Controversies in the medical clearance of recreational scuba divers: updates on asthma, diabetes mellitus, coronary artery disease, and patent foramen ovale.

Primary care and sports medicine physicians are frequently consulted on medical clearance for prospective recreational divers. We discuss four common and controversial medical conditions--asthma, diabetes mellitus, coronary artery disease, and patent foramen ovale--as they relate to fitness to dive. For each condition we review the relevant anatomy and physiology, current recommendations, and the pertinent medical literature. Finally, we offer evidence-based recommendations regarding fitness to dive for potential divers with these conditions.