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Update on Swimming Induced Pulmonary Edema (SIPE)

May 26, 2015 By Larry Creswell, MD 6 Comments

I saw this week that there was an important new paper on swimming induced pulmonary edema (SIPE). Richard Moon, MD, and his colleagues at Duke University published a report entitled, “Immersion Pulmonary Edema and Comorbidities: Case Series and Updated Review” in a recent edition of the sports medicine journal, Medicine & Science in Sports & Exercise (1).

SIPE is known to occur not only in recreational or competitive swimmers, but also in divers. In fact, the condition was first recognized because of breathing difficulties encountered by military divers. As triathlete and swimmer readers here will know, there are many reasons why an athlete might develop shortness of breath during an open water swim. Water conditions, water and air temperature, exertion, and anxiety all play a role. SIPE is something different, altogether, though. This is a condition that develops because of immersion in the water, in which fluid builds up in the lungs and makes breathing difficult. The condition is believed to be self-limiting; if a swimmer gets out of the water, the condition will resolve. The underlying mechanisms and risk factors are not completely understood.

I’ve written about this condition in 2 previous blog posts….SIPE and More on SIPE. These posts might be a good starting point.

The newly published report is important because it reviews the medical literature and gathers all of the pertinent information about pre-existing medical conditions, or so-called comorbidities, in victims of SIPE. Dr. Moon is probably the world’s foremost authority on the topic of SIPE, so this new report deserves our attention.

The Study

There are 2 parts to the study: 1) a look at the Duke University experience with recreational swimmers who’ve had a SIPE episode and 2) a review of the medical literature on SIPE cases, both in military and recreational divers and swimmers.

In the first part, the investigators collated information on 41 swimmers who, over the past several years, had been studied at Duke University after reporting a SIPE episode. The mean age was 50.1 +/- 10.8 years (range, 25-71 years). Complete medical history data was available for 36 of the 41 swimmers.

In the second part, the investigators collected 45 previously published articles in the medical literature that reported on 292 cases of SIPE. There were 156 recreational swimmers or divers (89 men and 67 women), with a mean age of approximately 47.8 +/- 11.3 years. There were also 136 military swimmers or divers (135 men and 1 woman), with a mean age of approximately 23.3 years (range, 18-47 years).

For each of these groups, the investigators gathered information about pre-existing medical conditions in order to determine potential risk factors for the development of SIPE, focusing on: hypertension (high blood pressure), lung disease, overweight/obesity, sleep apnea, hypothyroidism, and cardiac abnormalities).

The Results

Among the Duke University group, 9 (25%) of the 36 swimmers with available health history were completely healthy. The remaining 27 (75%) had 1 or more medical/health conditions, including:

overweight/obesity in 12
hypertension in 7
cardiac arrhythmias in 4
heart valve problem (mitral valve prolapse) in 1
reduced heart function in 2
repaired congenital heart conditions in 2
asthma in 3
COPD in 1
reactive airways disease in 1
hypothyroidism in 3
diabetes in 2
polycystic ovary syndrome in 1
obstructive sleep apnea in 2

Twelve subjects had more than one of these conditions.

In the literature review, all of the 136 military swimmers and divers were healthy; they had none of the pre-existing medical/health conditions that were surveyed. In contrast, 70 (45%) of the 156 recreational swimmers or divers had one or more significant pre-existing risk factors:

asthma in 4
enlarged heart in 2
arrhythmias in 2
coronary artery disease in 3
diabetes in 4
exercise-induced cough in 1
Elevated serum lipids in 22
hypertension (high blood pressure) in 25
thickening of the left ventricle in 9
peripheral vascular disease in 1
sleep apnea in 6

As a side note, approximately 17% of cases in the literature review reported similar previous episodes or follow-up episodes that were suggestive of SIPE, giving an important look at the potential recurrence rate. And in total, 6 fatal cases of SIPE were identified in the literature review.

My Thoughts

How can all of this collated information be useful to us?

First, it’s important to note that all of the military swimmers and divers included in the literature review were healthy. We shouldn’t overlook the possibility that even completely healthy swimmers may experience SIPE.

Second, the recurrence rate of ~17% in the literature review is probably an underestimate. No doubt, some swimmers who experienced a worrisome episode of SIPE might avoid future swimming altogether. It’s very important to remember that this condition may recur.

Third, it’s very apparent that, among recreational swimmers who experience SIPE, the prevalence of important pre-existing medical conditions is rather high, at 75% in the Duke group and 45% in the recreational swimmers in the literature review. I suspect that the Duke investigators were more thorough in their history-taking and the 75% is probably more reflective of the reality.

