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EN4.43 | Stridor — SDL Guide (Part 2)
Assessment and Investigation of Stridor
The assessment of a patient with stridor must begin with immediate severity evaluation — before any investigation is ordered, before a history is taken in detail, and before any instrument is placed in the throat. The first clinical question is always: 'Is this airway about to obstruct?' The answer determines whether this is a clinic assessment or a resuscitation room emergency. This distinction must be made at the bedside within seconds of seeing the patient: a child sitting bolt upright with intercostal retractions and SpO2 88% is in imminent danger; an infant who stridors only when feeding, is thriving, and settles easily is not. Mixing up these two patients — treating a mild case as an emergency, or dismissing an impending obstruction as benign — are both potentially fatal errors. The clinical parameters that allow this triage are straightforward and require no investigation: they are the work of breathing, the oxygen saturation, the mental state, and whether the stridor is audible at rest or only on exertion.
Clinical severity assessment uses the following parameters in order of urgency:
1. SpO2 and respiratory rate — oxygen saturation below 94% on room air or respiratory rate more than double the age-adjusted normal indicates impending respiratory failure.
2. Work of breathing — subcostal, intercostal, and suprasternal retractions indicate that the patient is using accessory muscles; tracheal tug (downward pull of the trachea during inspiration) is a sign of severe suprasternal negative pressure generation.
3. Stridor at rest (vs. only with effort) — stridor audible only during exertion or agitation is mild; stridor audible with the patient at rest indicates significant obstruction.
4. Mental status — agitation in a previously calm child or drowsiness/exhaustion in a child who was previously agitated are both ominous signs of impending respiratory failure.
5. Cyanosis — a pre-terminal sign; by the time cyanosis appears, the airway is critically compromised.
For childhood croup, the Westley croup score provides a standardised severity tool: scores 0-2 = mild; 3-5 = moderate; ≥6 = severe. The five components scored are stridor (0-2), retractions (0-3), air entry (0-2), cyanosis (0-4), and level of consciousness (0-5).
Investigation sequence for stable patients:
- Flexible fibre-optic nasolaryngoscopy (FFNL): the primary diagnostic investigation for adult stridor and for infant laryngomalacia; performed in clinic under topical anaesthesia; directly visualises the supraglottis, glottis, and cord movement.
- AP and lateral neck X-ray: steeple sign (croup), thumb sign (epiglottitis), radiopaque foreign body. In emergencies, do not delay airway management for X-rays.
- CT of the neck and chest: for subglottic or tracheal stenosis (extent, level, grade); for laryngeal masses or carcinoma; for bilateral VCP (to assess the RLN course).
- Microlaryngoscopy and bronchoscopy (MLB/DLB) under general anaesthesia: the definitive investigation for paediatric airway evaluation; required when FFNL is insufficient; allows simultaneous intervention (biopsy, dilation, foreign body removal).
- MRI brain: for neonatal bilateral VCP — to exclude Arnold-Chiari malformation.
- Echocardiogram: for subglottic haemangioma (propranolol contraindicated in cardiac disease requiring a beta-blocker).
SELF-CHECK
A 52-year-old woman underwent total thyroidectomy for multinodular goitre 6 hours ago. She now has progressive inspiratory stridor, difficulty breathing, and an SpO2 of 89% on 4L oxygen via nasal prongs. The wound site is swollen. The most appropriate immediate management is:
A. Arrange urgent flexible nasolaryngoscopy to confirm bilateral vocal cord palsy
B. Open the wound at the bedside to decompress a haematoma, prepare for urgent intubation or tracheostomy
C. Administer nebulised adrenaline and dexamethasone while arranging CT neck
D. Place the patient in a sitting position and observe for spontaneous improvement
Reveal Answer
Answer: B. Open the wound at the bedside to decompress a haematoma, prepare for urgent intubation or tracheostomy
Post-thyroidectomy stridor with a swollen wound within hours of surgery represents a post-operative haematoma compressing the trachea — a surgical emergency. Management: open the wound immediately at the bedside to evacuate the haematoma and relieve tracheal compression; simultaneously prepare for urgent orotracheal intubation (and tracheostomy if intubation fails) to secure the airway. SpO2 89% indicates critically impaired oxygenation — further investigation or observation is not safe. Flexible nasolaryngoscopy (to confirm bilateral VCP) is appropriate in the more common delayed-onset bilateral VCP (which typically presents as mild hoarseness or stridor in the first 24-48 hours without dramatic haemodynamic compromise) — but in this acute haematoma scenario, airway decompression takes absolute priority. Nebulised adrenaline/steroids are for croup, not haematoma.
