[ Home ] [ Up ]

Should Asthmatics Not Scuba Dive?

This question is commonly asked in the diving community. Not surprisingly, there is no simple answer. In this chapter I will present background information on the question and offer some general recommendations. The final answer in all cases should rest with an informed patient, the patient's physician and, for open water students, the scuba instructor.

Asthma is probably the most controversial medical condition affecting recreational divers. An estimated 10% to 15% of children have some history of recurrent wheezing, and an estimated 5% to 8% of adults are diagnosed as "asthmatic." Added to these statistics are an estimated several million certified scuba divers, with several hundred thousand newly certified every year, and it is no surprise that many current and would-be divers have some history of asthma.

Asthma is a disease of the airways. Patients prone to asthma can develop intermittent attacks of cough, wheezing, chest tightness, and/or shortness of breath. These symptoms are due to narrowing of the air tubes (bronchi) within the lungs. One major cause of the narrowing is excess mucous in the airways. Because symptoms occur episodically, and often unpredictably, there is no way to know when someone with an asthma history will have an "asthma attack."

Scuba divers breathe compressed air under water, so they must have unobstructed flow of air in order to equalize air pressures. Unequal air pressures are the cause of all barotrauma, including ear and sinus squeeze, and air embolism. Since asthmatics may develop air flow obstruction in the lungs at any time, the question of when, if ever, asthmatics may safely dive is problematic. For reasons which I will discuss, there are many opinions and no uniform agreement. Quotes in the following table, taken from the medical literature, reflect this difference of opinion. Note that recommendations range from 'never' to 'not with a history of asthma over the previous five years' to 'no diving within two days of wheezing.'

WHY IS THERE A WIDE RANGE OF OPINION ON ASTHMA AND DIVING?

There are three basic explanations, which are summarized below and then discussed at length in the following pages.

• Asthma is a condition with a wide range of both the frequency and
  severity of symptoms such as wheeze and chest congestion; when used
  without precise definition or description, the term "asthma" may mean
  different things to different people.
• Despite sound theoretical objections as to why asthmatics should not
  dive, there is no solid evidence that scuba-diving asthmatics have
  an in-creased accident rate.
• There are differences in philosophy among physicians and scuba
  professionals about personal risk-taking.

1. Asthma is a disease with a wide range of frequency and severity of symptoms.
Some authors have recommended that anyone "with asthma" not go scuba diving. However, such a broad prohibition flies in the face of reality, since it includes a large group of people with a history of asthma who, in fact, dive often and without any problem.

On the other hand, any asthmatic who is constantly wheezing and coughing should obviously not scuba dive. So where should the line be drawn between remote history of asthma and active disease? It seems that most experts would draw the line at some arbitrary point, usually denoted by patient symptoms and need for medication (see quotes in table). However, none of the guidelines for deciding who should not dive is established by any studies of which I am aware; they are all "best guess" recommendations. If there is a line to draw somewhere, and I believe there is, it should be based on individual evaluation as opposed to something as arbitrary as "5 years" or "2 days" without symptoms. (In contrast to many earlier recommendations, the importance of an open mind and individual assessment are becoming increasingly recognized; see Neuman, et. al., 1994.)

To demonstrate variability of the label "asthma," I have made up 10 different scenarios for a hypothetical 30-year-old man with some history of asthma (next page). Each scenario is ranked for severity of the asthma, from 1 (least) to 10 (most). In each case the subject might legitimately check "yes" to a scuba diving questionnaire asking if he ever had asthma. If the questionnaire is for a certification course, a "yes" answer in each case would result in the requirement that the applicant obtain "medical clearance."

The consensus among dive medicine physicians would probably be to say "yes" to scenarios 1-3 (he may dive), and a clear "no" to scenarios 8-10 (he may not dive). Nos. 4-7 are problematic; most likely the percentage of diving physicians saying "no" would increase as we go from number 4 to 7. The point is that there is asthma and there is asthma. The worse the asthma, in terms of need for medication, symptoms, or degree of air flow obstruction, the riskier the diving (at least physicians perceive it this way). There can be no rule about diving that fits all asthmatics, except for the no-brainer that if you never dive you'll never have a diving accident. Ultimately the "line" for diving vs. no diving should be based on a thorough evaluation of the individual, and not on any arbitrary and unproven criteria.

