What is SIPE?

While planning the Portland Bridge Swim in 2024, one of the participants informed the safety crew that she had previously had SIPE, and although it hadn't recurred in a while, she wanted to give us a heads up. The biggest indicator of a SIPE episode is having had the condition before, so knowing there was as risk, we came up with some safety protocols in case SIPE struck again. We had ropes pre-tied to both the front and back of her paddler's kayak, and we informed all of our safety volunteers and the EMS team the day-of. Thankfully, the swimmer didn't have any issues during the swim, but it lead me to learn more about the condition.

Swimming-Induced Pulmonary Edema, known as "SIPE" for short, is a condition where fluid accumulates in the lungs. Although relatively uncommon, it can be fatal if untreated. The reported incidence in open water swimmers is around 0.75% in females and 0.09% in males, but this is likely extremely underreported.

While vending at the Castle 2.5/5/10k swim in Baily, CO, I met Dr. Kathryn Vidlock MD, Associate Professor of Family Medicine and Ultrasound, Director of Ultrasound, Director of Rural and Wilderness Medicine Track at Rocky Vista University, College of Osteopathic Medicine. Dr. Vidlock is studying SIPE, and even travels to events to offer pulmonary screenings to athletes to determine how often signs of SIPE and other issues go unreported.

In the swimming world, swimmers affected by SIPE often write the symptoms off as minor irritation and try to swim through it. Unfortunately, that's exactly the wrong thing to do. Due to lack of symptom reporting and subsequent pulmonary screening, it's unknown how many deaths have occurred due to SIPE.

Swimming Induced Pulmonary Edema was first described in scuba divers in 1981 and later reported by open water swimmers. SIPE can occur across all populations and skill levels, including elite athletes. Even Navy Seals can be affected by SIPE.

What causes SIPE?

Sadly, the root causes of SIPE aren't fully understood. There's a lot of missing data due to underreporting and lack of screening. But, there are some proposed causes:

1. Cold water exposure: swimming in water ranging below 59F (15C) degrees. This is due to vasoconstriction of the skin and extremities, redirecting blood to the core organs, which causes increased blood flow to the heart and lungs. The increased blood flow can exert pressure on the lungs, leading to fluid leakage and pulmonary edema. This means that cold water swimmers are at a higher risk for SIPE.

2. Intense physical exertion: swimming over long distances or with high intensities can stress the cardiovascular and respiratory system. The heart and lungs have to exert more energy to circulate oxygen. The harder and/or longer you swim, the higher the risk for SIPE.

3. Chest compression: the repetitive motion of rapidly inhaling and applying force to the torso, especially when combined with the compression of a wetsuit, can result in higher pressure on the lungs and chest cavity.

4. Higher altitude: some studies have found that swimming at higher altitude, where the air pressure is lower, can also trigger SIPE. The added effort of maintaining oxygen levels can stress the heart and lungs. Dr. Vidlock's studies are partially focus on screening athletes at slightly higher altitudes to gather data.

5. SIPE previously: Having had SIPE before is a very strong predictor of having another SIPE episode.

Who does SIPE affect?

Anyone can develop SIPE, but certain groups might be at higher risk based on their activities:

1. Cold water swimmers

2. Competitive swimmers and endurance athletes

3. Swimmers with pre-existing health conditions, like cardiovascular issues, respiratory illnesses, obesity, or asthma

What does SIPE look like?

Symptoms vary by swimmer, and can range in severity. Although these are the most common symptoms in reported cases, it's important to remember that in the cases not reported, there either may not have been symptoms, or they may have felt/displayed differently enough that the individual didn't seek medical attention. It's also possible that some of the individuals reporting believed they were experiencing these symptoms with SIPE for the first time, but they may not have known they had already experienced SIPE with other symptoms, and were at increased risk.

• Shortness of Breath (Dyspnea): the most common symptom, where swimmers feel they cannot catch their breath, even after moderate exertion.

• Coughing: some swimmers may develop a dry cough. In severe cases, the cough may produce pink, frothy sputum.

• Chest Pain or Tightness: a swimmer might feel discomfort or tightness in their chest as the fluid builds up in the lungs.

• Fatigue: a swimmer might feel unusually tired and weak, even after finishing a relatively short swim.

• Cyanosis (Bluish Skin): in severe cases, the skin around the lips and fingertips may turn blue due to low oxygen levels.

• Anxiety: although less frequently reported and not always reported in studies, feelings of anxiety can be an indicator as well.

What happens if you think you have SIPE?

If a swimmer experiences symptoms of SIPE or they or their crew believe there's a risk of SIPE:

1. Stop and check vitals. SIPE is serious, and continuing to swim can increase risk of it becoming fatal. Respiratory rate may be high, and oxygen can be given as needed.

2. A medical care provider can use a portable ultrasound at the site of the swim to easily get imaging to confirm if there's fluid inside the lung(s). [Race directors, take note: do your EMS crews have a portable ultrasound? Are they able to perform this screening if the event is in a remote location?]

3. If there's fluid in the lung(s), or there's no way to perform an on-site ultrasound, the swimmer should seek medical attention. The medical professional will take a history of activity levels, exertion, and medical issues. They might also ask about water temperature and obtain oxygen saturation levels. An ultrasound, X-rays, or CT imaging may be performed.

How is SIPE treated?

The treatment of SIPE focuses on reducing symptoms and managing fluid buildup in the lungs. The vast majority of individuals will have their symptoms resolve very quickly simply by exiting the water and resting. If the swimmer is wearing a wetsuit, it should be removed to increase blood flow to the chest and reduce constriction. Help increase blood flow and warm the swimmer by placing them in a warming tent or using a hot compress.

Oxygen therapy can be used if the oxygen saturation is low. Sitting upright or a partially reclined position may help also. Dr. Vidlock states that "We generally monitor patients until they have stable normal vital signs and no shortness of breath for 15 minutes."

If the individual isn't improving or if their oxygen saturation stays low, then they need to head to the hospital as quickly as possible. Common treatments for severe cases include diuretics, beta agonists, steroids, and a CPAP machine.

How can I avoid/prevent SIPE?

Although there's a lot of info still needing to be studied and analyzed, Dr. Vidlock offers these strategies for reducing the risk of SIPE or preventing a recurrence:

1. Warm up properly: warming up before swimming helps prepare the body for the exertion, which helps relieve stress on the cardiovascular system. When entering cold water, adapt more slowly, rather than diving in.

2. Adapt to lower temps: take the time to swim down the water temps, and acclimate slowly to the colder conditions.

3. Avoid hitting "overexertion" levels: listen to your body and don't push yourself past your safety limits in colder water or high altitudes. If you start to feel something weird with your breathing, stop and rest.

4. Use proper breathing technique: exhaling consistently underwater and using bilateral breathing can help avoid hyperventilation and increased lung pressure. Try to breathe the side (rather than the front) to minimize chest pressure and avoid inhaling water.