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Scuba diving

Introduction

Every year in the United States, approximately 400,000 individuals become officially certified scuba divers (scuba = self contained underwater breathing apparatus). Additionally, nearly 1 million Americans travel out of the country each year to dive. While diving can be a pleasant and fun experience, it is wise to be prepared for potential hazards.

Malaria and insect precautions

You will need malaria prevention treatment if you will be diving in certain areas of the tropics or subtropics. Your travel medicine provider may prescribe Malarone (currently the drug of choice for diving trips of less than a few weeks), mefloquine, or doxycycline to prevent malaria. The older drug chloroquine is still effective in a few areas of Central America, the Caribbean, or the Middle East.

Although the mosquito that transmits malaria bites in the evening, daytime-biting mosquitoes also can cause diseases such as dengue fever (found in tropical regions of Africa, the Americas, Asia, the Caribbean, and the Pacific Islands) and yellow fever (found in many countries in Africa and South America). There is a vaccine available for yellow fever but none for dengue fever. You should use a waterproof insect repellent any time mosquitoes are present. For more information, see "Malaria" and "Insect Precautions."

Immunizations

Regardless of the purpose of your trip, you should have your immunization needs evaluated by a travel medicine provider well in advance of your departure date. Divers may have special immunization concerns. Typhoid vaccine may be recommended if you will be diving in potentially polluted waters. You may also be offered hepatitis A vaccine.

Other travel medicine concerns

If you will be diving in freshwater bodies, you may be at risk for schistosomiasis, caused by parasites that live in certain freshwater snails. You should also be alert to the possibilities of sunburn, hypothermia (low body temperature), motion sickness, injuries from boat propellers, and drowning.

Less common concerns include barotrauma, or problems related to pressure changes associated with being underwater; pressurized gases and the problems with breathing them at depth; and hazardous marine life, including those creatures which bite, sting, shock or poison. See "Marine Envenomation."

Barotrauma

Imagine taking a large balloon underwater with you. Because of the compressing pressure of the seawater, the deeper you go, the smaller the balloon will get. Similarly, as you ascend, the balloon will enlarge as the water pressure lessens. While you probably won't be diving with a balloon, you do have several important and similar air spaces. Inner ears, sinuses, dental fillings (with small amounts of trapped air), and the gastrointestinal tract can all be "squeezed" - even in water as shallow as 1 meter (3 feet). You should "equalize" these pressures early and often while descending. Equalization is achieved by pinching your nostrils shut, closing your mouth, and attempting to exhale. That forces air up the eustachian tubes into the middle ear air spaces. It only takes one dive to appreciate the pain and potential hazard of diving with nasal or sinus congestion.

Pulmonary barotrauma while ascending can be life threatening. Pulmonary Over-Pressurization Syndrome (POPS) occurs when divers ascend while holding their breath. Diving students are taught never to hold their breath and to "blow bubbles" while rising to the surface. Breaking these rules converts the lungs into a "balloon" (trapped air space) that will expand as you ascend. Air can be forced into the skin, chest, and abdomen. Results may be as minor as mild skin irritation or as significant as a collapsed lung. More disastrous are "air emboli" that lodge in the brain or other vital organs. Symptoms are those of acute stroke: confusion, numbness, weakness, or loss of consciousness. Treatment requires oxygen and evacuation to a hyperbaric oxygen (HBO) treatment facility.

Pressurized gases ("Nitrogen narcosis" and "The bends")

This category of diving-related injury results from breathing pressurized gas mixtures at depth. The deeper you dive, the more you are breathing principally nitrogen and oxygen. At about 30 meters (100 feet) this amount of dissolved nitrogen can make you feel "drunk." By 200 feet this "rapture of the deep" makes the dive dangerous. Be aware of your limitations and avoid excessively deep dives (more than 100 feet).

"The bends" or decompression sickness (DCS) is a much more hazardous complication of breathing pressurized gas at depth. If you rise faster than nitrogen can be ventilated back out through the lungs, nitrogen bubbles may form in your tissues. This can be prevented by never rising faster than 1 foot per second (approximately the same rate as your bubbles) and by carefully following the guidelines laid out in one of the many available sets of "dive tables."
Dive tables are recommendations (based on both calculations and actual testing) for maximum time at depth and the possible need for a decompression stop or "safety stop" on the way to the surface. If these recommendations are ignored, you may experience a variety of symptoms including rash and itching (as microscopic bubbles form in the skin), joint pain - particularly in the elbows and shoulders (hence the term "the bends"), and/or neurologic symptoms including numbness or weakness as bubbles form in the central nervous system.
The symptoms of decompression sickness usually begin 1 to 6 hours after surfacing, in contrast to the immediate onset of symptoms associated with pulmonary barotrauma/air embolism described above. Since the long-term effects of the bends on the central nervous system, even with only the mildest of symptoms, may be significant, all decompression sickness should be treated as a medical emergency. Treatment requires oxygen therapy and evacuation to a hyperbaric oxygen treatment center where you can be "dived" again to drive the dangerous bubbles back into their liquid phase.

Flying after diving

Flying ("ascending") too soon after diving carries the risk of decompression sickness. This is particularly true if you fly after diving while at high altitudes. Unfortunately, there is not much data available, so the following guidelines represent the current "best guess" suggestions for flying after diving.

Recommended surface intervals for flying after diving

  • 12 hours after a non-decompression dive
  • 24 hours after a dive requiring a decompression stop
  • 24 hours for divers who make daily, multiple, dives for several days

Divers Alert Network

Every diver should be aware of the Divers Alert Network (DAN). Based in Durham, North Carolina and founded in 1980 at Duke University Medical Center, DAN has become an international leader in dive safety. You may become a member of DAN and enjoy numerous benefits including dive accident insurance eligibility and access to emergency medical evacuation. Most domestic health insurance will not cover repatriation or treatment in an overseas hyperbaric treatment facility. DAN can be reached at (919) 684-2948 or www.diversalertnetwork.org.