Dr. P. J. Farrell
The theoretical reasons why asthmatics should not scuba dive are well
known. In the U.K. the British Sub-Aqua Club (BSAC) has always allowed
certain asthmatics to dive. The subjective opinion has been that we do
not see asthmatics at the hyperbaric treatment centres in the U.K. and
hence our practices work. In 1994 the reality of the situation was investigated.
Are asthmatics over-represented in our accident statistics?
To determine the prevalence of asthmatics in the U.K. diving population,
twenty five BSAC medical referees were randomly selected who determined
the total number of divers in their diving clubs and the number of asthmatics.
The data was pooled to provide the prevalence figures. Members of the
British Hyperbaric Association and Royal Navy were asked to provide the
number of cases of dysbaric illness (decompression illness and gas embolism)
treated in the period 1989 to the end of 1993 and the number of asthmatics
Out of twenty five BSAC medical referees questioned, nineteen replied.
They recorded 813 active divers of which 31 were asthmatics giving a prevalence
of 3.96%. The chambers reported 402 cases of treated dysbaric illness
in the period 1989 to 1993 of which 9 were asthmatics. Statistically chi-squared
with Yates correction was 3.607 (P > 0.5) i.e. asthmatics showed no
increase in dysbaric illness over the general population.
The 4% prevalence of asthmatics in the U.K. scuba-diving population is
interestingly similar to Bove et al.  where 2.6% of his sample dived
despite being asthmatic, in a country where asthma is considered to be
an absolute contra-indication to diving. I included all cases of decompression
illness and air embolism as one illness as many people believe that they
cannot be separated clinically in most cases. Only one of the chambers
contacted failed to record if a patient was asthmatic and so their data
are not included. However all the hospital case notes were reviewed and
asthma was not mentioned in a single medical history.
In the U.K. the National Sport Diving Medical Committee (representing
the BSAC, the Sub-Aqua Association and the Scottish Sub-Aqua Club) are
happy with the existing guidelines in allowing carefully selected asthmatics
to dive, as there is no evidence that asthmatics are more at risk of decompression
illness than the rest of the U.K. diving population.
Interestingly, Corson et al.  in their survey from "Alert Diver"
found 279 asthmatics of whom 26.4% had been hospitalized for asthma; of
these 5.8% had been hospitalised 6 times or more and they had a highly
significant increased risk of decompression illness.
The authors commented that the risk needs quantifying according to the
severity of the asthma. It is suspected that in the U.K. many of the divers
in this group would have been advised not to dive. The U.K. policy of
enabling some asthmatics to dive has allowed the exclusion of the more
severe cases of asthma. The asthmatics who are allowed to dive have been
educated as to the safest way of diving.
Interestingly, a recent paper by Neuman et al.  has come to much the
same conclusions concerning the fitness of asthmatics to dive. The medical
ban on asthmatics diving has not prevented them diving in the rest of
the world, where an unselected and uneducated group have been shown to
be at increased risk of suffering from decompression illness.
The current U.K. National Sport Diving Medical Committee is currently
reviewing the old BSAC asthma standard to bring it into line with the
British Thoracic Society Guidelines for the treatment of asthma.
- Bove, A.A. et al. Skin Diver Magazine, May 1992.
- Corson, Moon, Bennett et al. Alert Diver Magazine 1992.
- Neuman, T.S., Bove, A.A., O'Connor, R.D. & Kelsen, S.G. "Asthma
and diving" Ann. Allergy 73(1994)344-50.