EARLY SIGNS OF STRIDOR IN CHILDREN EVERY PARENT SHOULD KNOW

Stridor, derived from the Latin word “stridor” meaning a harsh, grating, or creaking sound, is a high-pitched, monophonic sound produced by turbulent airflow through a narrowed or partially obstructed upper airway. Unlike wheezing, which typically originates from the lower airways, stridor indicates a compromise at or above the thoracic inlet, involving the pharynx, larynx, or trachea. In children, stridor is a particularly concerning symptom as their smaller, more compliant airways are highly susceptible to obstruction, potentially leading to rapid respiratory decompensation and life-threatening situations. Understanding its nuances is crucial for timely diagnosis and effective management.

Definition of Stridor

Stridor is best defined as an abnormal, high-pitched respiratory sound, most often inspiratory, resulting from partial obstruction of the large conducting airways. The character of the sound provides clues to the level of obstruction:

• Inspiratory Stridor: Suggests obstruction at or above the vocal cords (e.g., laryngomalacia, croup, epiglottitis). It is exacerbated by inspiration due to negative intrathoracic pressure collapsing the extrathoracic airway.
• Expiratory Stridor: Indicates obstruction in the intrathoracic trachea or bronchi (e.g., tracheomalacia, foreign body in the lower trachea). It is more prominent during expiration when positive intrathoracic pressure collapses the intrathoracic airway.
• Biphasic Stridor: Implies a fixed, severe obstruction, often at the glottis or subglottis, where airflow is restricted during both inspiration and expiration (e.g., severe subglottic stenosis, large foreign body).

The presence of stridor always signals an urgent need for evaluation, as it reflects compromised airflow in the main conduit for respiration.

Causes of Stridor in Children

The etiology of stridor in children is diverse, encompassing congenital anomalies, infectious processes, inflammatory conditions, traumatic injuries, and foreign body aspirations. Given the dynamic nature of a child’s developing airway, both acute and chronic causes are common. Causes can broadly be categorized by their onset (acute vs. chronic) and by the presence or absence of fever (pyrexial vs. apyrexial).

(a) Causes of Pyrexial Stridor in Children

Pyrexial stridor in children typically indicates an acute inflammatory or infectious process affecting the upper airway. These conditions often progress rapidly and can be life-threatening.

1. Croup (Laryngotracheobronchitis):
   • Description: The most common cause of pyrexial stridor in children, typically affecting those aged 6 months to 3 years. It is usually caused by viral infections (most commonly parainfluenza virus).
   • Presentation: Gradual onset of a characteristic “barking” or “seal-like” cough, hoarseness, inspiratory stridor, and low-grade fever. Symptoms are often worse at night.
   • Airway Level: Larynx and trachea (subglottic).
2. Epiglottitis (Supraglottitis):
   • Description: A severe, rapidly progressive bacterial infection (historically Haemophilus influenzae type b, now less common due to vaccination) leading to inflammation and swelling of the epiglottis and surrounding supraglottic structures.
   • Presentation: Abrupt onset of high fever, severe sore throat, dysphagia, drooling, muffled voice (not hoarse), and inspiratory stridor. The child often assumes a “tripod” or “sniffing” position. This is a medical emergency.
   • Airway Level: Supraglottic.
3. Bacterial Tracheitis:
   • Description: A less common but severe bacterial infection of the trachea, often secondary to a viral upper respiratory infection. Caused by Staphylococcus aureus or other bacteria.
   • Presentation: Presents similarly to severe croup, with high fever, progressive inspiratory and expiratory stridor, brassy cough, and often appears more toxic than a child with viral croup. May have thick purulent secretions in the trachea.
   • Airway Level: Subglottic and tracheal.
4. Retropharyngeal Abscess (RPA):
   • Description: A collection of pus in the retropharyngeal space, usually secondary to a bacterial infection of the pharynx, tonsils, or adenoids. Common in children under 6 years.
   • Presentation: High fever, difficulty swallowing, drooling, stiff neck (torticollis), muffled voice, and inspiratory stridor due to anterior displacement of the posterior pharyngeal wall.
   • Airway Level: Pharyngeal.
5. Peritonsillar Abscess (PTA):
   • Description: A collection of pus between the palatine tonsil and the superior constrictor muscle. More common in older children and adolescents.
   • Presentation: Severe sore throat, unilateral pain, fever, trismus (difficulty opening mouth), “hot potato” voice, and occasionally inspiratory stridor if the swelling is significant enough to compromise airflow.
   • Airway Level: Pharyngeal.

