but the ventilator may cause additional injury to the lungs due to either overdistention or airway collapse and reopening. Clinical trials have demonstrated a substantial reduction in mortality in ARDS patients when ventilation strategies are used that reduce overdistention (lower tidal volumes) and minimize airway collapse and reopening (positive end expiratory pressure). The lung is a mechanically dynamic organ, and cells in the lung are subjected to shear stress due to fluid flow, tensile and compressive forces due to respiratory motion, and normal forces due to vascular or airway pressure. High tidal volume mechanical ventilation in injured lungs induces mechanical stresses that increase injury to the lung epithelium, stimulate inflammatory responses, and decrease repair mechanisms. We are focusing on the ...
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
Mechanical ventilation with a lower tidal volume resulted in decreased mortality in patients with acute lung injury and the acute respiratory distress syndrome ...
Objective: To determine whether Tidal Volume (Vt) between 6 and 10 ml/kg affects outcome for children with ALI.; Methods: Review of PICU admissions from 2000-2007. Inclusion criteria were intubation and ventilation with at least one PaO2/FiO2 ratio < 300.; Results: 398 patients were included. Overall mortality was 20% with a median Vt of 7.4 ml/kg. Median Vt on the first day of mechanical ventilation was lower in the group that died, although not statistically significant (p=0.06). After controlling for year, Delta P (PIP-PEEP), PEEP, and severity of lung disease, Vt was not associated with mortality (p>0.1), but higher Vt on day one of ventilation was associated with more ventilator free days ( ...
Objective: To determine whether Tidal Volume (Vt) between 6 and 10 ml/kg affects outcome for children with ALI.; Methods: Review of PICU admissions from 2000-2007. Inclusion criteria were intubation and ventilation with at least one PaO2/FiO2 ratio < 300.; Results: 398 patients were included. Overall mortality was 20% with a median Vt of 7.4 ml/kg. Median Vt on the first day of mechanical ventilation was lower in the group that died, although not statistically significant (p=0.06). After controlling for year, Delta P (PIP-PEEP), PEEP, and severity of lung disease, Vt was not associated with mortality (p>0.1), but higher Vt on day one of ventilation was associated with more ventilator free days ( ...
High tidal volumes in mechanically ventilated patients increase organ dysfunction after cardiac surgery.: Tidal volumes of more than 10 ml/kg are risk factors f
... This analysis emphasizes the need to obtain data on the size and shape of riprap pieces as a function of movement, data which are surprisingly difficult to obtain from published studies. This analysis also indicates why riprap design for sites subject to reversible tidal flow must be somewhat more conservative for uniform flows of the same velocity.
Protective lung ventilation is the current standard of care for mechanical ventilation. It is synonymous with low tidal volume ventilation (4-8 mL/kg) and often includes permissive hypercapnia
Evaluation of peak inspiratory pressure, tidal volume and respiratory rate during ventilation of premature lambs using a self-inflating bag . Carlos A. M. Zaconeta ; Antonio C. P. Ferreira ; César A. M. Silva ; Marcelo P. Rodrigues ; Celso M. Rebello ; Paulo T. Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
Importance: Despite its efficacy, low tidal volume ventilation (LTVV) remains severely underutilized for patients with acute respiratory distress syndrome (ARDS). Physician under-recognition of ARDS is a significant barrier to LTVV use. We propose a computational method that addresses some of the limitations of the current approaches to automated measurement of ...
BACKGROUND: The effects of individualised perioperative lung-protective ventilation (based on the open-lung approach [OLA]) on postoperative complications is unknown. We aimed to investigate the effects of intraoperative and postoperative ventilatory management in patients scheduled for abdominal surgery, compared with standard protective ventilation. METHODS: We did this prospective, multicentre, randomised controlled trial in 21 teaching hospitals in Spain. We enrolled patients who were aged 18 years or older, were scheduled to have abdominal surgery with an expected time of longer than 2 h, had intermediate-to-high-risk of developing postoperative pulmonary complications, and who had a body-mass index less than 35 kg/m2. Patients were randomly assigned (1:1:1:1) online to receive one of four lung-protective ventilation strategies using low tidal volume plus positive end-expiratory pressure (PEEP): open-lung approach (OLA)-iCPAP (individualised intraoperative ventilation [individualised PEEP ...
