Thursday, September 3, 2009

Hyperbaric files: diving accidents.(HYPERBARIC MEDICINE).

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Scuba Diving is a safe sport. As with any activity, it is safe as long as you are knowledgeable about the diving process and the potential problems that can occur. This translates into proper training, certifications, continued education with practice and properly maintained equipment. Although accidents and deaths do occur, their frequency is minimal compared to the number of dives made each year throughout the world. According to the Divers Alert Network (DAN), serious injuries and deaths are rare today. Those that are seen tend to be associated with "unsafe behavior or hazardous conditions, although some may occur without apparent cause". DAN is a nonprofit organization based at Duke University Medical Center in Durham, North Carolina. The mission statement for DAN is to "help divers in need of emergency assistance and promote diving safety through research, education, products and services". They operate a 24-hour emergency phone service to provide medical advice for dive injuries that can occur anywhere on the globe. Under the heading of research and education, DAN collects data regarding dive injuries from treating hyperbaric facilities. From this data they publish the "Annual Report on Decompression Illness, Diving Fatalities and Project Dive Exploration". The 2004 edition, based on 2002 statistics, recorded just over 1,000 accidents and 89 fatalities in the United States and Canada for that year.

Most accidents occurred to divers with five or less years experience (46%) and to divers with over 10 years experience (34%). We can easily understand new diver injuries due to inexperience but the more experienced divers were surprising. Did these divers tend to do more dangerous dives or were they more complacent in regard to practicing basic safety procedures? Another factor would be the number of dives they actual did each year to stay proficient. Over 50% of the accidents occurred to divers with less than 20 dives in the previous year. Many factors can contribute to accidents and fatalities. Some divers like the excitement of risk and may dive beyond their training and abilities. There are others who may not be able to effectively manage stressful situations, which can arise without warning. Divers who are in poor cardiopulmonary condition pose an additional risk. Although the number one cause of death associated with diving is drowning, cardiovascular disease was found in 30% of the cases. DAN recommends a cardiac stress test for divers over the age of 50 a fast growing segment of the dive community. There are also special categories of diving, which require special training to ensure safety. These would include deep decompression diving, wreck diving, cave diving, night diving, and so on.

Dive equipment problems were associated with 50% of the injuries. In this equipment category, the buoyancy compensator (air-filled vest) was reported as most problematic followed by the breathing regulator. Accidents in this category may not only be the result of equipment failure but also the failure of the diver to properly respond when the problem arises. A rapid ascent to the surface was the result of these equipment problems 25% of the time. Two of the most notable problems associated with rapid ascents while diving are; decompression sickness (the bends) and air embolism. Fortunately, they have a low occurrence rate of 3-6% per 10,000 dives, but may require hyperbaric treatment.

Decompression sickness (DCS) is caused by nitrogen gas in the body bubbling out of solution in the blood and tissues resulting in joint pain, paralysis and possibly death. This can occur when a diver ascends to the surface too quickly or after too long a period underwater. For divers who do experience decompression sickness, symptoms typically occur within an hour of the their last dive up to about 24 hours. Surprisingly there is a spike in the statistics under the heading of "symptoms seen just prior to their last dive", which accounted for 14% of the cases. These divers were either not aware of the signs for DCS or were in denial long enough to finish their dive vacation. For 6% of the cases, DCS occurred during or after their flight home from the dive location. This can occur if the diver does not wait 18-24 hours before flying after their last dive since air flight altitude can bring on DCS. The treatment for decompression sickness is immediate administration of 100% oxygen. If symptoms are serious or persist, hyperbaric oxygen is indicated. An air embolism can occur when air leaks into the blood and tissues from a pressure-caused injury. An example of this can be seen when someone holds his breath ascending to the surface; as pressure decreases (upon ascent), volumes increase (in your lungs).

This is a classic example of Boyle's law. The volume of air in your lungs will actually DOUBLE with an ascent of only 33 feet. For more detailed information about decompression sickness and air embolism see the summer 2004 issue of Focus.

Here are some non-hyperbaric treated types of injuries, which I place in three categories; boats and tanks, the marine environment and the diving process.