2. Air trapping can lead to fatal air embolism, yet many asthmatics do dive, and without any definite evidence for increased accident rate.
The major theoretical concern is an increased risk of air embolism. This can occur if an area of the lungs traps air under water. In theory, mucous in the airways may allow air to pass by as the diver descends, but then trap the air on ascent. On ascent the trapped air will expand and could rupture the lungs, putting bubbles into the circulation. The result can be a non-fatal or fatal stroke Other theoretical asthma-related problems, all of which may lead to drowning, include:

• the possibility of asthma exacerbation from physical exertion,
  inhalation of hypertonic saline (seawater), or from breathing dry,
  compressed air (Edmunds 1991);
• increased work of breathing due to increased air density at depth;
• increased risk of heart rhythm disturbance in people using a
  bronchodilator (the most common type of asthma medication)
  (Millington 1988);

• potential of bronchodilator drug to cause enlargement of blood vessels
  in the lungs. These blood vessels normally capture small venous
  bubbles and keep them from entering the arterial circulation.
  Drug-induced dilation may allow the venous bubbles to enter the arterial
  circulation as gas emboli (Edmunds 1992, Jenkins 1993);
• increased risk to diving companions if the asthmatic gets into trouble.
  Despite all these theoretical objections, many asthmatics do
  dive, and without mishap. Information in this area is based mainly on surveys
  of active divers and retrospective compilation of accident data.

This information appears in bits and pieces in the medical literature, in Divers Alert Network's annual accident reports, and in surveys of diving asthmatics (see box). There is no statistically valid, published study that definitively answers the question heading this chapter (and there may never be). What follows is a summary of data and information relevant to the question.

A survey of responders to a British dive magazine questionnaire found that: 89 of 104 had asthma since childhood; 70 wheezed less than 12 times a year; and 22 wheezed daily (Farrell 1990). The entire group had cumulatively made 12,864 dives and not suffered any instances of pneumothorax or gas embolism; only one diver reported decompression sickness. Interestingly, 96 of the divers reported using an asthma inhaler just before diving and some were also using preventive medication such as steroids. The authors' conclusion that "the British Sub Aqua Club's recommendation to divers not to dive within 48 hours of wheezing is safe" met with strong disagreement in subsequent letters to the medical journal (Martindale 1990, Watt 1990). In a clarification, the authors of the original paper stated the word "reasonable" should have been substituted for the word "safe," and reaffirmed their recommendation (Glanvill 1990).

Of 10,422 responders to a survey in Skin Diver, 870 (8.3%) answered yes to the question "Have you ever had asthma?"; 343 (3.3%) indicated they "currently have asthma"; 276 (2.6%) stated that they dive with asthma ( Bove 1992). Diving accident experience among the asthmatics was not reported.

Of responders to a questionnaire in Alert Diver, DAN's bimonthly magazine published, 88.7% (243 divers) reported taking some medication for asthma, and 55.8% took medication just before a dive (Corson 1992). Of this group, 73 (26.4%) had a history of hospitalization for asthma. A total of 56,334 dives were reported by 279 individuals. Eleven cases of "decompression illness" (AGE or DCS) were reported in 8 individuals, or one in 5100 dives, "significantly exceeding" the estimated risk for unselected recreational divers by a factor of 4.16. The authors concluded that "the risk of decompression illness is higher in the surveyed asthmatics than in an unselected recreational diving population" (Corson 1992).

Admittedly, there are problems with reader surveys.

• Surveys presumably include only asthmatics who continue to dive
  and maintain enough interest to read scuba periodicals; as a result,
  they may under-represent asthma-related problems because they
  don't count asthmatics who quit diving (Watt 1990). However, it
  is also true that many current asthmatics choose not to admit that
  they scuba dive (Lin 1987), so by not counting all scuba-diving
  asthmatics the surveys may over-represent asthma-related problems.
• The survey data don't permit comparison of scuba diving asthmatics
  with and without accidents as to severity of asthma, level of control
  with medication, and reason for any pre-dive medication (prevention
  vs. treatment of symptoms).
• The surveys don't reveal the character of the dives, e.g., the depths
  achieved, episodes of rapid or uncontrolled ascent, and the water
  conditions.

A retrospective review to assess the risk of asthma for arterial gas embolism (AGE) and type II decompression sickness (neurologic impairment from nitrogen bubbles) was made by DAN for the four years 1987-1990 (Corson 1991).

