Hypobaric Atmosphere as a Prophylactic Measure Against Decompression Sickness During Repetitive EVA

The risk of decompression sickness (DCS) inherent in extra-vehicular activity (EVA) is reduced through the usage of hypobaric normoxic atmosphere. The safety of decompression protocols was evaluated during EVA simulation in the PCC-270 pressure chamber complex according to DCS frequency and tissue supersaturation ratio. The test program included 15 man rated test runs (1828 man- runs) with 123 test subjects aged 19-54. The aim of the test program was to select decompression safe protocols for transfer from hypobaric environment to a reduced pressure mode in the Russian space suit.

These experiments allowed to display in nomogramm form the ratio of operative pressure mode in the extravehicular space suit to the duration of a preliminary exposure in normoxic hypobaric conditions. Two other nomogram allowed to estimate variants of the compatible atmosphere parameters (total pressure, nitrogen partial pressure, oxygen content) and allowable value of the space suit pressure for denitrogenation-free egress without oxygen prebreathing.

This paper presents experimental data base to verify safety of repetitive EVA sorties from the orbital space stations.