[abstract] DECOMPRESSION IN SIMULATED MICROGRAVITY; BEDREST AND ITS INFLUENCE ON STRESS-ASSISTED NUCLEATION.

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[abstract] DECOMPRESSION IN SIMULATED MICROGRAVITY; BEDREST AND ITS INFLUENCE ON STRESS-ASSISTED NUCLEATION.

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Title: [abstract] DECOMPRESSION IN SIMULATED MICROGRAVITY; BEDREST AND ITS INFLUENCE ON STRESS-ASSISTED NUCLEATION.
Author: Powell, MR; Waligora, JM; Norfleet, W
Abstract: There is a discrepancy between the incidence of decompression sickness reported by astronauts (from both the USA and the USSR) during extravehicular activity and the expected incidence based on studies conducted under unit gravity conditions in Earth-based laboratories. This "decompression risk anomaly" is more than would statistically be allowed by chance alone; a biophysical explanation has been proposed for this difference based upon the mechanism of stress-assisted nucleation. The original decompression paradigm as proposed by John S. Haldane postulated that a gas phase forms in tissues when the partial pressure of the dissolved gases exceeds a specified level of supersaturation. Since the partial pressure ratio at which this gas phase forms is considerably smaller in living systems than in quiescent in vitro models, it was proposed (eg, E. N. Harvey, mid 40's) that mechanical forces are involved. In that the lower extremities of astronauts are not gravitationally loaded in microgravity, it is possible that tissue gas micronuclei are but minimally regenerated. Most likely, gas micronuclei formed on Earth [by ambulation under 1-g conditions] would be eventually depleted. In a cross-over study, individuals were decompressed (from 1 ATA to 0.43 ATA for 3 hours) following either being fully ambulatory at unit gravity or following being hypokinetic and adynamic (simulated microgravity of 3-day bed rest). The subjects were monitored for gas phase formation by means of precordial Doppler monitoring. The results indicate a reduction in whole body gas phase formation in individuals who were bedrested as compared with themselves when fully ambulatory. These results are compatible with a hypothesis relating stress-assisted nucleation to the continual formation of tissue gas micronuclei and their gradual depletion with hypokinesia.
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held June 23-27, 1992. Hyatt Regency Bethesda Hotel, Bethesda, Maryland (http://www.uhms.org)
URI: http://archive.rubicon-foundation.org/6502
Date: 1992

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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