By Tom Phipps
Swimming-Induced Pulmonary Edema (SIPE) is an uncommon condition that is associated with abnormal fluid collection in the lungs, in the absence of actually breathing in water, that occurs during or shortly after swimming. First described in 1989, it is a subtype of immersion pulmonary edema, which is more typically associated with SCUBA diving.
The true incidence of this condition is hard to judge, and it is probably under-reported. The problem may occur in as many as 1.4% of triathletes and as many as 1-2% of competitive open water swimmers. I did not find any reference to this condition in pool swimmers. Many of the case reports seem to describe triathletes and some wonder if the deaths in triathlons (which almost always occur on the swim portion) may be related to this condition. It is difficult to know because the fluid filled lungs of a drowning victim and those with pulmonary edema may appear rather similar.
SIPE frequently occurs in fit and healthy individuals, the information I could find did not seem to differentiate experienced swimmers from the population as a whole. Risk factors include advanced age, female sex, high blood pressure, longer swimming distance, cooler water temperature and pre-existing heart or lung disease.
The exact cause is uncertain but likely involves increased pressure in the arteries of the lung. Factors include an increase in central blood volume due to blood vessel constriction in cold limbs, which causes the heart to pump against higher pressure. At the same time the heart is trying to pump more associated with exercise and the air pressure in the lungs may be lower associated with inspiration. Add in some external pressure on the chest from the water and perhaps a tight fitting wetsuit and the stage is set for fluid to leak from the blood vessel of the lung into the air spaces.
Symptoms and signs typically include shortness of breath, cough that may be productive of sputum that may be frothy or blood-tinged, and low blood oxygen levels that occur during or shortly after swimming. Often these symptoms are mild and easily discounted if not recognized for what they represent but occasionally they may be more severe and may even require hospitalization. The problems generally resolve in 24-48 and leave no apparent trace although heart and lung testing may remain abnormal for some time.
Findings on testing may include evidence of heart muscle strain. A recent report described evidence of edema in the heart muscle associated with the typical lung findings. Those lung findings on exam and imaging are typical of any cause of fluid on the lungs.
Treatment is supportive and includes removal from the water and from exercise and placement in a seated position. Oxygen is sometimes required and EMT care should be obtained if this condition is suspected.
It is important to recognize this condition in yourself or others. Unusual or unexpected shortness of breath or cough during or shortly after swimming that lasts longer than expected but resolves in a day or two should not be ignored. Some people turn out to have underlying heart, lung or blood pressure issues that need to be addressed. Between 13 and 22% of people experience recurrent episodes, which may be more severe.
While there is some guidance for divers there are no specific guidelines, especially for swimmers, It is felt that return to swimming should be gradual beginning with shorter, less intense swims in warmer water and without a wetsuit. Non-steroidal anti-inflammatory drugs like ibuprofen should be avoided. Sildenafil (yes, the generic form of Viagra) appears to be an effective preventative drug for those with recurrent SIPE.
If you experience this condition you should talk to your medical provider. Be prepared to educate your provider as this uncommon condition is likely to be unknown to them. Up To Date (a common medical database used by many doctors) has a brief description of Immersion Pulmonary Edema in the Section on Complications of SCUBA Diving. Wikipedia has a fairly detailed and accurate description of the condition.
As always, know yourself and your situation in the water and be safe.
Reference: Oldman J, et al. BMJ Case Rep 2023; 16:e251274. Doi:10.1136/bcr-2022-251274