A rebreather diver developed IPE symptoms at 291 fsw (87 msw) and managed to complete her decompression obligation. (2012, USA)
Reported Story
Dive gear: Commercially available rebreather; diluent 10/50; set point 1.2; bailouts 15/50 and 50/10
Reported conditions prior to dive: 86°F (30°C) to thermocline at 200 fsw (61 msw), 52°F (11°C) at bottom
Profile: 291 fsw (97 msw)/81 minutes, completed decompression obligation + 10 min.
With the reported cold conditions at the bottom, I borrowed a 5mm wetsuit and hood, as all I had was a 3mm wetsuit and hood. My buddy wore a drysuit.
The descent was uneventful. I noted the thermocline at 186 fsw (57 msw). It continued to get colder as we descended, reaching a low of 52ºF (11°C) at the bottom. Our plan was to swim along the bottom until we got too cold and then ascend. After a few minutes at depth, I had a tickle in my throat and coughed a few times. I continued to cough a bit every 30 seconds or so, and after about 10 minutes at depth I felt like I was working hard and breathing hard while diving. (I’m an excellent swimmer and endurance triathlete, so this is not normal for me.) I was getting really cold and signaled my buddy to ascend.
During the ascent, somewhere around 200 fsw (61 msw), I noticed a “gurgle” in my breathing. It felt like I was gargling water right behind the top of my breastbone, below my Adams’ apple. I continued coughing and gurgling, which was not normal. I had 52 minutes of decompression remaining at that point. I decided that I would simply focus on staying on the loop, exercising as little as possible, to get as far through deco as I could.
As we got to the first deco stops in the 90 fsw (27 msw) range, we were back in the warm 86°F (30°C) water. My buddy pulled back the hood from his drysuit to cool off. Since I was still coughing, he pointed at my throat, and I nodded, yes, still coughing.
Around 70 fsw (21 msw), I was having a hard time breathing over the gurgling and was very hot, so I wanted to take off the hood. It was too complicated, and I ended up cutting it off by scissors. I was a bit better off without the hood, and I focused on my breathing and maintaining buoyancy so that I wouldn’t stress my lungs with exercise.
At 30 fsw (9 msw), I realized that my buddy didn’t know I was in trouble. I took the slate and wrote that I was “badly bent” (I wasn’t bent, and I knew that I wasn’t bent, but writing “immersion pulmonary edema” was beyond me at that point) and asked him to deploy the yellow surface marker buoy, which he did with alacrity.
The boat rapidly came to us as is our emergency protocol, and the safety diver entered the water with an open-circuit tank of O2. She offered it to me and was going to clip it to me, but I waved her off and wrote on the slate: “No exercise, can’t breathe.” I was quite worried that the O2 bottle would compromise my buoyancy, and I would need to swim. The safety diver clipped the O2 bottle to my buddy and swam back to the boat to report in.
We completed decompression with me coughing and gurgling as I breathed. My buddy’s computer is more conservative, so for me it was deco cleared plus 10 minutes.
On the live boat pickup, the captain placed the boat where I didn’t have to swim at all, and the safety diver removed my bail-out bottles and fins in the water. As soon as I was on deck, many hands removed my rebreather and wetsuit, and I got started breathing 100 percent O2. The improvement on O2 while we steamed the several miles to dock was very good — the coughing slowed down, and the gurgling was only in the bottom of my lungs, not so much at the top. The ambulance was at the dock when we got there. The local hospital took X-rays and confirmed pulmonary edema; they kept me overnight for observation and released me next morning.
The outcome is good, with good health and no lingering issues.
Comment
The diver was experienced but improperly prepared for the thermal stress of the dive. The equipment improvisation may or may not have contributed to the event, but fit issues did add some discomfort as evidenced by actions taken during ascent. The diver was generally cool-headed and exercised good judgment in what would undoubtedly be a stressful situation. With the support of her buddy, she likely avoided a much more complicated outcome that would have arisen following an abbreviated or aborted decompression.
The key weakness in this case was likely communication, with contradictory messages leading to confusion for both the buddy and the surface team. Expecting some degree of confusion in any evolving case, the need for clear, ongoing and flexible communication is clear. Divers often focus on decompression stress, but it is important to remember that a variety of problems may arise.
Immersion pulmonary edema likely results from a combined effect of increased central blood volume and increased work of breathing. Central blood volume is increased by immersion, cold stress and possibly high levels of fluid intake. Work of breathing is increased by the breathing circuit, body position, gas density and physical exercise and stress. Problems are more likely to arise when multiple factors, possibly each modest individually, act together.
Anyone with a history of immersion pulmonary edema is encouraged to contact Dr. Richard Moon of Duke University to see if participation in a laboratory study of the effects is appropriate. The knowledge gained may be useful both on an individual basis and for the wider diving community.
To learn more, read this article.
Neal W. Pollock, Ph.D.