Approach to stridor

Algorithmic Approach To Stridor

graph TD
    A([Stridor in a Child]) --> B{Assess Severity}

     Acute vs Chronic
    F -->|Acute| G{Presence of Fever?}
    F -->|Chronic / Recurrent<br/>Months/Congenital| H{Clinical Features}

     Acute Afebrile
    G -->|Afebrile| N{History & Exam}
    N -->|Sudden choking episode| O[Foreign Body Aspiration]
    O --> O_Tx[Rigid Bronchoscopy<br/>Heimlich if immediate obstruction]
    N -->|Other Causes| P[Anaphylaxis / Spasmodic Croup / Trauma / Hypocalcemia]

     Investigations Link
    E -.-> V[<b>Key Diagnostics when stable:</b><br/>- AP X-ray: Steeple sign Croup<br/>- Lateral X-ray: Thumb sign Epiglottitis<br/>- Awake Flex Laryngoscopy: Chronic causes<br/>- Bronchoscopy: FB / Tracheitis / Stenosis sizing]
    
    %% Styling
    classDef emergency fill:#ffcccc,stroke:#ff0000,stroke-width:2px,color:#000;
    classDef diagnosis fill:#e1f5fe,stroke:#0288d1,stroke-width:1px,color:#000;
    classDef treatment fill:#e8f5e9,stroke:#388e3c,stroke-width:1px,color:#000;
    class C,D emergency;
    class J,K,L,M,O,Q,R,S,T,U diagnosis;
    class J_Tx,K_Tx,L_Tx,O_Tx,Q_Tx,R_Tx,S_Tx treatment;

Definition And Pathophysiology

• Indicates acute or chronic upper respiratory tract obstruction.
• Characterized by high-pitched, harsh, or metallic/brassy sounds.
• Produced by turbulent airflow across narrowed segments of respiratory tract.
• Airway resistance inversely proportional to fourth power of airway radius.
• Minor reductions in cross-sectional area exponentially increase airway resistance and work of breathing.
• Anatomic factors predisposing infants include small laryngeal size, loose submucous connective tissue around glottis, and rigid cricoid cartilage encircling subglottic zone.
• Cricoid cartilage represents narrowest portion of upper airway in children under 10 years.

Classification

Anatomic Classification Based On Respiratory Phase

Phase	Sound Character	Anatomic Location	Common Etiologies
Inspiratory	High-Pitched	Extrathoracic / Supraglottic / Glottic	Laryngomalacia, Bilateral Vocal Cord Paralysis, Epiglottitis
Biphasic	Intermediate	Subglottic / Glottic / Fixed Tracheal	Subglottic Stenosis, Subglottic Hemangioma, Bacterial Tracheitis
Expiratory	Wheeze-Like / Prolonged	Intrathoracic / Tracheal / Bronchial	Tracheomalacia, Bronchomalacia, Foreign Body
Stertor	Low-Pitched Snoring	Nasal / Nasopharyngeal / Pharyngeal	Adenotonsillar Hypertrophy, Choanal Atresia

Etiological Classification

Acute Stridor

Category	Sub-Category	Etiologies
Acute Febrile	Low-Grade Fever	Viral Croup (Laryngotracheobronchitis), Diphtheria
Acute Febrile	High-Grade Fever	Acute Epiglottitis, Bacterial Tracheitis, Retropharyngeal Abscess, Peritonsillar Abscess
Acute Afebrile	Non-Infectious	Foreign Body Aspiration, Hypocalcemia (Tetany), Angioedema/Anaphylaxis, Caustic Ingestion, Trauma, Spasmodic Croup, Neurogenic Stridor (Chiari Crisis)

Chronic Or Recurrent Stridor

• Laryngeal Causes:
  • Laryngomalacia: Most common, collapse of supraglottic structures during inspiration.
  • Congenital Subglottic Stenosis: Second most common, cricoid diameter <3.5 mm in term newborn.
  • Vocal Cord Paralysis: Third most common, bilateral or unilateral.
  • Congenital Subglottic Hemangioma: Associated with cutaneous beard-distribution hemangiomas.
  • Laryngeal Webs/Atresia: Failure of laryngeal recanalization.
  • Laryngoceles And Saccular Cysts: Abnormal fluid/air-filled dilations.
• Tracheobronchial Causes:
  • Tracheomalacia/Bronchomalacia: Chondromalacia causing insufficient cartilage support.
  • Vascular Rings: Extrinsic compression.
  • Mediastinal Masses: Lymphangioma, bronchogenic cysts, congenital goiter.

Clinical Evaluation

History

• Onset And Duration: Acute onset suggests infection or foreign body. Onset at birth suggests severe anatomic anomaly. Onset at 2 weeks peaking at 6 months suggests laryngomalacia or hemangioma.
• Triggers And Modifying Factors: Worsened by feeding, crying, or supine position indicates laryngomalacia. Worsened by neck flexion indicates vascular ring.
• Associated Symptoms:
  • Barking cough, coryza indicates viral croup.
  • Dysphagia, drooling, toxic appearance indicates epiglottitis.
  • Cutaneous hemangiomas indicate subglottic hemangioma.
  • Breathy cry indicates unilateral vocal cord paralysis or laryngeal web.
• Birth History: Prematurity, prolonged intubation indicates acquired subglottic stenosis.