End-tidal CO2 (ETCO2) is important for monitoring CPR quality as a surrogate for coronary perfusion pressure (CPP) and flow. We hypothesized that sufficient minute volume ventilation is not only needed to control CO2 buildup, but also for the exhaled CO2 to CPP relationship to remain valid.. To test our hypothesis, we measured minute volume ventilation together with CPP, arterial PCO2 (PaCO2), and ETCO2 in a pig model. Ventricular fibrillation was induced in 24 pigs, after which automated CPR (5 cm, 100 cpm) followed for 20 minutes. Animals were ventilated manually using a bag-mask-valve, either continuously at 10 min-1 (group 1, n=8) or 30:2 mode (group 2, n=16). Correlation coefficients between CPP and ETCO2 were calculated for each pig during the CPR interval.. Minute volume ventilation during CPR was 3.4 ± 1.0 L/min for group 1 and 2.2 ± 0.3 L/min for group 2 pigs. In group 1, PaCO2 changed little during CPR (41.1 ± 7.6 mmHg initially vs. 38.6 ± 16.5 mmHg at 20 minutes), indicating ...
We conduct laboratory experiments and direct numerical simulations on internal gravity waves generated by tidal flow over a model three-dimensional Gaussian mountain on the sea floor. When 2? < N (where ? is the tidal frequency and N is the buoyancy frequency), the flow generates second harmonic internal waves that propagate perpendicular to the tidal forcing direction. These unexpected harmonics are observed only when the maximum slope of the bottom topography is greater than the slope of internal wave propagation. The out-of-plane harmonics saturate at a higher tidal forcing amplitude than the normal in-tidal-forcing-plane harmonics, and could lead to increased wave breaking and mixing near rough topography in the ocean. ...
... Pressure Support with Volume Target Stabilizing Tidal Volume with ease SleepOne ProVT constantly monitors changes in the Tidal Volume of the patients. With Tidal Volume Targeting, It changes patients Pressure Support according to the Volume Target set. Pressure support ventilation for moving patient needs, easy as Bilevel therapy. SleepOne ProVT monitors the patients Tidal Volume changes, and reacts according to the set Tidal Volume. Result is a much more stable Ti
This disclosure describes systems and methods for ventilating a patient with a tidal volume that adjusts based on patient compliance. The disclosure describes a novel breath type or setting for existing breath types, that automatically and continuously varies the delivered tidal volume based on patient compliance and/or other monitored parameters.
Inflammation in the lung occurs during ARDS as a consequence of cell injury. Depending on the ventilator strategy, the initial injury may be amplified, mediating pulmonary edema, alveolar disruption and release of cytokines [17]. Thus, a potential means of quantifying the protectiveness of a ventilation mode is the measurement of inflammatory cytokine and mRNA concentrations in BAL fluid and lung tissue, respectively.. In tracheal aspirates from oleic acid‐injured pigs, IL‐8 concentrations decreased after 5 h of variable controlled mechanical ventilation compared to conventional controlled mechanical ventilation but the investigated pro‐inflammatory cytokines, tumor necrosis factor‐α (TNF‐α) and IL‐6, were not measurable in serum or in tracheal aspirates. The concentration of the anti‐inflammatory cytokine, IL‐10, did not differ between groups in serum or tracheal aspirate samples. In HCl‐injured mice, IL‐1β levels, as measured by Western Blot Analysis, were significantly ...