The investigators’ aim was to identify risk factors for SIPE. Sadly, there’s obviously no single, unifying thread here. Hypertension (high blood pressure) was the most commonly identified condition among the cases, but this accounted for only ~15% of the cases. As I mentioned at the top, the physiologic underpinnings of SIPE are not completely understood and indeed there may be more than one responsible mechanism leading to some common final pathway by which fluid accumulates in the lungs. All of the various cardiovascular abnormalities identified in the cases might conceivably play a role. There’s more to learn.

It’s worth noting that the long list of medical conditions that were identified deserve careful medical attention before participating in recreational swimming events.

Advice

I’ll reprint here my best advice to athletes and event organizers regarding SIPE. I originally included this in another blog post, but this is still my best advice!

Triathletes and open water swimmers should be aware of SIPE and the possibility that this condition can be lethal.
Symptoms of SIPE can manifest for the first time even in experienced swimmers. Symptoms may develop rapidly, be unexpected, and confuse the athlete about the cause.
The development of SIPE does not appear to be confined to cold water swims or only to victims who are wearing a wetsuit at the time.
SIPE appears to be self-limiting–that is, the symptoms will subside if the victim stops exercising and gets out of the water.
Because of #2, #3, and #4, athletes who experience breathing difficulties in the open water should treat the problem like a medical emergency and STOP swimming and SEEK immediate assistance. Because of the challenges of rescue in the open water, your life could depend on recognizing a problem early and getting out of the water. I would encourage affected athletes to get complete medical evaluation as soon as possible after an episode.
There appear to be no effects on lung function after an episode of SIPE, but repeat episodes of SIPE may occur.
Affected athletes have described a variety of strategies for preventing repeat episodes of SIPE. From athlete accounts, no single strategy appears to be universally successful.
Affected athletes should use EXTREME CAUTION in subsequent open water training and races, being hypervigilant for warning signs.
Event organizers and on-water rescue personnel should be familiar with SIPE. The safety plan should allow for athletes with breathing difficulties to be removed from the water as quickly as possible.

Reference

1. Peacher DF, Martina S, Otteni C, et al. Immersion pulmonary edema and comorbidities: Case series and updated review. Med Sci Sports Exerc 2015;47(6):1128-1134.

2. More on Swimming Induced Pulmonary Edema (SIPE)

More on Swimming Induced Pulmonary Edema (SIPE)

September 12, 2012 By Larry Creswell, MD 3 Comments

In the aftermath of several recent triathlon fatalities, I’ve been a part of several conversations about swimming-induced pulmonary edema (SIPE). These conversations all got started with somebody asking the question: could these recent deaths be due to SIPE? I truthfully don’t know the answer.

I recently wrote a blog post where I introduced the topic of SIPE. I discussed a liitle bit about the physiology, provided some information from the scientific literature, and shared personal stories from a couple affected triathletes. You might start with reading that post and then continue reading here.

Today, I thought I’d draw your attention to some additional sources of information about SIPE.

A Book

In my opinion, the most useful narrative about SIPE in layman’s terms is in a recent book by Ingrid Loos Miller, entitled Fearless Swimming for Triathletes. Ingrid has long had an interest in triathlon swim safety. She’s a USAT certified coach and a member of the United States Lifesaving Association. The book is good reading for any triathlete. In Appendix C, though, Charles “Trey” Miller writes on the subject of SIPE. For those who don’t know Trey, he is a PhD epidemiologist and Chair of the Department of Biomedical Sciences, Associate Dean for Research, and Associate Dean for the Graduate School of Biomedical Sciences at the Texas Tech School of Medicine. He is a triathlete with personal experience with SIPE and has authored one of the very few scientific reports on triathletes and SIPE–which I mentioned in my first blog piece about SIPE. His section of Ingrid’s book very clearly explains what is known about SIPE in language that makes the topic accessible.

Some Articles in the Non-Medical Press

One article that’s received some attention is by Rudy Dressendorfer, Ph.D., who wrote an editorial in the Sports Medicine Bulletin published by the American College of Sports Medicine. I mentioned this article briefly in my earlier post. The discussion about SIPE physiology is worthwhile. He speculates about how SIPE might affect triathletes and offers some suggestions for affected athletes. I’d caution that his recipe for prevention may not be broadly applicable; it seems from athlete reports that successful prevention strategies might be very individualized and not always broadly applicable or successful.

Kat Calder-Becker and Trey Miller wrote a niece article for Slowtwitch in 2007 in which they describe the general features of SIPE and share personal experience with the condition. They conclude the article by writing that “more research is needed.” That’s certainly true.

