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 autopsy 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.
