Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. In this prospective cohort study, there was an increased incidence of physician-confirmed decompression illness (DCI) in divers with high-risk patent foramen ovale (PFO) compared to those without.

2. The study could not evaluate the significance of low-risk PFO on the incidence of decompression illness due to the low sample size.

Evidence Rating Level: 2 (Good)

Study Rundown:

Divers may experience DCI during ascents without proper decompression procedures. This occurs due to the rapid formation of nitrogen gas bubbles in the bloodstream. Observation studies have previously demonstrated that PFO is present at a higher prevalence among divers who have experienced DCI compared to those who have not. Prospective studies are still needed to elucidate a causal relationship between PFO and DCI. In this prospective cohort study, adult divers with more than 50 dives annually were enrolled after the presence of PFO was determined. Divers were then followed at three and six months and then every six months for a three-year period using self-reported questionnaires about symptoms of DCI. The presence of DCI was adjudicated by blinded physicians. PFO was detected in over two-thirds of enrolled divers. Twelve divers in the PFO group experienced self-reported and physician-adjudicated symptoms of DCI, while none in the non-PFO group did. As a limitation, a small sample size and a study population of only high-frequency divers may reduce the generalizability of the study. In summary, the results of the present study suggest that rates of decompression illness are higher in adults with high-risk PFO.

In-Depth [prospective study]:

In this prospective cohort study, a total of 100 adult divers with more than 50 dives annually were enrolled to evaluate the association between PFO and DCI. The presence of PFO was determined by transthoracic and transesophageal echocardiography with saline contrast. In terms of follow-up, participants were assessed for three years at six-month intervals. The primary outcome was the total incidence of DCI (defined by any DCI events), DCI symptoms that required medical intervention, any DCI symptoms within 30 minutes of resurfacing from a patient-reported diver, or unexplained death within two weeks of a dive. Sixty-eight participants were found to have PFO, with over 80% being grade three which is classified as over 20 microbubbles that appeared in the left atrium using echocardiography. Across all participants, the mean follow-up period was 28.7 months. Participants reported that a total of 33,531 expected dives occurred during the study period. Twelve participants (12 events) and no participants in the PFO (19%; 5.5 per 10,000 person-dives) and non-PFO group (0%), respectively, had self-reported DCI symptoms that were adjudicated by blinded physicians (p=0.012). Ten of the twelve participants with DCI had a high-risk PFO (8.4 per 10,000 person-dives), while two had a low-risk PFO (2.0 per 10,000 person-dives; p=0.090). In summary, the present study demonstrated that high-risk PFO may be associated with an increased risk of DCI among experienced and frequent divers.

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