Observation of increased venous gas emboli after wet dives compared to dry dives.

INTRODUCTION: Testing of decompression procedures has been performed both in the dry and during immersion, assuming that the results can be directly compared. To test this, the aim of the present paper was to compare the number of venous gas bubbles observed following a short, deep and a shallow, long air dive performed dry in a hyperbaric chamber and following actual dives in open water.

METHODS: Fourteen experienced male divers participated in the study; seven performed dry and wet dives to 24 metres' sea water (msw) for 70 minutes; seven divers performed dry and wet dives to 54 msw for 20 minutes. Decompression followed a Bühlmann decompression procedure. Immediately following the dive, pulmonary artery bubble formation was monitored for two hours. The results were graded according to the method of Eftedal and Brubakk.

RESULTS: All divers completed the dive protocol, none of them showed any signs of decompression sickness. During the observation period, following the shallow dives, the bubbles increased from 0.1 bubbles per cm ² after the dry dive to 1.4 bubbles per cm ² after the wet dive. Following the deep dives, the bubbles increased from 0.1 bubbles per cm ² in the dry dive to 2.4 bubbles per cm ² in the wet dive. Both results are highly significant (P = 0.0001 or less).

CONCLUSIONS: The study has shown that diving in water produces significantly more gas bubble formation than dry diving. The number of venous gas bubbles observed after decompression in water according to a rather conservative procedure, indicates that accepted standard decompression procedures nevertheless induce considerable decompression stress. We suggest that decompression procedures should aim at keeping venous bubble formation as low as possible.