SAFETY Confronting the Danger from Within Immersion Pulmonary Edema (IPE) – by Dan Orr, President, Dan Orr Consulting
I recently had the pleasure and honor to be a keynote speaker for the British SubAqua Club Convention in Birming- ham, England. My keynote presentation was “Mistakes Divers Make,” and I also did a
uted from our peripheral circulation to the body core and the pulmonary circulation. If there is a significant differ- ential in pressure in the lungs caused by an increase in the work of breathing, negative pressure in the lungs may exist potentially causing fluids to leak from the surround- ing lung tissue into the air sacs in the lungs. The result is fluid buildup in the diver’s lungs. This fluid collects in the many air sacs in the lungs, making it difficult to breathe. Fluids can, however, collect in the lungs for a number of reasons. These include heart conditions, pneumonia, con- tact with certain toxins, medications, trauma to the chest, and exposure to high altitudes. IPE may develop suddenly and is considered a serious medical emer- gency and potentially life-threatening condition requiring immediate medical attention. There is significant evidence suggesting that negative pressure breathing when diving or snorkeling increases the risk of IPE. This may be due to surface swimming while breathing through a small diameter snorkel, breath- ing against a negative pressure gradient from a poorly tuned regulator in open-circuit diving or breathing against a negative pressure between the diver’s lungs and the counter-lung in CCR diving. Breathing against a negative pressure has the effect of pulling body fluids through the thin alveolar membrane causing fluid to build up in the lung’s air sacs. There is also research evidence suggesting that repeti- tive deep dives may result in an increased risk of IPE. This may be due to intravascular bubbles affecting the walls of the blood vessels in the diver’s lungs resulting in fluid leaking into the lungs. In one research finding, 40% of cases, IPE occurred following intense physical exercise. However, this associ- ation was observed in only 26% of recreational divers, compared to 86% of military divers. Among civilian recreational divers, no cases of IPE were observed in sub-
breakout session presentation entitled, “Safety Issues for the Older Diver.” Both presentations were well attended and well received. Following both presentations, attendees
asked many questions re- garding diving safety issues for divers of all ages. There was, however, a number of questions about immersion pulmonary oedema (spelled edema in the U.S.).
Immersion pulmonary edema (IPE) is a potentially se- rious condition that can have significant respiratory and cardiac consequences and, in some cases, be fatal for both scuba divers and snorkelers. IPE is a poorly understood and possibly underdiagnosed condition among divers and snorkelers in the U.S. but considered by divers in the BSAC to be a significant safety issue. According to Dr. Peter Wilmshurst, “Immersion pulmonary oedema prob- ably causes more deaths in scuba divers than any other condition. IPE also affects surface swimmers, including snorkelers. Most deaths in triathletes occur during the swim phase of the event and there is evidence that a major cause of those deaths is IPE.” While IPE was first identified around 40 years ago, the mechanism of injury is still not well understood. IPE is likely underreported since autopsy findings on potential victims of IPE may be similar to drownings or those who have been subject to prolonged resuscitation efforts. Basically, when the diver enters the water, blood shifts from the peripheral circulation to the body core which includes the lungs. During immersion in water, approxi- mately 700 milliliters of blood is immediately redistrib-
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