Reprinted from Scuba Diving:::::
But the tide is slowly turning. For more than two decades, the Divers Alert Network has compiled information on divers from around the globe, many who continued diving despite disqualifying diseases. Likewise, dive doctors and scientists like those belonging to the Undersea & Hyperbaric Medical Society (UHMS) have conducted their own studies.
"When we first started devising prescriptive guidelines for who was fit to dive and who wasn't, we didn't have hard data, so all the axioms were based on theoretical risk," says Edmond Kay, M.D., a diving medical officer at Seattle's University of Washington. "We now have facts and figures." He has studied dive fitness for the past 20 years, and in that time, he has seen a lot of changes in the way medical professionals approach diving with certain conditions. "The thinking has turned from 'If you have this disease, you can't dive' to 'If you have this disease, you must be able to manage the symptoms, and then you may be fit to dive.'"
Kay helps us explain the newest approaches for managing some of the most common dive disqualifiers.
Back in the day, if you mentioned asthma to a dive instructor, you'd likely hear a firm "No, you can't dive." The disease affects those all-important diving organs, the airways, making them inflamed and susceptible to irritation. At its worst, asthma attacks tighten the muscles around your airway and constrict airflow to the point where you can barely breathe. Therein lies the risk. A number of factors inherent to diving can trigger an attack, including exercise and breathing cold and/or dry air, and an underwater attack can easily escalate to panic and drowning. Doctors theorized that this narrowing of the airways could also trap breathing gas in the lungs, which could expand before it could be exhaled during ascents, causing lung-expansion injuries. However, data presented during a 1995 international asthma symposium sponsored by UHMS showed no increased risk for lung injuries among asthmatic divers.
Diving with asthma: Anyone with severe asthma — meaning they have daily, chronic symptoms — should not dive. If your asthma is mild, intermittent and controllable, you may get clearance if you can show that you're functionally normal — that you manage it with medication to the point that exercise and typical asthma triggers don't cause an incident.
Today, DAN estimates about 4 to 5 percent of the diving population has asthma. To see if you qualify, take an airway challenge — a test where you exercise at increasing intensity on a treadmill, while a doctor measures your airflow to ensure you're stable even during vigorous exertion. You'll also need to show stability when exposed to triggers like cold, dry air, which is what you breathe from a scuba tank, Kay says.
Talk to your doctor about dive-friendly medications. Aminophylline, an older oral medication that opens air passages in the lungs, not only dilates the smooth muscles of the airways but also the arteries in the lungs, which decreases your lungs' ability to filter bubbles and increases your risk for DCS. Newer medicines, bronchodilators like Albuterol for example, can relax the airways for four to six hours and haven't been found to dilate the arteries in the lungs, Kay says.