Overview
Paediatric airway stenosis refers to abnormal narrowing of any segment of the conducting airway, from the nasal passages to the main bronchi, resulting in increased airway resistance, increased work of breathing, and potential respiratory failure. It may be congenital or acquired, fixed or dynamic, and can affect neonates through to adolescents.
A critical physiological principle is the relationship between airway radius and resistance:
$$R \propto \frac{1}{r^4}$$
Halving the airway radius increases resistance 16-fold. This explains why even modest anatomical narrowing, from oedema, granulation tissue, or structural stenosis, causes disproportionately severe obstruction in infants and young children. The narrowest fixed point of the paediatric airway is the subglottis at the cricoid ring (in adults, the narrowest point is the glottis at the vocal cords), making subglottic pathology the most clinically significant site of stenosis in children. In infants, 50% of total airway resistance is located in the upper airway, amplifying the impact of any narrowing at this level.
Developmental Anatomy and Physiological Vulnerability
- The laryngotracheal groove forms at approximately 4 weeks of gestation; its cranial end becomes the larynx, with the trachea below and lung buds arising caudally
- Infants are obligate nasal breathers; nasal obstruction (e.g. choanal atresia) is immediately life-threatening
- The tongue is proportionally larger and the mandible smaller, predisposing to posterior pharyngeal obstruction
- The epiglottis is floppy and omega-shaped in infancy
- The trachea is short and soft; hyperextension or flexion of the neck may cause obstruction
- The chest wall is more compliant, ribs are horizontal, and the diaphragm is the dominant respiratory muscle but fatigues rapidly, children are highly susceptible to respiratory decompensation
- Airways are proportionally smaller; airway resistance is inversely proportional to the fourth power of the radius, meaning mucosal inflammation produces far greater resistance than in adults
Epidemiology and Aetiology
Congenital Causes
| Aetiology | Key Features | Age of Presentation |
|---|---|---|
| Laryngomalacia | Supraglottic collapse on inspiration; most common cause of neonatal stridor; usually improves after 6 months | Neonatal / early infancy |
| Congenital subglottic stenosis (SGS) | Fixed narrowing of the cricoid; may be associated with syndromes | Neonatal |
| Laryngeal web | Anterior glottic fusion; ranges from thin membrane to thick plate | Neonatal |
| Laryngeal atresia / CHAOS | Life-threatening; associated with fetal hydrops; EXIT procedure may be required | Neonatal |
| Laryngeal cleft | Posterior midline defect; associated with aspiration and stridor | Neonatal / infancy |
| Congenital tracheal stenosis | Long- or short-segment; may be associated with aberrant left pulmonary artery (sling) | Infancy |
| Vascular ring / pulmonary artery sling | Extrinsic tracheal compression; may cause biphasic stridor and dysphagia | Infancy |
| Cystic hygroma | Cervical or mediastinal lymphatic malformation causing extramural compression | Infancy |
| Subglottic haemangioma | Most common laryngeal tumour in infants; presents at 6-8 weeks with inspiratory stridor; 50% have cutaneous haemangiomata | 6-8 weeks |
| Choanal atresia | Failure of posterior nasal opening; membranous or bony (most commonly bony stenosis with thin bony/membranous plate); unilateral or bilateral; associated with CHARGE syndrome and Treacher Collins syndrome; incidence ~1 in 7000 | Neonatal |
| Pierre Robin sequence | Micrognathia, cleft palate, glossoptosis; prone to severe upper airway obstruction, especially when supine | Neonatal |
Acquired Causes
The most common acquired cause is post-intubation subglottic stenosis, particularly in VLBW infants following prolonged neonatal ventilation. ETT size relative to the subglottis is a key determinant.
