There are specific reccommendations available about asthma and diving published by the Undersea and Hyperbaric Medical Society. They are summarized as:
1). Exercise or cold induced asthmatics should not dive
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.
3) Mild to moderate asthmatics with normal screening spirometry can be considered candidates for diving.
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.
It really is a decision that needs to be made between each indivudal patient and a QUALIFIED physician.
For anyone else reading in the Northeast Ohio area looking for physicians specializing in dive medicine, there are two hyperbaric chambers in that area. The chamber than can handle multiple patients is at Cleveland Clinic Huron Road Hospital in East Cleveland. In downtown Cleveland, St. Vincent's Charity Hospital has a single patient hyperbaric chamber. Both of these hospitals have physicians specializing in dive medicine. For those in other areas, the list of hyperbaric chambers and the physicians running those chambers can be found at:
http://www.scuba-doc.com/listchmbr.htm