Online Forum Discussions

There have been recent threads about SIPE at a variety of online forums, including Slowtwitch, dctriclub, U.S. Masters Swimming, Beginner Triathlete, and IAmTri, among others. You can search for SIPE at the forums to find the pertinent discussions. Oftentimes, the information shared about SIPE is factually incorrect, but the valuable portions are from athletes who share stories related to breathing difficulties during races. Our fellow triathletes and open water swimmers should learn from these stories that breathing difficulties during a race indicate an emergency.

I’ll draw your attention to 2 recent threads at Slowtwich that deserve special mention. In the first, simply entitled Swimming Induced Pulmonary Edema, a triathlete identified as KAP shares her story of breathing difficulties during an Olympic distance triathlon. She was eventually treated at the Johns Hopkins Hospital, where the suspicion of SIPE as a diagnosis was confirmed with x-rays. Her story is good reading. It should serve as additional warning to athletes who experience breathing difficulties during a race.

The second thread worth mentioning is entitled SIPEsters: please stop spreading misinformation. The valuable portion here is the exchange at the end between me and Trey Miller. Athletes should read Trey’s response to the question: Given what we know about SIPE, what should athletes, event organizers, and USAT do? His suggestions are thoughtful.

From the Medical Literature

Virtually the entire medical literature on the clinical aspects of SIPE has its origins in the experiences of scuba divers or military divers. A small number of deaths attributable to SIPE have been reported in that setting. Some of the reported accounts have dealt with cases of SIPE that has developed in surface swimmers, though. One important feature of the various reports is that recovery from an episode of SIPE appears to be complete, most often with just supportive care–that is, the condition resolves with cessation of exercise and removal from the water. One article documents that typical parameters of lung function normalize after SIPE episodes:

1. Ludwig BB, et al. Cardiopulmonary function after recovery from swimming-induced pulmonary edema. Clin J Sport Med 2006;16:348-351.

I’m aware of only 2 articles in the medical literature that deal with SIPE specifically in triathletes:

2. Miller CC et al. Swimming-induced pulmonary edema in triathletes. Am J Emerg Med 2010;28:941-946.

3. Carter EA and Koehle MS. Immersion pulmonary edema in female triathletes. Pulm Med 2011;1-4.

I summarized the important information from the first article in my previous blog post. Again, this article reports on a survey of triathletes regarding their symptoms that might be suggestive of SIPE. The second article reports on 3 cases of female triathletes, ages 43 to 59, who were diagnosed with having SIPE. In 2 of these athletes the symptoms developed during training swims. In the 3rd athlete, there were 2 documented episodes of SIPE during triathlon race swims. In all 3 cases, the diagnosis of SIPE was supported by chest x-ray evidence of pulmonary edema without other explanation.

I understand from my reading that establishing SIPE as a cause of death at autopsy is difficult because pulmonary edema is a common finding in drowning victims. Some of the forensic challenges in this setting are summarized in an article:

4. Papadodima SA, et al. Forensic investigation of submersion deaths. Int J Clin Pract 2010;64:75-83.

Warnings from Event Organizers and Athlete Organizations

With a growing recognition that SIPE can affect recreational athletes during open water swim competitions, it’s not surprising that we’d begin to see warnings to athletes about this possibility. As an example, there is an annual Horsetooth Open Water Swim (with various events up to 10K distance) held in Ft. Collins, Colorado. I noticed that their website information about athlete safety now includes a warning about the possibility of SIPE, pointing out that breathing difficulties during the swim constitute a medical emergency and that athletes with these symptoms should stop immediately and seek assistance. As another example, I saw that the U.S. Open Water Swimming Connection sent an email to its membership that addressed the issue of SIPE and included an athlete account of an episode during a 40K swim.

A Couple Notable Athlete Accounts

I came across an account from an triathlete, Andrea Himmel, who competed at the recent Ironman New York triathlon. His account is chronicled in a post at www.policymic.com and has been shared or reprinted in several other online venues as well. His story is worth reading. His troubles with breathing started during the swim portion of the race and continued during the bike portion, where he had to drop out at about the halfway point. Although he didn’t immediately seek medical attention outside the race venue, he suspects that his symptoms were due to SIPE. His account seems to be similar to those shared by other triathletes at the various Forums that I mentioned above.

