title: The effect of straining maneuvers on G-protection during assisted pressure breathing.
abstract: BACKGROUND
  Pilots flying high-performance aircraft increase their acceleration tolerance by using straining maneuvers and anti-G suits. Recently, assisted positive pressure breathing has been added in some aircraft systems. This study assessed the effect of anti-G straining maneuvers on the G-protective properties of one such system, the AGE-39 anti-G ensemble used in the Swedish JAS 39 Gripen aircraft.
  
  
  METHODS
  Ten subjects were studied in a centrifuge using each of the following: 1) the AGE-39 in combination with anti-G straining maneuvers (AGSM) throughout each high-G exposure (full maneuver; FM); 2) the AGE-39 in combination with AGSM only during the initial part of each high-G exposure (reduced maneuver; RM). G-tolerance was established during exposures to rapid onset rate (ROR) G profiles with plateau levels ranging from 6.5 to 9.0 G.
  
  
  RESULTS
  Mean G-tolerance was > or = 8.8 G (range: 8.5 to > or = 9.0 G) in the RM condition and > or = 9.0 G in all subjects in the FM condition. Mean arterial pressure was 30-50 mm Hg higher (p < 0.001) in the FM than in the RM condition at any given ROR G-load.
  
  
  CONCLUSIONS
  AGE-39 in combination with a brief period of straining provide efficient G-protection as illustrated by the finding that all subjects could tolerate 8.5 G while performing AGSM during the initial part of the high-G exposures. However, at 9.0 G, 40% of the subjects had to perform AGSM throughout the duration of the G-exposure. That arterial pressure was only 30-50 mm Hg higher in the FM than RM condition suggests that in the presence of straining maneuvers, pressure breathing makes only a minute contribution to the arterial-pressure response.
authors.affiliation: Defence Research Agency, Karolinska Institutet, Stockholm, Sweden. ola.eiken@fyfa.ki.se
authors.forename: O
authors.initials: O
authors.lastname: Eiken
authors.forename: R
authors.initials: R
authors.lastname: Kölegård
authors.forename: B
authors.initials: B
authors.lastname: Lindborg
authors.forename: I B
authors.initials: IB
authors.lastname: Mekjavic
authors.forename: J
authors.initials: J
authors.lastname: Linder
mesh_terms: D000328:Adult; D001794:Blood Pressure; D004576:Electromyography; D006112:Gravitation; D005676:Gravity Suits; D006339:Heart Rate; D006801:Humans; D008297:Male; D011175:Positive-Pressure Respiration