What is stridor and how should it be urgently managed in patients presenting with it?

Stridor: Definition and Urgent Management

What is Stridor?

Stridor is a high-pitched respiratory sound caused by turbulent airflow through a narrowed airway, indicating at least 50% airway narrowing and representing imminent complete obstruction. 1, 2

• Stridor results from turbulent airflow through the trachea due to upper airway obstruction 2
• The sound can originate from obstruction anywhere in the extrathoracic airway (nose, pharynx, larynx, trachea) or intrathoracic airway 3
• Stridor is a clinical sign, not a diagnosis - the underlying cause must be identified 3

Stridor Characteristics Guide Diagnosis

• Inspiratory stridor indicates supraglottic or glottic obstruction 4
• Biphasic stridor suggests glottic or subglottic lesions, such as subglottic stenosis or fixed airway lesions 5, 6
• Fixed lesions of the glottis or subglottis produce biphasic stridor, whereas dynamic lesions usually cause only inspiratory stridor 5

Immediate Severity Assessment

Assess immediately for signs of critical airway obstruction: oxygen saturation <90%, bradycardia, inability to speak or drink, accessory muscle use, and retractions - if present, initiate emergency airway management while calling for help and ENT consultation. 5, 1, 6

Critical Signs of Severe Respiratory Distress

• Oxygen saturation <90% 5, 6
• Bradycardia or heart rate changes 5, 6
• Inability to speak or drink 5, 6
• Accessory muscle use 4, 5, 6
• Tracheal tug 4, 6
• Sternal, subcostal, or intercostal retractions 4, 5, 6
• Agitation, restlessness, or obvious distress 4, 1
• Cyanosis 4, 5

Note that signs may become absent as obstruction worsens - an agitated child may have severe obstruction even without obvious retractions 4

Urgent Management Protocol

Step 1: Immediate Stabilization (First 60 Seconds)

Position the patient upright (or optimize airway positioning with chin lift and jaw thrust) and apply high-flow humidified oxygen immediately to both the face and tracheostomy site if applicable. 5, 1, 6

• In children under 2 years, a more neutral position with a pillow or rolled towel under the shoulders may improve airway patency 4
• Apply oxygen to the face AND to the tracheostomy if present - this requires two oxygen sources 4
• If only one oxygen supply is available, apply it to whichever airway shows spontaneous breathing 4

Step 2: Call for Help

Immediately summon advanced help including experienced ENT surgeon availability, anesthesia with advanced airway skills, and prepare emergency airway equipment. 4, 5, 1

• Have equipment for emergency intubation or tracheostomy readily available, as deterioration can be rapid 5
• In hospital: call resuscitation team ("2222") 4
• Outside hospital: call emergency services ("999" or "911") 4

Step 3: Apply Waveform Capnography

Apply waveform capnography immediately if available - this is a key intervention to improve airway management safety. 4, 1

• Capnography should be immediately available in pediatric critical care areas 4
• Movement of the breathing circuit bag can indicate gas movement via airways 4

Step 4: Pharmacologic Intervention

Administer nebulized epinephrine 1 mg immediately for rapid relief of laryngeal edema while steroids take effect. 5, 1, 6

• Epinephrine provides symptomatic relief but effect is transient (1-2 hours) 1, 6
• This is particularly effective for post-extubation stridor and inflammatory causes 1

Administer intravenous dexamethasone for anti-inflammatory effect in all cases of acute stridor. 5, 6

• For high-risk patients, begin dexamethasone at least 12-24 hours before planned extubation if applicable 5, 1
• Recommended dose: equivalent to 100 mg hydrocortisone every 6 hours (or dexamethasone 8 mg every 8 hours), continued for at least 12 hours 1
• Single-dose steroids immediately before extubation are ineffective 1

Context-Specific Management

Post-Extubation Stridor

Prepare for reintubation with videolaryngoscopy as first-line approach to maximize success in edematous airways, with neck access equipment ready. 1

