Des Gorman and Andy Veale
Introduction
The Society's workshop on asthma and diving was held as part of the 1995 Annual Scientific Meeting at Castaway Island, Fiji. The open forum component of the workshop was prefaced by a series of presentations (a single written submission was received from Dr Douglas Walker) which are published in this issue of the Journal.
Considerable consensus was apparent from these presentations. In particular, it was clear that there are few controlled data on which to base risk assessments for asthmatics who dive (let alone a consistent definition of asthma) and that some data sets (e.g. BSAC survey) were of little or no value (at the least being rich in selection bias).
Drs Fred Bove and Andy Veale agreed that what data did exist suggested that the relative risk for those asthmatics who dived was about twice that of the non-asthmatic population (not withstanding the observation that these data did not reach statistical significance) and that it was important to remember that this was in effect a doubling of a very low rate of injury and illness.
Dr Sandra Anderson described various provocation tests and in particular, exercise and hypertonic saline challenges. The most interesting aspect of her presentation was the report that regular budesonide (Pulmicort) inhalation eliminated the hyperresponsiveness in many asthmatic patients. The fitness of such a patient to dive is obviously difficult to determine. It is noteworthy in this context that the Undersea and Hyperbaric Medical Society (UHMS) has just conducted a similar workshop and it was agreed at this forum that asthmatics who are well-controlled (i.e. not responsive to exercise or salt water) on inhaled steroids are "fit for recreational diving".
The utility of provocation testing was also discussed in their presentations by Drs Cathy Meehan, Graham Simpson, Peter Chapman-Smith and Robyn Walker. Despite the differences in approach, it was clear that there was a significant false negative rate in asthmatics (and especially those on regular steroid medication). Again, it is worth mentioning the UHMS Workshop, at which there was considerable support for exercise as the primary form of provocation testing (remembering that inhalation of hypertonic saline is a "model" of exercise-induced asthma).
SPUMS policy statement on the prevalence of asthma in Australasian diving candidates
1 A history of asthma is common in diving candidates.2 The assessment of risk for a diving candidate with a history of asthma should be conducted by a medical practitioner who has had training in diving medicine (i.e. suitable for admission to the SPUMS list).
SPUMS policy on the importance of asthma in diving
1 Asthma is a potential cause of morbidity and mortality in divers. The level of risk in this context needs to be measured.2 Diving may precipitate (an) asthma (attack).3 Asthmatics may have limited exercise capacity and are at risk of shortness of breath, panic and drowning on the water surface.4 Asthmatics who dive may be a self-selected (i.e. survivor) population and hence their experience may not be representative of the risks of diving for the general asthmatic population.5 Current information (from descriptive databases) suggests that the relative risk for asthmatics who dive (compared with non-asthmatics) for a decompression illness is about 2.
SPUMS policy on the assessment of risk for a diving candidate with a history of asthma.
1 The determination of risk for diving in someone with a history of asthma requires a gradation of the severity and currency of their asthma.2 Risk stratification for someone with a history of asthma who wishes to dive will require a thorough history and examination and often lung function testing, which may include provocation testing (and especially with exercise and/or hypertonic saline). This may need to be repeated if the person elects to dive.3 Provocation testing with exercise and/or hypertonic saline (rather than with histamine and methacholine) may be more specific for asthma that is of concern in diving. The significance of a positive result is more easily understood by the diver.4 As the risk for diving in someone with a history of asthma is uncertain, permanent records should be retained as part of a SPUMS-sponsored study.
Key words
asthma, diving fitness, provocation testing, hypertonic saline.
Dr Des Gorman, FAFOM, PhD, is a consultant to the Royal New Zealand Navy and Head, Occupational Medicine, School of Medicine, The University of Auckland. His address is Private Bag 92 019, Auckland, New Zealand.
Dr Andy Veale, FRACP, is a consultant to the Royal New Zealand Navy and Auckland HealthCare. His address is 42 Omahu Road, Remeura, Auckland, New Zealand.
