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S Survanshi

Publications and source records attributed to S Survanshi.

6 recordsLinked to original sources
PubMed2000

Natural history of severe decompression sickness after rapid ascent from air saturation in a porcine model.

We developed a swine model to describe the untreated natural history of severe decompression sickness (DCS) after direct ascent from saturation conditions. In a recompression chamber, neutered male Yorkshire swine were pressurized to a predetermined depth from 50-150 feet of seawater [fsw; 2.52-5.55 atmospheres absolute (ATA)]. After 22 h, they returned to the surface (1 ATA) at 30 fsw/min (0.91 ATA/min) without decompression stops and were observed. Depth was the primary predictor of DCS incidence (R = 0.52, P < 0.0001) and death (R = 0.54, P < 0.0001). Severe DCS, defined as neurological or cardiopulmonary impairment, occurred in 78 of 128 animals, and 42 of 51 animals with cardiopulmonary DCS died within 1 h after surfacing. Within 24 h, 29 of 30 survivors with neurological DCS completely resolved their deficits without intervention. Pretrial Monte Carlo analysis decreased subject requirement without sacrificing power. This model provides a useful platform for investigating the pathophysiology of severe DCS and testing therapeutic interventions. The results raise important questions about present models of human responses to similar decompressive insults.

Air Pressure↗
PubMed1990

How countercurrent blood flow and uneven perfusion affect the motion of inert gas.

Monte Carlo simulations of the passage of inert gas through muscle tissue reveal that countercurrent gas exchange is more important than heterogeneity of flow in determination of the shape of inert gas washout curves. Semilog plots of inert gas washout are usually curved rather than straight. Two explanations often offered are that countercurrent flow may distort the shape and that uneven perfusion of the tissue gives rise to nonuniform washout. The curvature of the semilog plot may be summarized by the relative dispersion (RD), which is the ratio of the standard deviation of transit times to the mean transit time. For straight semilog plots, RD is 1. Semilog plots of data showing xenon washout from dog tissues are curved and have and RD of approximately 2. We have simulated the transit of gas particles through a vascular bed composed of repeating units of 100 mg of tissue perfused by three small vessels 80 microns in diameter and several levels of branching that direct flow through 190,000 capillaries. Geometric distribution of flow is important. Similar degrees of flow heterogeneity affect the curvature of the washout curve more if regions of heterogeneous flow are widely spaced than if they are close together. Diffusion blunts the effects of heterogeneous flow by mixing particles in high-flow regions with particles in low-flow regions. Because of this mixing, alternating regions of high flow and low flow spaced at intervals of less than 0.5 cm are unlikely explanations for the curved semilog plots.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Nitrogen gas exchange in the human knee.

Human decompression sickness is presumed to result from excess inert gas in the body when ambient pressure is reduced. Although the most common symptom is pain in the skeletal joints, no direct study of nitrogen exchange in this region has been undertaken. For this study, nitrogen tagged with radioactive 13N was prepared in a linear accelerator. Nine human subjects rebreathed this gas from a closed circuit for 30 min, then completed a 40- to 100-min washout period breathing room air. The isotope 13N was monitored continuously in the subject's knee during the entire period using positron detectors. After correction for isotope decay (half-life = 9.96 min), the concentration in most knees continued to rise for at least 30 min into the washout period. Various causes of this unexpected result are discussed, the most likely of which is an extensive redistribution of gas within avascular knee tissues.

Half-Life↗
PubMed1984

Morphological and physiological responses of the lungs of dogs to acute decompression.

The lung's response to decompression was studied in dogs anesthetized with pentobarbital sodium. Arterial pressure, hematocrit, right ventricular pressure, left ventricular end-diastolic pressure (LVEDP), dynamic compliance (CL), pulmonary resistance (RL), and arterial PO2, PCO2, and pH were measured prior to and for 3 h after a simulated air dive to 300 feet of seawater. Bronchoscopy was performed predive and at 3 h postdive. At 3 h animals were killed, and sections of lung were excised for histological examination. The decompression profile used regularly produced pulmonary hypertension, systemic hypotension, hemoconcentration, and arterial hypoxemia. CL fell in all but one dived animal. RL was more variable but remained unchanged postdive in most animals. The decompression stress did not alter the bronchoscopic and histological appearance of the airway mucosa. Pulmonary edema was regularly observed in histological sections and occurred without elevations of LVEDP. We concluded that noncardiac pulmonary edema is the principal response of the lung to decompression stress.

Animals↗
PubMed1981

Distribution of xenon gas exchange rates in dogs.

The kinetics of xenon gas uptake and elimination in seven anesthetized dogs were studied by simultaneous external recording of gas concentrations in several thousand anatomic sites during 7-h experiments. The data were analyzed by a previously described method of extracting moments of the distribution of gas residence times. Mean residence times (first moment) varied by more than a factor of 50 within a single animal: the fastest exchange was in the lungs (under 2 min), and progressively slower exchange occurred in the brain, spinal cord, ears, peripheral joints, and shoulder (over 2 h). Variance of the residence time (second moment) was found to approximate four times the mean residence time squared. This ratio was nearly the same throughout the body. Indications of unexpectedly high xenon solubility in the ear and joint regions were also found.

Animals↗