Arterial gas bubbles after decompression in pigs with patent foramen ovale.

With patent foramen ovale (PFO), thought to be a risk factor for some forms of DCS, venous bubbles may pass through the patent opening to become arterial bubbles. We exposed 14 anesthetized, spontaneously breathing pigs to air at 5 bar (500 kPa, absolute pressure) for 30 min and then rapidly decompressed at 2 bar/min to 1 bar. We measured intravascular pressures, blood gases, and, with transesophageal echocardiology, bubbles in the pulmonary artery and ascending aorta. Autopsy showed that six of the pigs had a PFO. Arterial bubbles occurred more frequently in the PFO group (in six out of six) than in the non-PFO group (in two out of eight, P < 0.01). When arterial bubbles were detected, the venous bubble count and the pulmonary artery pressure tended to be lower in pigs with PFO than in pigs without a PFO. We conclude that a PFO increases the risk of arterial bubbles after decompression.