Fifty-four out of 1213 divers reported to DAN with AGE or type II DCS had a history of asthma, of which 25 were currently asthmatic (defined as having an asthma attack within one year or taking bronchodilator therapy). For a control population, 1000 questionnaires were sent to a randomly selected group of DAN members, of which 696 were returned; 37 control divers admitted a history of asthma, of which 13 were currently asthmatic. There was no statistically significant increase in risk for type II DCS in the asthmatics. The data for AGE suggested an approximately two-fold increase in risk for asthmatics, but did not reach statistical significance (Corson 1991).

The 1994 DAN Accident Report confirmed 465 cases of decompression illness (including DCS and AGE) among North American divers during 1992 (DAN 1994). Of this group, there was a history of current asthma in eight and past asthma in 20, representing 1.7% and 4.3% of the total, respectively. Except for the comment that "two individuals were using over-the counter inhalers for asthma," no information is provided about disease severity or the role of asthma in any specific accident (DAN 1994).

Scuba diving deaths linked to asthma are infrequent. In the 1970s and 1980s the University of Rhode Island's National Underwater Accident Data Center kept dive fatality statistics on U.S. divers. Asthma was not noted as a cause of death in any of the 1183 autopsies recorded during this period (McAniff 1991). A review of scuba death reports from the early 1980s found that, whenever asthma was mentioned, there was either no explanation of the circumstances, or another, and preventable, cause of death was present, such as out-of-air-at-depth or uncontrolled ascent (Neuman 1987).

A review of 18 consecutive scuba diving fatalities at the Los Angeles Coroner's office between 1985 and 1990 found "apparent air embolism or lung barotrauma" in four patients; in none was death linked to asthma (Schanker 1991).

One autopsy report has been published of an asthmatic who died from scuba diving. She was an obese, 40-year-old diver with a history of: asthma for four years; an emergency room visit for asthma three months before her demise; using an asthma inhaler eight times a day; breathing difficulties on the day of her dive. The autopsy confirmed arterial gas embolism and asthmatic bronchitis (Marraccini 1986). (It is noteworthy that the deceased had denied respiratory problems on her written dive school application.)

DAN also keeps data on all recreational scuba diving deaths among North American residents. Ninety-six recreational scuba diving fatalities were reported for 1992 (DAN 1994). DAN's analysis found that "Cardiovascular disease is a prominent immediate cause of death...diabetes mellitus and bronchial asthma do not appear prominently in this series."

In contrast to the U.S. and British experience, asthma was found to be a contributing factor in 8% of 124 scuba diving deaths in Australia and New Zealand (Edmunds 1991, Edmunds 1992). Most of these deaths were in clinically mild asthmatics who were otherwise physically fit young men. In a number of cases the diver was returning to obtain a bronchodilator spray; in others, medication had been used immediately before the dive. Edmonds has provided several case histories of asthmatics who have died during or just after a scuba dive (Edmunds 1991, Edmunds 1992).

I cannot explain the difference in mortality data between Australia/New Zealand and the rest of the world. Certainly in England and the U.S. there appears to be no conclusive evidence for an increased accident or mortality rate among asthmatics who dive. This does not mean that diving can be considered "safe" for asthmatics; it would be a foolish reader who interprets the data this way. It only means that available information does not confirm a statistically significant increase in accidents among divers who admit to having asthma. As with diabetes, it is quite possible that asthmatics who would get into trouble scuba diving (for all the theoretical reasons listed) have 'selected' themselves out of the activity, for one reason or another.

3. Differing opinions may be based on differences in personal philosophy.
This is the third explanation for varying opinion about asthma and scuba diving. I mentioned this reason in discussing the 10 asthma scenarios; for scenarios in the middle group (4-7), the difference between saying "yes" and "no" to scuba diving may be attributable to philosophical differences over "taking risks."

Recreational scuba diving is an inherently risky activity for anyone; physicians believe that any condition characterized as "asthma" might well add some extra measure to the sport's inherent risk. But how much extra risk? No one knows, of course. Surely the answer must largely depend on the vagaries of a particular diver's asthma. But even if some precise measurement of extra risk were known, there is no agreement over what would constitute unacceptable additional risk for scuba diving.

