What are the causes and management of stridor?

Causes and Management of Stridor

Stridor is primarily caused by airway obstruction, with laryngomalacia being the most common cause in children, while in adults it often results from acute or post-extubation laryngeal edema, vocal cord dysfunction, or airway trauma. 1, 2

Causes of Stridor

Congenital Causes

• Laryngomalacia is the most common congenital laryngeal anomaly and the most frequent cause of persistent stridor in children 1, 2
• Other congenital anomalies include laryngoceles, saccular cysts, laryngeal webs and atresia, laryngotracheal stenosis, laryngeal and tracheal clefts, congenital neoplasms such as hemangiomas, and bifid epiglottis 1
• Vocal cord paralysis is the third most common congenital laryngeal anomaly producing stridor in infants and children, usually resulting from central nervous system anomalies 1, 2
• Tracheomalacia and bronchomalacia (primary or secondary to vascular compression) can cause persistent wheezing and stridor 1

Acquired Causes

• Foreign body aspiration can cause localized monophonic wheeze or stridor 1
• Post-extubation laryngeal edema is a significant cause of stridor in hospitalized patients 1
• Laryngospasm, a protective exaggeration of the normal glottic closure reflex, can cause stridor and airway obstruction 1
• Exercise-induced laryngeal dysfunction (EILD) can present with inspiratory stridor during exercise 1
• Paradoxical vocal cord motion, where vocal cord adduction occurs on inspiration, can cause stridor following extubation 1
• Acquired subglottic stenosis, reported in 1.7-12.8% of previously intubated neonates 1

Clinical Assessment

Timing and Character of Stridor

• Inspiratory stridor typically indicates supraglottic or glottic obstruction 3
• Expiratory stridor suggests obstruction at or below glottic level 3
• Biphasic stridor often indicates fixed lesions of the glottis or subglottis 1
• Exercise-induced stridor that resolves within 5 minutes of stopping exercise suggests EILD 1

Associated Symptoms

• Severe or persistent symptoms, hoarseness, oxygen desaturation, or apnea warrant immediate investigation 1
• Cyanotic or life-threatening episodes, chronic wheezing unresponsive to bronchodilators, recurrent atelectasis, or failure to wean from mechanical ventilation may indicate central airway obstruction 1
• Post-extubation stridor is a significant marker for moderate to severe subglottic stenosis or laryngeal injury 1

Diagnostic Approach

Primary Diagnostic Tool

• Flexible endoscopy of the airways is the diagnostic procedure of choice in most circumstances 1, 2, 3
• Examination should include both upper and lower airways, as abnormalities below the epiglottis are found in up to 68% of cases 1

Additional Diagnostic Methods

• Cuff leak test should be performed before extubation to predict laryngeal edema in at-risk patients 1
• Waveform capnography can aid in assessment of airway patency 1
• Direct observation of vocal cord adduction by laryngoscopy and flattening of the inspiratory portion of the flow-volume loop are diagnostic for vocal cord dysfunction 1
• Continuous laryngoscopy during exercise challenge can diagnose exercise-induced laryngeal dysfunction 1

Management

Immediate Management of Acute Stridor

• Assess airway patency using clinical assessment and suction initially 1
• Position the patient appropriately - chin lift with or without jaw thrust is useful in children of all ages 1
• Deliver high-flow oxygen to the patient's face and to the tracheostomy if present 1
• For post-extubation laryngeal edema, corticosteroids should be started at least 6 hours before extubation 1

Management Based on Specific Causes

• For laryngomalacia, most cases can be managed conservatively with resolution by 2 years of age; severe cases may require supraglottoplasty 4
• For post-intubation subglottic stenosis, prevention strategies include appropriate endotracheal tube sizing and minimizing duration of intubation 1
• For exercise-induced laryngeal dysfunction, a multidisciplinary approach including speech therapy may be required 1
• For paradoxical vocal cord motion, treatment with anxiolytic, sedative, or opioid agents may be effective 1

Risk Factors and Prevention

Risk Factors for Post-Intubation Stridor

• Intubation for 7 days or more and three or more intubations 1
• Use of inappropriately large endotracheal tubes (tube size-to-gestational age ratio greater than 0.1) 1
• Female gender, nasal route for intubation, difficult/traumatic/prolonged intubation, and high tracheal cuff pressures 1

Prevention Strategies

• Appropriate sizing of endotracheal tubes has been shown to decrease the incidence of subglottic stenosis 1
• Reducing length of tracheal intubation or avoiding intubation altogether (using nasal CPAP instead) has been associated with prevention of subglottic stenosis 1
• Corticosteroids should be prescribed if the cuff leak volume is low or nil before extubation 1

Special Considerations

• Stridor in older children is rare but, if not due to recent endotracheal intubation, always warrants endoscopy of the airways 1, 2
• In infants, apnea can replace the usual sign of stridor due to easy fatigability and paradoxical response to hypoxemia 1
• Laryngeal pathology is present in more than 75% of ventilated patients, including edema, mucosal ulceration, vocal cord paresis, and granuloma 1
• If not relieved promptly, laryngospasm may result in post-obstructive pulmonary edema and hypoxic cardiac arrest 1