Diving + Asthma, does it mix?

[starfish365]

Sorry I just reread the original post.

yes I dive - yes I have asthma - yes I use my inhaler before a dive - usually about half hour before get ready. Haven' had any ill effects.

 

[DCROOK]

What is asthma?

Asthma is a long-term disease which can be controlled with proper treatment. Unfortunately it cannot be cured. It affects as many as 1 in 5 children and 1 in 10 adults in Australia. It is the cause of many lost school days and a lot of time off work.

People with asthma have episodes of shortness of breath which may be brought on or made worse by certain trigger factors. Shortness of breath is due to narrowing of the small airways within the lungs as a result of inflammation and muscle spasm.

How do the lungs work?

Every breath you take draws air into the windpipe or trachea. The windpipe splits into two further tubes called the bronchi, which then divide into smaller and smaller airways called bronchioles, eventually leading to small air sacs called alveoli. It is here in the alveoli that oxygen in the air passes into the bloodstream. At the same time, carbon dioxide produced in the tissues of the body moves from the blood into the air sacs and then out of the body.

What happens during an asthma attack?

Asthma is due to constriction and inflammation of the small airways . In asthma, there is a special type of inflammation which narrows the small airways and makes them 'twitchy' and very sensitive to any environmental changes. The airways also become blocked with sticky mucus, and this blockage can come on very quickly.

During an asthma attack breathing becomes harder, even at rest. There may be a cough or wheezing, which is a musical noise when you breathe. Asthma can also occur at night during sleep. Asthma can vary in severity from mild chest tightness with cough and wheeze during exertion, to a life-threatening attack of severe breathlessness requiring urgent medical attention.

What is Scuba?

Scuba means Self Contained Underwater Breathing Apparatus. Developed by Jacques Costeau, scuba has opened up a whole new world of underwater exploration, without the heavy diving gear with air pipes to the surface. In the last 20 years there has been a tremendous increase in the use of scuba equipment for recreational purposes, particularly in Australia with its unique Great Barrier Reef. Opportunities now abound for tourists to experience the beauty of the underwater environment including corals and exotic fish.

What are the dangers of scuba diving?

Many sporting activities have risks and scuba is no exception. The chance of dying while scuba diving is somewhat higher than boxing and over 40 times higher than playing football or water-skiing.

Many of the dangers are to do with pressure. A diver breathes air into his/her lungs at a pressure the same as that of the depth of water in which the diver is swimming. Pressure increases rapidly under water, and at 10 metres (30ft) depth, pressure is double that at the surface.

If the diver inhales into his/her lungs from a scuba cylinder whilst at 10 metre depth and then comes to the surface, the air in the chest expands as the air pressure falls. The expanding air will need to escape, usually through the mouth or nose, bubbling its way to the surface. If any of the air passages become closed (as can happen in asthma), the air cannot escape and will expand within the lungs, eventually causing the lung to burst. The consequences can be life threatening. Air can escape from the burst lung into the chest cavity (a condition called pneumothorax) causing breathing trouble, chest pain and sometimes death, or escape into blood vessels, carrying bubbles to the heart and brain (a condition known as air embolism), which is often fatal. These two events are known as barotrauma.

Why is scuba diving so dangerous for asthmatics?

Scuba diving is a particular risk for people with asthma. Some of the typical trigger factors of asthma are present in scuba diving. Use of any other underwater breathing system also carries the same risks.

Breathing cool dry air is very irritating to asthmatic airways. Diving gas is dry and when released through a small valve, causes a cooling effect. Thus a diver inhales a cold and dry air mixture which is potentially very dangerous for people with asthma to breathe. Heavy physical exercise such as swimming against a current with a heavy tank on the back can produce breathlessness and even exercise induced asthma. Accidental inhalation of salt or fresh water can produce coughing and a fine mist of sea water can cause the airways to narrow by direct airway irritation.

The general stress and anxiety of diving may add to the situation, setting the scene for a very serious attack of asthma. Picture the scene for a person with asthma who develops an asthma attack underwater. Using a reliever puffer is obviously out of the question. When the diver tries to return to the surface, there may be some areas of the lung which are blocked off due to closure of asthmatic airways, and the expanding air in these areas will no longer have anywhere to escape. The person with asthma is thus at much greater risk of barotrauma.

What might be the scenario?

The following example occurs all too frequently in Australian waters. Jenny Morris, a 32 year old merchant banker with otherwise mild asthma, is a very fit swimmer, who has been diving without problems for a few months. Then one day, after 20 minutes at 18 metres depth, without any warning she indicates to her diving buddy that she is having some difficulty with breathing and heads rapidly for the surface. On arrival at the surface she is breathless and confused. Within a few minutes she becomes paralysed down the left side of her body and becomes unconscious. She is taken ashore, treated fully for asthma and eventually placed in a recompression chamber to reduce the size of any air bubbles blocking the blood supply to her brain. After three days of intensive treatment, her condition deteriorates and she dies without ever having gained consciousness. At autopsy, there is a torn lung from which air has travelled through the blood via the heart to her brain. A coroner would find that she had died of air embolism and asthma.

Are people with asthma allowed to dive?

People with asthma are at risk of developing asthma at any time, but more so when trigger factors are likely to be present, as in scuba diving. The risks are now so well known that no reputable diving company would allow a known asthmatic to dive. This is one of the many reasons for insistence on a diving medical examination prior to enrolment on a diving course. Asthma is the most common reason for a person to fail a diving medical. Many people with asthma are not aware of the high risks which diving poses for them; and for such people, having these risks pointed out during a diving medical can be a life-saver. Those who attempt to conceal their asthma do so in reckless disregard not only for their own lives, but also for those who might be called upon to rescue them.

Does this mean a person with asthma can never dive?

Not always. Although the majority of people with asthma are troubled by asthma at least sometimes throughout their lives, some really do appear to grow out of it; and for them, scuba diving may be no more risky than for the general population. Most diving medical experts agree that if a person has had no symptoms or signs whatsoever of asthma for at least five years and has required absolutely no anti-asthma medication for this period, and has a normal diving medical examination including breathing tests, then they should be allowed to dive, after explanation of the risks.

Can adults with childhood asthma be sure that asthma will not recur during diving?

Although one can never be 100% sure that asthma will not recur, it is possible to undergo a hypertonic saline challenge test. This test, which can be performed in most specialist lung function laboratories, involves breathing a salt water mist from an ultrasonic nebuliser, with breathing tests to determine whether bronchial narrowing results. If it does, then the person is still susceptible to an acute asthma attack while underwater, and should not dive. A negative test provides additional reassurance that the person is unlikely to develop asthma while diving.

Is snorkel diving also dangerous for people with asthma?

Snorkel diving is much less risky for people with asthma than scuba diving. The main reason for the difference is that snorkellers do not take air in while at depth, and thus there is much less risk of bursting the lung during ascent. Common sense dictates, however, that one's asthma should be stable and controlled before snorkelling as accidental aspiration of water and exercise associated with swimming against a current can also lead to an asthma attack. Some of the best underwater videos and films have been made by divers using a snorkel, goggles and a hand-held camera.

 

[rcohn]

What is asthma?

.

A few questions.

1. Where is your medical degree from and where do you practice medicine?

2. Do you see any possibility that a diver experiencing difficulty breathing underwater (whatever the cause) and rushing to the surface, might hold his or her breath and embolize? Was that an asthma accident or a breath-holding accident?

3. Are you aware that many people with active asthma are fully controlled and never experience attacks when using their medication?

4. In your medical practice, how well are your asthma patients controlled?

5. Are you aware that their are thousands of asthmatic divers (3 to 8 percent of the diving population) apparently diving safely, as demonstrated by the statistics?

6. Have you read reports (I have) of asthmatics suffering underwater attacks and surfacing safely in a controlled manner?

6. Have you read the proceedings of the workshop on asthma and diving and noted the opinions of several asthma experts that the air trapping you describe does not occur?

7. Are you familar with the YMCA diving with asthma protocol (now adopted by SSI and others?) which resulted from their physicians studying the information on diving with asthma?

We'll eagerly await your response.

Ralph

 

[DCROOK]

Hi rchon,

I am not quite sure why you launched this public attack. I don't ever remember saying I was an expert in this field. I did say that I am trying to choose a topic for a thesis, and as this interests me, it had potential. The last post that I made was in juxtaposition with a pharmaceutical global research company, with the home office in Toronto.

Please don't take my findings as strict medical advice, only research, as I pointed out early in the thread. As such, I will not respond to any of your questions, as they are medical in nature. Your questions are interesting, and I'm sure they are factual, but the problem is they can be open to debate depending on which expert you talk to.

