PILOT PERFORMANCE OF THE ANTI-G STRAINING MANEUVER - RESPIRATORY DEMANDS AND BREATHING SYSTEM EFFECTS

Introduction: The anti-G straining maneuver (AGSM) is still an importa nt part of pilot protection for G-induced loss of consciousness. The s pecific requirements for and the effects of breathing systems on the p erformance of the AGSM are essential elements to designing compatible breathing systems. Methods: Subject pools of 27 and 34 naval aviators were recruited and used to measure the inhalatory and exhalatory flow requirements for the AGSM and the breathing system effects of mask cav ity pressure during AGSM performance on the Naval Air Warfare Center D ynamic Flight Simulator at acceleration levels up to 8 Gz. Results: Th e mean peak inhalatory flow was 125.5 L . min(-1) (n = 135, SD = 42.1) with a maximum value of 274 L . min(-1). The mean peak exhalatory flo w was 154.4 L . min(-1) (n = 135, SD = 49.6) with a maximum value of 3 08 L . min(-1). For the effects of the breathing system on AGSM perfor mance, inhalatory mask cavity pressures were not above 30 mmHg with th e majority less than 10 mmHg. Exhalatory mask cavity pressures did not exceed 60 mmHg but predominated in the 20-30 mmHg range. In compariso n to accepted guidelines, 67-77% of inhalatory mask cavity pressures w ere below and 91% of the exhalatory mask cavity pressures were above t he Air Standardization and Coordination Committee (ASCC) limit of +/- 14 mmHg. Conclusions: The difference in the peak inhalatory and exhala tory flows measured during this study and clinically can be attributed to different test conditions and performer techniques. The reduction in inhalatory flow with increasing G is consistent with the increase i n breathing difficulty due to the G load and the inflation of the anti -G suit. However, exhalatory mechanics appear unaffected by the G load and the inflation of the anti-G suit. Since 23-33% of the inhalatory mask cavity pressures were above this ASCC limit, improvements in regu lator performance are still needed. For exhalatory effects of the brea thing system, the main contributor is the mask valve. While no pilot s uffered unconsciousness or expressed complaints with the breathing sys tems used, these exposures were of short duration. The additional work of breathing during a combat engagement may further compromise the pi lot's ability to retain consciousness with the AGSM.