Simulated shuttle egress: Comparison of two space shuttle protective garments

Background: In a previous study from our laboratory, we observed carbon dio xide (CO,) accumulation in the helmet of the NASA Launch and Entry Suit (LE S) during a simulated emergency egress from the Space Shuttle. Of 12 subjec ts, 8 were unable to complete the egress simulation with a G-suit inflation pressure of 1.5 psi. The purpose of this report was to compare CO, accumul ation and egress walking time in the new Advanced Crew Escape Suit (ACES) w ith that in the LES. Methods: Four male subjects who previously were unable to complete the egress in the LES performed a simulated egress while weari ng the AGES with the C-suit inflated to 1.5 psi. The egress simulation cons isted of 6 min of seated rest, 2 min of standing, and 5 min of walking on a treadmill at 1.56 m . s(-1) (3.5 mph) and 0% grade. The helmet visor was c losed with the subjects receiving 100% oxygen throughout the simulation. In spired CO, and walking time were measured. Results: The rate of CO, accumul ation was significantly less (ACES: 0.53 +/- 0.03, LES: 1.07 +/- 0.15 %CO2 . min(-1); p = 0.05) and walk time was greater in the AGES (ACES: 5.0 +/- 0 .0, LES: 2.7 +/- 0.2 min; p = 0.002). Conclusions: Changes in the design of the AGES from the LES resulted in a decreased rate of CO, accumulation and an improved egress walking time compared with the LES.