Exercise-induced bronchoconstriction — formative SAQs

SAQ 1 — The school-age child who wheezes with sport (20 marks, ~15 minutes)

An 8-year-old boy is referred because he coughs and wheezes when he runs. His mother says the trouble starts a few minutes into a game and is worst just after he stops, then eases with rest over half an hour. He has eczema, and he coughs at night in winter. Between episodes he is well and his chest is clear today. He has borrowed a friend's blue inhaler once or twice and felt it helped. [3]

Questions

1. Give the most likely diagnosis and the features in this history that support it. (4 marks) [3]
2. He is 8 years old. State the single most useful confirmatory investigation, the result that would confirm the diagnosis, and why a normal resting spirometry would not exclude it. (5 marks) [10]
3. Explain the mechanism by which exercise narrows his airway. (4 marks) [5]
4. Outline your management plan, naming the most important first step and the role of a pre-exercise reliever. (5 marks) [12]
5. State the danger in relying on a daily short-acting beta-agonist to get through sport. (2 marks) [5]

Model answer (must-hit)

1. The most likely diagnosis is exercise-induced bronchoconstriction, most probably as part of asthma. Supporting features are the characteristic timing (symptoms a few minutes into exercise, worst after stopping, settling with rest over about thirty minutes), the exercise trigger, the personal atopy (eczema) and nocturnal winter cough suggesting underlying asthma, the normal chest between episodes, and the reported benefit from a bronchodilator. [3]
2. The single most useful confirmatory investigation is an objective challenge test measuring the fall in FEV1 — a standardised exercise challenge or eucapnic voluntary hyperpnoea, which he is old enough to perform. The result that confirms the diagnosis is a fall in FEV1 of ten percent or more from baseline after the challenge. A normal resting spirometry does not exclude it because the airway is open between episodes; the diagnostic value lies in the provocation, not the baseline. [10]
3. Exercise makes him breathe large volumes of cold, dry air through the mouth, bypassing nasal conditioning. The airway lining loses water warming and humidifying this air, and the airway surface liquid becomes hyperosmolar. This osmotic stress activates airway mast cells to release histamine, cysteinyl leukotrienes and prostaglandin D2, which contract airway smooth muscle and cause mucosal swelling and mucus, narrowing the airway transiently before it recovers. [5]
4. The most important first step is to control the underlying asthma with a regular inhaled corticosteroid, because in most children exercise symptoms signal inadequate control; I would also check adherence and inhaler technique. Non-drug measures — a warm-up before exercise, warming inspired air with a scarf in the cold, and avoiding the worst conditions — are added for every child. A pre-exercise short-acting beta-agonist taken ten to fifteen minutes before exercise covers breakthrough symptoms and protects for two to three hours. The goal is full participation in sport. [12]
5. Daily use of a short-acting beta-agonist induces tolerance and reduces its bronchoprotective effect, so the child loses the very protection they depend on; daily need is also a marker of poor control and should prompt stepping up the controller rather than supplying more reliever. [5]

SAQ 2 — The adolescent athlete with exertional breathlessness (20 marks, ~15 minutes)

A 15-year-old competitive middle-distance runner reports breathlessness during races. She describes noisy breathing on breathing in and a tight throat at maximal effort, which clears within a minute or two of stopping without any inhaler. Her coach has given her a salbutamol inhaler, which she says makes no difference. Her resting spirometry is normal, and a supervised exercise challenge shows no significant fall in FEV1. [3]

Questions

1. What is the most likely diagnosis, and how does its pattern differ from exercise-induced bronchoconstriction? (5 marks) [3]
2. Why is the normal exercise challenge important in reaching this diagnosis? (3 marks) [10]
3. In a different athlete in whom you did suspect exercise-induced bronchoconstriction, why is objective testing essential rather than treating on symptoms alone? (4 marks) [8]
4. Outline how you would manage a competitive athlete with confirmed exercise-induced bronchoconstriction, including two issues specific to athletes. (6 marks) [8]
5. State the goal of management for any child or adolescent with exercise-induced bronchoconstriction. (2 marks) [12]

Model answer (must-hit)

1. The most likely diagnosis is inducible laryngeal obstruction (vocal cord dysfunction). Its pattern differs from exercise-induced bronchoconstriction in several ways: the breathlessness comes on at the peak of exertion rather than after it, the noise is inspiratory stridor rather than an expiratory wheeze, the tightness is felt in the throat rather than the chest, and the symptoms clear within a minute or two of stopping without needing a bronchodilator. Airway bronchoconstriction, by contrast, peaks after effort and settles over thirty to sixty minutes. [3]
2. The normal exercise challenge is important because it objectively refutes airway bronchoconstriction: there is no significant fall in FEV1, so the airways are not the problem. This prevents her being labelled asthmatic and escalated on inhaled therapy, and redirects the workup toward the larynx (ideally continuous laryngoscopy during exercise) and speech-therapy-based management. [10]
3. Objective testing is essential because symptoms alone are unreliable — both over-diagnosis (treating deconditioning, dysfunctional breathing or laryngeal obstruction as asthma) and under-diagnosis are common, especially in athletes who may under- or over-report. A documented fall in FEV1 on challenge confirms the diagnosis, grades severity, and is also required for anti-doping certification of some inhaled medicines in competitive sport. [8]
4. Management confirms the diagnosis objectively, controls any underlying asthma with an inhaled corticosteroid, and adds a warm-up, inspired-air conditioning and a pre-exercise short-acting beta-agonist, while avoiding the tolerance that daily reliever use in heavy training produces. Two athlete-specific issues are anti-doping documentation (a confirmed diagnosis is needed for some inhaled therapies) and the environmental exposures of the sport (cold dry air, chlorinated pools, pollutants), which should be modified where possible. Persistent symptoms despite this warrant add-on therapy and specialist review. [8]
5. The goal is full, unrestricted participation in exercise and sport; exercise-induced bronchoconstriction should never be a reason to restrict physical activity. [12]