For example, according to DAN, in the last 10 years an average of 85 Americans have died each year while engaging in recreational scuba diving (DAN 1995). There are a variety of explanations for these deaths, including diver error and stupidity, but overall the figure is an accepted fact of recreational diving; no one seeks to ban the sport because of these deaths, only to make it safer for all participants. Now, if one out of these approximately 85 scuba diving deaths per year could be blamed on asthma, would that be sufficient to ban all asthmatics from diving? Two? Three?

Similarly, there are an estimated 800 non-fatal accidents a year reported to DAN, of which about half are confirmed as DCS or AGE. Again, this is an accepted aspect of the sport and no one seeks to squelch recreational scuba diving because of its inevitable accident rate. When it comes to asthma, however, statistics are examined for some justification to recommend that asthmatics as a group not dive. But how many accidents attributable to asthma would trigger this recommendation? Fifteen? Ten? Five?

I doubt there would be any consensus in answering these questions. Instead, there would likely be more questions about the statistics. For example, some might want to know: 'Why did these divers get into trouble, and not all the other asthmatics who also dive? Was their asthma worse? Their dive profiles more extreme? Was there some pattern of behavior that could be identified and perhaps changed?'

Interpretation of statistics can be subjective, so even as more studies accumulate the issue will likely remain unsettled and argued. At the 1995 meeting of the Undersea and Hyperbaric Medical Society, two eminent dive medicine physicians took opposite sides of the debate, "Should asthmatics not dive?" Both physicians know all the literature, and have had experience treating dive accident victims. With similar knowledge and backgrounds the two physicians eloquently argued two different ways. (There was no "winner" but the emerging consensus from the 1995 UHMS meeting seems to be a more liberal attitude, as expressed in the 1994 article by Drs. Neuman and Bove.)

Future debates might focus on the methodology of the studies or the validity of the statistics, but the real argument is likely to be over something more subtle: philosophical differences in personal risk taking. Simply put, any given study on the subject may be interpreted in different ways, depending on inherent biases. As a result, for people with mild and non-limiting asthma, the answer to the question "Should asthmatics not dive?" will largely depend on who you ask.

WHAT ARE SPECIFIC RECOMMENDATIONS?

My recommendations are presented here for the recreational scuba diver and would-be diver. These recommendations, based on both the theoretical risk of AGE and the information at hand, are not to be construed as specific for any given individual.

"ACTIVE" ASTHMA.

If the asthma is "active" requiring daily or frequent medication to control symptoms I would advise against diving altogether. This is particularly true for any prednisone-dependent asthmatic. Prednisone is a corticosteroid in pill form, widely used to treat asthma symptoms.
Prednisone-dependent asthma suggests a severe degree of impairment, and would probably disqualify for diving.

On the other hand, an asthmatic who is well-controlled on an inhaled steroid (three types: beclomethasone, flunisolide, triamcinolone) is likely using the drug not to treat symptoms but to prevent them, and may be able to dive safely.

I would also classify as "active" any asthmatic with a demonstrably abnormal test of vital capacity (standard pulmonary function test, called spirometry), physical examination (wheezing) or chest x-ray. "Demonstrably abnormal" means there is no doubt as to the abnormality. This is an important qualification because sometimes changes are noted on tests which don't really reflect any significant abnormality, but instead only a normal variation. If there is any doubt or question about an abnormality, the patient should be referred to a diving medicine specialist.

For anyone classified as having "active asthma" the theoretical risks seem too great for what amounts to a purely recreational activity. Although some asthmatics do use a bronchodilator inhaler just before a dive (Farrell 1990, Lin 1987, Corson 1992) this practice is certainly not recommended by physicians. Thus there is an admitted paradox: "active" asthmatics do engage in a theoretically risky recreational activity without apparent mishap, but physicians> (myself included) are not willing to condone it. Nor are we willing to provide sanction for "active" asthmatics to begin scuba diving as a new activity.

At some point it must be acknowledged that diving is different from swimming or jogging; any asthma exacerbation under water could lead to panic and drowning. I would advise people in this group to go snorkeling instead, or take up some other water sport such as swimming, sailing or windsurfing.

"CHILDHOOD-ONLY" ASTHMA.

If someone had childhood asthma, and as an adult has had no asthma symptoms or required asthma medication, and is otherwise in good physical condition, there should be no medical restriction to scuba diving. I would not require an examination for people in this group, but if one is done it should reveal no wheezing. A breathing test and chest x-ray, if done, should be normal. While this recommendation for childhood-only asthma appears to reflect a consensus among diving-trained physicians it should be pointed out that some experts feel even remote asthma poses an unacceptable risk for diving-related barotrauma (Linaweaver 1982, Greer 1990).

