Protection of PHP Maneuver Against Human Centrifuge-induced Acceleration Atelectasis

Xu Yan; Zhang Lihui; Yan Guiding; Jin Zhao; Li Baohui; Wang Hong; Li Xiaoqiu; Yang Chao; Geng Xichen

Abstract：Objective To explore the protective effects of PHP maneuver against centrifuge-induced acceleration atelectasis. Methods Seven subjects were exposed to centrifuge simulated aerial combat maneuvers (SACM) profile composed of two respective +4.5 Gz for 45 s and +5.0 Gz for 15 s and 45 s superimposed on + 3 Gz baselines.Using 100％ oxygen,experiment was carried out under 3 conditions:group A,with safety overpressure of 30 mm H2O to the mask; group B,without safety overpressure; group C,without safety overpressure,but with PHP maneuver.Chest X-ray,vital capacity (VC),forced vital capacity (FVC),forced expiratory volume ( FEV),and subjective ratings of chest pain,coughing,and shortness of breath were measured.Results Group A experienced an average of 0.27 L (P ＜0.05 ) reduction in post-SACM VC,and the subjective ratings were low (2.5 ±2.6).An average of 0.69 L (P ＜0.05 ) and 0.29 L (P ＜0.01 ) reduction in post-SACM VC and FVC were found in group B,and chest pain,coughing,and shortness of breath were reported by all subjects.The subjective ratings (8.1 ± 2.2 ) were higher than those of group A ( P ＜0.05 ).Six subjects had radiological changes typical of acceleration atelectasis.In group C,there was no significant reduction in post-SACM VC and FVC,and the subjective ratings (0.8 ±0.9) were lower than those of group B (P ＜0.01 ).There were still some radiological appearances of atelectasis in the same 6 subjects,but the severity was reduced obviously.Conclusion PHP maneuver can provide a satisfactory protection against centrifuge-induced acceleration atelectasis.