I would take issue with Andrea’s speculation about the cause of death for Andrew Naylor, another athlete who competed in the race. Yes, Mr. Naylor died during the swim portion of the race. I’m not sure who Andrea was referring to in the article when he mentioned, “now we hear from people involved in the Ironman medical circles that the man who died after the swim likely died from SIPE.” I certainly don’t know what caused Mr. Naylor’s death, but I’ve spoken with the medical director for the race and learned that his cause of death has not yet been determined. I’m equally certain, though, that when all of the relevant testing is completed that we’ll hear from the medical examiner about the autopsy findings and conclusions that can be drawn about the cause of death.

Another recent account comes from a triathlete who competed in my hometown race, the Heatwave Classic Triathlon in June. This athlete shared his story at Slowtwitch and I’ve since had a chance to speak with him about his experience on race day. As you’ll read, this is an accomplished open water swimmer who had a very uncharacteristic problem with breathing during the 1/2-mile swim at the event. He was unable to continue the race after completing the swim, received medical attention at the race venue, but did not immediately go to the hospital for further evaluation. He shares his story with subsequent evaluation that led to a diagnosis of exercise-induced asthma. I bring this athlete’s story to your attention simply to point out that there are many possible explanations for new breathing difficulties. In my view, breathing problems should be evaluated carefuly to determine a cause.

My Thoughts and Observations

1. Triathletes and open water swimmers should be aware of SIPE and the possibility that this condition can be lethal.

2. Symptoms of SIPE can manifest for the first time even in experienced swimmers. Symptoms may develop rapidly, be unexpected, and confuse the athlete about the cause.

3. The development of SIPE does not appear to be confined to cold water swims or only to victims who are wearing a wetsuit at the time.

4. SIPE appears to be self-limiting–that is, the symptoms will subside if the victim stops exercising and gets out of the water.

5. Because of #2, #3, and #4, athletes who experience breathing difficulties in the open water should treat the problem like a medical emergency and STOP swimming and SEEK immediate assistance. Because of the challenges of rescue in the open water, your life could depend on recognizing a problem early and getting out of the water. I would encourage affected athletes to get complete medical evaluation as soon as possible after an episode.

6. There appear to be no effects on lung function after an episode of SIPE, but repeat episodes of SIPE may occur.

7. Affected athletes have described a variety of strategies for preventing repeat episodes of SIPE. From athlete accounts, no single strategy appears to be universally successful.

8. Affected athletes should use EXTREME CAUTION in subsequent open water training and races, being hypervigilant for warning signs.

9. Event organizers and on-water rescue personnel should be familiar with SIPE. The safety plan should allow for athletes with breathing difficulties to be removed from the water as quickly as possible.

Swimming Induced Pulmonary Edema (SIPE)

April 13, 2012 By Larry Creswell, MD 36 Comments

I’ve been learning about swimming induced pulmonary edema (SIPE) and I thought I’d offer an introduction here based on my reading and conversations with experts in the field as well as affected athletes.

The problem of SIPE, or immersion pulmonary edema (IPE) as it was first known, was recognized at least as far back as the mid-1990s. Early reports in the scientific literature focused primarily on a small number of healthy scuba divers who experienced problems with unusual breathlessness (dyspnea), particularly when diving in cold water. Medical evaluation for the problem showed that the divers had low levels of oxygen in the blood (hypoxemia), often reported coughing up frothy, blood-tinged secretions, and had findings on chest x-ray that suggested pulmonary edema. In the setting of immersion in cold water, this collection of difficulties–dyspnea, hypoxemia, excess lung secretions, and pulmonary edema–became known as IPE.

Interestingly, the victims of IPE were often very experienced swimmers who had difficulties only with swimming and/or diving in cold water (~50-60 degrees Fahrenheit).

It’s worth taking a moment to review a few important facts about the anatomy and physiology of the lungs. We have two lungs, each about the size and shape of a 2-liter soda bottle. Healthy lungs are extraordinarily light and very spongy. For our discussion today, it will help to think of the lungs as sponges. The lungs are ordinarily almost colorless, but take on a pink hue because of blood that flows throughout the lung tissue.

The right ventricle of the heart pumps blood to the lungs through the pulmonary arteries which branch into smaller and smaller branches and eventually into miscrosopically small capillaries which come into contact with the air-filled spaces in the lungs. It’s here where the blood unloads carbon dioxide and picks up oxygen. The blood then flows into increasingly larger veins and eventually into the pulmonary veins that carry the blood back to the left side of the heart where it is pumped to the rest of the body.

Like I mentioned, the lungs are usually extraordinarily light. But when fluid escapes the bloodstream and collects in the spongy lung tissue outside the blood vessels, the lungs become water-logged, much the way that a sponge becomes heavy once it soaks up water. One of the consequences is that it is much more difficult for oxygen to get into the bloodstream and much more difficult for carbon dioxide to get out. We call this situation pulmonary edema.

