Sunday, November 20, 2005

Diving Risk

When asked about "risk" in scuba diving, one almost automatically thinks of ratios, percentages and comparisons with other activities. Various estimates are published, varying from a risk of 3% (3% of what?) estimate of causing death during a lifetime to one dive equaling certain known dangerous activities; such as 1.4 cigarettes, or 1 hour in a coal mine or eating 40 tablespoons of peanut butter. You can see the absurdity in trying to place numbers on any activity that could cause death or injury - but the insurance planners have to do this in order to apply a monetary value to their protection.

Scuba diving does not allow for accurate accounting of risk because we have only vague ideas of what numbers we should fit into any equation that we might want to use. We have incomplete figures for deaths and injuries (numerator)and absolutely no true values for how many dives are made over a period of time(denominator). This is all guesswork. Divers Alert Network makes a valiant (and intelligent) effort to do this every year in their publication, 'Report on Decompression Illness, Diving Fatalities and Project Dive Exploration: 2002 Edition', but it should be apparent that their figures are incomplete for the general diving population.

I have long thought that a more sensible approach to assessing risk to the individual would be to identify factors that increase risks and to offer some guidelines to the diver for reduction of these risks. DAN's follow-up and assessments of individual diving deaths comes the closest to offering this solution to the problem. Undercurrent Newsletter ( has long had a section on why divers die and other books and agencies use this method effectively,;e.g., Carl Edmonds book, Diving and Subaquatic Medicine.

An injured or dead diver represents a 100% statistic for that individual, and a study of "who, what, where when and why" often provides an insight into scuba risks that will not be found in any actuarial compendium. Risks arise from some identifiable hazard. A hazard is a source of danger, whether this is derived from the diver (host factors) or from external (environmental) factors. It seems to me that this can also be simplified into knowledge (training) and fitness (both physical and medical). Knowledge comes from training and experience. Types of fitness come from directed physical activity and from medical awareness of conditions dangerous to a diver under pressure.

On the positive side of the ledger (factors that decrease risk), knowledge of and sensible motivation to carry out activities that decrease risk include:
---Training and certification for the diving activity that is to be undertaken. (E.g., technical diving done by a diver who has only basic or advanced skills). In 10 years of DAN's collection of diver fatalities, uncertified divers accounted for 7.7% (70) of the fatalities and students for 5.2% (47).
---Experience. This is a factor that cannot be quantified but which obviously decreases risk. (unless it leads to repeating the same mistake over and again).
---Being physically fit requires conscious effort and motivation from the knowledge that this will be beneficial.
---Good health or the absence of conditions that are adverse to diving. The diver should have knowledge that the diver does not have disorders that lead to altered consciousness, disorders that inhibit the "natural evolution of Boyle's Law" or disorders that may lead to erratic and irresponsible behavior.
---Knowledge about the appropriate age of safe diving. Debatable, but there are many reasons why divers below 14 and above 70 should not dive.
---Knowledge of the positive effects of not smoking, using drugs and drinking alcohol
---Knowledge of the benefits of excellent, well-maintained equipment.

Negative factors increasing risks of diving include some or many of the following:
---Lack of proper (or no) certification for the dives undertaken. This includes clearing technique, ascent and deco technique. Poorly planned dives.
---Technical Diving (Inadequate knowledge for the dives undertaken) DAN's collection of diver fatalities show recreationally certified divers making a technical dive accounted for 10.4% (95) of the fatalities.
---Commercial diving (a catch 22 of having to dive for a living but knowledge that prolonged work at depth can be detrimental, a whole 'nother subject!)
--Water --currents, surges, wave action, boat traffic, overhead diving (wrecks, caves)
--Marine Life
---Buddy factor. A stranger or poorly trained buddy; buddy inadequate to rescue due age, strength or maturity. (Buddy separation occurred in 39.7% (362) of deaths and 14.4% (132) of divers were diving without a buddy).
---Equipment Malfunction. For whatever reason. This is rare.
---Air. Bad air, out of air, air never there. Happens more often than it should.
---Medical problems as outlined above (natural disease). Australian figures show that 9% of divers who die have been specifically advised by a diving medical expert or their dive instructor that they were unfit to dive. At least 25% of those who died while diving were medically unfit to dive and should not have been doing so.
---Cognizant/psychiatric problems. Diminished mentation from whatever cause. Mental illness, drugs, buccaneers.
---Age factors (see above) Knowledge and mentality to apply that information. See my web page at

Interesting information is gleaned from ten years of diving fatality epidemiology: Divers Alert Network database, 1989-1998. Figures indicate that for the 912 diving fatalities a thorough investigation usually reveals a critical error in judgment or a violation of recommended safe diving procedures. (James Caruso, MD, in Journal of the Marine Medical Society, India,)

Dr. Caruso has also noted that in the 1995 review of this data, there are several recurring themes associated with fatal recreational diving accidents. He states, "Divers with little or no experience in more challenging types of diving are disproportionately represented in the DAN diving fatality database. Common causal and contributing factors include running out of air, cardiovascular disease, and buddy separation. Emphasizing increased training and experience, identifying significant pre-existing natural disease processes, and adhering to the recommended diving safety guidelines should reduce the annual number of diving fatalities."

So it seems to boil down to knowledge and the application of that knowledge as the prime factors in risk management of diving injuries and fatalities. Of course, one cannot teach intelligence or common sense - but it would appear that our teaching agencies are all generally doing a good job in the training sphere, with the possible exception of training children.

What do you think?

References to "Risks" in Scubadoc's Diving Medicine Online