Severity Assessment

Clinical Parameter	Mild	Moderate	Severe	Life-Threatening
Sensorium	Alert	Irritable But Comforted	Restless, Agitated	Lethargic, Pain Responsive, Unresponsive
Stridor	Audible On Coughing, None At Rest	Stridor At Rest, Worse On Agitation	Severe Stridor At Rest, Worsens On Agitation	Audible Stridor Becoming Quiet Without Improved Consciousness
Respiratory Distress	None	Tachypnea, Suprasternal/Subcostal Retractions	Marked Tachypnea, Severe Retractions	Declining Intensity Of Retractions Without Clinical Improvement
Heart Rate	Normal	Tachycardia	Tachycardia	Bradycardia
SpO2 (Room Air)	>95%	>92-95%	<92%	<90%, Cyanosis

Specific Physical Signs

• Tripod Posture: Sitting upright, leaning forward, chin thrust forward, mouth open indicates acute epiglottitis.
• Preferred Posture: Neck hyperextension preferred in vascular rings or retropharyngeal abscess.
• Drooling And Dysphagia: Strongly points towards supraglottic pathology.
• Tracheal Tenderness: Specific to bacterial tracheitis.

Differential Diagnosis Of Acute Infectious Causes

Feature	Viral Croup	Acute Epiglottitis	Bacterial Tracheitis	Retropharyngeal Abscess
Age	6 Months To 3 Years	3–14 Years	6 Months To 14 Years	2–4 Years
Onset Speed	Gradual	Very Rapid (Hours)	Rapid (Biphasic)	Gradual
Appearance	Non-Toxic	Toxic	Toxic	Toxic
Fever	Low Grade	High Grade	High Grade	High Grade
Cough	Barking	Absent	Barking, Productive	Absent
Dysphagia/Drooling	Absent	Severe	Absent	Present
Voice Quality	Hoarse	Muffled	Very Hoarse	Muffled
Neck Stiffness	Absent	Absent	Absent	Present
Tracheal Tenderness	Absent	Absent	Present	Absent
Lateral Neck X-Ray	Normal	Thumb Sign	Normal	Enlarged Prevertebral Space
AP Neck X-Ray	Steeple Sign	Normal	Steeple Sign	Normal
Adrenaline Response	Very Good	None	Minimal/None	None

Diagnostic Investigations

General Precautions

• Avoid invasive/painful procedures in young children with impending airway obstruction.
• Postpone intravenous access attempt or blood tests until stabilized.
• Do not use tongue depressors or examine oral cavity directly if epiglottitis suspected.
• Do not sedate child until airway secured.

Imaging Modalities

• Anteroposterior Neck Radiograph: Demonstrates steeple sign in croup and bacterial tracheitis.
• Lateral Soft-Tissue Neck Radiograph: Demonstrates thumb sign in epiglottitis. Shows enlarged prevertebral space in retropharyngeal abscess.
• Chest Radiograph (Inspiratory/Expiratory): Expiratory films helpful in foreign body aspiration revealing obstructive emphysema, air trapping, mediastinal shift.
• Barium Swallow: Evaluates vascular rings, slings, and tracheoesophageal fistulas.
• CT/MRI Scan: High-resolution CT delineates aberrant anatomy.

Endoscopy

• Awake Flexible Laryngoscopy: Gold standard for diagnosing laryngomalacia and vocal cord paralysis.
• Direct Laryngoscopy And Rigid Bronchoscopy:
  • Essential for diagnosis and sizing of congenital subglottic stenosis.
  • Mandatory for diagnosis and management of bacterial tracheitis.
  • Definitive modality for removal of foreign bodies.
  • Must be performed in controlled settings with anesthetist and otolaryngologist present.

Laboratory Studies

• Complete Blood Count shows neutrophilic leukocytosis in bacterial causes.
• Blood and surface cultures indicated only after securing airway in epiglottitis/tracheitis.

Management Principles

Initial Stabilization

• Ensure minimal handling.
• Keep baby on mother’s lap.
• Administer supplemental oxygen in non-threatening manner to maintain SpO2 >95%.
• Emergency call for anesthesiologist and otolaryngologist if signs of severe airway obstruction present.

Specific Interventions

Viral Croup

• Mild: Single dose oral dexamethasone (0.6 mg/kg) or nebulized budesonide (2 mg). Discharge with parental counseling.
• Moderate-To-Severe:
  • Hospitalization preferable.
  • Nebulized L-epinephrine (undiluted 1:1000, dose 0.5 mL/kg, max 5 mL). Constricts precapillary arterioles reducing edema.
  • Mandatory systemic corticosteroids (Dexamethasone 0.6 mg/kg max 8 mg) to prevent rebound after epinephrine wears off.
  • Observe for minimum 4 hours.

Foreign Body Aspiration

• Immediate Heimlich maneuver if complete laryngeal obstruction.
• Prompt removal via rigid bronchoscopy under general anesthesia.

Congenital And Chronic Lesions

• Laryngomalacia: Conservative management. Anti-reflux medication for concurrent GERD. Supraglottoplasty indicated for severe cases including cyanosis, cor pulmonale, failure to thrive.
• Subglottic Stenosis: Endoscopic dilation/laser for mild cases. Anterior cricoid split or laryngotracheal reconstruction for severe grades.
• Subglottic Hemangioma: Propranolol (1-3 mg/kg/day). Monitor for hypoglycemia and bradycardia.
• Saccular Cysts/Laryngoceles: Endoscopic CO2 laser excision or marsupialization.
• Vascular Rings/Masses: Surgical excision or division of offending structures.