"INACTIVE" ASTHMA.

The person in between the "childhood only" and "active asthma" groups presents the most difficult problem: the asthmatic who wheezes infrequently, or uses a bronchodilator or steroid medication occasionally, or who feels normal and well-controlled with routine (not-for-symptoms) inhaled medication. This might include the asthmatic with exercise-induced asthma who has learned to prevent symptoms with inhalation medication. On theoretical grounds, this person should probably not take up scuba diving, although there are no compelling data
to support this position. Patients with inactive asthma who wish to dive should have a physical exam, chest x-ray and a test of vital capacity (spirometry). As explained above, these tests should show no demonstrable abnormality.

Some physicians recommend specialized pulmonary function tests, including exercise tests and something called "inhalation challenge," which involves inhaling an asthma-provoking drug in the pulmonary function lab. Only people susceptible to asthma attacks react to this drug; the rest of the population does not. The idea with both tests is to induce a potential asthmatic to have an attack under stressful or abnormal conditions; if an attack occurs under stressful conditions in the lab, diving would then be considered too risky an activity.

That is the theory, but I don't believe these asthma-provoking tests are particularly useful for answering the question about diving. Simulation of what may happen in the water cannot be had by exercising someone on a treadmill or having them inhale a noxious agent in the lab. There are no studies showing that these "stress" tests are any more useful in answering the asthma question than are the basic tools available to all doctors: a test of vital capacity (spirometry), a careful history and a good physical examination. (Still, since the issue is unsettled either way, some doctors may choose to rely upon stress tests to reach a decision.)

WHAT IS THE INFORMED CONSENT APPROACH?

For the inactive asthmatic who wishes to take up scuba diving, I recommend an "informed consent" approach. He or she should receive an explanation of the theoretical risks. I have already explained that many people with "inactive asthma" do dive, but that doesn't mean it is safe. The would-be diver needs to understand that air flow obstruction might increase the risk of barotrauma, and that stressful conditions (cold water, strenuous activity) could trigger an asthma exacerbation. Particularly, the potential diver should understand that open water conditions are very different from the swimming pool (where scuba training initially takes place), and may lead to problems not encountered in the more benign pool environment (Martindale 1990).

Ultimately, the decision should be left up to the individual. How is this done? After the risks are explained, he or she must re-affirm their wish to dive. Then, if a note is required by the training agency, the examining physician should not sign or offer any statement that diving "is safe" for the individual, but instead write a brief note summarizing the patient's condition. The note should state that the patient's asthma history is not a prohibition to diving and that the potential diver understands the risks. Diving is inherently a risky activity anyway, so this type of informed consent makes sense. As example only, I recommend the type of note shown below.

It is important to emphasize that the physician should never approve an asthmatic for "shallow water diving only." Barotrauma is actually more apt to occur closer to the surface than in deeper water. This is because the greatest pressure changes occur near the surface. From 33 feet depth to the surface, ambient pressure decreases 100%, whereas from 66 to 33 feet the pressure decreases only 50%.

If a note is not required for the training agency, the patient might still be asked to sign such a statement to keep in the medical file. This will indicate that the physician and the patient discussed the issues, and that an informed decision was made by the patient.

Some people have criticized this approach, on the grounds that individuals referred to a doctor deserve a medical decision on whether they should or should not dive. One doctor stated, "Either you are going to take responsibility for the situation or you are not. To try and leave the decision up to the individual or agency is not only inappropriate but not serving the patient very well."

I strongly disagree with this attitude, and believe it is one reason most doctors seem reluctant to get involved in this issue. For a doctor to simply tell a patient with asymptomatic asthma that he or she can or cannot scuba dive, given all the data I have presented, implies that the physician has a crystal ball. The patient could rightly infer that "Dr. X said it is OK to dive so I assumed it was safe." This approach would place an impossible burden on the examining doctor, especially when the activity is inherently risky.

I believe this critic's comment reflects an outdated, paternalistic attitude, one that the practice of medicine has moved away from over the years. In fact, if a patient with inactive or childhood-only asthma is clueless as to the risks, seems unable to accept his or her own responsibility for diving, and has a "You're-the-doctor-tell-me-what-to-do" attitude, I would not be able to write the kind of letter shown on the previous page. Such a patient would simply not receive my sanction for scuba diving.