One thing I have found interesting though, you mentioned that 3% - 8% of the diving population has asthma. I am sure many people with asthma have been told as children that they "cannot dive" because of there disability. This would give them the urge to dive just to prove that comment wrong (human nature). In many cases, this would not be reported to instructors or dive shops. I would imagine the population that dives is most likely a lot higher then 8%, probably somewhere more around 15 - 25% (just a guess).

As I acquire more information, I will post my research. Some of it might contradict my previous posts.

 

[DCROOK]

Effects of scuba diving on Asthma

Opinions about the advisability of scuba diving by asthmatics do vary among those writing about this subject.

Nothing is really new about this topic. The bottom line is that asthmatics probably do have a slightly increased risk but the increase is small. There probably is a spectrum. Someone who only had asthma as a child and now has totally normal PFTs may well be a candidate for diving certification. Many physicians will sign for such a patient. On the other hand someone who is on a high potency steroid inhaler, a long acting beta agonist, a leukotriene controller and still is up 3 nights a week with symptoms and has PFTs that are 60% of predicted is probably not a candidate for diving. But some physicians may even argue about the last patient. One concern that is not often mentioned is panic. Even if the asthma does not cause problems panic attacks can be a problem. Another problem that is not often mentioned is sinus disease, which can also cause considerable disability.
I am conservative. Not all of my colleagues are conservative. In the end both the diving candidate and his or her physician must be comfortable and this can only be determined on a case-by-case basis with a physician participating who fully understand the issues, which should probably include an understanding of diving physiology. Dr. Weiler
Source: http://www.aaaai.org/aadmc/ate/scuba.html

 

[DCROOK]

Traditionally, asthma has been thought to be an absolute contraindication to diving. The classical thought is that the asthmatic has air trapping associated with the constrictive airway disease, bronchospasm and mucous plugging. Because of these factors -the vast majority of diving physicians feel that the risk for developing arterial gas embolisms to be great and that asthmatics should not be permitted to dive.
More recently, workshops have been conducted and the consensus felt that asthma should no longer be considered the absolute contraindication to diving that it was previously thought to be. Rather, the potential diver must be made aware that they are facing a relative risk of an event that occurs in less than 1 in 250,000 dives. They came up with some recommendations included below:
1). Exercise or cold induced asthmatics should not dive. (BS-AC adds 'emotional attacks')
2). Asthmatics requiring 'rescue or reliever' medication should not dive. Asthmatics on chronic maintenance bronchodilation ('controller') and inhaled steroids are thought to be able to dive. Recommendations vary, however, and the BS-AC recommends that asthmatics should not dive if

He/she has needed a therapeutic bronchodilator in the last 48 hours or has had any other chest symptoms. They feel that the asthmatic should not need more than occasional bronchodilators, i.e. daily usage would be a disqualifying factor, but inhaled steroids/cromoglycate/nedocromil are permissible.
3). Mild to moderate asthmatics with normal screening spirometry can be considered candidates for diving. (FEV1/FVC ratio above 85% of predicted)
4). If an asthmatic has an attack, screening spirometry should be done and the individual should not dive until his airway function returns to normal.
Finally, it would appear that our fears about the dangers of asthmatics diving have been overstated and that there is a sizable group of asthmatics that can dive at an acceptable level of risk.
*A copy of the workshop on Asthma and diving entitled "Are Asthmatics Fit to Dive?" can be obtained from the Undersea and Hyperbaric Medical Society, 10531 Metropolitan Ave., Kensington, Md. 20895. The cost is $20.00 plus $2.50 additional for postage and handling.

 

[DCROOK]

Here is what the UKSDMC (United Kingdom Sport Diving Medical Committee) has to say about asthmatics and diving:

"Asthma may predispose to air-trapping leading to pulmonary barotrauma and air embolism, which may be fatal. An acute asthma attack can also cause severe dyspnoea, which may be hazardous or fatal during diving. These theoretical risks should be explained fully to the asthmatic diver. There is little if any evidence that the mild controlled asthmatic that follows the guidelines below is at more risk:

---Asthmatics may dive if they have allergic asthma but not if they have cold, exercise or emotion induced asthma.
---All asthmatics should be managed in accordance with British Thoracic Society Guidelines.
---Only well-controlled asthmatics may dive.
---Asthmatics should not dive if he/she has needed a therapeutic bronchodilator in the last 48 hours or has had any other chest symptoms.

