I. Clinical Summary & Definition

• Stridor: Harsh, high-pitched respiratory sound caused by turbulent airflow due to partial airway obstruction.
• Key Differentiator: The presence of fever excludes non-infectious causes like Foreign Body Aspiration (unless secondary infection is present) or Angioedema.

II. Differential Diagnosis (Prioritized)

1. **Acute Laryngotracheobronchitis (Viral Croup)

   • Probability: Most common cause (>80%).
   • Etiology: Parainfluenza virus (Types 1, 2, 3).
   • Classic presentation: Barking cough, hoarseness, low-grade fever.

2. Acute Epiglottitis (Supraglottitis):

   • Probability: Rare post-HiB vaccination but a medical emergency.
   • Etiology: H. influenzae type b (classic), Staph. aureus, Strep. pyogenes.
   • Classic presentation: High fever, toxic look, drooling, no cough.

3. Bacterial Tracheitis:

   • "Super-Croup" (Secondary bacterial infection of viral croup).
   • Etiology: Staph. aureus.
   • Presentation: Patient looks toxic like epiglottitis but has a cough like croup.

4. Retropharyngeal Abscess:

   • Fever, stridor, difficulty swallowing, stiffness of neck.

III. Clinical Evaluation & Comparison

Distinguishing the two main causes is the primary diagnostic task.

IV. Diagnostic Approach

1. Immediate Assessment (Pediatric Assessment Triangle)

• Assess Appearance (Tone, interactivity), Work of Breathing (Retractions), and Circulation.
• WARNING: If Epiglottitis is suspected (Drooling, Toxic, Tripod):
  • Do NOT examine the throat using a tongue depressor (risk of laryngospasm).
  • Do NOT upset the child (keep in parent's lap).
  • Secure airway immediately in OT.

2. Physical Examination (If stable/Croup suspected)

• Evaluate respiratory distress.
• Westley Croup Score: Used to grade severity of Croup.
  • Parameters: Stridor, Retractions, Air Entry, Cyanosis, Level of Consciousness.
  • Score: <2 (Mild), 3–5 (Moderate), >6 (Severe).

3. Radiological Investigation

X-ray Neck (AP and Lateral views) is useful if the diagnosis is unclear.

• Croup:

  • AP View: Steeple Sign (Subglottic narrowing/tapering of the trachea).
  • Lateral View: Distention of hypopharynx only.

• Epiglottitis:

  • Lateral View: Thumb Sign (Enlarged, swollen epiglottis).
  • Aryepiglottic folds: Thickened.

• Retropharyngeal Abscess:

  • Lateral View: Increased prevertebral soft tissue thickness (> width of adjacent vertebral body).

4. Laboratory Investigations

• CBC:
  • Croup: Lymphocytosis (Viral picture).
  • Epiglottitis/Tracheitis: Neutrophilic leukocytosis with shift to left.
• Blood Culture: Indicated in Epiglottitis or Bacterial Tracheitis.

V. Management of Stridor in Children

I. Immediate Resuscitation (ABC Approach)

Stridor indicates partial airway obstruction. Management begins with assessing stability.

1. Airway & Breathing:
   • Assess Pediatric Assessment Triangle (PAT): Appearance, Work of Breathing, Circulation.
   • "Keep the child calm": Agitation worsens obstruction. Allow child to sit in parent's lap.
   • Oxygen: Administer 100% humidified $O_2$ (blow-by or mask) if hypoxic.
   • Heliox: Helium-oxygen mixture (70:30) decreases airflow resistance (useful in temporary bridging).
2. Red Flags (Impending Failure):
   • Drooling, Tripod position, Silent chest, Altered sensorium.
   • Action: Secure airway immediately (Intubation/Tracheostomy) in OT with ENT backup.
   • Caution: Do NOT examine throat if Epiglottitis is suspected.

II. Diagnostic Evaluation (Concurrent with Stabilization)

• History:
  • Acute: Croup (viral prodrome), Foreign Body (choking episode), Epiglottitis (toxic).
  • Chronic: Laryngomalacia (since birth), Vascular ring.
• Examination (Level of Obstruction):
  • Inspiratory: Supraglottic/Glottic (e.g., Laryngomalacia, Croup).
  • Expiratory/Biphasic: Tracheal/Bronchial (e.g., Foreign body, Tracheomalacia).
• Investigations:
  • X-ray Neck (Lat/AP): Steeple sign (Croup) vs Thumb sign (Epiglottitis).
  • Flexible Laryngoscopy/Bronchoscopy: Definitive for structural/dynamic lesions.

III. Specific Management by Etiology

IV. Disposition

• