Case Control Study of Type II Decompression Sickness Associated with Patent Foramen Ovale in Experimental No-Decompression Dives

Abstract

This is a retrospective case control study comparing decompression sickness (DCS) risk in experimental Navy divers with a patent foramen ovale/right-to-left shunt (PFO/RLS) and in age-matched experimental Navy divers without a PFO/RLS. Eighty-eight subjects completed 432 man-dives in an empirical evaluation of extensions to air diving no-stop limits at Navy Experimental Diving Unit. Six subjects experienced neurologic DCS. Review of transthoracic echocardiography and transcranial Doppler imaging discovered a PFO/RLS in five of those subjects who experienced DCS and in six of 24 divers who had no DCS and had been recruited from the 82 remaining divers participating in the evaluation of the air diving no-stop limits. Logistic regression analysis indicates that after completing selected experimental no-stop dives to at least 150 feet of seawater with bottom times extended beyond current Navy diving limits, divers with a PFO/RLS are at increased risk for DCS.