A study on Belgian decompression sickness (DCS) cases looked at patent foramen novale (PFO) presence, patency of present PFOs, and personality traits in divers who suffered cerebral DCS one or more times. Over the study’s 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 first episode of DCS, 70 involved second episodes, and 14 involved patients experiencing a third 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 first episode of DCS was found to have a PFO prevalence of 64 percent, while the groups with multiple episodes of DCS had a PFO prevalence of 100 percent. 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, 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 first 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.
References
Lafère P, Balestra C, Caers D and Germonpré P (2017) Patent Foramen Ovale (PFO), Personality Traits, and Iterative Decompression Sickness. Retrospective Analysis of 209 Cases. Front. Psychol. 8:1328. doi: 10.3389/fpsyg.2017.01328.