Decompression Sickness During Simulated Extravehicular Activity: Ambulation vs. Non-Ambulation

摘要

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 earth-bound 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 incidence during ambulatory and non-ambulatory exposures are comparable and provide analogous estimates of risk under otherwise identical conditions. A retrospective analysis was accomplished on DCS symptoms from 2010 ambulatory and 330 non-ambulatory exposures. 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.0.1). Non-ambulatory exposures terminated more frequently with non-joint-pain DCS (17%) or upper-body-only joint pain (18%) as compared to ambulatory exposures;9% and 11% (P.0.01) respectively. 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. 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.