Simulated shuttle egress: Role of helmet visor position during approach and landing

Background: We previously reported that carbon dioxide (CO,) rapidly accumu lates in the helmet of the NASA launch and Entry Suit (LES) during a simula ted egress from the Space Shuttle Following 6 min of visor-closed seated re st to simulate approach and landing. The purpose of this study was to deter mine if CO2 accumulation and walking time in the LES would be improved by h elmet visor-open rather than visor-closed seated rest prior to the performa nce of the simulated egress. Methods: Wearing the LES, 12 male subjects per formed 4 laboratory egress simulation; consisting of 6-min seated rest, 2-m in stand, and 5-min walk at 1.56 m s(-1) (3.5 mph). During seated rest, sub jects sat either with the Visor open, breathing room air until the visor wa s closed on standing, or with the visor closed for the duration of the simu lation. For all visor-closed operations 100% O-2 was supplied. The G-suit w as either deflated (0.0 psi) or inflated to 1.5 psi. Inspired CO2 and walki ng time were measured. Data were analyzed at the end of seated rest, standi ng, and after 5 min of walking at 0.0 psi or after 2 min of walking at 1.5 psi (>90% of data available). Results: Walk time was not different followin g visor-open (0.0 psi: 5.0 +/- 0.0; 1.5 psi: 3.4 +/- 0.3 min) or visor-clos ed (0.0 psi: 4.8 +/- 0.2, 1.5 psi: 3.5 +/- 0.4 mini seated rest at either G -suit pressure. Inspired CO2 levels were not different between the two cond itions during walking at 5 min at 0.0 psi (p = 0.50; Open: 4.39 +/- 0.14. C losed: 4.48 +/- 0.18%) or at 2 min at 1.5 psi (p = 0.53; Open: 3.59 +/- 0.1 2; Closed: 3.65 +/- 0.21%). Conclusions Visor position during seated rest i mmediately preceding the egress walk had no effect on inspired CO2 or walki ng time.