Subglottic Stenosis

Subglottic stenosis is narrowing of the airway between the undersurface of the vocal folds and the lower border of the cricoid cartilage. The cricoid is the only complete cartilaginous ring in the airway, so it cannot expand, and a small reduction in radius produces a large rise in resistance.

• Congenital subglottic stenosis: arrested recanalisation of the laryngotracheal tube or abnormal cricoid shape; in a term infant a subglottic diameter under 4 mm defines stenosis.
• Acquired subglottic stenosis is the commonest in children and adults:
  • Post-intubation (prolonged intubation, oversized tube, repeated intubation, traumatic intubation, infection, reflux), usually after 7 to 14 days of ventilation.
  • Tracheostomy complications and external trauma.
  • Inflammatory and systemic disease: granulomatosis with polyangiitis, sarcoidosis, relapsing polychondritis, amyloidosis, and inflammatory bowel disease.
  • Chemical injury, thermal burns, radiotherapy.
  • Idiopathic subglottic stenosis: almost exclusively women aged 30 to 50 years, with a fibrous circumferential web just below the cords; hormonal and reflux contributions are suspected.
• Laryngopharyngeal and gastro oesophageal reflux worsen scar formation.

• Progressive exertional dyspnoea, reduced exercise tolerance, and noisy breathing.
• Biphasic stridor (inspiratory and expiratory), and a stridor that does not respond to bronchodilators.
• Misdiagnosis as asthma, recurrent croup, or chronic bronchitis is common, with failed response to inhaled steroids and bronchodilators.
• Hoarse or weak voice and cough.
• In infants: recurrent croup, stridor with intercurrent respiratory infections, failure to extubate, feeding difficulty, and sleep disordered breathing.
• Acute decompensation can follow a mild upper respiratory infection because mucosal oedema narrows an already compromised lumen.

• Awake flexible nasolaryngoscopy shows the glottis and often the upper subglottis; it excludes vocal fold paralysis and supraglottic pathology.
• Rigid bronchoscopy or microlaryngoscopy under general anaesthesia (spontaneous ventilation) is the definitive assessment: location, length, and degree of stenosis, mature versus soft (inflamed) scar, presence of tracheal or bronchial disease, and posterior glottic involvement.
• Grading by percentage of luminal obstruction using calibrated endotracheal tubes: grade I under 50 percent, grade II 51 to 70 percent, grade III 71 to 99 percent, and grade IV no detectable lumen.
• Pulmonary function testing: flattening of the inspiratory and expiratory limbs of the flow volume loop (fixed obstruction), reduced peak expiratory flow, and raised FEV1 to peak expiratory flow ratio (above 8 mL per L/min).
• CT of the neck and chest with airway reconstruction: length, thickness, and associated tracheal disease; MRI is less helpful.
• Aetiology workup for adults with no clear cause: ANCA (PR3 and MPO), antinuclear antibody, rheumatoid factor, ESR, CRP, serum ACE, urinalysis, chest imaging, and when appropriate biopsy. pH and impedance studies for reflux.
• Infant and child evaluation includes a full airway endoscopy, evaluation for reflux, and assessment of synchronous airway lesions.

• Acute airway compromise:
  • Humidified oxygen, upright position, and avoid sedation.
  • Nebulised adrenaline 1:1000 (1 mg/mL): 0.5 mL/kg up to 5 mL by nebuliser, which can be repeated every 30 to 60 minutes while preparing for definitive airway control, with continuous monitoring (rebound oedema may occur).
  • Dexamethasone 0.15 mg/kg to 0.6 mg/kg (adult 8 mg to 10 mg) intravenously or orally as a single dose.
  • Heliox (helium 70 percent and oxygen 30 percent) can reduce the work of breathing as a temporising measure.
  • Secure the airway under anaesthesia with a small endotracheal tube or by tracheostomy when impending failure.
• Gastric acid suppression for all patients: omeprazole 20 mg to 40 mg once daily in adults, or 1 mg/kg/day in children; continue long term, because reflux promotes restenosis.
• Treat underlying systemic disease. Granulomatosis with polyangiitis: induction with prednisolone 1 mg/kg daily (maximum 60 mg) tapering, plus rituximab 375 mg/m2 intravenously weekly for 4 weeks or cyclophosphamide 2 mg/kg daily orally (adjust for renal function), with maintenance azathioprine 2 mg/kg daily or rituximab. Active disease should be controlled before elective reconstruction.
• Endoscopic management (soft, short, thin web or grade I to II scar):
  • Radial laser incisions (CO2 or diode) at 3 or 4 sites, avoiding the posterior commissure, followed by balloon dilation (4 mm to 12 mm balloon with sizing to the normal airway diameter, inflated for 1 to 2 minutes at the stated pressure, repeated).
  • Adjuncts to reduce restenosis: topical mitomycin C at 0.4 mg/mL applied on a pledget for 2 to 4 minutes (benefit is debated), and intralesional triamcinolone 40 mg/mL injected into the scar, which is routine in idiopathic disease.
  • Repeat procedures at 4 to 12 week intervals, depending on recurrence.
  • Idiopathic subglottic stenosis: serial endoscopic dilation with steroid injection is often combined with oral trimethoprim-sulfamethoxazole 160 mg/800 mg twice daily for several months in some centres; the evidence is limited, and treatment of reflux is routine.
• Open reconstruction for grade III to IV, mature fibrous, long (more than 1 cm), or recurrent stenosis:
  • Anterior cricoid split (infants with failed extubation and a soft stenosis).
  • Laryngotracheoplasty with costal cartilage graft (anterior, posterior, or both) with temporary stent or single stage without stent.
  • Cricotracheal resection with primary thyrotracheal anastomosis: highest success rate (over 90 percent), indicated for severe grade III and IV and for adults; requires a competent glottis and adequate trachea.
  • Tracheostomy as a bridge or definitive airway in unsuitable patients.
• Perioperative care: intravenous antibiotics (cefazolin 1 g to 2 g every 8 hours), corticosteroids (dexamethasone 0.25 mg/kg every 6 hours for 24 hours), humidified air, head flexion avoidance after resection (a guardian suture), and early extubation planning.
• Follow up: regular airway endoscopy and spirometry, long term reflux suppression, and review for recurrence.
• Complications: restenosis, granulation tissue, voice change, aspiration, anastomotic dehiscence, and recurrent laryngeal nerve injury in resection.