Lung scintigraphy is the primary tool for diagnostics of pulmonary embolism. A perfusion study is often complemented by a ventilation study. Intermediate probability scans are frequent. Our goal was to develop a fast method for tomographic ventilation and perfusion scintigraphy to improve the diagnostic value of lung scintigraphy. METHODS: SPECT was performed with a dual-head gamma camera. Acquisition parameters were determined using a thorax phantom. Ventilation tomography after inhalation of 30 MBq (99m)Tc-diethylenetriaminepentaacetate (DTPA) aerosol was, without patient movement, followed by perfusion tomography after an intravenous injection of 100 MBq (99m)Tc-labeled macroaggregated albumin (MAA). Total SPECT acquisition time was 20 min. (99m)Tc-DTPA clearance, calculated from initial and final SPECT projections, was used for correction of the ventilation projection set before iterative reconstruction of ventilation and perfusion. The ventilation background was subtracted from the perfusion tomograms. A normalized ventilation/perfusion quotient (V/P quotient) image set was calculated. The method was evaluated on a trial group of 15 patients. RESULTS: Ventilation and perfusion images had adequate quality and showed ventilation/perfusion (V/Q quotient) relationships more clearly than did planar images. Frontal and sagittal slices were superior to planar scintigraphy for characterization of embolized areas. The V/Q quotient was supportive, particularly in the patients with chronic obstructive pulmonary disease. CONCLUSION: Fast, high-quality, ventilation/perfusion SPECT with standard isotopes doses is feasible and may contribute to higher objectivity in evaluating lung embolism as well as other lung diseases. The costs for the procedure and patient care until diagnosis are low because of the comprehensive system for the study and, particularly, the short time for its completion. (+info)
PURPOSE: The treatment of patients with abdominal aortic aneurysms (AAAs) is typically based on the potential for rupture. Current rupture assessments are in turn based on statistics from aggregate populations and are incapable of providing precise risk estimates for individual AAAs. Significant benefit could be realized if rupture potential for individual AAAs could be reliably determined on the basis of simple geometric characteristics or the results of symmetric thin-shell analysis. This study seeks to determine whether it is possible to estimate wall stresses by use of these simple measures. METHODS: Linear finite element analysis was used to estimate the distribution of von Mises stresses in a series of homogeneous, isotropic, three-dimensional AAA models subject to static loading and assumed to have zero residual stresses. The magnitude of the peak stress was tabulated for each model along with the following characteristics: aneurysm volume; maximum diameter; maximum radius; maximal wall distention; aspect ratio (ratio of greatest anteroposterior diameter to transverse diameter); local radii of curvature (in both longitudinal and circumferential directions); and maximum symmetric thin-shell stress estimates (on the basis of the meridional contour). The relationship between peak stress and each of the characteristics was assessed by use of Spearman rank correlation coefficients, with values less than 0.95 interpreted as signifying unreliable associations. RESULTS: Peak stresses in the individual models ranged from 1.79 x 10(6) dyne/cm2 to 15.1 x 10(6) dyne/cm2. The circumferential and longitudinal radii of curvature were frequently able to predict the locations of high stress, but were unreliable in predicting the magnitude of peak stress. The aspect ratio showed the strongest correlation with peak wall stress (r = 0.88, 95% CI, 0.68-0.96), whereas the other characteristics showed even less correlation. Symmetric thin shell analysis accurately predicted stresses in axially symmetric models, but it was incapable of predicting either the location or magnitude of peak stress in asymmetric models. CONCLUSIONS: Simple geometric criteria and symmetric thin shell analyses are unreliable in predicting AAA stresses. Future attempts to estimate wall stress and assess risk of rupture for individual AAAs may require detailed three-dimensional modeling. (+info)
Fiberoptic orotracheal intubation on anesthetized patients: do manipulation skills learned on a simple model transfer into the operating room?
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BACKGROUND: With increasing pressure to use operating room time efficiently, opportunities for residents to learn fiberoptic orotracheal intubation in the operating room have declined. The purpose of this study was to determine whether fiberoptic orotracheal intubation skills learned outside the operating room on a simple model could be transferred into the clinical setting. METHODS: First-year anesthesiology residents and first- and second-year internal medicine residents were recruited. Subjects were randomized to a didactic-teaching-only group (n = 12) or a model-training group (n = 12). The didactic-teaching group received a detailed lecture from an expert bronchoscopist. The model-training group was guided, by experts, through tasks performed on a simple model designed to refine fiberoptic manipulation skills. After the training session, subjects performed a fiberoptic orotracheal intubation on healthy, consenting, anesthetized, paralyzed female patients undergoing elective surgery with predicted "easy" laryngoscopic intubations. Two blinded anesthesiologists evaluated each subject. RESULTS: After the training session, the model group significantly outperformed the didactic group in the operating room when evaluated with a global rating scale (P < 0.01)and checklist (P0.05). Model-trained subjects completed the fiberoptic orotracheal intubation significantly faster than didactic-trained subjects (P < 0.01). Model-trained subjects were also more successful at achieving tracheal intubation than the didactic group (P < 0.005). CONCLUSION: Fiberoptic orotracheal intubation skills training on a simple model is more effective than conventional didactic instruction for transfer to the clinical setting. Incorporating an extraoperative model into the training of fiberoptic orotracheal intubation may greatly reduce the time and pressures that accompany teaching this skill in the operating room. (+info)
Gel lubrication of the tracheal tube cuff reduces pulmonary aspiration.
