An observation of venous gas emboli in divers and susceptibility to decompression sickness.

INTRODUCTION Decompression sickness (DCS) results from the formation of bubbles within the tissues and blood in response to a reduction in environmental pressure. Venous gas emboli (VGE) are common after diving and are usually only present in small numbers. Greater VGE numbers are an indication of decompression stress, and can be reliably detected using ultrasound imaging. AIM To examine the relationship between production of VGE following a routine dive and the risk of DCS. METHODS A matched population of divers with and without a history of DCS were monitored for the production of VGE at 15-minute intervals using ultrasound, following a 405 kPa air dive in a hyperbaric chamber using the DCIEM air decompression table. VGE production was graded using a validated grading system and the data analysed to compare maximum VGE grade and duration of VGE formation. RESULTS Eleven divers with a history of DCS were compared with 13 divers with no history of DCS. Divers with a history of DCS demonstrated both a higher maximum grade (P=0.04) and longer duration (P=0.002) of VGE production compared to divers without a history of DCS. CONCLUSION Higher maximum VGE grades and longer durations of VGE following decompression were associated with a history of DCS and, in particular, musculoskeletal DCS. Although the exact mechanism of DCS remains poorly understood, our data suggest some individuals are inherently more prone to develop VGE, increasing the probability of DCS. Modification of diving practices in those with high VGE grades could potentially decrease DCS risk in these individuals.