Objective System of pressure breathing for +Gz (PBG) has been incorporated into service in the high performance fighter aircraft,but there were significant differences among PBG pressure schedules used in different countries.The purpose of this study was to define an optimal pressure schedule in PBG system.Method Five male subjects wearing GZ-2 anti-G suit and medium-sized bladder vest,plus PBG with 1.6,2.4,and 3.2 kPa/G pressure schedules,respectively,were exposed to rapid onset (3.0 G/s) centrifuge +Gz runs.+Gz protection of PBG with each of the three pressure schedules were measured and the subjective ratings were collected.Result The +Gz protection afforded by PBG with 1.60,2.40,and 3.20 kPa/G pressure schedules were 2.00±0.31,2.54±0.32,and 2.44±0.31 G,respectively.Subjective ratings showed that the PBG with 2.40 kPa/G pressure schedule was better than the other two.Conclusion Our data suggest that a PBG pressure schedule of 2.4 kPa/G in PBG system is optimal.It not only assures the anti-G performance of PBG,but also reduces its side effects.

Objective To observe the protection effects of a new combined anti-G measure, which is composed of new bladder anti-G system, unassisted positive pressure breathing for G (PBG) and PHP maneuver. The problem of fatigue and pain when using this measure is also discussed. Method Each of the six fully qualified centrifuge subjects experienced 5 groups of centrifuge runs:1) relaxed +Gz tolerance without anti-G equipments and PHP maneuver;2) +Gz tolerance with FLH-x+KT-x;3) +Gz tolerance when performing PBG with FLH-x, KT-x, YM-x and TK-x;4) +6.5 Gz for 45 s using the same anti-G equipments as the 3rd group;5) +9.0 Gz for 15 s using the same anti-G equipments as the 3rd group and performing PHP maneuver. Result There were no incidents of G-induced loss of consciousness in this study. The protective effects of FLH-x+KT-x, PBG and PHP maneuver were 2.5 G, 1.67 G and 1.23 G respectively. All the subjects had accomplished the 6.5 G 45 s and 9.0 G 15 s runs with the new combined anti-G measure. The pain occured on neck, waist, arm and hands. Conclusion The new combined anti-G measure can provide enough anti-G protection for modern high performance aircraft. How to prevent the occurrence of neck injury and alleviate the pain induced by G when using this measure needs further investigation.