Control

The asthmatic should not need more than occasional bronchodilators, i.e. daily usage would be a disqualifying factor, but inhaled steroids/cromoglycate/nedocromil are permissible. During the diving season he/she should take twice daily peak flow measurements. A deviation of 10% from best values should exclude diving until within 10% of best values for at least 48 hours before diving.

The medical examiner should perform an exercise test such as the 18 in (43 cm) step test for three minutes, or running outside (not a bicycle ergometer) to increase the heart rate to 80% (210-age). A decrease in PEFR of 15% at three minutes post exercise should be taken as evidence of exercise induced bronchoconstriction and hence disbars. The patient should be off all bronchodilators for 24 hours before the test.

A beta-2 agonist may be taken pre-diving as a preventative but not to relieve bronchospasm at the time."
Source: http://www.scuba-doc.com/asthma.htm

 

[DCROOK]

Are Asthmatics Fit to Dive? By Edmond Kay, M.D.

Asthmatics as a group should not be routinely disqualified. I personally do not think any mild asthmatic should be disqualified. By the newest national guidelines, these are asthmatics that fall into the first (Mild Intermittent) and second (Mild Persistent) steps of severity. What they do need is a quantifiable, verifiable test to show that they are FUNCTIONALLY normal on medication with exercise. They also need careful counseling as to the known and theoretical risks of diving with bronchospasm. Asthmatics also must be willing to be on aggressive medication, which completely controls all symptoms and underlying inflammatory processes. The asthmatic athlete has proven in competition that maximal performance is possible and in fact, safe. My role as a physician with regard to asthma is to assess the diver's physical and psychological condition, treat the underlying airway inflammation and the resulting airway obstruction, and to teach patients the true limitations of their disease. Many divers with asthma fail to realize the most basic facts about bronchospasm. Even mild asthma is a chronic inflammatory disorder with underlying airway pathology early in the course of the disease. Helping the diver to fully understand the disease process goes hand in hand with helping them to pass the physical exam.

An international symposium was held on the subject in 1995 sponsored by the Undersea and Hyperbaric Medical Society (UHMS) in conjunction with Dr. David Elliott, OBE. of the UK. Dr Elliott's symposium was actually a consensus conference on various issues related to diving risk (theoretical vs. real). The conference proceedings are published in a book titled "Are Asthmatics Fit To Dive?" and it can be purchased from the UHMS or by calling (301) 942-2980. In a nutshell, our previous attitudes regarding Asthma were based on a theoretical risk to the diver, which was overwhelmingly negative. Now that accident reporting and data collection have improved worldwide, no greater incidence in pulmonary barotrauma has been found. This fact has put additional pressure on the American diving medical community to justify its position (prohibition of diving) with data. There isn't any. This happened to correspond with the timing of an article by Tom Neuman, MD and Fred Bove, MD on asthma (Annals of Allergy 1994; 73-Oct: 344-350). The article concludes that "...available data suggest asthmatic patients with normal airway function at rest, and with little airway reactivity in response to exercise or cold air inhalation, have a risk of pulmonary barotrauma similar to that of normal subjects."

The consensus from international experts in diving medicine is that emphasis should shift away from an exclusionary view to one that emphasizes "function". For sport divers, the position of that international group is to challenge a diver candidate with a maximal exercise test followed by PFT's (methylcholine has too many false positives). The diver is allowed to use a bronchodilator, inhaled steroid, inhaled anti-inflammatory or any of the drugs indicated for the treatment of asthma, just so long as he or she uses it all the time before exercise or diving. Bear in mind these are known asthmatics, so we just want to know if they will have bronchospasm with provocation after taking their regular medication. Of course the diver must be fit enough to take an exercise test maximal enough to induce bronchospasm (13 mets or greater).
The test should be relatively brief and maximal, and can be a treadmill or stair step protocol or even a vigorous supervised run outside (as is often done in the UK), but does not usually require EKG monitoring (unless the testing facility requires it, or the diver has cardiac risks). Remember, it is an "airway challenge" not a "cardiac challenge". Fitness has enormous significance as exercise induced asthma gets worse and sometimes first appears as an individual becomes less fit. There should be less than 15% reversible airway obstruction after the test for it to be considered negative. The diver fails the test if the reversible obstruction is greater than 20%. Between 15 and 20% the test is equivocal and the outcome of the test is not clear. Any of my diver candidates with greater than 15% obstruction have their medication "fine tuned" to improve control of bronchospasm. Then the test is repeated. No one is permanently disqualified unless they are unwilling to improve control of their airway function with more vigorous attention to medication.

