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Towards Probablistic Assessment of Hypobaric Decompression Sickness TreatmentINTRODUCTION: Pressure, oxygen (O2), and time are the pillars to effective treatment of decompression sickness (DCS). The NASA DCS Treatment Model links a decrease in computed bubble volume to the resolution of a symptom. The decrease in volume is realized in two stages: a) during the Boyle's Law compression and b) during subsequent dissolution of the gas phase by the O2 window. METHODS: The cumulative distribution of 154 symptoms that resolved during repressurization was described with a log-logistic density function of pressure difference (deltaP as psid) associated with symptom resolution and two other explanatory variables. The 154 symptoms originated from 119 cases of DCS during 969 exposures in 47 different altitude tests. RESULTS: The probability of symptom resolution [P(symptom resolution)] = 1 / (1+exp(- (ln(deltaP) - 1.682 + 1.089×AMB - 0.00395×SYMPTOM TIME) / 0.633)), where AMB is 1 when the subject ambulated as part of the altitude exposure or else 0 and SYMPTOM TIME is the elapsed time in min from start of the altitude exposure to recognition of a DCS symptom. The P(symptom resolution) was estimated from computed deltaP from the Tissue Bubble Dynamics Model based on the "effective" Boyle's Law change: P2 - P1 (deltaP, psid) = P1×V1/V2 - P1, where V1 is the computed volume of a spherical bubble in a unit volume of tissue at low pressure P1 and V2 is computed volume after a change to a higher pressure P2. V2 continues to decrease through time at P2, at a faster rate if 100% ground level O2 was breathed. The computed deltaP is the effective treatment pressure at any point in time as if the entire deltaP was just from Boyle's Law compression. DISCUSSION: Given the low probability of DCS during extravehicular activity and the prompt treatment of a symptom with options through the model it is likely that the symptom and gas phase will resolve with minimum resources and minimal impact on astronaut health, safety, and productivity.
Document ID
20140002873
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Conkin, J. (Universities Space Research Association Houston, TX, United States)
Abercromby, A. F. (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Feiveson, A. H. (NASA Johnson Space Center Houston, TX, United States)
Gernhardt, M. L. (NASA Johnson Space Center Houston, TX, United States)
Norcross, J. R. (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Ploutz-Snyder, R. (Universities Space Research Association Houston, TX, United States)
Wessel, J. H., III (Wyle Integrated Science and Engineering Group Houston, TX, United States)
Date Acquired
April 11, 2014
Publication Date
November 15, 2013
Subject Category
Aerospace Medicine
Meeting Information
Meeting: 2014 Human Research Program Investigators'' Workshop
Location: Galveston, TX
Country: United States
Start Date: November 15, 2013
Sponsors: Universities Space Research Association, National Space Biomedical Research Inst., NASA Human Research Program
Distribution Limits
Public
Copyright
Public Use Permitted.

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