| Aetiology | Key Risk Factors / Notes |
|---|---|
| Post-intubation SGS | Prolonged intubation, oversized tube, repeated trauma, movement, VLBW; most common cause of acquired SGS |
| Post-infectious | Mucosal injury with fibrotic scarring; e.g. following severe croup (laryngotracheobronchitis) or bacterial tracheitis |
| Post-traumatic | External laryngeal trauma |
| Post-surgical (tracheostomy-related) | Suprastomal granulation tissue; tracheomalacia at stoma site from cartilage resorption |
| Recurrent respiratory papillomatosis (RRP) | HPV types 6 and 11 (occasionally type 16); most common benign laryngeal tumour in children; two-thirds of patients <15 years; highest incidence <5 years; strong association with maternal condylomata acuminata |
| Inflammatory / systemic | Rare in children (e.g. granulomatosis with polyangiitis, relapsing polychondritis) |
Pathophysiology: Classification of Obstruction by Site
| Level | Characteristic Sound | Common Causes |
|---|---|---|
| Nasal / nasopharyngeal | Stertor (snoring quality) | Choanal atresia, adenoidal hypertrophy, cystic hygroma |
| Supraglottic | Low-pitched inspiratory stridor | Laryngomalacia, epiglottitis, retention cysts, vallecular cyst |
| Glottic / subglottic | Higher-pitched inspiratory stridor; hoarse / absent cry | SGS, laryngeal web, haemangioma, RRP |
| Extrathoracic tracheal | Inspiratory stridor | Subglottic haemangioma, extrinsic compression, tracheal stenosis |
| Intrathoracic tracheal | Expiratory stridor / wheeze | Tracheomalacia, vascular ring, intrathoracic tracheal stenosis |
| Bronchial | Wheeze; unilateral air-trapping | Bronchomalacia, foreign body, lymphadenopathy (e.g. TB) |
Key distinction: extrathoracic obstruction produces predominantly inspiratory stridor; intrathoracic obstruction produces predominantly expiratory stridor or wheeze; fixed obstruction (e.g. complete ring tracheal stenosis, laryngeal web) produces biphasic stridor.
Tracheomalacia
- Presents with biphasic or predominantly expiratory stridor, recession, and a barking cough
- Worsens with increased activity, respiratory effort, agitation, or concurrent infection
- May be primary (intrinsic cartilage weakness) or secondary (extrinsic compression, post-tracheostomy, post-surgical)
- Dynamic MLB under spontaneous breathing with light general anaesthesia (without CPAP from the anaesthetic circuit) is required for diagnosis; CPAP splints the airway and will mask dynamic collapse
Cotton-Myer Grading System for Subglottic Stenosis
| Grade | Degree of Luminal Obstruction |
|---|---|
| I | <50% |
| II | 51-70% |
| III | 71-99% |
| IV | No detectable lumen |
Clinical Features
Cardinal Signs of Upper Airway Obstruction
- Stridor: character and phase (inspiratory, expiratory, biphasic) localises the level
- Suprasternal, intercostal, and subcostal retractions; sternal retraction in infants
- Tachypnoea: early compensatory response (age-dependent normal rates must be known)
- Paradoxical chest/abdominal movement: dissociation indicating severe obstruction
- Hoarse, weak, or absent cry: glottic or subglottic involvement
- Croupy cough: classical sign of subglottic/tracheal pathology
- Cyanosis: late, pre-terminal sign, secondary apnoea and bradycardia follow
- Feeding difficulty and faltering growth: common in infants with chronic obstruction
- Alae nasi flaring: attempt to reduce upper airway resistance, particularly in infants
Age-Specific Presentations
| Age Group | Predominant Presentation |
|---|---|
| Neonate | Stridor at birth or within hours; cyanosis with feeds (choanal atresia); weak or absent cry; respiratory distress |
| Young infant (0-3 months) | Inspiratory stridor worsening with feeds or agitation; subglottic haemangioma at 6-8 weeks |
| Infant (3-12 months) | Progressive biphasic stridor; failure to thrive; recurrent croup-like episodes suggesting fixed lesion |
| Toddler / preschool | Recurrent "croup" not responding to standard therapy; hoarse voice; exercise intolerance |
| School-age / adolescent | Exertional dyspnoea; stridor misdiagnosed as asthma; dysphonia; flow-volume loop abnormality |
Specific Diagnoses to Recognise
- Subglottic haemangioma: biphasic stridor at 6-8 weeks; 50% have cutaneous haemangiomata; associated with PHACE syndrome; propranolol has transformed management
- RRP: progressive hoarseness, recurrent "laryngitis" or "croup," intermittent stridor; history of maternal condylomata; persistent or progressive huskiness in any child should raise suspicion
- Tracheomalacia: expiratory or biphasic stridor; barking cough; worsens with agitation; improves with CPAP
- Vascular ring: persistent biphasic stridor from infancy; dysphagia; often misdiagnosed as refractory asthma; posterior oesophageal indentation on contrast study
- Vallecular cyst: mucus retention cyst at the tongue base; visible on lateral soft-tissue neck X-ray; undiagnosed can be fatal; requires drainage/marsupialisation
- Bilateral vocal cord paralysis: cause of stridor in ~10% of infants with airway obstruction; commonly associated with central nervous system anomaly (e.g. Arnold-Chiari malformation); usually requires tracheostomy
Investigations
Important principle: No child with significant respiratory compromise should be sent for imaging without immediate access to skilled airway management personnel and equipment.