• Post-extubation stridor occurs in 1-30% of patients and increases reintubation risk to approximately 15% 1
• Perform cuff leak test before extubation in any patient with at least one risk factor for laryngeal edema 1, 6
• If leak volume is low or nil, prescribe corticosteroids (prednisolone 1 mg/kg/day or equivalent) starting at least 6-12 hours before extubation 1

Stridor After Trauma

Stridor after trauma indicates progressive edema that will worsen, not resolve spontaneously - administer inhaled racemic epinephrine immediately while preparing for intubation in a controlled environment. 1, 6

• Transfer to controlled environment with most experienced operator available 1
• Steroids reduce inflammatory edema from direct injury (surgical, anesthetic, thermal, chemical) 1
• Steroids have no effect on mechanical edema from venous obstruction (e.g., cervical hematoma) - these require different interventions 1

Upper Airway Tumor

Do not use videolaryngoscopy if there is an upper airway tumor with stridor - consider alternative difficult airway techniques with the most experienced operator. 1

• The combination of difficult upper airway and deteriorating gas exchange is extremely challenging 1

Post-Thyroidectomy Hematoma

Use the SCOOP approach at bedside immediately: Skin exposure, Cutting sutures, Opening skin, Opening muscles (strap muscles), Packing wound - do not wait for the operating room. 1

Diagnostic Evaluation

When stridor persists or is severe, perform flexible fiberoptic laryngoscopy - this is the diagnostic procedure of choice for examining laryngeal structure and function. 1, 6, 3

• Inspect both upper and lower airways, as anomalies below the epiglottis occur in up to 68% of cases 1
• About 1 out of 10 infants have lesions in more than one anatomical site 3
• Direct observation of vocal cord adduction by laryngoscopy is the hallmark for diagnosing vocal cord dysfunction 4

Rule Out Upper Airway Obstruction

Evaluate for upper airway obstruction causes including foreign bodies, epiglottitis, organic laryngeal diseases, vocal cord dysfunction, and tracheal narrowing. 4

• Clues to upper airway obstruction: dysphonia, inspiratory stridor, monophonic wheezing loudest over central airway, normal PaO2, complete resolution with intubation 4
• If suspected, evaluate using flow-volume curves and laryngoscopy 4

Common Pitfalls to Avoid

Do not attempt awake intubation in an angustic patient with evolving airway obstruction - this will worsen the obstruction. 6

Do not perform blind digital sweeps in suspected foreign body aspiration - this can push objects deeper into the pharynx. 6

Do not use excessive positive pressure ventilation immediately post-intubation - this can cause hemodynamic collapse. 1

Do not assume steroids will work for mechanical obstruction (hematoma, tumor) - these require surgical intervention. 1, 6

Do not underdose steroids - ensure adequate dosing equivalent to 100 mg hydrocortisone every 6 hours. 1

Do not order routine imaging in typical presentations - this delays treatment and exposes patients to unnecessary radiation. 6

Special Considerations

Paradoxical Vocal Cord Motion

• Paradoxical vocal cord adduction occurs on inspiration and can cause stridor following extubation 4
• More common in young females and those with emotional stress 4
• Often misdiagnosed as laryngospasm or bronchospasm 4
• Diagnosis requires direct observation of vocal cords 4
• Responds to anxiolytic, sedative, or opioid agents 4

Exercise-Induced Laryngeal Dysfunction (EILD)

• Inspiratory stridor is the hallmark differentiating sign of EILD versus exercise-induced bronchoconstriction 4
• Onset occurs and peaks during exercise, resolving within approximately 5 minutes of stopping 4
• Beta-2 agonists are ineffective for EILD 4
• More common in young adult female elite athletes 4

Pediatric Considerations

• In children 6 months to 5-6 years, croup is the most likely diagnosis, presenting with barking cough, hoarse voice, and inspiratory stridor 6
• Laryngomalacia is the most common cause of inspiratory stridor in infants 4
• Recurrent episodes (two or more per year) justify evaluation for underlying conditions including asthma, anatomical abnormalities, and gastroesophageal reflux 6