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Diving fatality analysis.

It has been a while since I wrote about diving accidents and having treated four divers in the past month I thought the topic deserved a revisit. The last diver I treated in the hyperbaric chamber had moderate decompression sickness. He presented with symptoms of numbness in hands, mild pain in both knees and itching on both forearms. The patient was treated on U.S. Navy Dive Table 6 and released with relief of most symptoms. The diver in this case violated one of the rules for diving by not completing a "mandatory" decompression stop at the end of an extended deep dive to 120 feet. You might ask why someone would do that and I can tell you it is usually not intentional, but in this case the diver made a conscious decision to cut his decompression time in half which he felt his situation justified. He ascended in the water to his required decompression stop depth without using an anchor line because he could not find it. (The anchor line is there to lead the diver back to the dive boat, make the ascent easier to perform and keeps the diver from drifting away if there is a current). As he hung in the water at his decompression depth he realized the current was very strong and he was being pushed further away from the dive boat. He decided to "take a chance" (reducing his decompression time) in order to prevent possibly being lost at sea due to the current. It is never easy when choosing the lesser of two evils, but experienced divers must realize that decompression stops are called "mandatory" for a reason. In addition, divers must carry various signaling equipment to help dive boats (or the coast guard) find them when lost and adrift at sea. A diver has much more of a challenge when numerous issues arise during the dive and preparation is inadequate. This diver made two additional mistakes. He refused oxygen therapy when offered on the dive boat and waited five days, with symptoms, before seeking hyperbaric treatment. Successful resolution of decompression sickness decreases the longer one waits for therapy. I always recommend continuing advanced training for divers especially as they choose more complex dive experiences. The following review of dive statistics may explain why this is so important.

For an updated review of diving problems, I chose an article from the Undersea & Hyperbaric Medicine journal, November/December 2008 issue, which examined 947 diving fatalities for the time period 1992 to 2003. The research categorized data into four groupings; triggers, disabling agents, disabling injuries and cause of death (COD). A trigger is an event that occurred during the dive which "transformed" a normal dive into an emergency. A disabling agent is a hazardous behavior or circumstance and is usually associated with the trigger. The disabling injury was directly responsible for the fatality and then the actual cause of death or COD. To better understand the relationship between the categories, this article sites the following example. "A diver became entangled in a fish net, ran out of gas, suffered asphyxia and drowned. Entrapment was the trigger, insufficient gas was the disabling agent, asphyxia was the disabling injury and drowning was the COD." The purpose of analyzing this data is to identify the most frequent problems, how they might relate to each other and whether opportunities for prevention can be discovered. The analysis demonstrated that the "majority of fatalities were associated with a minority of triggers and disabling agents." Therefore if the dive industry and divers in general, focused their attention upon these few highlighted problem areas, then theoretically and hopefully, future fatalities could be reduced. The first problem the analysis identified as the most frequent trigger was "insufficient gas", which accounted for 41 % of the total fatalities. Proper gas management includes frequent checking of the air supply, bringing a sufficient amount for the planned dive and having an extra gas source(s) if required. It appears that gas management may need greater emphasis in dive training. It should be noted that an extra gas source is actually your dive buddy, but not if that buddy can not be reached or found. Better dive buddy training is another area of focus, which might make diving safer. The second most common trigger was entrapment (20%). More attention to avoidance of these causes and resolution techniques might help reduce this problem. Entrapment is always covered in advanced dive training but it receives little attention in basic "open water" certification courses. Equipment was the third most frequent problem (15%) but no single item stood out, although proper and regular maintenance of equipment is always recommended. The most common disabling agent was rapid, emergency ascent (55%). The contributing reason for this disabling agent was running out of air but that in itself does not justify a rapid ascent if other remedies are available. Improved buddy skills and alternate air sources address out of air situations and eliminate negative outcomes. Unfortunately, in 57% of these cases the assigned "buddy diver" was separated from the diver in trouble. Disabling injury was determined to be more important then COD for drawing conclusions for prevention. The top three injuries identified were; asphyxia (33%), arterial gas embolism (29%) and cardiovascular disease (26%) accounting for 88% of the total fatalities. Some of the lesser injuries were trauma (5%) and decompression sickness (2.5%). Asphyxia was associated with triggers such as insufficient gas and entrapment. Arterial gas embolism was mostly associated with rapid emergency ascent (96%). Cardiovascular (CV) disease is one issue that deserves some discussion. Most CV cases affected divers over age 40 years and they tended to have had underlying CV disease prior to diving. What is noteworthy about these cases is that 60% of the decedents had complained of dyspnea, chest pain, or feeling ill during the dive trip and 10% prior to their last dive (but they still did the dive). The Divers Alert network (DAN) highly recommends that divers over age 40 need to seriously evaluate their fitness to dive. Maintaining good health and fitness along with getting an annual medical physical exam is important. A cardiac stress test is also a good idea as we get older. Diving can expose an individual to physical and psychological stress and good health and preparation can improve one's chances for survival when problems arise. Finally, getting that last dive in before the end of the trip, even though you have chest pain, is a very bad idea

Decompression stops during diving ascents are mandatory for a reason

by Kenneth Capek, RRT, CHT, MPA


Ken Capek, RRT, CHT, MPA is Director of Respiratory Care and Hyperbaric Oxygen Therapy at Englewood Medical Center in Englewood, NJ.
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Author:Capek, Kenneth
Publication:FOCUS: Journal for Respiratory Care & Sleep Medicine
Geographic Code:1USA
Date:Sep 1, 2009
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