title: Simulated shuttle egress: role of helmet visor position during approach and landing.
abstract: BACKGROUND
  We previously reported that carbon dioxide (CO2) rapidly accumulates in the helmet of the NASA Launch and Entry Suit (LES) during a simulated egress from the Space Shuttle following 6 min of visor-closed seated rest to simulate approach and landing. The purpose of this study was to determine if CO2 accumulation and walking time in the LES would be improved by helmet visor-open rather than visor-closed seated rest prior to the performance of the simulated egress.
  
  
  METHODS
  Wearing the LES, 12 male subjects performed 4 laboratory egress simulations consisting of 6-min seated rest, 2-min stand, and 5-min walk at 1.56 m x s(-1) (3.5 mph). During seated rest, subjects sat either with the visor open, breathing room air until the visor was closed on standing, or with the visor closed for the duration of the simulation. For all visor-closed operations 100%, O2 was supplied. The G-suit was either deflated (0.0 psi) or inflated to 1.5 psi. Inspired CO2 and walking time were measured. Data were analyzed at the end of seated rest, standing, 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 following visor-open (0.0 psi: 5.0 +/- 0.0; 1.5 psi: 3.4 +/- 0.3 min) or visor-closed (0.0 psi: 4.8 +/- 0.2; 1.5 psi: 3.5 +/- 0.4 min) seated rest at either G-suit pressure. Inspired CO2 levels were not different between the two conditions during walking at 5 min at 0.0 psi (p = 0.50; Open: 4.39 +/- 0.14; Closed: 4.48 +/- 0.18%) or at 2 min at 1.5 psi (p = 0.53; Open: 3.59 +/- 0.12; Closed: 3.65 + 0.21%).
  
  
  CONCLUSIONS
  Visor position during seated rest immediately preceding the egress walk had no effect on inspired CO2 or walking time.
authors.affiliation: Wyle Laboratories, Life Sciences Systems and Services Division, Houston, TX, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Lee
authors.forename: P A
authors.initials: PA
authors.lastname: Bishop
authors.forename: S M
authors.initials: SM
authors.lastname: Schneider
authors.forename: L L
authors.initials: LL
authors.lastname: Clapp
authors.forename: W J
authors.initials: WJ
authors.lastname: Williams
authors.forename: N
authors.initials: N
authors.lastname: Conza
authors.forename: M C
authors.initials: MC
authors.lastname: Greenisen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D002245:Carbon Dioxide / Q000032:analysis*; D006260:Head Protective Devices; D006801:Humans; D008297:Male; D011187:Posture; D019442:Space Suits; D016138:Walking
chemical_list: D002245:Carbon Dioxide