Diagnosis: Differentiating Causes of Stridor
The differential diagnosis of stridor is narrowed decisively by integrating three clinical variables: the age of the patient, the speed of onset, and the associated features. A systematic approach using these three variables prevents both under-treatment of emergencies and unnecessary investigation of benign conditions.
Age: as established above, laryngomalacia dominates the infant differential; croup and epiglottitis dominate the childhood differential; bilateral VCP and subglottic stenosis dominate the adult differential.
Speed of onset is critically discriminating. Stridor that develops over hours (epiglottitis, croup after a URI, post-thyroidectomy haematoma) demands immediate assessment. Stridor that has been present since birth (laryngomalacia, congenital subglottic stenosis, bilateral VCP in a neonate) is usually less immediately threatening. Progressive stridor over weeks to months in an adult (carcinoma, subglottic stenosis) requires urgent but not necessarily emergency evaluation.
Associated features resolve ambiguous presentations:
- Drooling, toxic appearance, hot-potato voice, tripod posture: epiglottitis. Do NOT examine throat.
- Barking cough, preceded by URI, afebrile or low-grade fever, child alert: croup.
- Sudden onset choking episode, then stridor in a toddler: foreign body aspiration.
- Stridor better when prone/neck extended, feeding-triggered, thriving neonate: laryngomalacia.
- Progressive hoarseness then stridor in an adult smoker: laryngeal carcinoma.
- Post-thyroidectomy stridor: bilateral VCP or haematoma — wound examination distinguishes them.
- Stridor months after prolonged ICU intubation: post-intubation subglottic stenosis.
Red flags indicating imminent total obstruction — these require immediate airway intervention without delay for investigation:
- SpO2 <90% on high-flow oxygen.
- Cyanosis.
- Obtunded consciousness, extreme agitation, or exhaustion.
- Paradoxical (see-saw) breathing — chest falls while abdomen rises, indicating diaphragmatic breathing with complete supraglottic obstruction.
- Silent chest (no stridor despite respiratory distress) — because the airway is so narrow that no airflow passes to create turbulence.
Principles of Management of Stridor
The management of stridor follows a universal hierarchy regardless of the cause: first, assess severity and protect the airway if necessary; second, identify and treat the underlying cause. Every treatment decision must be made with the question: 'Can this airway obstruct completely if I delay intervention?' in mind. This framework is more useful than trying to memorise separate management protocols for each cause, because in a clinical emergency the cause may not yet be known — but the severity is always assessable at the bedside within seconds. A clinician who can reliably assess severity, initiate appropriate immediate airway protection, and then move deliberately to cause-specific treatment will manage stridor safely across any age group and any aetiology. The cause-specific treatments that follow — dexamethasone for croup, supraglottoplasty for severe laryngomalacia, tracheostomy for bilateral VCP — are applied AFTER the airway is considered safe; they are never the first step in a severe case. Understanding this hierarchy is the central practical learning point of this SDL.
The general airway-protection interventions available, in order of escalating invasiveness, are:
1. Positioning: upright sitting, jaw thrust, neck extension — reduce dynamic collapse in laryngomalacia and improve airway patency in any supraglottic obstruction.
2. Supplemental oxygen: via face mask; maintains SpO2 while the cause is being treated.
3. Nebulised adrenaline (epinephrine 1:1000, 0.5 mL/kg, max 5 mL): for subglottic oedema (croup, post-extubation stridor) — produces transient vasoconstriction and reduction of mucosal oedema; onset within minutes; duration 2-3 hours; patient must be observed for rebound.
4. Systemic corticosteroids (dexamethasone 0.15-0.6 mg/kg oral/IV; prednisolone; budesonide nebulised): reduce inflammatory oedema; onset over hours; reduce severity and duration of croup.
5. Orotracheal intubation: definitive airway access for patients who cannot be managed with the above; in epiglottitis, performed in theatre under controlled RSI with anaesthetic team present.
6. Tracheostomy: the gold standard for definitive long-term airway management; performed at 2nd-3rd tracheal ring in elective or semi-elective settings (details covered in EN4.44).
7. Cricothyroidotomy: emergency procedure through the cricothyroid membrane when intubation is not possible ('can't intubate, can't oxygenate' scenario); provides a temporising airway until a definitive tracheostomy can be performed.
Cause-specific management:
- Laryngomalacia: most cases = conservative (reassurance, anti-reflux therapy as laryngopharyngeal reflux worsens laryngomalacia); indications for supraglottoplasty (surgical division of shortened aryepiglottic folds and trimming of redundant arytenoid mucosa) = failure to thrive, obstructive apnoea, aspiration pneumonia, cor pulmonale.