The correlation between heart rate (HR) and three respiratory parameters, minute ventilation (VE), tidal volume (Vt), and respiratory rate (RR), were studied. Four healthy subjects performed four exercise tests (duration 30 seconds at 50, 100, 150, o
The study by van der Gugten et al. [1] employed the minimally invasive single-breath occlusion technique to measure lung function; follow-up data included spirometry and information collected from general practitioners electronic patient files. Strengths of this approach are large sample size (549 infants) and availability of data describing symptom frequency. Our study included additional measurements of forced expiratory flows but respiratory resistance and wheeze frequency data were not available. Our asthma outcome was not directly comparable to that of van der Gugten et al. [1], as it was based upon a doctors diagnosis irrespective of primary care contacts, current symptoms or medications.. Impaired neonatal lung function, characterised by reduced values for the fraction of expiratory time to peak tidal expiratory flow to total expiratory time, has previously been found to be associated with childhood asthma [4]. Our approach is unique, however, in employing the raised volume ...
Purpose: To develop a quantitative decision making metric for automatically detecting irregular breathing using a large patient population that received phase-sorted 4DCT. Methods: This study employed two patient cohorts. Cohort#1 contained 256 patients who received a phasesorted 4DCT. Cohort#2 contained 86 patients who received three weekly phase-sorted 4DCT scans. A previously published technique used a single abdominal surrogate to calculate the ratio of extreme inhalation tidal volume to normal inhalation tidal volume, referred to as the κ metric. Since a single surrogate is standard for phase-sorted 4DCT in radiation oncology clinical practice, tidal volume was not quantified. Without tidal volume, the absolute κ metric could not be determined, so a relative κ (κrel) metric was defined based on the measured surrogate amplitude instead of tidal volume. Receiver operator characteristic (ROC) curves were used to quantitatively determine the optimal cutoff value (jk) and efficiency cutoff ...
NRCLSE, Seattle, WA 98115 and Rush Medical College, Chicago, IL 60612.. Over half of undergraduate students entering physiology hold the misconception that when ventilation increases during exercise, tidal volume either decreases or remains unchanged (Michael, Adv. Physiol. Educ., 19: S90-S98, 1998). We examined how three different protocols directing students in a laboratory exercise impacted conceptual change. Students (404 undergraduates at 4 institutions) were tested to see if they held the misconception before and after performing an experiment in which they measured the effect of exercise on tidal volume and frequency. The first group followed a traditional written "observe and record" protocol. Students in the second group were given a written protocol asking them to complete a prediction table before running the experiment. Students in the third group were given the written "prediction" protocol, but were also required to tell the instructor their predictions before running the ...
Guesstimates and assumptions have no place in an emergency situation. An accurate low tidal volume calculation can help medical professionals improve their treatment of acute respiratory issues, whilst an incorrect measure can have the opposite effect - for example, lung damage, or possibly even threatening the patients life.. Dr Pickworth contacted Spentex and asked for our help. The original method he and his medical colleagues employed to calculate low tidal volume involved cumbersome charts crammed full with numeric tables, that needed to be consulted once the patients gender and height had been determined (imagine capturing the latter if the patient in question is writhing in pain!). Dr Pickworth, and his colleague Dr Rivers, were in desperate need of a better process.. An accurate measure was required - a product that was easier to use by design, that provided the right calculation in double-quick time, and which wouldnt prove a financial drain on already-shrinking public funds. Which ...
Mechanically, breath design is usually either flow/volume-targeted or pressure-targeted. Both approaches can effectively provide lung-protective ventilation, but they prioritize different ventilation parameters, so their responses to changing respiratory-system mechanics and patient effort are different. These different response behaviors have advantages and disadvantages that can be important in specific circumstances. Flow/volume targeting guarantees a set minute ventilation but sometimes may be difficult to synchronize with patient effort, and it will not limit inspiratory pressure. In contrast, pressure targeting, with its variable flow, may be easier to synchronize and will limit inspiratory pressure, but it provides no control over delivered volume. Skilled clinicians can maximize benefits and minimize problems with either flow/volume targeting or pressure targeting. Indeed, as is often the case in managing complex life-support devices, it is operator expertise rather than the device ...
