Experimental research on the effects of air pre-saturation at shallow depths on safety of 150 m fast buoyancy ascent in submarine escape

Abstract

Objective To explore the safety of 150 m fast buoyancy ascent in submarine escape following air saturation at various depths.Methods Eight adult goats with average body mass of 18-20 kg were used in our experiment.Followingpre-air-saturation at simulated depths of 60,70,80 and 120 kPa,the animals underwent a series of escape experiments.First,the experimental animals were pressurized to pre-airsaturation depths,then,received rapid pressurization in accordance with the 150 m fast buoyancy ascent profile,had a brief stop and were fast decompressed to the surface.After exposure,Doppler ultrasonic grading of vascular air bubbles and clinical manifestations were compared both before and after exposure.Results Following pre-air-saturation and escape at simulated depths of 60 and 70 kPa,no obvious abnormal manifestations could be seen in all the animals.However,following pre-air-saturation and escape at a simulated depth of 80 kPa,one animal displayed some light DCS symptoms,but was recovered without any treatment.Following pre-air-saturation and escape at a simulated depth of 120 kPa,grade 3 air bubbles (Spenser classification) were detected in all the 3 animals,one of which died 4 days later.Anatomy revealed that congestion of the lung tissue was quite apparent,but without obvious cerebral hemorrhage and infarct foci.Conclusions Following pre-air-saturation at a simulated depth of 70 kPa,fast buoyancy ascent escape at a depth of 150 m was relatively safe.Nevertheless,greater pre-air-saturation exposure could induce relatively high incidence of DCS,with the prevalent lethal factor being serious damage to the lung tissue. Key words: Fast buoyancy ascent escape; Pre-saturation; Decompression sickness; Goat