Risks factors for recurrent neurological decompression sickness in recreational divers: a case-control study

Individual or environmental factors that predispose to the recurrence of neurological decompression sickness (DCS) in scuba divers are not known and preventive measures designed to mitigate the risk of a subsequent episode remain empirical. The aim of this controlled study was to examine some potential risk factors predictive of recurrent DCS event that may lead to practical recommendations for divers who wish to continue diving after an initial episode.

Age, gender, diving experience, presence of a large right-to-left shunt (RLS) and diving practice following post-DCS resumption were evaluated as potential predictors of a further DCS in recreational divers admitted in our hyperbaric facility over a period of 12 years.

Twenty-four recurrent cases and 50 divers treated for a single DCS episode which continued diving were recruited after review of medical forms and follow-up interview by telephone. After controlling for potential confounding variables between groups, multivariate analysis revealed that experienced divers (OR, 3.8; 95%CI, 1.1-14; P=0.03), the presence of large RLS (OR, 5.4; 95%CI, 1.5-19.7; P=0.006) and the lack of changes in the way of diving after prior DCS (OR, 8.4; 95%CI, 2.3-31.1; P=0.001) were independently associated with a repeated episode.

The findings highlight the importance for divers to adopt conservative dives profiles or to use preferentially oxygen-enriched breathing mixtures after an initial DCS. Closure of a documented RLS through a large patent foramen ovale as a secondary preventive procedure for individuals that cannot adapt their diving practice remains debatable.