Abstracts of current literature| Volume 12, ISSUE 3, P215, September 2001

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Respiratory effects of a single dive to 50 meters in sport divers with asymptomatic respiratory atopy

        International Journal of Sports Medicine

        Respiratory effects of a single dive to 50 meters in sport divers with asymptomatic respiratory atopy

        The threat of bronchoconstriction prevents severe asthmatics from scuba diving, but it is unknown whether individuals with asymptomatic respiratory atopy are safe to dive. Thus far, there is no definitive evidence demonstrating that individuals with asymptomatic respiratory atopy are at risk while scuba diving. As scuba diving becomes more popular, this issue will likely affect more people. The authors of this study evaluate the effects of a single wet dive on the pulmonary function of 9 sport divers with asymptomatic respiratory atopy.
        The subjects were confirmed as having asymptomatic respiratory atopy if they had a positive skin prick reaction to at least one common airborne antigen but did not experience wheezing or use bronchodilators on a regular basis. Nine healthy sport divers of similar age, height, and weight were chosen as control subjects. All subjects wore wet suits and full scuba gear. Each spent 15 minutes at a depth of 50 m in the wet compartment of a hyperbaric chamber in Germany. Timed decompression stops were made during ascent, so that the total of each dive was 32 minutes. The water temperature was held at 24°C. Pulmonary function tests were performed before the dive, 3 hours after the dive, and 24 hours after the dive. Parameters measured were specific airway conductance, forced vital capacity, forced expiratory volume in 1 second, minimum expiratory flow at 50% of vital capacity, hemoglobin concentration, and transfer factor of the lung for carbon monoxide. Methacholine challenges were performed 4 weeks after the dive.
        Results showed no significant differences in pulmonary function before the dive. After the dive, only airway conductance was significantly different between the groups. Three hours after the dive, conductance increased to 14% above baseline in the group with respiratory atopy. Twenty-four hours after the dive, conductance fell to 15% below baseline in this group. Methacholine challenges at follow-up were normal. In their discussion, the authors state that the changes in airway conductance might represent a bronchoconstrictive response. In the control group, airway conductance did not change with time. The authors speculate that these results could indicate that individuals with respiratory atopy are more susceptible to the hazards of diving than the normal population. On the other hand, since no other measure of pulmonary function changed, including expiratory flow, the authors note that their results might not be clinically significant.
        The key feature of this study is that the subjects actually performed a wet dive wearing full gear. According to the authors, this is the first study of its kind. At the same time, however, the size of the study group was very small. Larger numbers might be needed to detect subtle differences between groups. Furthermore, it is not known if the lungs of individuals with asymptomatic respiratory atopy would respond in the same manner if dives were performed at various times of the year, when different airborne antigens might be higher in concentration. A larger, longer term study will be needed to determine whether the results of this study have any clinical significance.
        (Int J Sports Med. 2001;22:85–89) K. Tetzlaff, C. M. Staschen, N. Struck, and T. S. Mutzbauer.