There Are Dives . . .

In the former, it is surprising that some divers sur¬vive. This is because of extreme depth, absurd diving times or hostile surroundings. Indeed, there are subjects who dive to more than 200 meters, for more than 12 hours, inside dark caves, carrying lots of ironware. And paradoxically, while surfacing, they do not feel relief that they are still alive, but they are already planning the next dive, even deeper, even longer, always challenging.

In the latter, it is surprising that a diver dies: The water is warm and clean, the body is healthy and the technical equipment works fine. But something happens and things go so badly that the diver will not have any opportunity to work out the lesson. Death comes.

In fact, the fatality rate in recreational diving is half of the death rate from injuries in the general population, and is similar to the death rate due to heart attack while jogging. lf one accepts this risk, it means that ...every day somewhere in the world, underwater deaths will always be with us. This is due to the fatal combination of ruth¬less numbers and general truth, described by the British mathematician Augustus De Morgan who, in 1866, wrote: "Whatever can happen, will happen if we make trials enough." This adage, often later referred to as "Murphy's Law," essentially states, "Anything that can go wrong, will go wrong."

What we can do later, after the post-mortem exam¬ination of the diver's corpse, is the analysis of factors involved in the accident. And there is the root cause analysis, which is a useful tool for decoding the chain of death sequence. This method identifies the sequence of events preceding an untoward outcome. The first link in the chain is the "trigger" or "the earliest identifiable event that appears to transform an unremarkable dive into an emergency." The second step, linked with the trigger, is the "disabling agent," a "hazardous behavior or circumstance that was temporally or logically associated with the trigger and perhaps caused the event" Both links -- trigger and disabling agent -- are the last steps before the fall. If a diver will not take corrective measures, he/she can progress into the horror of an accident, when the window of opportunity for survival shrinks rapidly. The "disabling injury" comes at this point, the step "directly responsible for death or for incapac¬itation followed by death due to drowning." The final step, "cause of death," is "specified by the medical examiner."

The method of root cause analysis has been used successfully for investigation of accidents on dry land, and it was introduced in diving in 2008 by a team led by Petar DeNoble, director of medical research at Divers Alert Network. Using this method, the group analyzed 351 diving fatalities observed over 34 years (1972-2005) in a paper presented in the journal Underwater and Hyperbaric Medicine. More than one-third of the triggers were related to equipment or gas supply (each accounting for 18 percent of accidents), and almost 50 percent of the cases were covered by gas supply or ascent-related disabling agents. Those findings strongly support the "first rule of safe diving": Never dive alone.

While there are some exceptions to this rule, the golden truth is still valid: Always have spare air (particularly on a buddy), and do not treat escape to the surface as an emergency exit. Try to solve the problem with your buddy while underwater.

Jacek Kot, M.D., is the international editor of the journal Underwater and Hyperbaric Medicine, and a professor at the National Center for Hyperbaric Medicine, Medical University of Gdansk, Poland. This editorial, which Undercurrent has shortened, appeared in Underwater and Hyperbaric Medicine, vol 40, no.1. In future issues, we will report on the analysis of diver deaths referred to by Kot.