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BACKGROUND: Leakage of fluid occurs along the longitudinal folds within the wall of an inflated high-volume, low-pressure cuff. Theoretically, lubrication of the cuff with a water-soluble gel might prevent aspiration by plugging the channels in the cuff wall. Pulmonary aspiration during anesthesia has been linked with postoperative pneumonia and during critical illness causes ventilator-associated pneumonia. METHODS: Lubricated cuffs were compared with nonlubricated cuffs for leakage of dye placed in the subglottic space to the tracheobronchial tree in a benchtop model (n = 5) and in a prospective double-blinded randomized controlled trial of anesthetized patients (n = 36). The duration of the efficacy of the lubricant was determined in a prospective open observational study of critically ill patients with tracheostomies (n = 9). Dye was detected clinically by dye coloration of secretions during tracheal suctioning. RESULTS: In the benchtop model the incidence of leakage was 0% in the lubrication group and 100% in the nonlubrication group (P < 0.01). Dye leakage in anesthetized patients was 11% in the lubrication group and 83% in the nonlubrication group (P < 0.0001). In the critically ill patients with lubricated cuffed tracheostomy tubes, leakage first occurred after a median period of 48 h (range, 24-120 h). CONCLUSIONS: Cuff lubrication with a water-soluble gel reduces pulmonary aspiration in anesthetized patients. In the critically ill patient with a tracheostomy the protective effect is lost after 24-120 h. (+info)
A qualitative and quantitative study of the lung of an ostrich, Struthio camelus.
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The ostrich lung, with its lack of interparabronchial septa, the presence of very shallow atria and exceptional morphometric refinement, structurally resembles those of small, energetic flying birds, whereas it also displays features characteristic of the flightless ratites in which the neopulmo is relatively poorly developed and a segmentum accelerans may be generally lacking. The large size of the bronchial system of the ostrich may help explain the unique shifts in the airflow pathways that must occur from resting to panting breathing, explaining its insensitivity to acid-base imbalance of the blood during sustained panting under thermal stress. The mass-specific volume of the lung is 39.1 cm(3)kg(-1) and the volume density of the exchange tissue is remarkably high (78.31%). The blood-gas (tissue) barrier is relatively thick (0.56 microm) but the plasma layer is very thin (0.14 microm). In this flightless ratite bird, the mass-specific surface area of the tissue barrier (30.1 cm(2)g(-1)), the mass-specific anatomical diffusing capacity of the tissue barrier for oxygen (0.00 22 ml O(2) s(-1) Pa(-1) kg(-1)), the mass-specific volume of pulmonary capillary blood (6.25 cm(3)kg(-1)) and the mass-specific total anatomical diffusing capacity for oxygen (0.00073 ml O(2) s(-1) Pa(-1) kg(-1)) are equivalent to or exceed those of much smaller highly aerobic volant birds. The distinctive morphological and morphometric features that seem to occur in the ostrich lung may explain how it achieves and maintains high aerobic capacities and endures long thermal panting without experiencing respiratory alkalosis. (+info)
Flextube reflectometry for localization of upper airway narrowing--a preliminary study in models and awake subjects.
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The aim of this study was to examine an acoustic reflection method using a flexible tube for identifying the obstructive site of the upper airway in snorers and patients with obstructive sleep apnoea (OSA). As a preliminary study it was performed n models and subjects in the awake state. Flextube narrowing was produced in a model of the nose and pharynx and three blinded observers assessed the obstructive level. The correlation between pharyngeal narrowing assessed by endoscopy and by acoustic measurement during Muller manoeuvres was also examined in 10 OSA patients and 11 healthy non-snoring, adults. Three blinded observers dentified the level of 176 of 180 random cases of flextube narrowing in a polycarbonate model correctly The level of narrowing was always correctly evaluated within 1.9 mm. Pharyngeal area decrease was measured by the flextube method during the Muller manoeuvre but it was not closely related to the findings by endoscopy. In conclusion the flextube reflectometry method was able to demonstrate narrowng in a model of the nose and pharynx in a precise way. Narrowing was also observed during Muller manoeuvres. Flextube reflectometry may be a promising method to detect upper airway narrowing but further evaluation during sleep is required. (+info)
Cranial neural crest cells contribute to connective tissue in cranial muscles in the anuran amphibian, Bombina orientalis.
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The contribution of cranial neural crest cells to the development and patterning of cranial muscles in amphibians was investigated in the phylogenetically basal and morphologically generalized frog, Bombina orientalis. Experimental methods included fluorescent marking of premigratory cranial neural crest and extirpation of individual migratory streams. Neural crest cells contributed to the connective tissue component, but not the myofibers, of many larval muscles within the first two branchial arches (mandibular and hyoid), and complex changes in muscle patterning followed neural crest extirpation. Connective tissue components of individual muscles of either arch originate from the particular crest migratory stream that is associated with that arch, and this relationship is maintained regardless of the segmental identity-or embryonic derivation-of associated skeletal components. These developmental relations define a pattern of segmentation in the head of larval anurans that is similar to that previously described in the domestic chicken, the only vertebrate that has been thoroughly investigated in this respect. The fundamental role of the neural crest in patterning skeleton and musculature may represent a primitive feature of cranial development in vertebrates. Moreover, the corresponding developmental processes and cell fates appear to be conserved even when major evolutionary innovations-such as the novel cartilages and muscles of anuran larvae-result in major differences in cranial form. (+info)
Carotid arterial supply of the feline brain. Applications to the study of regional cerebral ischemia.
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A study of the supply to the feline brain by the carotid-middle cerebral arteries was conducted using in vivo transcardiac injection with a mixture of micropaque and carbon black. Modifications in the filling pattern of the arterial vessels were visualized following short-term occlusion of a middle cerebral artery. A modified surgical method to induce occlusion of the M-l segment of the middle cerebral artery is also described. (+info)