To the Editor:. Following publication of our article "Variability in mechanical ventilation: whats all the noise about?"1 an oversight has been brought to our attention. We erroneously stated that "There are no commercially available ventilators capable of performing variable ventilation." However, the Evita Infinity V500 (Dräger, Lubeck, Germany) has a variable pressure support option. The percentage of desired variation (0-100%) is chosen with the pressure support range varying between pressure support + 100% and the set CPAP for the upper and lower limits, respectively. ...
Forrests indomitable spirit is peeking through the post surgical fog and already he is winning the hearts of his Critical Care nurses. During his first breathing trial this morning when they turned the ventilator support off he quickly started breathing on his own amazing the respiratory therapist with his large tidal volume. The breathing tube was removed and he continues to breathe well on his own. When asked he will open his eyes and do his best to move his arms & wiggle his toes. We are settling back into the ICU routines that are all too familiar to us. Morning rounds with doctors residents & nurses, tracking every medication & treatment, repositioning every two hours, moving & massaging his arms & legs, watching the monitors & reading your wonderful messages aloud. Austin spent the night bedside & went with Forrest for a Cat Scan at 5:00 AM, reassuring him along the way. The results are encouraging, but of course only time will tell ...
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(12-09-2016, 09:45 AM)Sleeprider Wrote: Normal tidal volume in a young healthy person is 7 mL/kg, or for your 77 kg weight 539 mL, which is considerably higher than your 340. Lower night tidal volume
The De-part-ment of Trans-porta-tion and Works up-dated the pub-lic last week about how work to re-move the old lift bridge in Pla-cen-tia will af-fect mariners.. Ac-cord-ing to the news re-lease, the chan-nel will be closed to all boat traf-fic re-quir-ing the bridge to lift for ap-prox-i-mately one month start-ing Dec. 10. Boats look-ing to get through the chan-nel will need to com-mu-ni-cate those plans with the bridge op-er-a-tors and pro-ceed with cau-tion.. Con-trac-tors will use in-fill to help re-move the bridge, and government ex-pects this will in-crease tidal flow through the chan-nel. The in-fill ma-te-rial will be re-moved once de-mo-li-tion work is com-pleted.. Fur-ther ad-vi-sories will be is-sued as work pro-gresses, ac-cord-ing to government. Re-moval of the old lift bridge will not af-fect mo-torists.. The new lift bridge in Pla-cen-tia of-fi-cially opened in Septem-ber and was built at a cost of al-most $48 mil-lion. The orig-i-nal ten-der in-cluded the de-mo-li-tion ...
Hi, just wondering what normal/average stats should be for data such as Tidal Volume, Inspiratory/Expiratory Times, Respiratory Rate, and Minute Ventilation. I see all those numbers in SleepyHead, but
Quantity Available: 1. ________________________________. Draeger Babylog VN500 Ventilator. The Babylog VN500 is an integrated ventilation solution for the tiniest of patients. The Babylog lets your choose from a range of options, such as Smart Pulmonary View, APRV, NIV, and Volume Ventilation option, making it highly customizable, adapting to your individual needs.. Features and Benefits:. ...
A machine that can give readings of tidal volume and breathing rate.. 1) has oxygen filled chamber with moveable lid. 2) A person breathes through a tube connected to the oxygen chamber. 3) As the person breathes in, the lid of the chamber moves down. When they breathe out, moves up.. 4) These movements are recorded by a pen attached to the lid of the chamber - this writes on a rotating drum, creating a spirometer trace. 5) the soda lime in the tube the person breathes into absorbs carbon dioxide. Can be used to investigate the effects of exercise. ...