In summary, a patient with inactive asthma, who wishes to scuba dive, should be approached with an open mind. The theoretical risks should be explained. A physical exam, detailed medical history, and perhaps a chest x-ray and simple test of lung function (spirometry) may be all that are needed to reach a reasonable assessment; the exam and basic tests should be normal. If there are any questions regarding subtle abnormality, the applicant should be referred to a diving medicine specialist.

I realize the safest approach (for doctor and patient) might be to "just say no." However, such a dogmatic response might lead some people to seek a more favorable second opinion, or to file a new medical questionnaire with a different dive shop and omit the asthma history.

WHAT ABOUT MEDICOLEGAL CONCERNS?

Underlying any evaluation for diving fitness is concern about legal liability. The agency and scuba instructor are wary of being sued if one of their trainees has a mishap. The trainee signs all kinds of waivers, but pieces of paper don't always eliminate the possibility of lawsuit.

Doctors, of course, are always concerned about malpractice suits and protect themselves with malpractice insurance. But nobody wants to be sued; it is painful even when you are insured and have done nothing wrong. Doctors win about 80% of all malpractice cases that come to trial, but each "won" case still leaves a trail of stress, lost work time, and a demoralized feeling.

Even when a doctor is named in a lawsuit from which he or she is eventually dropped (50 out of every 100 initial claims are dropped with no further action), the whole process takes from one to three years and costs thousands of dollars. Until the suit is dropped against the doctor, he or she must report the existence and nature of the lawsuit on every professional application, such as for hospital staff privileges, renewal of existing privileges, licensure renewal, etc. For the sloppy lawyer who files a meritless lawsuit, there is no penalty.

Understandably, some doctors figure it is not worth "taking a chance" on a lawsuit by passing judgment on a patient for scuba diving. Other doctors feel that "just saying no" is the safest route, since that stance surely eliminates any legal risk. This is unfortunate, because the risk in most cases should be with an informed diver, not with the training agency or the doctor.

Surely, if the training agency lies to the trainee, or the doctor gives false assurances, that might be actionable. Such is rarely, if ever, the case. Agencies are explicit in explaining to trainees the potential hazards of scuba diving, and all trainees sign informed consent waivers of one sort or another. Physicians certainly have nothing to gain monetarily or otherwise by inducing someone to dive.

This is not to say that concern about liability is misplaced. Even if the doctor does his or her best to fully inform about the risks, an accident is an accident, and an enterprising lawyer will look for someone to blame (except the diver, of course). So medicolegal concerns are real and something we all have to live with. For the doctor, there are three options: stay out of the arena altogether; say "no" without performing a thorough evaluation; or evaluate and fully inform the patient about the potential risks (preferably in a face to face meeting, with clear documentation about the communication). For the potential diver, I believe there is only one option: become fully informed about the risks of diving, not dive when ill or unfit, and strive to make every dive as safe as possible.

REFERENCES AND BIBLIOGRAPHY

Quoted sources and general references are listed by section or sections, in alphabetical order. An asterisk indicates references that are especially recommended. Medical textbooks and journal articles can be obtained from most public libraries via inter-library loan.

Bove AA, Neuman T, Kelsen S, Gleason W. Observations on asthma in the
recreational diving population. (Abstract). Undersea Biomedical Research
1992;19(Suppl.):18.

Butler BD, Hills AB. Transpulmonary passage of venous air emboli. J Appl
Physiol 1985; 59:543-47.

Corson KS, Dovenbarger JA, Moon RE, Bennett PB. Risk assessment of
asthma for decompression illness. (Abstract). Undersea Biomed Research
1991;18 (Suppl.):16-17.

Corson KS, Moon RE, Nealen ML, Dovenbarger JA, Bennett PB. A survey of
diving asthmatics. (Abstract).

Undersea Biomed Research 1992;19
(Suppl.):18-19.

DAN 1992. Fitness for Diving. Divers Alert Network, Duke University, 1992.

Davis JC, Bove AA, Struhl TR. Medical Examination of Sport Scuba Divers,
2nd edition, 1986. San Antonio, Tx: Medical Seminars, Inc.

Denison D. Disorders associated with diving, in Murray JF, Nadel JA, eds.,
Textbook of Respiratory Medicine, W.B. Saunders Co., Philadelphia, 1988.

