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

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Webb JT, Beckstrand DP, Pilmanis AA, Balldin UI. Decompression sickness during simulated extravehicular activity: ambulation vs. non-ambulation. Aviat Space Environ Med 2005; 76:778–81.

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. Discussion : 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.

Keywords: DCS; adynamia; denitrogenation; exercise; prebreathe; preoxygenation

Document Type: Research Article

Publication date: August 1, 2005

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