In a prospective study, all cases of decompression illness occurred in patients with patent foramen ovale. 

Decompression illness occurs when dissolved nitrogen forms bubbles in a diver’s vasculature due to pressure changes during ascent. According to one theory, patent foramen ovale (PFO) contributes to decompression illness by allowing venous nitrogen bubbles to enter the arterial system. To examine a possible association between PFO and decompression illness, 100 experienced divers were surveyed about self-reported decompression illness episodes during a mean follow up of nearly 2.5 years. At baseline, participants underwent transthoracic and transoesophageal echocardiogram (with bubble studies and Valsalva manoeuvre) to assess presence and grade of PFO; high-risk PFO was defined as shunting prior to Valsalva, larger PFO size (2 mm or more), hypermobility or septal aneurysm. Divers were blinded to echocardiogram results.

After an estimated 33,500 dives, decompression illness had occurred in 13% of divers (19% with PFO vs 0% without PFO). Incidence of decompression illness symptoms was significantly higher in divers with high-risk PFO and nonsignificantly higher in divers with low-risk PFO than in those without PFO (28%, 7.5% and 0%, respectively). 

Comment: These findings suggest that paradoxical embolisation of nitrogen bubbles via PFO is the primary underlying mechanism of decompression illness. Divers with high-risk PFO should consider their risk for decompression illness and possibly refrain from diving or follow conservative diving protocols.

Daniel D. Dressler, MD, MSc, MHM, FACP, Professor of Medicine, Emory University School of Medicine, Atlanta, USA.

Lee H-J, et al. Decompression illness in divers with or without patent foramen ovale: a cohort study. Ann Intern Med 2023; 176: 934-939.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine, Hospital Medicine, Cardiology.