Divers Alert Network 1992 Report on Diving Accidents & Fatalities. Divers
Alert Network, Box 3823, Duke University Medical Center, Durham, NC
27710; 1994.

Edmonds C. Asthma and diving. SPUMS Journal 1991;21:70-74.

Edmonds C, McKenzie B, Thomas R. Diving Medicine for Scuba Divers. J.L.
Publications, Melbourne, 1992.

Edmonds C, Lowry L, Pennefather J. Diving and Subaquatic Medicine.
Butterworth Heinemann, Oxford, 1992.

Farrell PJS, Glanvill P. Diving practices of scuba divers with asthma.
Brit Med J 1990; 300:166.

Glanvill P, Farrell PJS. Scuba divers with asthma. (Letter).
Brit Med J 1990;300:609-10.

Greer HD. Neurological Consequences of Diving. Chapter 19 in:
Bove AA, Davis JC, eds. Diving Medicine, 2nd Edition. W.B. Saunders Co., Philadelphia, 1990.

Harrison LJ. Asthma and diving. Florida Med J 1991;78:431-33.

Melamed Y, Shupak A, Bitterman H. Medical problems asso-ciated with underwater diving.
New Engl J Med 1992;326;30-5.

Hickey DD. Outline of medical standards for divers.
Undersea Biomed Res 1984;11:407-32.

Jenkins C, Anderson SD, Wong R, Veale A. Compressed air diving and respiratory disease.
Med J Austr 1993;158:275-79.

Lin LY. Scuba divers with disabilities challenge medical protocols and ethics.
The Physician and Sports Medicine 1987;15:224-35.

Linaweaver PG, Jr. Asthma and diving do not mix.
Pressure, June 1982, pages 6-7.

Linaweaver PG, Vorosmarti J. Fitness to Dive. Thirty-fourth Undersea and
Hyperbaric Medical Society Workshop, May 1987.
UHMS, 9650 Rockville Pike, Bethesda, Maryland 20814.

Linaweaver PG, Bove AA. Physical examination of divers. Chapter 25 in:
Bove AA, Davis JC; Diving Medicine, 2nd Edition, W.B. Saunders Co., Philadelphia, 1990.

Marraccini JV, Friedman PL. Scuba death due to asthmatic bronchitis, air embolism, and drowning.
Forensic Pathology No. FP 86-6 (FP-149)
1986;28:1-4.

Martin L. The medical problems of underwater diving. (Letter). New Engl J
Med 1992;326: 1497.

Martindale JJ. Scuba divers with asthma. (Letter). Brit Med J 1990;300:609.

McAniff JJ. United States Underwater Diving Fatality Statistics, 1989. Report
No. URI-SSR-91-22.
University of Rhode Island, National Underwater
Accident Data Center, 1991.

Mellem H. Emhjellen S, Horgen O. Pulmonary barotrauma and arterial gas
embolism caused by an emphysematous bulla in a SCUBA diver.
Aviat Space Environ Med 1990:61:559-62.

Millington JT. Physical standards for scuba divers.
J Am Board Fam Pract 1988;1:194-200.

Neuman T. Pulmonary Considerations I, in Linaweaver PG, Vorosmarti J. Fitness to Dive.
Thirty-fourth Undersea and Hyperbaric Medical Society Workshop, May 1987.

Undersea & Hyperbaric Medical Society, 10531
Metropolitan Ave., Kensington, MD 20895.

Neuman TS, Moon RE. Are people with asthma fit to dive?
Pressure, November/December 1991, page 3.

Neuman TS. Pulmonary Disorders in Diving. Chapter 20 in:
Bove AA, Davis JC; Diving Medicine, 2nd Edition, W.B. Saunders Co., Philadelphia, 1990.

Neuman TS, Bove AA, O'Connor RD, Kelsen SG. Asthma and Diving.
Annals Allergy, 1994;73:349.

Schanker H, Spector S. Relationship between asthma and scuba diving
mortality. (Abstract).
J Allerg Clin Immunol 1991;81:313.

Smith TF. The medical problems of underwater diving. (Letter).
New Engl J
Med 1992; 326,1497-8.

Strauss RH. State of the art: Diving medicine.
Am Rev Resp Dis 1979;119:1001-23.

Watt SJ, Gunnyeon WJ. Scuba divers with asthma. (Letter).
Brit Med J 1990;300:609.