Aligned with the same platform as our System One sleep therapy technology, the Philips Respironics BiPAP AVAPS Non-Invasive ventilator provides the comfort of pressure ventilation and the consistent efficacy of assured tidal volume ...
Bob Felstead2018-02-02T08:03:58+00:00. From a business point of view, theres more than one way to measure success. For Spentex, being approached by renowned medical practitioners for our expertise was flattering, but knowing that the result of this meeting of minds was a product that improves mortality rates, well…how can you possibly put a measure on that? The act of measuring is at the core of this story, as its why the Spentex Pickworth Rivers Tidal Volume Calculator was created. Guesstimates and assumptions. Guesstimates and assumptions [...]. ...
Plasmid pBW211J109-Amp32C from Dr. Baojun Wangs lab contains the insert J109-30hrpR-32hrpS-t-hrpL-30gfp-t and is published in Nucleic Acids Res. 2014 Aug;42(14):9484-92. doi: 10.1093/nar/gku593. Epub 2014 Jul 16. This plasmid is available through Addgene.
Variable ventilation has been shown to improve lung function and reduce lung damage as well as inflammation in different models of the acute respiratory distress syndrome. Also, variable ventilation is able to recruit lungs. The present study will investigate whether variable as compared to non-variable ventilation improves post-operative lung function and reduces systemic inflammation in patients submitted to open abdominal surgery ...
In patients presenting with the acute respiratory distress syndrome (ARDS), mechanical ventilation with low tidal volume (6 ml/kg predicted body weight) is the current gold standard for supportive care. However, despite a relative low tidal volume, approximatively one third of patients will experienced tidal hyperinflation, a phenomenon known to induce pulmonary and systemic inflammatory response. A further reduction of the tidal volume to 4 ml/kg (PBW) will prevent pulmonary area from tidal hyperinflation. As a result, hypercarbia and respiratory acidosis are commonly observed with such very low tidal ventilation. Extra corporeal CO2 removal is one of a mean to normalize arterial CO2 tension.. Patients with ARDS also frequently develop acute renal failure which may required Renal Replacement Therapy. Some data suggests that starting early the RRT may favor outcome.. The investigators hypothesized that a strategy combining ECCOR and RRT early in the course of patients presenting ARDS and acute ...
The pattern of breathing was modified markedly by increasing the level of pressure support, with increased tidal volume and reductions in respiratory rate, WOB and P0.1. Furthermore, our data indicate that arterial carbon dioxide tension, minute ventilation and inspiratory flow were maintained nearly constant, independent of pressure support level. This suggests that there are different mechanisms of adaptation resulting in different breathing patterns at different levels of pressure support, from a pattern similar to rapid shallow breathing (pressure support at 5 cmH2O) to one similar to completely passive pressure control ventilation (pressure support at 25 cmH2O). The relationship we found between respiratory rate and tidal volume, for different f/Vt isopleths, was similar to that reported by Yang and Tobin [20] in spontaneously breathing individuals. Few previous studies have systematically investigated the effects of pressure support level on breathing pattern in non-COPD patients with ...
Objectives To establish whether aminophylline, administered at usual doses for rodents in pharmacological studies, induces brain injury in systemic hypoxaemia in guinea-pigs.. Methods A hypoxaemia (partial oxygen tension of arterial blood (PaO2) = 40-60 mmHg) model was developed by low tidal volume mechanical ventilation in guinea-pigs.. Key findings Under hypoxic conditions, aminophylline significantly increased the concentration of brain-specific creatine kinase in the serum in a dose- and time-dependent manner. A reduced number of hippocampal neuronal cells in the CA1 region, an increase in the concentration of neuron-specific enolase (NSE) in cerebrospinal fluid (CSF), an increase in lipid hydroperoxides and a decrease in the ratio of glutathione to glutathione disulfide in the brain tissues were also observed. These effects were not observed when aminophylline at the same doses was administered under normoxic conditions (PaO2 = 80-100 mmHg). There was no difference in either serum or CSF ...
