What is Cystic Fibrosis?
Cystic fibrosis or ‘mucoviscidosis’ is an inherited condition where there is considerable thickening of the mucous production of the body in several places but with effects occurring mainly in the lungs, nose, sinuses and ears.
Why is it dangerous to divers?
There is the production of inspissated (dried, thickened) plugs in the terminal bronchioles of the lungs with significant air-trapping. This air-trapping is quite dangerous to the scuba diver due to the obligatory pressure changes that occur with descent in the water column and then ascent after breathing compressed air. In essence, the trapped air enlarges, bursts and causes significant pulmonary barotrauma with air getting into the arterial circulation and causing a stroke-like picture with unconsciousness and possibly death. See Arterial Gas Embolism
In addition, there may be problems in clearing the ears and sinuses from the pressure changes during the dive. Many of these patients (10%) have had long-standing middle ear and sinus infections from the thick, dry mucous produced by the disease. Nasal polyposis is a definite problem.
Are there other similar conditions?
Yes, for a summary of pulmonary barotrauma read:
What are recommendations for diving with this condition?
Persons with cystic fibrosis, even if asymptomatic, should not participate in compressed air diving unless proven to be free of terminal airway obstruction by pulmonary function studies and/or spiral CT scans of the chest. There should be an ENT evaluation to rule out chronic rhinitis, polyposis and sinus pathology – and these problems should be cleared before diving is allowed. Snorkeling, swimming and other water sports should be encouraged.