Inducible Laryngeal Obstruction

Inducible laryngeal obstruction is transient, reversible narrowing of the larynx at the glottic level (vocal folds) or supraglottic level (arytenoids, aryepiglottic folds, epiglottis) in response to a trigger, causing inspiratory (and sometimes expiratory) airflow limitation, noisy breathing and breathlessness. It is the preferred umbrella term, and includes vocal cord dysfunction and exercise induced laryngeal obstruction.

• Subtypes:
  • Glottic: paradoxical adduction of the vocal folds on inspiration.
  • Supraglottic: inward collapse of the arytenoid cartilages, aryepiglottic folds and epiglottis towards the airway, which is the commonest pattern in exercise induced obstruction.
  • Mixed.
• Triggers are exercise (exercise induced laryngeal obstruction), irritants (smoke, strong odours, cold air), laryngopharyngeal reflux, postnasal drip, emotional stress, and speech.
• Prevalence: up to 5 to 8% of adolescents and young athletes, and it is found in about 35% of patients with unexplained exertional breathlessness. It affects females more (about 2 to 3 times), and is commonest in adolescents and young adults aged 10 to 35 years.
• Mechanism: laryngeal hypersensitivity, reflux or postnasal irritation, high inspiratory airflow velocity during exercise (the suction effect of fast inspiratory airflow pulling soft supraglottic tissue inward), muscle fatigue, and altered neural control. Anxiety, perfectionism and competitive pressure may contribute.
• Misdiagnosis as exercise induced asthma is common, leading to years of ineffective treatment. Both conditions coexist in about 25 to 30% of athletes with exertional breathlessness.

• Breathlessness and noisy breathing (inspiratory stridor, heard at the neck) that begin during peak exercise (not after exercise), a sensation of throat tightness or strangling, a hoarse voice, and sometimes cough. Symptoms resolve rapidly (within 2 to 5 minutes) after stopping effort, with no refractory period and no response to bronchodilators.
• Onset is often sudden, at high intensity (running, swimming, team sports, cycling), and in the competitive setting. Non-exercise episodes can be triggered by irritants, and at rest by stress.
• Between episodes, examination and spirometry are normal. During symptoms, there is loud inspiratory stridor (louder over the neck than over the chest), voice change, and normal oxygen saturation.
• Differential diagnosis: exercise induced bronchoconstriction and asthma, dysfunctional breathing, cardiac causes (arrhythmia, cardiomyopathy, congenital heart disease), anaemia, deconditioning, subglottic stenosis, laryngomalacia, vocal fold paralysis, laryngeal papillomatosis and tumour, and anaphylaxis.
• Red flags: stridor at rest, progressive symptoms, hoarseness lasting more than 3 weeks, haemoptysis, neck mass, difficulty swallowing, syncope or chest pain on exertion, family history of sudden death, and failure of all treatments.
• Complications: exercise avoidance, withdrawal from sport, anxiety, unnecessary treatments with inhaled and oral steroids, and rare hypoxia and collapse.

• Suspect in any patient with exertional or irritant triggered inspiratory noise, a throat location of symptoms, rapid recovery after stopping, and no response to asthma treatment.
• Continuous laryngoscopy during exercise (a flexible nasolaryngoscope held in place with a headset while the patient runs or cycles at maximum effort) is the best diagnostic test for exercise induced laryngeal obstruction. It shows inward movement of the supraglottic structures or adduction of the vocal folds at peak exercise. Grade the severity of obstruction and compare it with the resting appearance.
• Laryngoscopy at rest or during a provoked episode when the trigger is an irritant or stress.
• Spirometry with a flow volume loop (flattened inspiratory limb during an episode, with a normal tracing between episodes), and a post-exercise loop.
• Test for asthma and exercise induced bronchoconstriction (spirometry, reversibility, fractional exhaled nitric oxide, eucapnic voluntary hyperpnoea, mannitol, or exercise challenge), because both are often present.
• Cardiopulmonary exercise testing for unexplained exertional breathlessness, to exclude cardiac, metabolic and ventilatory limitation.
• Evaluate and treat triggers: reflux symptoms, rhinitis and postnasal drip, and psychological factors.
• Electrocardiogram and echocardiogram for exertional chest pain, syncope, or a family history of sudden cardiac death.

• Explain the condition, giving reassurance that it is harmless, and treat triggers.
• Laryngeal control and breathing therapy by a speech and language therapist or a physiotherapist trained in laryngeal disorders (3 to 6 sessions):
  • Education, relaxed throat breathing, diaphragmatic breathing, and control of the inspiratory flow rate.
  • A breathing technique for exercise: inhale through the nose and mouth with a controlled slow inspiration, a relaxed jaw and tongue, and a longer, relaxed expiration, perhaps through pursed lips, or using a "sniff" or a "dry swallow" at the first sign of tightness.
  • Reduce rate and intensity of effort at the first warning, then increase gradually.
  • Inspiratory muscle training is sometimes used, with limited evidence.
• Treat trigger conditions:
  • Reflux: omeprazole 20 to 40 mg orally once or twice daily before meals for 8 to 12 weeks, with an alginate (sodium alginate and potassium bicarbonate 10 to 20 mL after meals and at bedtime) and avoidance of late meals.
  • Rhinitis and postnasal drip: fluticasone propionate nasal spray 50 micrograms per spray, 2 sprays into each nostril once daily, and saline irrigation.
  • Asthma and exercise induced bronchoconstriction when proven: salbutamol 200 to 400 micrograms 10 to 15 minutes before exercise, and an inhaled corticosteroid such as budesonide 200 to 400 micrograms twice daily. Stop inhaled and oral steroids that are not helping.
  • Anxiety: cognitive behavioural therapy, and sertraline 25 mg daily increased to 50 to 100 mg daily where needed.
• Acute episode: stop exercise, sit upright, and use relaxed nose and mouth breathing with long expiration, or the sniff technique, with calm support. Episodes settle in 2 to 5 minutes. No bronchodilator or oxygen is needed unless saturation falls below 94%.
• Surgical treatment (specialist) for severe supraglottic exercise induced obstruction that fails therapy: endoscopic supraglottoplasty (laser or microinstrument trimming of redundant arytenoid mucosa and aryepiglottic folds) in carefully selected, highly symptomatic athletes. Good results are reported in 70 to 80%, but the evidence is limited, and speech and swallowing complications are possible.
• Botulinum toxin A injection of the thyroarytenoid muscles (2.5 to 5 units per side) for glottic closure that is refractory to therapy.
• Special groups:
  • Adolescents and athletes: involve the coach, family and school, adjust training, teach the breathing techniques, and avoid labelling them as having asthma without proof.
  • Pregnancy: use non-drug treatment, alginates and omeprazole for reflux when needed, and avoid surgery and toxin.
  • Children: exercise induced laryngeal obstruction is commoner in adolescents, and in young children laryngomalacia should be considered.
  • Elderly: investigate for tumour, vocal fold paralysis, neurological disease and stenosis.
  • Cardiac disease: exclude arrhythmia and structural heart disease before attributing exertional symptoms to the larynx.
• Follow up: review at 4 to 6 weeks, and after the next period of exercise. Refer to ENT for laryngoscopy, to sports medicine, to speech and language therapy, to respiratory medicine for asthma assessment, and to psychology when anxiety or performance pressure is prominent.