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Pressure Breathing Without a Counter-Pressure Vest Does Not Impair Acceleration Tolerance Up to 9 G

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Balldin UI, O’Connor RB, Isdahl WM, Werchan PM. Pressure breathing without a counter-pressure vest does not impair acceleration tolerance up to 9 G. Aviat Space Environ Med 2005; 76:456–462.

Introduction: This study was to determine whether safe and adequate G-protection by pressure breathing during G (PBG) could be maintained if the COMBAT EDGE counter-pressure vest were eliminated to ensure aircrew do not unnecessarily endure a possible in-flight discomfort or distraction. Methods: Centrifuge exposures up to +9 Gz were completed by 11 subjects, including 5 F-15 aircrew, using PBG at 60 mmHg pressure with and without the counter-pressure vest. Additional G-exposures using pressures of 0, 30, and 45 mmHg were performed without the vest. Results: Elimination of the COMBAT EDGE counter-pressure vest did not significantly reduce G-tolerance. During gradual onset G exposure, the mean G level reached with PBG was 8.4 G without the vest and 8.2 G with the vest. In comparison, 6.7 G was reached without PBG. Mean times at G with rapid onset G exposure were 59 and 60 s, respectively, compared with 49 s without PBG. PBG, with or without the vest, was preferred by all test subjects. PBG at 60 mmHg produced the highest G protection and was preferred by the test subjects over lesser pressures. Subjects reported no adverse effects from the use of PBG without chest counter-pressure. Conclusion: The use of PBG and the anti-G straining manuever (AGSM) together enhances G tolerance and comfort more than AGSM alone. Elimination of the counter-pressure vest during use of PBG does not hinder an individual’s ability to reach +9 Gz or complete a short duration simulated aerial combat maneuver G exposure. Further research is needed to determine if use of PBG without chest counter-pressure increases fatigue during multiple sorties or produces other aeromedical problems in operational environments.

Keywords: G protection; G tolerance; G-LOC; acceleration; anti-G suit; counter-pressure vest; pressure breathing; thorax counter-pressure

Document Type: Research Article

Publication date: May 1, 2005

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