TY - JOUR. T1 - Hemodynamic benefit of positive end-expiratory pressure during acute descending aortic occlusion. AU - Johnston, William E.. AU - Conroy, Brendan P.. AU - Miller, Gregory S.. AU - Lin, Cheng Y.. AU - Deyo, Donald J.. PY - 2002/10/1. Y1 - 2002/10/1. N2 - Background: Acute aortic occlusion in vascular surgery patients abruptly increases arterial resistance and blood pressure, which, in turn, makes subsequent volume expansion during cross-clamp application difficult. The use of vasodilatory drugs or volatile anesthetic agents to attenuate this response may have persistent detrimental effects after clamp removal. Another potential therapy that produces rapid effects on myocardial loading conditions is positive end-expiratory pressure (PEEP). In a porcine model of acute aortic clamping, the hemodynamic consequences of 15 cm H2O PEEP with and without plasma volume expansion were studied. Methods: Forty anesthetized pigs underwent 30-min occlusion of the abdominal aorta 1 cm above the ...
JAMA. 2008 Feb 13;299(6):637-45. doi: 10.1001/jama.299.6.637. Comparative Study; Multicenter Study; Randomized Controlled Trial; Research Support, Non-U.S. Govt
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Results 1456 (74%) were only ventilated with T-piece resuscitator and 506 (26%) with the self-inflating bag. The characteristics of those ventilated with T-Piece resuscitator versus self-inflating bag were birth weight 969 ± 277 vs 941 ± 279 g, gestational age 28.2±2.5 vs 27.8±2.7 weeks and survival to hospital discharge without major morbidities 47% vs 35%. Logistic regression adjusted for maternal characteristics, obstetric and neonatal morbidities showed that the T-piece resuscitator increased the chance of survival to hospital discharge without major morbidities (OR=1.38; 95% CI 1.06 to 1.80; Hosmer-Lemeshow goodness of fit: 0.695). ...
In a volume-targeted mode (e.g., volume control; Figure 29B-1), the ventilator provides an inspiratory flow over time to target a set volume. To avoid ventilator-induced injury, multiple trials have shown that limiting the tidal volume improves patient outcomes compared to using the larger volumes more common in the past (often ≥10 mL/kg to start).3-6 One approach is to start volume-targeted ventilation at 6 mL/kg ideal body weight for patients with or at risk for acute respiratory distress syndrome and 6 to 8 mL/kg ideal body weight for other patients. The definition of acute respiratory distress syndrome is provided in Table 29B-1. Those at risk for acute respiratory distress syndrome have pneumonia, sepsis, trauma, pancreatitis, or any shock state.7 To choose ventilation settings, calculate ideal body weight using the patients height, an important caveat in obese patients in whom harm is risked if tidal volumes choice is based on actual body weight. ...
Editors Synopsis: Motion in the Ocean. The Earths climate is strongly affected by the ways in which energy moves into, out of, and around the oceans. One important component of energy flow is the conversion of tidal motionchanges in sea levels caused by gravitational effects of the Mooninto internal ocean waves. Such waves directly influence mixing of water from regions with different temperature and salinity, as well as overall circulation. In a paper in Physical Review Letters, Likun Zhang and Harry Swinney at the University of Texas at Austin, present numerical simulations of how tidal flow over seafloor ridges is transformed into wave energy. They find that only the topmost parts of seafloor topography contribute to wave generation, in effect creating a virtual seafloor.? It is only above it that tidal energy can be converted to wave energy.. The efficiency of tidal-to-wave energy conversion is difficult to calculate owing to the complex structure of the seafloor: When sea levels rise ...
