Historic Contra-indication to diving
Traditionally, asthma has been thought to be an absolute contraindication to diving. The classical thought is that the asthmatic has air-trapping associated with the constrictive airway disease, bronchospasm and mucous plugging. Because of these factors -the vast majority of diving physicians felt that the risk for developing arterial gas embolisms to be great and that asthmatics should not be permitted to dive.
In the recent past, workshops have been conducted and the consensus was that asthma should no longer be considered the absolute contraindication to diving that it was previously thought to be. Instead, the potential diver must be made aware that they are facing a relative risk of an event that occurs in less than 1 in 250,000 dives. Recommendations have been developed that include the following:
1). Exercise or cold induced asthmatics should not dive.(BS-AC adds ’emotional attacks’)
2). Asthmatics requiring ‘rescue or reliever’ medication should not dive. Asthmatics on chronic maintenance bronchodilation (‘controller’) and inhaled steroids are thought to be able to dive. Recommendations vary, however, and the BS-AC recommends that asthmatics should not dive if he/she has needed a therapeutic bronchodilator in the last 48 hours or has had any other chest symptoms.They feel that the asthmatic should not need more than occasional bronchodilators, i.e. daily usage would be a disqualifying factor, but inhaled steroids/cromoglycate/nedocromil are permissible.
3). Mild to moderate asthmatics with normal screening spirometry can be considered candidates for diving. (FEV1/FVC ratio above 85% of predicted)
4). If an asthmatic has an attack, screening spirometry should be done and the individual should not dive until his airway function returns to normal.
Finally, it might be that our fears about the dangers of asthmatics diving have been overstated and that there is a sizable group of asthmatics who can dive at an acceptable level of risk.
Recommendations from Others
Here is what the UKSDMC (United Kingdom Sport Diving Medical Committee) has to say about asthmatics and diving:
“Asthma may predispose to air-trapping leading to pulmonary barotrauma and air embolism, which may be fatal. An acute asthma attack can also cause severe dyspnoea which may be hazardous or fatal during diving. These theoretical risks should be explained fully to the asthmatic diver. There is little if any evidence that the mild controlled asthmatic who follows the guidelines below is at more risk:
—Asthmatics may dive if they have allergic asthma but not if they have cold, exercise or emotion induced asthma.
—All asthmatics should be managed in accordance with British Thoracic Society Guidelines.
—Only well-controlled asthmatics may dive.
—Asthmatics should not dive if he/she has needed a therapeutic bronchodilator in the last 48 hours or has had any other chest symptoms.
Control of the Condition
The asthmatic should not need more than occasional bronchodilators, i.e. daily usage would be a disqualifying factor, but inhaled steroids/cromoglycate/nedocromil are permissible. During the diving season he/she should take twice daily peak flow measurements. A deviation of 10% from best values should exclude diving until within 10% of best values for at least 48 hours before diving.
The medical examiner should perform an exercise test such as the 18 in (43 cm) step test for three minutes, or running outside (not a bicycle ergometer) to increase the heart rate to 80% (210-age). A decrease in PEFR of 15% at three minutes post exercise should be taken as evidence of exercise induced bronchoconstriction and hence disbars. The patient should be off all bronchodilators for 24 hours before the test.
A beta-2 agonist may be taken pre-diving as a preventative but not to relieve bronchospasm at the time.”
References to asthma and diving
(From Larry “Harris” Taylor, PhD)
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