Decompression sickness during simulated extravehicular activity: ambulation vs. non-ambulation.
BACKGROUND
Extravehicular activity (EVA) is required from the International Space Station on a regular basis. Because of the weightless environment during EVA, physical activity is performed using mostly upper-body movements since the lower body is anchored for stability. The adynamic model (restricted lower-body activity; non-ambulation) was designed to simulate this environment during earthbound studies of decompression sickness (DCS) risk. DCS symptoms during ambulatory (walking) and non-ambulatory high altitude exposure activity were compared. The objective was to determine if symptom incidences during ambulatory and non-ambulatory exposures are comparable and provide analogous estimates of risk under otherwise identical conditions.


METHODS
A retrospective analysis was accomplished on DCS symptoms from 2010 ambulatory and 330 non-ambulatory exposures.


RESULTS
There was no significant difference between the overall incidence of DCS or joint-pain DCS in the ambulatory (49% and 40%) vs. the non-ambulatory exposures (53% and 36%; p > 0.1). DCS involving joint pain only in the lower body was higher during ambulatory exposures (28%) than non-ambulatory exposures (18%; p < 0.01). Non-ambulatory exposures terminated more frequently with non-joint-pain DCS (17%) or upper-body-only joint pain (18%) as compared with ambulatory exposures, 9% and 11% (p < 0.01), respectively.


CONCLUSIONS
These findings show that lower-body, weight-bearing activity shifts the incidence of joint-pain DCS from the upper body to the lower body without altering the total incidence of DCS or joint-pain DCS.


CONCLUSIONS
Use of data from previous and future subject exposures involving ambulatory activity while decompressed appears to be a valid analogue of non-ambulatory activity in determining DCS risk during simulated EVA studies.
Webb
James T
JT
Life Sciences Group, Wyle Laboratories, San Antonio, TX, USA. chittim@swbell.net
Beckstrand
Devin P
DP
Pilmanis
Andrew A
AA
Balldin
Ulf I
UI
D003665:Decompression Sickness / Q000453:epidemiology* / Q000503:physiopathology*; D018478:Extravehicular Activity / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D007596:Joints / Q000502:physiology; D009068:Movement; D010146:Pain; D012189:Retrospective Studies; D012307:Risk Factors; D018561:Space Simulation