The pattern of breathing refers to the respiratory rate and rhythm, the depth of breathing or tidal volume, and the relative amount of time spent in inspiration and expiration. Normal values are a rate of 12-14 breaths per minute, tidal volumes of 5 mL/kg, and a ratio of inspiratory to expiratory time of approximately 2:3. Tachypnea is an increased rate of breathing and is commonly associated with a decrease in tidal volume. Respiratory rhythm is normally regular, with a sigh (1.5-2 times normal tidal volume) every 90 breaths or so to prevent collapse of alveoli and atelectasis. Alterations in the rhythm of breathing include rapid, shallow breathing, seen in restrictive lung disease and as a precursor to respiratory failure; Kussmaul breathing, rapid large-volume breathing indicating intense stimulation of the respiratory center, seen in metabolic acidosis; and Cheyne-Stokes respiration, a rhythmic waxing and waning of both rate and tidal volumes that includes regular periods of apnea. This last ...
Positive end-expiratory pressure (PEEP) has been demonstrated to improve systemic arterial oxygenation in respiratory distress secondary to interstitially edematous lung. Clinical improvements, however, may be limited by the adverse circulatory effects of PEEP impairing venous return and reducing cardiac output. In an effort to eliminate this variable experimentally, the effects of graded levels of PEEP in the isolated canine lung made edematous by venous constriction were studied. These observations suggested that the increased mean inflation pressures of PEEP do not facilitate mobilization of interstitial fluid nor improve lung mechanics and that the observed improvement in gas exchange probably relateds to inflation of previously collapsed alveoli. In clinical use, however, PEEP is applied at one level for a prolonged period of time. Therefore, to delineate the prolonged effects of static PEEP, isolated canine lungs made edematous by venous constriction were treated with various levels of PEEP
The purpose of the present investigation was to assess the effect of large tidal volumes and mean lung volumes on the viscoelastic properties of the respiratory system in normal humans; and to verify if in this case the results could be satisfactorily described by a simple linear viscoelastic model of the respiratory system. Twenty-eight subjects (7 females), aged 14-28 yrs, were studied before orthopaedic surgery on the lower limbs. None were obese, or had clinical evidence of cardiopulmonary disease. The interrupter conductance and the viscoelastic constants of the respiratory system were assessed using the rapid end-inspiratory airway occlusion method during mechanical ventilation with tidal volumes up to 3 L and applied end-expiratory pressures up to 23 cmH2O. It was found that the interrupter conductance increased linearly with lung volume over a larger range than used previously; and the viscoelastic resistance and time constant did not change over the entire range of tidal volumes and ...
One of the most challenging problems in intensive care is still the process of discontinuing mechanical ventilation, called weaning process. Both an unnecessary delay in the discontinuation process and a weaning trial that is undertaken too early are undesirable. In this study, we analyzed respiratory pattern variability using the respiratory volume signal of patients submitted to two different levels of pressure support ventilation (PSV), prior to withdrawal of the mechanical ventilation. In order to characterize the respiratory pattern, we analyzed the following time series: inspiratory time, expiratory time, breath duration, tidal volume, fractional inspiratory time, mean inspiratory flow and rapid shallow breathing. Several autoregressive modeling techniques were considered: autoregressive models (AR), autoregressive moving average models (ARMA), and autoregressive models with exogenous input (ARX). The following classification methods were used: logistic regression (LR), linear discriminant ...
One of the most challenging problems in intensive care is still the process of discontinuing mechanical ventilation, called weaning process. Both an unnecessary delay in the discontinuation process and a weaning trial that is undertaken too early are undesirable. In this study, we analyzed respiratory pattern variability using the respiratory volume signal of patients submitted to two different levels of pressure support ventilation (PSV), prior to withdrawal of the mechanical ventilation. In order to characterize the respiratory pattern, we analyzed the following time series: inspiratory time, expiratory time, breath duration, tidal volume, fractional inspiratory time, mean inspiratory flow and rapid shallow breathing. Several autoregressive modeling techniques were considered: autoregressive models (AR), autoregressive moving average models (ARMA), and autoregressive models with exogenous input (ARX). The following classification methods were used: logistic regression (LR), linear discriminant ...