There are many causes of pulmonary edema. The most commonly encountered cases are due to heart problems of one sort or another (eg, heart valve problems, weakness of the left ventricle), but other causes include: reactions to blood transfusion, direct injury to the lungs, infection, and perhaps various inflammatory conditions.

The exact cause of pulmonary edema with SIPE is not completely understood, but experts suspect that a combination of increased bloodflow into the lungs due to immersion combines with increased pressure in the pulmonary arteries and veins (because of exercise) to cause a leak of fluid out of the bloodstream and into the lung tissue.

It is not clear if exercise-induced pulmonary edema occurs on land.

SIPE and Triathlon

As many readers here will know, there have been a number of episodes of sudden cardiac death (SCD) in triathlons in recent years, and these episodes have occurred with a preponderance during the swim portion of triathlon events. The cause of most of these deaths appears to be typical sports-related SCD due to a sudden arrhythmia, but some have wondered if SIPE could have played a role. There have been a handful of thoughtful opinion pieces about this possibility and I’d refer you to one such article by Rudy Dressendorfer in a recent edition of Sports Medicine Bulletin, entitled “Triathlon Swim Deaths: Initial Steps Toward Prevention.” This article lays out one view on the issue. In my opinion, though, it is not at all clear that SIPE has had a role in triathlon-related swim deaths.

Charles Miller and colleagues at Texas Tech University Health Sciences Center published an interesting report in 2009 that dealt with the possibility of SIPE in triathletes. During late 2008, they distributed a questionnaire to the membership of USA Triathlon asking about athletes’ experiences with “swim-related breathing problems.” The response rate to the survey was tiny–at only 1.3%–and it’s important to remember that the low response rate might have tremendous bias with the results. Nonetheless, about 1.4% of respondents reported having a swim-related episode of “pink frothy or blood-tinged secretions” that was suggestive of pulmonary edema. Moreover, the authors identified several risk factors for this occurrence, including high blood pressure, female gender, increasing length of the swim, and use of fish oil supplements. Only a minority of reported episodes suggestive of SIPE occurred in the absence of one or more of these 4 risk factors.

I’ve heard from several triathletes about their personal experiences with SIPE and I thought I’d share their stories here.

Nathan Farrugia, an avid runner and triathlete from Malta, shares his story at his blog. He describes his experience of discovering the problem in 2009 and then learning about SIPE and eventually traveling to Duke University for detailed physiologic testing. He’s very thoughtful about the physiology of the condition and the factors that might promote SIPE while racing.

Katherine Calder-Becker, a triathlete from Montreal, wrote to me to share stories about her struggle with SIPE. You can read about her discovery of the problem, how it’s affected her triathlon racing, her visit to Duke University for testing, and her recipe for heading off the problem now at her website. In addition to her personal story, she shares useful links to additional scientific articles and press reports for those who might want to do some additional reading. Those of you with a physiology background, in particular, will enjoy reading about her visit to Duke Dive Medicine to participate in a study of athletes with SIPE.

I gather that Nathan’s and Katherine’s stories are typical. I know of other athletes who have experienced similar symptoms during open water swimming, particularly during races, who received medical attention, at the scene or the hospital, who were suspected of having pulmonary edema. Supportive care with rest and oxygen, if needed, resulted in a resolution of the symptoms. I’m not aware of any triathlon-related death where clinical or autopsy findings specifically suggested SIPE as a cause.

Athletes who have been bothered by SIPE have offered a variety of suggestions for how to avoid trouble. These are also summarized in the article by Dressendorfer:

1. Avoid overhydration on race morning (to limit the immersion-related increase in bloodflow to the lungs).

2. Become acclimated to the water conditions, and particularly the water temperature, immediately before a race with a gentle warm-up swim.

3. Avoid using a wetsuit that has a restrictive fit at the neck.

4. Think to signal and request assistance during the swim if symptoms of unusual breathlessness develop.

SIPE is an area of ongoing basic investigation. One prominent group of investigators is headed by Dr. Richard E. Moon at the Duke University Center for Hyperbaric Medicine and Environmental Physiology. This group continues to study (in human subjects) the various physiologic changes that accompany SIPE, trying to identify the causative mechanisms that are responsible. I’ve had a chance to speak with Dr. Moon recently and I’m encouraged that his team’s work will be productive in defining this condition more precisely, identifying the causes and risk factors, and suggesting ways to avoid or alleviate the problem among triathletes.

That’s what I can offer in the way of an introduction to this topic. It would be great to hear from readers who can share their experiences with SIPE so that we might all learn more about this condition.