This section is exclusively for physicians to provide the lastest medical information about various topics in the field of hyperbaric medicine. The current topic is "Asthma and the Sport Scuba Diver."

ASTHMA AND SPORT SCUBA DIVING

Asthma is a common medical condition affecting approximately 5 to 10% of the population. Asthmatics are encouraged by their physicians to "live a normal existence" utilizing bronchodilator medication as needed to do so. It is common for asthmatics to use inhalers and other medications prior to exercise to prevent or ameliorate symptoms. In fact asthma medications are one of only a few allowed participants in competitive events. Scuba diving is a very popular sport in the United States with over 5 million active certified divers and hundreds of thousands newly trained each year. Although asthma past or present has been considered a contraindication to scuba diving among diving and hyperbaric physicians, this position has been questioned recently.

Controversy exists regarding whether or not the scuba diver with asthma is at increased risk for sustaining a diving related injury. The possibilities include impaired exercise capacity with drowning, decompression sickness and air embolism due to increased susceptibility to pulmonary barotrauma. Scuba divers may breathe at times cold dry air at increased density while at depth. These factors coupled with emotional stress and strenuous exercise may potentially precipitate an attack of asthma. Despite these theoretical considerations, there is little objective data to support these concerns other than anecdotal case reports. The Dive Alert Network (DAN) collects records of dive accident data submitted from the United States, Canada and the Caribbean. In 3359 cases of decompression illness collected over 7 years there was no statistically significant difference in asthmatics versus non asthmatics in sustaining air gas embolism. In 1994 of 97 deaths reported by DAN in only one case was asthma even mentioned as a possible contributing factor.

In Britain, the British Sub-Aqua Club (BSAC) has allowed asthmatics to dive for years. In a survey conducted by Farrell and Glanvill 12,864 dives were logged by 104 asthmatic divers without any instance of pulmonary barotrauma. Some of the divers used inhalers regularly including the day of diving and some divers were on steroids. In this retrospective study there was no statistical difference between DCI or AGE in normal and asthmatic divers. (5,8) Unfortunately surveys and retrospective reviews have well recognized limitations and prospective data controlling for severity of asthma, pulmonary function tests, predive medication are not available.

International recommendations for diving and asthma vary widely. The UK Sports Diving Medical Committee Asthma Standard states that there is little evidence that moderate controlled asthmatics are at increased risk compared to the normal population. Only the other hand they state that cold induced asthmatics should be excluded from diving as well as asthmatics who have used a bronchodilator in the preceding 48 hours.(7) Recommendations from South Pacific Underwater Medicine Society (SPUMS) state that the relative risk for a decompression illness is about two in asthmatics compared to the normal population and recommends provocation testing with exercise and/or hypertonic saline to exclude the presence of asthma defined by abnormal responses on these tests. (3,6). The Undersea and Hyperbaric Medical Society (UHMS) held a symposium on asthma and diving in 1995.(4) They concluded that there may be an increased risk of dissolved gas decompression sickness, air gas embolism,and limited exercise capability in asthmatics compared to normal divers. Current policies may seem to be effective at reducing apparent asthma related incidents but may exclude unnecessarily many potentially safe divers and may increase the hazard for asthmatics who dive by discouraging appropriate assessment and treatment. Data are insufficient to implicate asthma as a significant risk factor for drowning, decompression illness or air gas embolism.

Until better data are available the following guidelines should be considered. It is probably safer for asthmatic divers to be clearly identified, under regular medical supervision, adequately treated and appropriately monitored rather than relegated to secrecy. A past history alone should not preclude an individual from diving. Current or chronic asthma that is well controlled as defined by normal pulmonary function at rest and exercise either on or off bronchodilator medications is probably compatible with the ability to dive safely. Prospective dive applicants should be screened for the presence of asthma by history, physical examination and screening spirometry. If there is a history compatible with asthma pulmonary function testing at rest and exercise should be performed. Divers should be required to have normal pulmonary function in order to dive. It may be reasonable to recommend that asthmatic divers use some means of pre dive bronchodilator prophylactically. In addition some assessment of pre dive pulmonary function such as peak flow determinations may be a useful guide to assessing the adequacy of asthma control. Asthmatic divers with abnormal peak flow rates at the time of anticipated dive should not do so.

DAN and other organizations should be supported in their efforts to continue to collect data on asthma and divers so that recommendations can be appropriately modified in accordance with the current scientific evidence.

Ralph Potkin, MD

1 Personal Communication, Professional Association of Dive Instructors, Santa Ana, California.

2 Davis JC,Bove AA,eds Medical Examination of Sport Scuba Divers,Medical Seminars,1986,p34.

3 Francis,TJR: Pulmonary. In Elliott D.(ed):Medical Assessment of Fitness to Dive, Proceedings of an International Conference at the Edinburgh Conference Centre,Biomedical Seminars,March,1994, pp109-111.

4 Elliott,D, Are Asthmatics Fit to Dive?Symposium, Undersea and Hyperbaric Medical Society,April, 1996.

5 Van Hoesen K,Neuman TS, Asthma and Scuba Diving, Immunology and Allergy Clinics of North America,15:917-928,1996.

6 Weiss LD,Van Meter KW,Cerebral Air Embolism in Asthmatic Scuba Divers in a Swimming Pool,Chest,107:1653-54,1995.

7 Jenkins C, Anderson SD, Wong R, Veale A,Compressed Air Diving and Respiratory Disease,Medical Journal of Australia,158:275-279,1993.

8 Farrell PJS,Glanvill P, Diving Practice of Scuba Divers with Asthma,British Medical Journal,300:166,1990.