Open water swimming poses a serious risk that few people know about: ScienceAlert

People love open water swimming, with more than 3 million taking part in England by 2021. But a new study warns there is evidence linking the sport to a lung condition called swim-induced pulmonary edema (SIPE).

Age, long swimming, cold water, being a woman, and high blood pressure or heart disease are risk factors. Doctors emphasize that SIPE often occurs in otherwise healthy people, making it difficult for swimmers to breathe and oxygen deprived.

The exact cause of SIPE is not fully understood, but it happens when fluid builds up in the lungs without the person taking in water. The person usually experiences severe shortness of breath, low oxygen levels, and a wet cough.

The risk of SIPE during open water swimming is also not well known, but it is probably uncommon, report cardiologists from the Royal United Hospitals Bath and the University of Bath, UK, after treating a woman with the condition.

“First reported in 1989, the incidence is probably underreported and is estimated to be between 1.1 percent and 1.8 percent,” the authors write in their case report.

However, once a person experiences an attack of SIPE, their chance of developing the condition again increases significantly.

Recurrence is common and has been reported at between 13 percent and 22 percent among divers and swimmers. Episodes vary in severity and often do not require hospitalization; however, patients should be properly informed about the high risk of recurrence and after an initial episode, should be presumed to have a predisposition,” the authors write.

The case study reports an important finding: the heart and lungs can be affected in SIPE, as seen in the case of a woman in her 50s who swam long distances, did triathlons and had no major health problems in the past.

While swimming in an open water event, she became short of breath and had to stop swimming, after which she felt out of breath for days.

The patient swam 3 kilometers (1.9 mi) the following weekend without any problems, but a week later the shortness of breath returned after 300 meters, and this time she coughed up blood.

She had been swimming in a wetsuit overnight in 17 °C (63 °F) water.

“While swimming in a quarry on a night swim, I started to hyperventilate and realized I couldn’t swim any further. Luckily I was able to call for help and was guided back to the dock by a paddleboard,” the woman said afterwards. to recover.

“When I got out I took off my wetsuit and immediately felt my lungs fill with fluid. I started coughing and had a metallic taste in my mouth. When I got into the light I noticed my sputum was pink and frothy.”

She was taken to hospital, where her shortness of breath persisted, her heartbeat was fast and she had a persistent cough. During a clinical examination, small lung sounds that may indicate fluid in the lungs were observed, and a chest x-ray confirmed the presence of fluid.

Blood tests revealed higher than normal levels of troponin, a protein found in muscle that can be released into the blood after heart damage. An MRI indicated myocardial edema – swelling in the heart muscle that can be attributed to fluid – and signs of possible fibrosis, indicating tissue damage.

The patient’s heart and lungs otherwise appeared normal, and her symptoms and heart rate resolved within 2 hours of arriving at the hospital.

Four days later, the patient’s troponin levels had returned to normal. A clinical exam showed that her lung and heart functions were normal, although a small amount of fibrosis remained.

Three months after the incident, she took an exercise stress test for no reason.

While this is only one case of SIPE, the team says it is the first published evidence of myocardial edema due to swimming documented using cardiac MRI. That should help doctors treating the condition know what to look for, while also making cold-water swimmers aware of what can happen.

Although more research is needed, SIPE is likely caused by changes in blood flow and a stronger response of the lungs’ blood vessels to cold during exercise. People with thickening of the wall of their heart’s main pumping chamber, structural heart disease, or high blood pressure are more likely to get SIPE.

Cardiologist James Oldman and co-authors say patients who experience shortness of breath while swimming should be tested for SIPE. They also recommend doctors do a thorough circulatory examination to look for heart problems that should go away in a few days, along with other symptoms.

“As cardiac MRI becomes mainstream worldwide, it is likely that more data will become available [immersion pulmonary edema] cases will emerge, allowing us to better characterize myocardial pathology in this underdiagnosed syndrome,” the authors write.

For swimmers experiencing symptoms, the researchers’ advice is to leave the water immediately and seek medical attention if necessary. Avoiding nonsteroidal anti-inflammatory drugs and swimming at a slower pace in warmer water without a tight wetsuit are other ways they suggest swimmers can minimize the risk of recurrence.

The peer-reviewed findings have been published in the journal BMJ case reports.

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