| Investigation | Purpose / Indication |
|---|---|
| Pulse oximetry | Continuous monitoring; severity assessment |
| AP and lateral soft-tissue neck X-ray | Steeple sign (croup/SGS); soft-tissue masses; retropharyngeal space; vallecular cyst on lateral view |
| Chest X-ray (AP and lateral) | Air trapping, mediastinal shift, tracheal deviation, consolidation; both views recommended |
| Contrast oesophagogram | Vascular ring (posterior oesophageal indentation); extrinsic oesophageal compression |
| CT neck and chest ± 3D reconstruction | Detailed stenosis anatomy; vascular anomalies; mediastinal masses |
| MRI / MR angiography | Vascular ring characterisation; soft-tissue detail; avoids radiation |
| Ultrasound neck / mediastinum | Cystic hygroma, thyroid goitre, lymphadenopathy |
| Flexible nasendoscopy (awake, office) | Dynamic supraglottic and vocal cord assessment |
| Microlaryngoscopy and bronchoscopy (MLB) under GA | Gold standard; structural and dynamic assessment; stenosis grading; vocal cord mobility; suprastomal granuloma |
| Echocardiography | Associated cardiac anomalies; vascular ring anatomy |
| Polysomnography | Quantify OSA severity; pre-operative and post-operative assessment |
MLB diagnostic principles:
- Must be performed with the child breathing spontaneously under light general anaesthesia
- No CPAP from the anaesthetic circuit, this splints the airway and will mask tracheobronchomalacia
- Flexible bronchoscopy via ETT on the NICU can also demonstrate malacia if no positive airway pressure is applied, though spontaneous breathing effort may exaggerate apparent collapse
- Contrast bronchogram under screening/video can demonstrate malacic airways and image distal to endoscopically impassable stenosis
Management
Principles
Management is tailored to site, aetiology, severity, and age. A multidisciplinary team including paediatric ENT surgery, respiratory medicine, paediatric anaesthesia (experienced in difficult airway), speech pathology, and paediatric intensive care is essential for moderate-to-severe cases.
