Released this year, an interesting study on Belgian DCS cases looked at PFO presence, patency of present PFOs, and personality traits in divers who suffered cerebral DCS one or more times. Over the studies 20.5 year period (1993-2013) there were a total of 595 DCS cases treated in three major centers in Belgium. Among them 286 were identified as cerebral DCS and 209 had all necessary information for the analysis. Out of those 209 cases, 125 involved a patient experiencing a 1st episode of DCS, 70 involved 2nd episodes, and 14 involved patients experiencing a 3rd episode of DCS.
There were no significant differences in age, body mass index or smoking habit between the subgroups. Divers with multiple episodes of DCS, however, dived deeper and more often than those with fewer episodes of DCS. All divers underwent PFO testing after each episode of DCS. When evaluated for PFO presence, the groups showed markedly different results. The group that had experienced only their 1st episode of DCS was found to have a PFO prevalence of 64%, while the groups with multiple episodes of DCS had a PFO prevalence of 100%. In addition, the amount of bubbles passing through the PFO increased in all divers with each subsequent episode of DCS.
All divers with diagnosed PFOs received consultation about their risks and advice to dive more conservatively if they decide to continue diving. However, a number of them apparently did not follow the advice. Contrary to the advice, they dived deeper and more often than they had before their DCS episode. A small sample of divers were tested for risk taking traits and those with multiple episodes of DCS scored higher indicating that they are more inclined to risky behavior.
There are several lessons learned from this study. First, let’s keep in mind that Belgium is relatively small country with a large number of scuba divers and a relatively small number of centers that evaluate and treat divers. The percentage of cerebral DCS among all treated DCS cases appears quite high in comparison with some other regions, but that may be a result of dive environment which results in deeper diving. It is also possible that cerebral DCS is under diagnosed in some other regions. It appears that testing for PFO in divers with cerebral DCS in Belgium became the norm in the early 1990’s, something which is still not a case in the United States. Thanks to this practice, we stand to learn several important lessons about PFOs and DCS risk. First, a presence of PFO represents an increased risk of cerebral DCS. After a 1st episode of cerebral DCS divers should be advised that they may have PFO and if they want to continue diving, they should follow more conservative pattern of diving. Divers who do not follow this advice risk repeated episodes of DCS, with each subsequent episode being more severe and more likely to leave functional disability. This study also indicates that the size, or patency, of a PFO increases with age and the risks of subsequent DCS probably increases. Additionally, the work illustrates that the effectiveness of medical consultations for divers with PFOs depends largely on a diver’s psychological profile, and that psychological testing should become a part of physician consultation.