Can you scuba dive with asthma?

DAN describes three main risks:

• Bronchospasm: narrowed airways reduce airflow and exercise capacity — and underwater you can't simply stop and rest.
• Air trapping: narrowed airways could trap gas in the lungs during ascent.
• Lung overexpansion injury: trapped, expanding gas can rupture lung tissue, potentially causing an arterial gas embolism or a collapsed lung.

DAN cites UHMS guidance that divers with mild intermittent, mild persistent or moderate persistent asthma may be allowed to dive provided it is well controlled. Prospective divers should have their lung function assessed and an exercise test; what matters is whether treatment returns results to normal, especially after exercise.

The 2023 UHMS physician guidance advises against diving with wheeze triggered by exercise, cold or emotion. Well-controlled asthma needs normal lung function and a negative exercise test; severe or unpredictable exacerbations preclude diving. DAN also describes the older British Thoracic Society guidance, including its 48-hour bronchodilator precaution. A diving physician must interpret these criteria for the individual.

A physician who knows both diving medicine and asthma. Every course and try dive starts with the diver medical questionnaire — if your answers call for a doctor's approval, you need it before you dive.

Tell us about your asthma when you book, bring your doctor's approval if you're taking a course, and keep your inhaler on the boat — DAN recommends both.