- Croup: mild = oral dexamethasone 0.15-0.6 mg/kg, discharge; moderate = nebulised adrenaline + dexamethasone + observation ≥4 hours post-adrenaline; severe = intubation.
- Epiglottitis: airway first (controlled RSI intubation), then IV ceftriaxone; ICU admission; extubate at 48-72 hours when epiglottitic swelling resolves.
- Bilateral vocal cord palsy: acute = tracheostomy to secure airway; once stabilised, treatment of underlying cause (e.g., steroids for RLN neuropraxia, remove thyroid mass if compressing); definitive = posterior cordotomy (CO2 laser, enlarges glottic aperture by vaporising posterior cord/arytenoid) or arytenoidectomy — at the cost of some voice quality.
- Post-intubation subglottic stenosis: Cotton-Myer grade I-II = endoscopic dilatation (balloon or rigid); grade III-IV = laryngotracheal reconstruction (cricoid split, rib-cartilage graft, T-tube stenting).
- Laryngeal carcinoma with stridor: tracheostomy to secure airway before definitive oncological treatment.
- Foreign body: rigid bronchoscopy for retrieval; if complete obstruction, Heimlich manoeuvre first in children ≥1 year.
CLINICAL PEARL
The single most dangerous error in managing a child with stridor is attempting to examine the oropharynx with a tongue depressor in a child with suspected epiglottitis. The second most dangerous error is discharging a child after nebulised adrenaline without adequate observation — adrenaline's effect lasts 2-3 hours and then wears off, causing a rebound. And there is a third, frequently overlooked error: interpreting a 'silent chest' (no stridor despite obvious respiratory effort) as improvement. In severe airway obstruction, the stridor disappears not because the obstruction has resolved but because the flow through the narrowed segment has become too slow to generate turbulence — this is a sign of pre-arrest exhaustion, not recovery. A silent, distressed child with intercostal recessions requires immediate airway intervention.
Self-Assessment: Stridor
Work through the following scenarios to confirm your clinical reasoning for stridor. Each scenario is designed around the three-variable framework covered in this SDL — age group, speed of onset, and associated features — that allows you to narrow the differential at the bedside before any investigation. For each scenario, identify the most likely cause, name the phase of stridor and what anatomical level it implies, state the severity category, and describe the first management step. The clinical principle being tested is not recall of a fact but application of a framework: can you use the limited information provided to make the correct triage decision and the correct management choice? These are the same decisions you will face in a paediatric emergency room, a postoperative ward, or a rural clinic without specialist backup.
Scenario A: A 4-week-old infant has had inspiratory stridor since the second week of life, worse during feeding and crying. Weight gain is normal. Between feeds the infant is quiet. FFNL shows an omega-shaped epiglottis.
- Diagnosis, management?
Scenario B: A 3-year-old presents at night with a 2-day history of runny nose followed by a barking cough and moderate inspiratory stridor audible at rest. SpO2 95% on room air. Subcostal retractions present.
- Diagnosis, Westley score category, immediate treatment?
Scenario C: A 60-year-old male underwent total thyroidectomy 18 hours ago. He is now sitting upright with increasing dyspnoea, biphasic stridor, and SpO2 88%. His neck wound appears tense and swollen.
- Diagnosis? What is the immediately life-saving intervention?
Key recall questions:
- What is the phase of stridor in croup and why?
- Why is laryngomalacia worse with feeding and crying?
- What is a 'silent chest' in a child with stridor, and what does it mean clinically?
- State three indications for supraglottoplasty in laryngomalacia.
- What is the Cotton-Myer grading system used for?
Answers:
- Croup = biphasic stridor (subglottic/tracheal level; cricoid ring is the narrowest fixed point, narrowing affects both inspiration and expiration).
- Inspiratory effort generates Bernoulli-effect negative pressure that sucks the floppy supraglottic structures inward; feeding and crying increase inspiratory effort.
- A silent chest in a distressed child means airflow through the critically narrowed segment is too slow to generate turbulence — this is a pre-arrest sign, NOT improvement; requires immediate airway intervention.
- Three indications for supraglottoplasty: failure to thrive, obstructive apnoea, aspiration pneumonia (also: cor pulmonale).
- Cotton-Myer grading classifies post-intubation subglottic stenosis severity: Grade I (<50% obstruction) to Grade IV (complete obstruction); guides choice of endoscopic vs open surgical treatment.