ASTHMA HAS BEEN A CONTROVERSIAL SUBJECT for divers ever since diving began. The numerous queries DIVER receives on the subject usually centre on the question of fitness to dive with the condition and the safety of the various medications when diving.
Most divers, new and old, seem to have very little understanding of how a condition that causes them so little trouble on the surface can cause potentially life-threatening complications under water.

The problem
The amount of asthma in the population seems to have been rising considerably for several years. Whether this is a true increase or simply down to better diagnosis and reporting is unclear, but up to 20% of some populations have suffered, or are still suffering, from asthma.
hspace=5 Diving has become an open sport, and as the population gets progressively wetter, so the problem of asthma and diving is increasingly being challenged.
Asthma is characterised by inflammation of the airways causing excessive mucous production and increased sensitivity that can result in broncho-constriction (closing down of the airways). This varies from sufferer to sufferer, and within the same sufferer from day to day.
Many things can aggravate the condition, including cold, emotion, exercise and allergies. Mainstays of treatment for asthmatics are the blue reliever inhalers that open up the airways, and the brown (or orange) preventor steroid inhalers.
Inhaled steroids reduce inflammation in the airways, making them less reactive and more stable. They may also reduce risk of long-term lung disease.

The risks
Asthma may cause very few problems at the surface. Under water, it is the immense changes in pressure that make the condition more severe in divers. The main objections to mixing asthma with diving are:
  • Closing of the airways and increased mucous production leading to gas-trapping and the potential for pneumothorax (burst lung), pneumomediastinum and CAGE (cerebral arterial gas embolism).
  • Asthma attacks under water, leading to shortness of breath, hyper-ventilation, panic and lack of exercise tolerance.
  • Increased air density and decreased respiratory reserve that occurs with increasing depth and aggravates the pre-existing lung condition.
hspace=5 Using medication to open the airways before diving has always been regarded as unacceptable, because of the patchy distribution and penetration of the drug into the airways. Standard blue reliever puffers can often deliver to only 20% of the lung tissue. This may help the asthmatic having an attack to feel better, but leaves large parts of the lung shut down and at risk.
It is difficult to gauge exactly how much of a problem asthma is to divers. Accurate records are not always kept, causes of death are not always accurate and there have been no good-quality controlled trials over a long-enough period to spell out the actual, as opposed to the theoretical, risk.
Studies of diving incidents from Australasia in the early 1990s suggested that 9% of deaths were in asthmatics, and that in 8% it was a contributory factor. These high incidences do not seem to have been repeated elsewhere or since.
Part of the problem in going by incidences is that just because a diver was asthmatic doesnt mean that that is what caused the problem. Equally, divers who die cannot tell us if it was the asthma attack that triggered the panic attack that led to the drowning.
What seems clear is that the worry about asthma, gas-trapping and pneumothorax seems to have been overdone. There is certainly a problem, but asthmatic divers do not seem to be having excessive numbers of lung barotraumas, even with the many who dive without obtaining medical advice, and fail to declare their problem on medical assessment forms.

In the UK...
Until 1990, the rule in the UK was that if you had asthma, you didnt dive. Even grown-out-of childhood asthma was frowned on. Then a breakthrough study by Farrell and Glanville (1990) changed the way in which asthma was regarded.
Asthmatics were asked to report back and, in 12,000 dives reported by 104 respondents, there were no incidences of pneumothorax or CAGE.
It was not a comprehensive study and involved self-selected divers, but it provided a catalyst for change. The UK Sport Diving Medical Committee changed its guidelines to allow certain well-controlled asthmatics to dive under guidance and with informed consent.
The current criteria state that the asthmatic should be stable, with no cold-, emotion- or exercise-induced components to their asthma. Allergic asthma is allowed.
Full lung-function tests are under-taken, looking at the amount of air the lungs hold, how it is breathed out and the flow (flow volume loop spirometry).
Provided these are normal, divers are exercised to 80% of their predicted maximal heart rate for five minutes. Running or step tests are used.
Then, at five, 15 and 30 minutes, the flow volume loop spirometry is repeated, to find early and late dippers in lung function. To pass, initial lung function must be normal, and there must be a less-than-15% dip in the follow-up tests.
Divers are then counselled to take peak-flow readings during the diving season, and not to dive if their peak flow drops further than 10%, or if their use of the blue reliever inhaler increases.
Divers are allowed to take inhaled steroids to control their asthma, but not drugs such as long-acting relievers such as salmeterol, or oral drugs like leucotreine antagonists or theophyllines.
This cautious approach reflects the lack of knowledge and data available.
It therefore excludes more severe asthmatics who need more medication to keep their lungs stable, and with compounds that carry even less data regarding their safety in diving.
Asthmatics should not smoke (nor should anyone), as risk of lung disease and pneumothorax will be increased even without the asthma. Asthma just adds to the risks, so must be taken into account when assessing fitness to dive.
It is unclear when or if formal retesting with an exercise provocation test should be undertaken. Some doctors insist on annual checks; others examine asthmatics just after chest problems, or if the condition/medication changes.

...and abroad
Abroad, the picture is less clear. The UK probably has the most relaxed attitude to asthma and diving of any country in which regulations exist. Many countries have no regulations, some have them but do not enforce them, and in some they are openly flouted.
The travel industry often seems to be more interested in taking the money than in properly assessing and advising divers, as can be judged by some of the alarming stories that come through DIVERs Medical Q&A column.
Australasia has one of the toughest stances, requiring full evaluation by a medical specialist using provocation tests such as exercise and hypertonic saline. Even then, there seems to be a reluctance to allow asthmatics to dive.
South Africa has no sports diving regulations, but its commercial attitude is similar to that of the UK.
The Undersea Hyperbaric Medical Society in the USA concluded in 1995 that if a person with asthma has a normal breathing test before and after a provocative manoeuvre such as exercise, the risk of gas embolism or pneumothorax is low. And the European Diving Technology Committee followed the UK approach, but recommended formal evaluation by a specialist.

hspace=5 The future
The pace of change has been fairly rapid. We have gone in about 10 years from no divers diving (or at least, admitting to it) to a workable policy, and as yet the accident statistics seem to give no rise for concern. Indeed, the most common form of medical-induced fatality is the heart attack, reflecting an increasingly old diving population.
The future would seem to offer a gradual loosening of the guidelines, as more data is collected and if there is no increase in problems.
Risks were probably exaggerated in the past. Cautious, sensible guidelines have allowed mild asthmatics to enter the water in apparent safety. There has also been a shift from dictat to informed discussion with divers, so that they can accept or reject the risks.
This approach is being taken in many other medical areas, such as diabetes and diving, but does rely on the diver taking some personal responsibility, and understanding the risk factors.
I do not believe that children can understand these discussions, or that a parent, however well-meaning, can make this risk assessment on a childs behalf. I still do not see any way to allow an asthmatic child to dive for now.
And there seems to be no good reason to leap further and allow more serious asthmatics, or those on multiple medications, to dive. This view will probably change over time as data is collected and asthmatic divers push the boundaries without medical supervision.
The question remains whether the medical profession will be proved wrong and castigated for being too cautious, or be left picking up the pieces of wrecked lungs and grieving relatives.