The problems with this approach are obvious as diving is not only exercise but also exposure to cold, dry air, and to unexpected stressful emergencies. Is the provocation adequate to give a realistic challenge? The consensus of medical experts now says "probably yes", which is a lot better than the old "definitely no". Studies are underway to provide even more data on the subject, which should quell the fears of the doubters. If you have bothered to read through all this, you will find the book mentioned above very interesting and informative. You might even want to give it to your favorite physician if they haven't heard of it yet. As always, let me know if you have any questions.
Please be aware that the opinions expressed herein are my own. My views are not sanctioned, supported or endorsed by either the University of Washington or the Undersea and Hyperbaric Medical Society (UHMS). As an opinion based on and expressing "state of the art" scientific knowledge, it might change as more data becomes available.

Source: http://faculty.washington.edu/ekay/asthma.html

 

[DCROOK]

Diving with Asthma?

Many asthmatics want to dive, but unfortunately, there are a number of concerns about the effect of asthma on dive safety. Dive physicians have traditionally taken a very conservative approach to asthma in dive fitness assessments. Mention of the word "Asthma" and potential divers were ejected from the surgery faster than you could say, "but it wasn't serious and it's gone away now"
More recently, some dive physicians have begun to take a more liberal, informed consent approach in assessing previous or mild asthmatics for diving. Some ex-sufferers previously prevented from diving can now dive, after making an informed choice about the possible risks.

Problems with Asthma in Diving
There are three main concerns about asthma and diving:
First, asthma may make divers more likely to suffer a dive-related illness. We are all taught that the most important rule in diving is to breathe normally and to never hold your breath. If a diver ascends while holding his breath, the expanding air can damage delicate lung tissue, and air may be introduced directly into the blood, travel to the brain and cause an arterial gas embolism (AGE). There is concern that an asthmatic may suffer narrowing or blocking of small airways during a dive, and that expansion of any trapped air during ascent may lead to the same problem. There is

Also concern that use of reliever medication, such as Ventolin, prior to diving may cause the lungs to be less efficient at filtering out the venous nitrogen bubbles we all have after dives. These bubbles may then circulate through the lungs and reach arteries where they might, in theory, be more likely to contribute to the development of decompression illness.
Second, it is recognized that an asthma attack in the water may severely compromise the diver's safety by incapacitating him and causing an inability to function effectively. Indeed, it is hard to argue that difficulty breathing would not be a decided disadvantage if you were caught in a current that was sweeping you away from your boat.
Third, it is a plausible concern that diving itself could precipitate asthma. Asthma can be precipitated by the exercise associated with diving, or by the irritant effect of breathing a cold, dry gas. It is also recognized that regulators frequently leak a little salt water, and that some of this may be nebulised into a mist during breathing. This mist can irritate the airways and precipitate narrowing in vulnerable individuals.
The problem with all these very plausible concerns is that we have no idea how truly significant they are as there has been very little historic research. There is some data from retrospective surveys and these reveal many asthmatics (including active asthmatics) do dive, and that while their relative risk in diving may be more, their absolute risk remains reasonably low e.g. one survey indicated that asthmatic is twice as likely to suffer an AGE as a non-asthmatic. Sound bad? Maybe. But if the risk of AGE for a non-asthmatic is one in every 50,000 dives, then the risk for an asthmatic is one in 25,000; a clear illustration of the fact that not very much multiplied by two is still not very much.

