Objective Fast buoyancy ascent escape used in submarine escape is the most probable choice of survival in case of a submarine accident.Rate of success for escape depends very much on the extent of training,in spite of the fact that rapid compression and decompression pose great challenges to the human body in terms of enormous stresses.To minimize stresses experienced during sub escape training has always been a research subject for us.Lungs are susceptible to rapid change in pressure during escape.Dynamic pulmonary function and the end-tidal PCO2 ( PETCO2 ) might be the best indicator for its effect on the pulmonary function of the submarine escapee.Methods Five male navy divers received submarine escape trainings,at different depths from 3-60 m.They were compressed at different rates (with pressure doubled every 20 s or 30 s),in the simulated submarine escape tower located in the Naval Medical Research Institute.The gas of end-expiration was collected immediately after escape,respiratory rate (RR) and dynamic pulmonary function were closely monitored,and PETCO2 was determined with the mass spectrometer.Results Experimental results showed that forced expiratory volume in 1 second (FEV1.0) tended to increase with increasing depth,and that it increased significantly at 50 m and 60 m,when compared with the basic data (P ＜ 0.05 ),and it was coupled with a decrease in forced expiratory flow at 25 ％ ( FEF25％ ),indicating that it had certain effect on the function of small airways.PETCO2 and RR all elevated markedly following escapes.No significant differences could be seen in RR following escapes at various depths.PETCO2 and depth ( r =0.387,P ＜ 0.01 ) were positively correlated with compression rate ( r =0.459,P ＜ 0.01 ) and RR ( r =0.467,P ＜ 0.01 ).CO2 retention might be attributed to pulmonary ventilation disorder induced by rapid changes in pressure.PETCO2 was within normal range,following escapes at various depths,suggesting that increased RR might be induced by stresses rather than CO2 retention.No significant differences could be noted in PETCO2 and RR,following escapes with different compression rates,indicating that lower compression rate might not necessarily mitigate stresses of the body.Conclusions Based on the pulmonary reaction experienced by the trainees,it was recommended that submarine escape training be conducted at a depth no deeper than 50 m,so that possible airway lesion might be minimized.The benefit of lower compressing rate at shallower escape depths remained to be identified.