Subglottic Stenosis After Intubation

Subglottic stenosis is a fibrotic narrowing of the airway at the level of the cricoid cartilage, under the vocal cords, after prolonged or traumatic intubation.

Epidemiology. It occurs in about 1% to 8% of neonates ventilated for a long period and in 1% to 10% of adult patients intubated for over 10 days. Weeks to months separate injury and symptoms.

Risk factors. Intubation over 7 to 10 days, oversized tube, high cuff pressure, repeated or traumatic intubation, movement of the tube, infection, reflux, steroids free sepsis, diabetes, prematurity, and autoimmune disease (granulomatosis with polyangiitis).

Grading. The Cotton-Myer system grades luminal narrowing: grade 1 under 50%, grade 2 51% to 70%, grade 3 71% to 99%, grade 4 no lumen.

Pathophysiology.

Pressure from the cricoid ring (the narrowest ring, completely circumferential) causes mucosal ischaemia, ulceration, perichondritis, granulation and scar contraction.

Exertional dyspnoea, stridor (biphasic or inspiratory), noisy breathing, cough, hoarseness, recurrent croup in children, failed extubation, and reduced exercise tolerance. Asthma may be diagnosed wrongly.

Red flags.

• Stridor at rest.
• Cyanosis or exhaustion.
• Rapid worsening after respiratory infection.

Flow volume loop shows a fixed upper airway obstruction (flattening of inspiratory and expiratory limbs). Flexible laryngoscopy and rigid bronchoscopy confirm the diagnosis and grade. CT with 3D airway reconstruction maps length and level. Screen for reflux and systemic disease (anti-neutrophil cytoplasmic antibody, inflammatory markers).

Differential diagnosis.

• Asthma.
• Vocal cord paralysis.
• Tracheal stenosis.
• Tracheomalacia.
• Laryngeal tumour.
• Granulomatosis with polyangiitis.
• Idiopathic subglottic stenosis.

Management depends on grade and symptoms.

• Grade 1 to 2, mild symptoms: observation, acid suppression, and endoscopic dilation (balloon or radial incision) with local steroid injection.
• Omeprazole: 40 mg orally once daily for at least 8 weeks, then reassess; maximum 80 mg daily; monitor symptoms; reduce in severe hepatic impairment.
• Triamcinolone: 10 to 40 mg injected into scar in a single endoscopic session; repeat at 4 to 8 weeks if needed; maximum 80 mg each session; monitor for infection.
• Mitomycin C topical (specialist use): 0.4 mg/mL applied for 2 to 4 minutes; single application each procedure; no systemic monitoring beyond wound review.
• Grade 3 to 4: open reconstruction (laryngotracheal reconstruction with cartilage graft, cricotracheal resection with end-to-end anastomosis).
• Tracheostomy secures the airway while awaiting reconstruction.

Prevention. Early tracheostomy when ventilation is expected beyond 10 to 14 days, appropriate tube size, cuff pressure of 20 to 30 cmH2O, minimal tube movement and sedation to prevent self-extubation.

Monitoring. Spirometry and flow volume loop, endoscopic review at 3 to 6 months.

Referral and escalation. Urgent ENT or airway surgery referral for stridor or rapid decline.

Special groups. Neonates and infants have a small subglottis, so a 1 mm reduction reduces the area by about 75%.