Assessing Suitability of Asthmatics for Diving
In this day and age where people do not want to take responsibility for their own actions, the most prudent thing for a dive physician to do when an asthmatic walks into his surgery is to say "Bog off, you're unfit". This happens frequently, and who can blame the doctors?
However, while it might be defensive medicine, it is not necessarily good medicine. Indeed, such subjective pronouncements often motivate the candidate to go to another doctor and lie about having asthma.
There is now an alternative informed consent basis of assessment. Fundamentally, this means clearly and comprehensively explaining the risks of diving to the candidate, and letting him make an informed choice about whether to proceed. However, there are some important provisos. In the context of asthma, most dive physicians would agree that the more active the asthma, the greater the risk in diving. Those candidates, who suffer serious attacks, wheeze relatively often or who use reliever medications regularly, cannot be considered for diving, even on an informed consent basis, because rightly or wrongly, the risks are perceived to be too high. On the other hand, previous asthmatics and milder cases may be subject to little extra risk, and it is reasonable to let them, as intelligent adults, make up their own minds on the matter.
Every day of our lives we make decisions that inherently involve weighing risk against benefit. We choose to get on planes, we choose to play rugby, we choose to ride bicycles on busy roads, and all because we decide the benefit outweighs the risk. There is no reason diving should be any different in this regard, although dive candidates are much less well-informed about its inherent risks than they are about these other intuitively obvious risk situations. It is the dive physician's role in this setting to sufficiently educate candidates so they can make an informed choice.
A sensible approach to the asthmatic dive candidate is to first take a detailed history of his problem. The obvious active asthmatics are told they cannot dive, and the reasons are clearly explained. Asthmatics who have not experienced symptoms of asthma or have not used medication for years are usually able to dive without any special investigations.
The most problematic are mild asthmatics i.e. those candidates who wheeze once or twice a year when they have colds; or who wheeze a little in the spring when certain pollens are around, etc. With these candidates, a long discussion about the potential risks in diving implied by their asthmatic history, is usually followed with tests to check that neither exercise nor the breathing of nebulised salt water (at the same concentration as sea water) provoke airway narrowing. If these tests are negative and patients exhibit a clear understanding of the issues and wish to proceed, then we should be happy for them to dive. Unfortunately, to conduct and document this process properly is a time consuming and expensive exercise, but at least it's better than being told to "clear off" without so much as an explanation.
Source: http://www.divetheworldthailand.com/newsletter-200404-asthma-diving.htm

 

[DCROOK]

