Diving with asthma is still a bit of a controversial issue due to insufficient research of how divers with asthma respond to dive conditions and lack of data on their dive safety. A recent study conducted by a group of researchers associated with DAN Europe contributes to current knowledge how diving may affect small airways function in divers with asthma. They conducted pulmonary function tests in 22 divers with asthma and 15 healthy control divers, before and after a single pool dive to 15 feet (5 meters). A single pool scuba dive to a depth of 15 feet may impair small airways function in divers with asthma. Among the subjects, no one experienced any symptoms, but the effect on small airways varied significantly among divers with asthma. Most showed a minimal reduction of function (3 – 10%) not seen in healthy divers, while one diver exhibited a reduction of 22-26% in FVC, FEV1 and PEF of the predive values. The latter change was significant enough to advise the diver against further diving.
It is important to notice that all divers with asthma participating in this study were previously cleared for diving and have been diving for an average of four years. They did not report any incident of asthma attack or difficulty breathing while diving although they recorded between 10 and 220 dives in the past.
Asthma manifests in various forms; provocative factors, frequency and severity of symptoms and fitness to dive should be evaluated on an individual basis. Obviously, not all people with asthma would qualify for diving. The individuals included in this study are those that passed medical evaluation. It appears that they and their physicians made a reasonable decision. The only diver who had significant changes in small airway functions somehow bypassed physical evaluation by a physician prior to diving and made his choice without a physician’s opinion.
The article is a good read for any diver or would-be diver with asthma as well as for diving physicians. It gives an overview of available literature on the topic and provides extensive discussion of factors that should be considered in the fitness evaluation process.
Post written by: Petar Denoble, MD, D.Sc.
The Dive Lab 
Any research like this done on divers who smoke?
A much bigger problem.
You mention small airways, but then state one diver had a significant reduction in FVC, FEV1 and PEF. FEF 25-75% is the small airway test. While the reduction in FVC, FEV1 and PEF are significant what did the FEF 25-75 look like?
FEF 25-75% were also decreased as follows:
“Results: Divers with asthma initially presented significantly lower values of FEV1/FVC%* (P < 0.01), FEF25 * (P < 0.01), FEF50 * (P < 0.001), FEF75 * (P < 0.01) and FEF25–75 * (P < 0.001) compared to controls. There were significant reductions in FEV1 (P < 0.01), FEV1 /FVC% (P < 0.05), FEF50 * (P < 0.01), FEF75 * (P < 0.05) and FEF25–75 * (P 0.05). Conclusions: A single, shallow, pool scuba dive to 5 metres’ depth may impair function of small airways in asthmatic divers. More studies are necessary to estimate the risks when divers with asthma practise scuba diving. PFT results should be analysed after replicated dives in deeper pools and controlled open-water conditions.”