Immersion pulmonary edema (IPE) or swimming-induced pulmonary edema (SIPE) manifests with coughing, blood in sputum, difficulty breathing and a drop in the oxygen content of arterial blood. It may occur during surface swimming or diving, and can affect subjects of all ages and levels of health. Risk factors include exaggerated vasoconstriction in cold water, strenuous exercise, negative static lung load caused by immersion, fluid overload and low vital capacity.
Richard Moon recently presented the results of a study he conducted at Duke University Medical Center that aimed to identify one or more simple screening tests to determine SIPE susceptibility. His study included subjects with and without histories of SIPE, who were asked to undergo a battery of tests while at rest and during exercise, in both dry atmospheres and immersed in water, and with and without liquid loading.
The purpose of his study—to help us to better understand the causes of SIPE so that we may identify susceptible individuals—was achieved. Moon found that the forced expiratory volume (FEV) in SIPE susceptible subjects was decreased by 10 percent or more after 40 minutes of exercise in cold water. The study also demonstrated that for subjects susceptible to SIPE, fluid loading before a swim (two liters of water or Pedialyte) increases the risk of SIPE.
The question is: Who should be tested? The incidence of SIPE among recreational divers diving in comfortable conditions is rather low, and screening all divers would be impractical. Divers with known history of SIPE are already proven susceptible and do not need to be tested. However, the incidence of SIPE is much higher among navy trainees and triathletes, and screening may be justified for these groups.
Post written by: Petar Denoble, MD, D.Sc.