Dive Medicine Rebreather Fatalities Statistics show that almost always the cause is diver error BY DR. DAVID SAWATZKY
Recreational CCR – maximum pO2 1.2 ata, max depth 70 fsw (21 msw), no decompression CCR Diver – maximum depth 140 fsw (42 msw), max decompression 15 minutes CCR Normoxic Trimix – maximum depth 200 fsw (60 msw) CCR Trimix – maximum depth 300 fsw (90 msw) CCR Expedition Trimix – maximum depth 400 fsw (120 msw) CCR Cave, Wreck, etc. The first rebreather course usually requires a
minimum of eight hours in water dive time to allow the student the opportunity to unlearn some of their open circuit habits and to learn a completely new, complex set of rebreather practices. In addition, a significant amount of diving should be done between every course. Rushing into advanced diving using a rebreather is also frequently a factor in rebreather fatalities. Open circuit diving fatalities are usually caused by
heart attack, arterial gas embolism, running out of gas or environmental factors (lost, trapped, etc.).
Check, check and check again. A good rebreather diver will always be aware of his system
I
n the last column I outlined how rebreathers work. There are many brands available and more coming on the market though the basic concepts for all of them are the same. Rebreathers are complicated. There are many correct responses for the problems that can develop and it’s also true that many of the reflexes we have developed diving open circuit are inappropriate and can kill us when we are diving a rebreather. When diving open circuit you are virtually always okay if you have gas
to breathe. This stops being true when you move into technical diving where breathing your decompression gas too deep can kill you from an oxygen (O2) seizure and breathing your bottom gas for a deep trimix dive too shallow can kill you from hypoxia. When diving a rebreather the gas you are breathing can kill you if the partial pressure of oxygen in the gas is too high or too low, or if the partial pressure of carbon dioxide is too high. Experienced open circuit divers intuitively believe that as long as they have gas to breathe they are okay and as a result often forget to monitor the partial pressure of oxygen (pO2) in the breathing loop on a rebreather. This is frequently a factor in rebreather accidents. In addition, when diving open circuit (no decompression), the ultimate
response to virtually any problem is to exhale and ascend to the surface. This is not an option when you are inside a wreck or cave. As well, if you have a significant decompression obligation, ascending directly to the surface can kill you from decompression sickness (DCS). These two situations are often factors in rebreather fatalities. As a result of the above, rebreather training is quite long and
complicated. In addition, every rebreather is different and requires specific training. I am an Instructor Trainer for the Inspiration (not currently active) and a certified diver on the Megalodon and the Optima. Training is organized roughly as follows by most agencies:
52 Magazine In
technical diving you also see oxygen seizures, hypoxia and decompression sickness (DCS). When diving a rebreather you see all of the above plus too much carbon dioxide and failure of the rebreather. Let’s look at some rebreather accidents/fatalities.
What Happened An experienced closed circuit rebreather (CCR) diver made a 300 fsw (90 msw) dive with a 20-minute bottom time. Decompression proceeded normally until the diver experienced a problem during the 60 fsw (18 msw) stop. The diver ascended directly to the surface. This diver’s partner still required approximately an hour of decompression and, wisely, he stayed at depth and finished his decompression. Had he ascended, likely he would have developed serious decompression sickness from which he could have died. The diver who did ascend directly to the surface
was recovered almost immediately (unconscious) and was promptly taken to a nearby hospital equipped with a hyperbaric chamber. Unfortunately this diver (age approximately 60, grossly obese, poor physical condition) had suffered a heart attack and was never stable enough to be placed in the recompression chamber for treatment of his serious DCS. He died five hours after arriving at the hospital. During an expeditionary caving trip, a diver died while
making a solo dive deep inside the cave. No defects were found with the CCR. He was a newly diagnosed diabetic in denial and in poor control. He almost certainly lost consciousness on the dive as a result of his diabetes, and drowned. A second diabetic on the trip who was in excellent control and who had never had a problem was found unconscious at an underground camp and was revived. When the stresses of daily living
Photo: Jill Heinerth
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