Medical Management
| Intervention | Indication / Notes |
|---|---|
| Supplemental oxygen | All cases with hypoxaemia or significant respiratory distress |
| Nebulised adrenaline (epinephrine) | Acute exacerbations of inflammatory or post-intubation SGS; short-term airway decongestant |
| Systemic / inhaled corticosteroids | Peri-extubation protocols to prevent acquired SGS; inflammatory airway oedema |
| Nasal CPAP | Laryngomalacia; tracheomalacia; pharyngeal obstruction (Pierre Robin sequence); bridge therapy |
| Heliox (helium-oxygen mixture) | Reduces turbulent airflow resistance; temporising measure in moderate-to-severe obstruction |
| Nasopharyngeal airway | Bypasses oropharyngeal obstruction; particularly useful in Pierre Robin sequence; facilitates CPAP delivery; note: stimulates secretions and may cause feeding difficulty, regular suctioning required |
| Intranasal corticosteroids | Adenoidal hypertrophy; allergic rhinitis contributing to upper airway obstruction; effective for residual OSA post-adenotonsillectomy |
| Montelukast (± intranasal corticosteroid) | Mild residual OSA following adenotonsillectomy |
| Propranolol (non-selective β-blocker) | First-line systemic therapy for infantile haemangioma including subglottic haemangioma; initiated under specialist supervision with monitoring for hypoglycaemia, bradycardia, and bronchospasm |
Surgical Management
| Procedure | Indication |
|---|---|
| Supraglottoplasty | Moderate-to-severe laryngomalacia not responding to conservative management |
| Laryngotracheal reconstruction (LTR), single-stage (SS-LTR) or staged | Grade II-IV SGS; rib cartilage graft augmentation; SS-LTR can avoid tracheostomy |
| Cricotracheal resection (CTR) | Severe Grade III-IV SGS, particularly in older children; superior outcomes in selected cases |
| Slide tracheoplasty | Long-segment congenital tracheal stenosis; preferred over resection for lengthy disease |
| Endoscopic balloon dilatation | Mild-to-moderate soft acquired stenosis; adjunct to open surgery; serial dilations |
| CO₂ laser | RRP debulking; soft stenoses; largely superseded by propranolol for subglottic haemangioma |
| Microlaryngeal surgery (repeated) | RRP, mainstay of treatment; recurrence tendency necessitates repeated procedures |
| Tracheostomy | Severe obstruction not amenable to immediate repair; bridge to definitive surgery; prolonged ventilation with ETT-related airway trauma; bilateral vocal cord paralysis; neuromuscular disease requiring long-term airway toilet |
| Vascular ring repair (cardiothoracic) | Symptomatic extrinsic tracheal compression |
| Adenotonsillectomy | Obstructive adenotonsillar hypertrophy; OSA; ~75% efficacy in improving or normalising sleep-disordered breathing |
| Mandibular distraction / maxillomandibular advancement ± tracheostomy | Life-threatening OSA in craniofacial syndromes |
| EXIT procedure | Antenatally diagnosed severe airway obstruction (e.g. large cystic hygroma, CHAOS/laryngeal atresia), maintains uteroplacental circulation at delivery |
| Cystic hygroma: surgical debulking, laser, or sclerosant (OK-432 or doxycycline) | Depending on extent and location |
Tracheostomy: Indications, Care, and Decannulation
Three broad indications:
- Airway obstruction not immediately correctable by other means
- Prolonged ventilation, especially where continued ETT use causes airway trauma or stenosis
- Pulmonary toilet and non-ventilatory support (e.g. neurological impairment, neuromuscular disease)
More than half of paediatric tracheostomies are performed in infants under 1 year of age; almost half are for airway obstruction in contemporary series.
Post-tracheostomy care:
- Chest X-ray immediately post-procedure to confirm tube position and exclude pneumothorax or consolidation
- Tracheostomy tapes and tube must not be changed for the first week (to allow tract formation), except in airway distress; first tube change by an experienced medical staff member
- Velcro tracheostomy tapes may be used after the first tube change
- Continuous humidification of inspired/ventilated air to prevent desiccation of secretions
- Self-ventilating infants: formal humidifier or "Swedish nose" (heat-moisture exchanger) attachment
- Regular suctioning: flexible catheter inserted only to the tube tip level, then suction activated, prevents mucosal trauma
- Emergency equipment at the bedside at all times: spare tube of the same size, one size smaller, and a tube introducer
Pre-decannulation assessment (MLB):
- Confirm adequate airway calibre
- Remove or treat any suprastomal granuloma
- Confirm vocal cord mobility
