Prevention of loss of consciousness with positive pressure breathing and supinating seat.Aviat Space Environ Med. 1988 Jan; 59(1):20-2.AS
Maintaining vision and consciousness at high sustained +Gz requires a total body effort for most people, and is very fatiguing. Currently, the only pieces of operational G-protective equipment are the anti-G suit and anti-G valve which provide relaxed G-tolerance protection to about 5.5 G. Protection above 5.5 G requires the anti-G straining maneuver (AGSM). Assisted positive pressure breathing (APPB) has been shown to augment sustained +Gz tolerance and reduce the amount of straining necessary to maintain a specific +Gz level. Moreover the supinating seat has been shown to double relaxed G tolerance at a back angle of 75 degrees from the vertical when compared to relaxed tolerance at a 13 degree or 30 degree position. Problems of cockpit engineering, escape, head-rest angle, restricted rear visibility, and pilot acceptance of a high angle supinated seat may preclude the use of a seat with sufficient back angle to provide "no strain" G protection. Thus, the addition of APPB to a limited protective seat may provide adequate and acceptable G tolerance.
