What are the recommendations for a patient with asthma, on an inhaled corticosteroid (ICS), planning to go scuba diving?

Asthma and Scuba Diving: Recommendations for Patients on Inhaled Corticosteroids

Patients with asthma on inhaled corticosteroids may be permitted to scuba dive if they meet strict criteria: they must be completely asymptomatic, have normal spirometry (FEV1 >80% predicted and FEV1/FVC ratio >70%), pass an exercise challenge test (<15% fall in FEV1 post-exercise), and have no wheeze triggered by exercise, cold, or emotion. 1

Absolute Contraindications to Diving

Patients with asthma should not dive if they have any of the following: 1

• Wheeze precipitated by exercise, cold, or emotion 1
• Active asthma symptoms requiring rescue medication within 48 hours of the planned dive 1, 2
• Reduced peak expiratory flow (>10% fall from best values) 1
• Increased peak flow variability (>20% diurnal variation) 1
• Abnormal baseline spirometry (FEV1 <80% predicted or FEV1/FVC <70%) 1

Pre-Dive Assessment Algorithm

Step 1: Clinical Evaluation

• Obtain detailed history focusing on asthma triggers, particularly exercise, cold air, and emotional stress 1
• Document current medication use and frequency of rescue inhaler use 1, 2
• Perform respiratory system examination 1

Step 2: Pulmonary Function Testing

• Measure FEV1, FVC, and PEF—all must show FEV1 and PEF >80% predicted and FEV1/FVC ratio >70% 1
• These values represent the minimum acceptable threshold for diving clearance 1

Step 3: Exercise Challenge Testing

• This is the critical determinant for diving clearance 1
• Withhold bronchodilators for 24 hours before testing 1
• Perform step test (43 cm step for 3 minutes) or free running to achieve 80% maximum heart rate 1
• Measure FEV1 at 1,3,5,10,15,20, and 30 minutes post-exercise 1
• A decrease in FEV1 of ≥15% from baseline at any time point is diagnostic of exercise-induced bronchoconstriction and absolutely contraindicates diving 1
• Even a 10% decrease should be considered abnormal and warrants serious reconsideration 1

Ongoing Monitoring Requirements

Patients cleared for diving must implement strict self-monitoring: 1

• Measure peak flow twice daily throughout the diving season 1
• Do not dive if any rescue medication was needed in the preceding 48 hours 1, 2
• Do not dive if peak flow drops >10% from personal best 1
• Do not dive if diurnal peak flow variation exceeds 20% 1

Understanding the Risks

The primary concern is pulmonary barotrauma resulting from air trapping during ascent: 1, 3, 2

• Bronchospasm can cause localized airway obstruction in distal airways 2
• Trapped gas expands during ascent, potentially causing pneumothorax, pneumomediastinum, or arterial gas embolism 3, 2
• Cold, dry compressed air, hyperventilation, and extreme exertion during diving can all trigger bronchospasm 1, 2
• Seawater aspiration may induce bronchospasm in susceptible individuals 2

Evidence Quality and Nuances

The British Thoracic Society guidelines 1 provide the most comprehensive and specific recommendations, explicitly stating that patients on inhaled anti-inflammatory agents (step 2 BTS therapy, which includes inhaled corticosteroids) may dive if they meet all criteria. This is consistent with American guidelines 1 that note patients with well-controlled asthma and normal pulmonary function have only slightly increased risk.

Critical caveat: The use of inhaled corticosteroids does not automatically clear someone for diving—it simply means they are not excluded solely based on medication use. 1 The patient must still meet all functional criteria, particularly the exercise challenge requirement.

Research evidence 4, 3, 2, 5 suggests that while theoretical risks exist, carefully selected asthmatic patients can dive without significantly increased adverse events. However, these studies acknowledge the risk is not zero, and individual assessment remains paramount.

Common Pitfalls to Avoid

• Do not clear patients based on spirometry alone—the exercise challenge is essential to unmask exercise-induced bronchoconstriction 1
• Do not allow diving during pollen season for patients with allergic asthma, as pollen contamination of equipment can trigger bronchospasm 1, 2
• Do not assume "mild" or "well-controlled" asthma is automatically safe—objective testing with specific thresholds must be met 1
• Referral to an allergist-immunologist for bronchoprovocation testing is recommended for subjects wishing to scuba dive with any history of asthma 1