Significance of Patent Foramen Ovale in Patients with GOLD Stage II Chronic Obstructive Pulmonary Disease (COPD)

Background: Patent foramen ovale (PFO) is a common finding in adults. A PFO is associated with right to left shunting but its importance in the aetiology of hypoxia in early COPD remains uncertain, although it has not proved possible to demonstrate a role for PFOs in the aetiology of hypoxia in patients with Global Initiative for chronic Obstructive Lung Disease (GOLD) stage III/IV disease. We compared the characteristics of GOLD stage II patients with or without a PFO and assessed its impact on exercise performance. Methods: In 22 GOLD stage II COPD patients we measured exercise performance, arterial oxygen tension and lung function and used contrast transcranial Doppler ultrasonography (TCD) to assess the presence of a PFO. Patients (n=20) underwent TCD measurements during incremental cycle ergometry with respiratory pressures measured using an esophageal balloon catheter (n=13). Results:Twelve individuals (54%) had a PFO. Patients with a PFO were more hypoxic; mean(SD) partial pressure of oxygen in arterial blood (PaO₂)10.2(1.1) kilopascals (kPa) vs. 11.7(0.9)kPa (p<0.01), but the presence of a PFO was not associated with reduced exercise performance either on cycle ergometry or a 6 Minute Walk Test (6MWT). A strong relationship was noted between the esophageal pressure swing (P_SwingEs) and the degree of shunting observed during exercise (r=0.7; p<0.001). Conclusions:The presence of a PFO in GOLD stage II COPD patients does not appear to influence exercise performance despite increased right-to-left shunting.