Some Statistics

Physicians are occasionally asked to certify that patients with asthma or other respiratory diseases may participate in scuba diving. Recent estimates suggest that there are 600,000 to 3,000,000 divers1 who perform as many as 30,000,000 dives each year. At least 7% of the United States population has a diagnosis of asthma,2 and some diving surveys indicate that 7% of divers consider themselves to have asthma.3
Whether there is any increased risk associated with asthma and diving is controversial. Approximately 500 to 600 cases of decompression sickness (DCS) or arterial gas embolism (AGE) are reported each year, constituting an overall risk for diving of 0.017% of 0.2%. It remains unclear whether patients with asthma or allergic disorders are overrepresented in these statistics.
Physiologic data suggest that active asthma should be an absolute contraindication to diving. Patients with asthma are at increased risk of pulmonary barotrauma and AGE, even in normal ascents without complications such as panic, out-of-air conditions, or breath holding. Airway obstruction and decreased lung compliance have been associated with AGE.4, 5 Melamed et al.6 have reviewed the physiologic consequences of diving and have discussed whether medical conditions, such as asthma, may predispose divers to have barotrauma, nitrogen narcosis, and DCS.
The complications associated with diving are related to the behavior of gases under the conditions of changing pressure during diving. Boyle's law states that at constant temperature, volume is inversely related to pressure. During ascent, gas within the lungs expands, and if a diver is unable to exhale properly, lung rupture may occur, resulting in pneumothorax, pneumomediastinum, or AGE. Barotrauma describes the injury that may result from failure to equalize internal pressures to changes in ambient pressure in a variety of organs such as the lungs, middle ear, and sinuses. With AGE, gas bubbles obstructing arteries may occlude blood flow in systemic vascular beds, resulting in a variety of consequences, the most severe of which may be neurologic or cardiovascular collapse and death. Those who survive may have severe disability.
Because of the potential severity of AGE, one authoritative source states: “Considering the potential catastrophic consequences of air embolism, it seems appropriate to recommend that asthmatics not dive.”5 This conservative view is not held by all diving authorities. In theory, patients with asthma should more frequently experience diving accidents. However, available data, although incomplete, do not confirm that asthmatic divers have more accidents.
Diving injuries associated with pneumothorax, AGE, or both occur more often for reasons other than asthma. The most common cause of lung overexpansion is a rapid or panicky ascent with breath holding. Limiting the depth of the dive would not preclude this risk, because pressure changes are greatest at more shallow depths.
A number of attempts have been made to quantify the risk of pulmonary diving injuries in patients with asthma. In a survey of divers conducted in 1988, 1745 questionnaires were distributed and 443 were returned.3 Thirty-one of the respondents reported a history of asthma. When questioned further, 19 of these asthmatic divers reported that they had made 100 dives without a case of AGE or DCS.
In 11 fatal diving accidents in New Zealand from 1981 to 1982, one subject had asthma.7 The circumstances surrounding this single accident indicate that factors other than asthma played a role. A 1985 report suggests that only one of 39 cases of AGE could be attributed to a medical predisposition.8 These limited data do not support the concept that asthmatic divers are at a significantly greater risk for AGE than the normal population.4
In a survey of divers in the United Kingdom,9 104 individuals who had performed 12,864 dives responded to a questionnaire addressed to asthmatic divers. No case of pneumothorax or AGE was reported. One diver had DCS on two occasions.
The Divers Alert Network (DAN), a national organization with headquarters at Duke University, reviewed accident data from 1987 to 1990. In 1213 cases of DCS, asthmatic divers constituted 16 of the 196 cases of AGE and 30 of the 755 cases of type II (more severe) DCS. Seven divers with AGE and 16 with type II DCS were said to have currently active asthma. A control group of 696 divers had no history of diving-related accidents. In this group, 37 subjects had a history of asthma and 13 had current symptoms of asthma with reactive airway disease. Odds ratio assessment of these data did not attribute an increased risk to asthma.10 Therefore analyses of these DAN data do not demonstrate a greater risk for diving in those who self-reported asthma.
The DAN investigators subsequently surveyed asthmatic divers by questionnaire.11 Two hundred seventy-nine questionnaires were returned, reporting 11 cases of DCS from a total of 56,334 dives. Eighty-eight percent of the individuals with asthma used medication for their reactive airway disease and 55.8% took the medication before diving. Thirty percent had asthma symptoms either daily or weekly, and 26.4% had been hospitalized at least once for treatment of asthma. These data suggest that most of the individuals returning the questionnaires had ongoing airway inflammation. The calculated risk of DCS in these divers (1 in 5100 dives) significantly exceeds previous estimated risks in recreational divers with an odds ratio of 4:16.
If we accept the premise that asthma increases risk, is an increase in risk acceptable? When does the risk become too great? At present, divers who apply to be certified, to participate in lessons, or to take additional training require physician approval. Physicians aware of the available data regarding diving and asthma may be hesitant to approve these applications. Current data are inadequate, and the interpretation of these data is an area in which there is an honest difference of opinion among asthma care providers. Until the actual degree and nature of risk associated with asthma and scuba diving are clarified further by additional studies, the final decision to certify an individual to dive remains with the asthmatic individual and his or her physician.
Additional data from larger groups are required in order to allow a reasonable judgment concerning the severity and presence of asthma and its relationship to diving risks. Although the data are reassuring, they suffer from “healthy worker” bias because asthmatic individuals with moderate to severe disease may have self-selected themselves, avoiding diving altogether. Patients with mild or asymptomatic asthma nevertheless have considerable airway inflammation, particularly in smaller airways, and the possibility exists that diving risk persists even in patients with asymptomatic asthma. It is not clear whether patients with a history of asthma who have normal pulmonary function test results and a normal measure of bronchial hyperresponsiveness (negative methacholine, histamine, cold air, or exercise challenge results) would have an increased risk for complications associated with diving. It is also unclear whether any history of asthma should preclude diving. British investigators9 suggest that diving should be prohibited within 48 hours of wheezing but do not indicate a need to monitor peak flow rates or comment regarding the degree of bronchospasm that would prohibit diving. If asthma is a risk factor for diving, an interval of 48 hours after the most recent episode of bronchospasm is insufficient time to allow normalization of airways.
The DAN, in reviewing various medically related areas and the risk of diving, states: “Ultimately, however, making the decision to accept risks involved in diving is each individual's responsibility.”14 Although, the final decision does remain with the individual who elects to dive, physicians also need to participate in this process by ensuring that patients are making an informed decision. Both patient and physician must consider the potential for serious consequences when an individual with asthma or allergic diseases participates in scuba diving.
Source: http://www2.us.elsevierhealth.com/s...earchDBfor=art&artType=fullfree&id=aai9606a00