Pulmonary edema is an abnormal leakage of fluid from the bloodstream into the alveoli, the microscopic air sacs in the lungs. It is most often the result of heart failure or other cardiac problems. Sometimes, however, pulmonary edema is observed in swimmers and divers when no underlying medical cause is apparent. This condition, immersion pulmonary edema (IPE), presents as a rapid onset of shortness of breath, cough, and sometimes blood-tinged, frothy sputum. Dive professionals should be aware of this phenomenon and be prepared to facilitate prompt evaluation by a doctor for any diver who experiences these symptoms.
Because the fluid builds up in the air-containing spaces of the lungs and interrupts gas exchange, IPE resembles drowning. The important difference is that the obstructing fluid comes from within the body rather than from inhalation of surrounding water.
Divers Alert Network receives a few calls each month in which divers report symptoms suggestive of IPE. Anyone who experiences sudden shortness of breath or persistent cough while diving should abort the dive quickly and safely and breathe 100 percent oxygen on the surface. Although IPE often resolves quickly once a diver has exited the water, a physician should be consulted because of the potential seriousness of respiratory distress in the diving environment.
Several factors may be involved in cases of IPE. Immersion in water causes physiologic effects including a rapid distribution of blood from the legs to the core, which increases the volume of blood in the core. Typically, healthy individuals are usually able compensate for this fluid shift. There may also be a genetic component to IPE.
Additionally, diving causes increased negative pressure in the alveoli due to denser breathing gas and when using a poorly tuned regulator. Strong inhalation against resistance (essentially overbreathing a snorkel or regulator) may cause the lungs to respond by leaking fluid out of the capillaries and into the alveoli.
Medical professionals treat IPE just as they would treat any other case of pulmonary edema — with oxygen and diuretic medications. Whether or not a diver should return to diving after an episode of IPE should be determined on a case-by-case basis. The decision should be made by the diver’s doctor based on the diver’s physical condition and the type of diving they intend to do. People who have a history of cardiovascular disease or potential cardiovascular disease (hypertension, advanced age, diabetes) should undergo further evaluation prior to diving to make sure they do not have heart valve problems or underlying blockages in their coronary arteries. A person who experiences recurrent episodes of IPE should probably refrain from diving again in the future.
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