- Assess for airway collapse on respiration
Complications
Complications of Inadequately Managed Stenosis
- Respiratory failure and hypoxic brain injury
- Pulmonary hypertension and cor pulmonale
- Faltering growth and neurodevelopmental delay
- Obstructive sleep apnoea with behavioural, cognitive, and cardiovascular sequelae
Complications of Tracheostomy
| Complication | Notes |
|---|---|
| Accidental decannulation | Most immediately life-threatening; tract may close rapidly in infants |
| Tube obstruction (mucus plugging) | Immediate suctioning or tube change required |
| False passage on re-insertion | May cause pneumomediastinum or pneumothorax |
| Suprastomal granuloma | Common late complication; may prevent decannulation |
| Wound infection | Peristomal skin care essential |
| Tracheomalacia at stoma site | Cartilage resorption from pressure or infection |
| Tracheo-innominate fistula | Rare; catastrophic haemorrhage |
| Chest infection, surgical emphysema | Recognised complications |
Complications of Laryngotracheal Surgery
- Restenosis (especially with inadequate stent duration or infection)
- Dysphonia / voice change
- Aspiration / dysphagia
- Failure to decannulate
Complications of Adenotonsillectomy (for OSA)
- Mortality ~1 in 4000-27,000; overall morbidity 5-10%; morbidity in OSA patients 18-34%
- Bleeding (immediate or delayed), upper airway obstruction, nasopharyngeal stenosis, pulmonary oedema, velopharyngeal insufficiency, anaesthesia complications
- High-risk groups for post-operative PICU admission: age <2 years, craniofacial anomalies (especially midface hypoplasia, retrognathia), failure to thrive, hypotonia, cor pulmonale, marked obesity, severe OSA on polysomnography, history of prematurity
Prognosis
| Condition | Prognosis |
|---|---|
| Laryngomalacia | Excellent; majority resolve by 12-18 months; supraglottoplasty has good outcomes for severe cases |
| Post-intubation SGS (Grade I-II) | Decannulation rates >80-90% with SS-LTR in experienced centres |
| SGS Grade III-IV | Major reconstructive surgery required; LTR and CTR have comparable long-term outcomes in appropriately selected patients |
| Congenital tracheal stenosis | Slide tracheoplasty has markedly improved survival; cardiac comorbidity (pulmonary artery sling) worsens prognosis |
| RRP | Chronic relapsing course; HPV-11 associated with more aggressive disease and distal spread; adjuvant agents (cidofovir, bevacizumab) used in refractory cases; HPV vaccination may reduce future incidence |
| Subglottic haemangioma | Propranolol has transformed management; most treated without tracheostomy; involution typically complete by 3-5 years |
| Bilateral vocal cord paralysis (CNS cause) | Often requires tracheostomy; prognosis depends on underlying CNS pathology |
Follow-up
- Regular flexible nasendoscopy or MLB to monitor airway calibre
- Speech and language therapy for voice and swallowing function
- Respiratory function testing in older children: flow-volume loops are sensitive for fixed extrathoracic obstruction (plateau of inspiratory limb) and fixed intrathoracic obstruction (plateau of expiratory limb)
- Developmental and growth monitoring
- Multidisciplinary review prior to tracheostomy decannulation: formal sleep study, MLB with suprastomal granuloma exclusion, and vocal cord mobility assessment
When to Refer or Admit
Immediate Emergency Admission
- Stridor at rest with accessory muscle use, hypoxia (SpO₂ <92% on air), or altered consciousness
- Cyanosis or impending respiratory failure
- Bilateral vocal cord paralysis with desaturation
- Neonatal stridor with feeding difficulty and oxygen requirement
- Sudden complete airway obstruction
Urgent Specialist Referral (Within Days)
- Persistent or progressive stridor in any infant beyond 4 weeks of age
- Stridor not responding to standard croup therapy (raises suspicion of fixed lesion)
- Hoarse or weak cry persisting beyond the neonatal period
- History of prolonged neonatal intubation with subsequent stridor
- Recurrent croup episodes (≥3 episodes warrants investigation for structural airway pathology)
- Progressive dysphonia in a toddler (consider RRP)
Referral Pathway
Referral to a paediatric ENT surgeon with access to a tertiary multidisciplinary paediatric airway team offering MLB, paediatric anaesthesia experienced in difficult airway management, and paediatric intensive care. For neonates with antenatally detected severe airway anomalies, delivery should be planned at a centre capable of performing the EXIT procedure if required.
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