(b) Causes of Apyrexial Stridor in Children

Apyrexial stridor typically suggests a congenital anomaly, a chronic inflammatory process, or a non-infectious acute event like foreign body aspiration.

1. Laryngomalacia:
   • Description: The most common cause of congenital stridor, resulting from immaturity and flaccidity of the laryngeal cartilages (omega-shaped epiglottis, short aryepiglottic folds).
   • Presentation: Inspiratory stridor that is present from birth or soon after, often worsens with crying, feeding, or supine positioning, and improves when prone. Usually benign and resolves by 12-18 months.
   • Airway Level: Supraglottic.
2. Vocal Cord Paralysis (VCP):
   • Description: Can be unilateral or bilateral. Unilateral VCP often causes a weak cry/hoarseness; bilateral VCP can cause severe biphasic stridor and respiratory distress due to adduction of both cords. Causes include birth trauma, neurological conditions (hydrocephalus, Chiari malformation), or idiopathic.
   • Presentation: Hoarse cry, feeding difficulties, and stridor (biphasic if bilateral).
   • Airway Level: Glottic.
3. Subglottic Stenosis (SGS):
   • Description: Narrowing of the airway below the vocal cords. Can be congenital (failure of complete recanalization of the cricoid ring) or acquired (most commonly due to prolonged endotracheal intubation, causing granulation tissue and scarring).
   • Presentation: Biphasic stridor, recurrent croup-like episodes unresponsive to standard treatment, and varying degrees of respiratory distress. Severity depends on the degree of narrowing.
   • Airway Level: Subglottic.
4. Tracheomalacia/Bronchomalacia:
   • Description: Weakness and collapse of the tracheal or bronchial walls, often due to congenital defects in cartilage formation or extrinsic compression (e.g., vascular rings).
   • Presentation: Expiratory stridor (or biphasic if severe), brassy cough, recurrent respiratory infections, and “dying spells” (apneic episodes). Worse with exertion or crying.
   • Airway Level: Tracheal/Bronchial.
5. Foreign Body Aspiration (FBA):
   • Description: An acute, non-infectious cause of stridor. Common in toddlers and preschoolers. Objects like nuts, seeds, small toys can lodge in the larynx, trachea, or bronchi.
   • Presentation: Sudden onset of choking, coughing, gagging, followed by stridor (if laryngeal/tracheal) or wheezing/decreased breath sounds (if bronchial). Can be life-threatening.
   • Airway Level: Any level, depending on impaction site.
6. Vascular Ring/Sling:
   • Description: Congenital anomalies of the great vessels (e.g., double aortic arch, right aortic arch with left ligamentum arteriosum) that encircle and compress the trachea and/or esophagus.
   • Presentation: Often present in early infancy with biphasic stridor exacerbated by feeding, recurrent respiratory infections, dysphagia, and a “brassy” cough.
   • Airway Level: Tracheal (extrinsic compression).
7. Laryngeal Cysts/Webs/Hemangiomas:
   • Description: Rare congenital lesions that can obstruct the airway. Laryngeal cysts can cause progressive stridor. Laryngeal webs are incomplete separation of vocal cords. Subglottic hemangiomas are vascular tumors that grow over time, causing progressive stridor.
   • Presentation: Varies with lesion type and size, usually progressive stridor, hoarseness, and sometimes feeding difficulties.
   • Airway Level: Laryngeal/Subglottic.

Investigations of Stridor in Children

The diagnostic approach to stridor in children is guided by the acuity of presentation, suspected cause, and the child’s clinical stability.