Boats and tanks: If you have ever been on a rocking boat you can imagine how easy it is get hurt especially in bad weather. I've seen divers take nasty falls while putting on their wet suits or just walking on wet boat decks. The air cylinders divers breathe from weigh on average of 40-50 pounds and some divers wear more than one cylinder. Then there are weight belts and other assorted equipment. Dropping heavy gear on a bare foot is a very unpleasant experience. The most dangerous and somewhat scary moment for me is when the dive is finished, and I have to get back on the boat. Imagine hanging onto a ladder in the water with one hand and removing your fins with the other. Now picture the boat swaying and bouncing up and down due to 2-3 foot swells. Actually many dives are cancelled due to 3 foot or higher wave conditions. Lastly of course, we can't discuss boats without mentioning motion sickness. Thanks to drugs (Dramamine) and smart eating strategies, most off us can be spared this gut wrenching experience.

The marine environment: Abrasions, contusions, puncture wounds and lacerations are all possibilities when swimming around coral reefs. This environment also has coral and creatures that can inject venom into a wound by means of nematocysts (stinging capsules) along with some nasty bacteria. Jellyfish can sting you and sea urchins can puncture you. Stingrays can inflict a serious wound if stepped on. While vacationing on Sanibel Island in Florida I was told to shuffle my feet when entering the water, to prevent upsetting a stingray. I never got comfortable with that. There are also fish that have spines capable of injecting venom. The lionfish also called the zebra fish is absolutely beautiful but can become a painful experience if stung. Stonefish, blue ring octopus, cone shells and sea snakes can cause paralysis and death with their sting or bite. Just when you thought it was safe to get back in the water, we finally have barracuda and sharks. Diving with these guys is usually not a problem although very large, sharp teeth are unnerving.

The Diving process: Prolonged and frequent exposure to water in your ears could cause an external ear infection called otitis externa, also known as swimmers ear. Antibiotic eardrops can cure this but it may be prevented with use of a vinegar and alcohol solution placed in your ears to keep them dry after swimming. A "squeeze" is a problem that can affect the ears, or any air-filled space, when pressure changes the volume of air in that space without a way to evacuate it. This is experienced when the eustachian tubes, which allow inner ear equalization, are blocked by congestion or if proper equalization is not performed while diving. The result is pain in the ears and possible rupture of the eardrum if not addressed. In most cases this problem is prevented by equalizing pressure using a valsava maneuver (exhale against a closed mouth and nose) or use of a decongestant. Another issue for divers today is oxygen toxicity, which I wrote about in the last issue of Focus. This has entered the diving arena due to the use of specialty gas mixtures with oxygen percentages above 21%. At various depths these changes in oxygen percent can have serious side effects on a diver. The worse side effect, acute oxygen toxicity, can result in a seizure, which is life threatening when underwater. When diving to depths typically beyond 100 feet, a phenomenon called nitrogen narcosis can occur. Nitrogen at higher levels in the body due to depth can produce an analgesic effect on a diver that is similar to alcohol intoxication (also called the martini effect). This effect varies by individual but it can impair judgment and coordination, which is most significant if trying to manage an emergency situation. The treatment is to ascend to a shallower depth until symptoms clear. I went to a photo presentation by an underwater photographer who showed a us a picture he took of a nameplate on a sunken tugboat. He said his buddy insisted they surface while he was shooting the picture. He asked his buddy once back on the surface why he stopped him from taking that picture. His buddy said, "because you were taking that same shot for 10 minutes".

In summary, despite everything you just read, scuba diving is safe sport. Many accidents that occur can be prevented with good training, good health and ongoing practice. In addition, proper equipment and maintenance and a careful conservative approach to diving will keep you safely diving for a long time.

by Kenneth Capek RRT, CHT, MPA

Source Citation:Capek, Kenneth. "Hyperbaric files: diving accidents." FOCUS: Journal for Respiratory Care & Sleep Medicine (Fall 2005): 50(3). General OneFile. Gale. Alachua County Library District. 3 Sept. 2009

Gale Document Number:A139854059

Disclaimer:This information is not a tool for self-diagnosis or a substitute for professional care.

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