A Diving Course Applicant with Airway Hyperresponsiveness and a Form to Sign

Interpretation

• Spirometry is within the normal range and the bronchodilator response (180 mL, 9%) does not meet the usual reversibility criteria (≥12% and ≥200 mL), so spirometry alone does not demonstrate active asthma.
• The methacholine PC20 of 2.1 mg/mL is clearly abnormal. Provocation thresholds vary between services (commonly 4, 8 or 16 mg/mL), but 2.1 mg/mL indicates significant bronchial hyperresponsiveness under any of them.
• The history matters: wheeze after a viral illness three years ago, treated with inhaled corticosteroids, indicates that the airway disease was active in adulthood, not only in childhood.

Why this matters underwater

• Gas in the lung expands during ascent. If a bronchus is narrowed by bronchospasm, mucosal oedema or mucus plugging, the affected segment traps gas; the pressure rises and can rupture alveoli, producing pneumothorax, mediastinal or subcutaneous emphysema, or arterial gas embolism. This is the same mechanism as breath-hold ascent, but it can occur at normal ascent rates.
• Cold, dry regulated gas, immersion, exercise, aspiration of small amounts of water and emotional stress are all bronchoconstrictor triggers in a hyperresponsive airway.
• An acute attack underwater impairs exercise capacity and can lead to panic, rapid ascent and loss of the regulator.

The risk is not theoretical but it is also not absolute; the decision requires the applicable standard and a specialist opinion, which is exactly why the technician's own interpretation must be referred onward rather than signed off.

Position

• The DMT's role is to take the history, perform and document the tests competently, and present the findings - not to make the fitness-to-dive determination for commercial diving. That determination belongs to a designated diving medical examiner or physician appointed under the relevant national or industry standard (for example a maritime or offshore authority, or the diving contractor's appointed examiner), and the standard that applies must be identified, because thresholds differ between jurisdictions and between commercial and recreational diving.
• Signing an "unrestricted" certificate would be outside scope and potentially a misrepresentation, regardless of what the school has requested. Pressure from a school or a candidate to sign is not a reason to sign.

How to handle it

• Record all findings objectively and completely, including the PC20, the bronchodilator response, the history of adult wheeze and the BMI.
• Explain to the applicant, in plain terms, what the results mean and why the decision must go to the medical examiner; give him the timescale and the options (referral to a respiratory physician, a treatment trial, a repeat challenge, a restricted certificate if the standard permits).
• Communicate to the school only the fitness outcome, not the medical details, and only with the candidate's consent. Tell the school explicitly that a technician's signature is not an acceptable substitute for the examiner's determination.
• Document the conversation and the referral; do not leave the form blank in a way that lets someone else sign it as if the tests were normal.

Can he be certified? Possibly, but not by the technician and not automatically. The answer depends on the standard that governs his course:

• Many standards do not regard a past history of asthma as an absolute bar to diving where there is no current symptoms, normal spirometry, and no demonstrable airway hyperresponsiveness off medication, often with a required symptom-free interval and a documented normal challenge.
• Others treat any history of adult asthma as a disqualifying condition for commercial diving, and some permit certification only with a specialist opinion and a time-limited certificate. The applicable standard must be identified before anyone advises him about his career.

Conditions and follow-up to recommend to the examiner

• Certification, if granted, should be time-limited (commonly 1–2 years) with review, and conditional on remaining symptom-free and off regular medication.
• Written advice to stop diving and seek review if wheeze, cough or breathlessness returns, after a chest infection, or if a reliever is needed.
• A low threshold for repeating spirometry and a provocation test if symptoms recur; a documented action plan with the training school.
• Address the modifiable factors: smoking status, weight, and fitness; both affect exercise capacity under a regulator.
• Note honestly that the risk of barotrauma is reduced, not eliminated, and that the certificate is a judgement based on the evidence available, not a guarantee.
• The final decision and any restriction must be made and signed by the diving medical examiner, with the DMT's findings attached.