1. Clinical Assessment (Crucial First Step):
   • History:
     • Onset: Acute (foreign body, epiglottitis) vs. chronic (laryngomalacia, subglottic stenosis).
     • Associated Symptoms: Fever, cough (barking vs. brassy), drooling, dysphagia, voice changes (hoarse, muffled), feeding difficulties, cyanosis, apneas.
     • Course: Progressive, intermittent, worse with crying/feeding/position.
     • Past Medical History: Prematurity, intubation, congenital anomalies, recurrent croup episodes.
     • Immunization Status: Pertinent for epiglottitis.
   • Physical Examination:
     • General Appearance: Alertness, level of distress, color (cyanosis, pallor).
     • Respiratory Effort: Retractions (supra-sternal, intercostal, subcostal), nasal flaring, head bobbing, accessory muscle use.
     • Characteristics of Stridor: Inspiratory, expiratory, biphasic; loudness (may decrease with worsening obstruction).
     • Auscultation: Air entry, presence of wheezing or rhonchi.
     • Oral/Pharyngeal Exam: Look for drooling, tonsillar enlargement, uvula deviation (caution with epiglottitis – avoid direct pharyngeal examination if suspected!).
     • Neck Exam: Masses, lymphadenopathy, tracheal deviation.
2. Imaging Studies:
   • Plain Radiographs:
     • Lateral Neck X-ray: Useful for identifying epiglottic swelling (“thumb sign”), retropharyngeal abscess, or widening of prevertebral space. In croup, can show subglottic narrowing (“steeple sign”).
     • Anteroposterior (AP) Neck X-ray: Best for “steeple sign” of croup.
     • Chest X-ray: To rule out lower airway pathology (pneumonia, foreign body aspiration).
   • Fluoroscopy/Barium Swallow: For suspected tracheomalacia, esophageal compression (vascular ring), or aspiration.
   • Computed Tomography (CT) Scan: Provides detailed cross-sectional images of the airway, superior for evaluating neck masses, mediastinal pathology, vascular rings, and confirming abscesses. Can be done with contrast.
   • Magnetic Resonance Imaging (MRI): Useful for soft tissue lesions, vascular anomalies, and neurological causes of vocal cord paralysis, particularly in the brain and brainstem.
3. Endoscopic Evaluation (Gold Standard for Direct Visualization):
   • Flexible Laryngoscopy (FLES): Performed awake or with mild sedation, allows visualization of the pharynx, larynx, and upper trachea. Can diagnose laryngomalacia, vocal cord paralysis, laryngeal cysts, webs, and papillomas. Less invasive but limited for subglottic and tracheal assessment.
   • Rigid Bronchoscopy: Performed under general anesthesia. Provides definitive diagnosis for most airway anomalies including subglottic stenosis, tracheomalacia, and is essential for foreign body removal. Allows for assessment of airway dimensions and dynamic collapse.
4. Laboratory Studies:
   • Complete Blood Count (CBC): May indicate infection (leukocytosis, elevated inflammatory markers).
   • Blood Cultures: If bacterial infection is suspected (e.g., epiglottitis, bacterial tracheitis, RPA).
   • Viral Panels (PCR): For viral causes like croup.
   • Arterial Blood Gas (ABG)/Venous Blood Gas (VBG): To assess severity of respiratory compromise (hypoxia, hypercapnia).

Management Protocol of Stridor in Children

The management of stridor in children is dictated by the underlying cause, but crucially, it prioritizes airway patency and respiratory support. A step-by-step approach emphasizes assessment, stabilization, and specific intervention.

Step 1: Immediate Assessment and Stabilization (ABCs – Airway, Breathing, Circulation)

• Secure Airway: The paramount concern. Assess severity of respiratory distress (retractions, tachypnea, nasal flaring, cyanosis, altered mental status).
  • Mild Stridor: Child is comfortable, good air entry.
  • Moderate Stridor: Visible retractions, moderate respiratory effort.
  • Severe Stridor: Significant retractions, marked distress, cyanosis, lethargy, decreased level of consciousness. This is an emergency requiring immediate intervention.
• Positioning: Allow the child to assume a comfortable position (e.g., tripod position for epiglottitis). Do not force supine position.
• Oxygen: Administer humidified oxygen, typically via face mask or nasal cannula, to maintain SpO2 > 92-95%.
• Minimize Disturbances: Keep the child calm. Avoid upsetting procedures (e.g., IV line insertion, throat examination for suspected epiglottitis) until the airway is secure or a definitive plan is in place.
• Prepare for Airway Intervention: Have intubation equipment (smaller ETT sizes), tracheostomy tray, and experienced personnel readily available.

