Venous and arterial bubbles at rest after no-decompression air dives

Abstract

Purpose: During SCUBA diving, breathing at increased pressure leads to a greater tissue gas uptake. During ascent, tissues may become supersaturated, and the gas is released in the form of bubbles that typically occur on the venous side of circulation. These venous gas emboli (VGE) are usually eliminated as they pass through the lungs, although their occasional presence in systemic circulation (arterialization) has been reported and it was assumed to be the main cause of the decompression sickness. The aims of the present study were to assess the appearance of VGE after air dives where no stops in coming to the surface are required and to assess their potential occurrence and frequency in the systemic circulation.

Methods: Twelve male divers performed six dives with 3 d of rest between them following standard no-decompression dive procedures: 18/60, 18/70, 24/30, 24/40, 33/15, and 33/20 (the first value indicates depth in meters of sea water and the second value indicates bottom time in minutes). VGE monitoring was performed ultrasonographically every 20 min for 120 min after surfacing.

Results: Diving profiles used in this study produced unexpectedly high amounts of gas bubbles, with most dives resulting in grade 4 (55/69 dives) on the bubble scale of 0-5 (no to maximal bubbles). Arterializations of gas bubbles were found in 5 (41.7%) of 12 divers and after 11 (16%) of 69 dives. These VGE crossovers were only observed when a large amount of bubbles was concomitantly present in the right valve of the heart.

Conclusions: Our findings indicate high amounts of gas bubbles produced after no-decompression air dives based on standardized diving protocols. High bubble loads were frequently associated with the crossover of VGE to the systemic circulation. Despite these findings, no acute decompression-related pathology was detected.