What is a Patent Foramen Ovale (PFO)

A PFO is a very small hole in the heart (often closed under normal circumstances) and which, during or after diving, can enable nitrogen bubbles to pass back into circulation in the blood rather than being expelled by the lungs, leading to DCI.  This diver's experience has become increasingly common over the past few years.

Indications that a diver may have a PFO:

These can range from an often mild mottled rash after diving to severe neurological symptoms, such as collapse, weakness, blurred vision, among others.

If a PFO is suspected, the treating physician will often refer the diver to be tested. A negative result on the test does not necessarily mean there is no PFO, however, if one is present it is likely to be very small. A positive test indicates there is an obvious route that bubbles in the venous blood can pass through the heart and enter the arterial blood, from where it can be taken to the brain, spine and elsewhere in the body. The PFO can often be repaired surgically, and some divers elect to have the hole closed. As with any surgical procedure there are associated risks and these need to be balanced against the desire to continue diving and the risk of diving without having the PFO repaired. This varies between individuals and is something that needs to be discussed between the diver, the diving physician and the cardiologist. Many divers continue to dive despite a small PFO and reduce the chances of a problem by limiting depths, repetitive diving, extending surface intervals, doing slow ascents and safety stops and using nitrox (with dive times based on air).