Patent Foramen Ovale & Diving

Pictured here is a rash suffered by a professional diver after a typical day of diving. The profile was well within no-deco limits and his dive computer showed that his nitrogen tissue saturation was not substantial. This diver suffered vertigo and dizziness along with the rash, making it a type II decompression sickness (DCS) event. This episode is an illustration of undeserved bends. The diver did everything right, yet suffered severe symptoms of DCS, requiring treatment in the chamber above.

What causes undeserved bends? Occasionally dehydration, illness, or abnormal complement immune function may contribute. However, the cardiac abnormality known as a patent foramen ovale can predispose to DCS in some divers.

Patent Foramen Ovale is an opening between the left and right atria in the heart, allowing blood to bypass the lungs. Divers often develop bubbles in veins, a common occurance (30-100% in some series). Most of the time these bubbles are harmless and are filtered out by the lungs. A patent foramen ovale allows these bubbles to pass by the lungs and go into the brain, where they can cause stroke-like symptoms. In fact, the onset of DCS in divers with a patent foramen ovale can occur rapidly. This can look like a arterial gas embolus, which generally occur when divers hold their breath during a rapid ascent. In PFO however, the diver may have just finished an uneventful dive with no warning from their dive table or computer - hence the term undeserved bends.

So this sounds scary and unavoidable. Scarier still if you consider that about 30% of the population has a PFO! And it seems to be even more prevalent in divers than in the general population. Even doing a valsalva maneuver may open up a closed PFO. Some depressing studies have illustrated a correlation between PFO and brain injury in recreational divers.

But don't quit diving yet. PFOs, while common, rarely cause DCS. And those brain injury studies are fraught with methodologic problems - so far.

We will discuss these issues in great detail this August in Kailua Kona. This information should be of great interest to anybody who dives. In particular, frequent divers, deep divers, and professional divers should know about this research.

Aloha,

Joe Alcock MD
www.MMMedicine.com
mail@MMMedicine.com
http://www.mountainandmarinemedicine.com/Kona2006.html