Step 2: Specific Medical Management (Based on Suspected Etiology)

• For Croup (Viral Laryngotracheobronchitis):
  • Dexamethasone: A single dose of oral (0.15-0.6 mg/kg) or intramuscular (0.6 mg/kg) dexamethasone is the cornerstone of treatment to reduce laryngeal edema.
  • Nebulized Epinephrine (Racemic or L-epinephrine): For moderate to severe croup or those with significant respiratory distress. Provides rapid, albeit temporary, vasoconstriction to reduce mucosal edema. Requires monitoring for rebound stridor.
  • Humidified Air: Can be soothing but not a primary treatment.
  • Antipyretics: For fever management.
• For Epiglottitis:
  • Do NOT Examine Throat: Avoid stimulating the airway, as it can precipitate complete obstruction.
  • Maintain Calm: Keep the child with parents.
  • Secure Airway: Urgent intubation in a controlled environment (operating theater) by the most experienced personnel (anesthesiologist, ENT surgeon) is the definitive management. If intubation fails, surgical airway (tracheostomy) may be necessary.
  • Antibiotics: Once airway is secure, administer intravenous broad-spectrum antibiotics (e.g., ceftriaxone, cefotaxime) to cover H. influenzae and other potential pathogens.
• For Bacterial Tracheitis:
  • Airway Management: Often requires intubation due to severe subglottic/tracheal edema and thick secretions. Frequent suctioning may be needed.
  • Antibiotics: Intravenous broad-spectrum antibiotics (e.g., vancomycin plus third-generation cephalosporin) to cover Staphylococcus aureus and other bacteria.
  • Bronchoscopy: Therapeutic bronchoscopy may be needed to remove thick purulent membranes and secretions.
• For Retropharyngeal Abscess/Peritonsillar Abscess:
  • Airway Vigilance: Monitor for airway compromise.
  • Antibiotics: Intravenous antibiotics.
  • Drainage: Surgical incision and drainage of the abscess is often required.
• For Foreign Body Aspiration:
  • Acute Choking: Back blows/chest thrusts (infants) or abdominal thrusts (children) if witnessed and child is conscious and suddenly unable to cough or breathe.
  • Stable but Suspected FBA: Urgent rigid bronchoscopy for direct visualization and removal of the foreign body.
  • Monitor: Watch for signs of worsening obstruction until removed.
• For Congenital/Chronic Causes (e.g., Laryngomalacia, SGS, Tracheomalacia):
  • Laryngomalacia: Most cases are mild and resolve spontaneously. Management is supportive (monitoring, feeding adjustments). Severe cases with significant respiratory distress, failure to thrive, or apneas may require supraglottoplasty (surgical modification of the larynx).
  • Subglottic Stenosis: Mild cases may be managed conservatively. More severe cases often require surgical intervention (e.g., endoscopic dilation, cricoid split, laryngotracheal reconstruction with cartilage grafts).
  • Tracheomalacia/Bronchomalacia: Mild cases are managed conservatively. Severe cases may require CPAP, stent placement, or surgical correction (aortopexy for vascular compression).
  • Vocal Cord Paralysis: Unilateral VCP often resolves spontaneously. Bilateral VCP may require tracheostomy for airway patency, followed by reinnervation procedures or arytenoidectomy if severe.
  • Vascular Ring: Surgical division of the constricting vessel is the definitive treatment.

Step 3: Ongoing Monitoring and Supportive Care

• Respiratory Monitoring: Continuous pulse oximetry, respiratory rate, work of breathing, and stridor characteristics.
• Fluid Management: Maintain hydration, often intravenously while airway is at risk.
• Nutritional Support: Ensure adequate caloric intake, especially if feeding difficulties are present.
• Parental Support: Reassure and educate parents; anxiety can exacerbate distress in children.

In conclusion, stridor in children is a critical sign demanding prompt and thorough evaluation. From its distinctive sounds providing clues to obstruction levels to its diverse etiologies, a structured diagnostic and management approach is essential. Rapidly distinguishing between acute, life-threatening causes and more chronic, benign conditions allows for appropriate and timely intervention, ultimately safeguarding the child’s airway and promoting optimal outcomes.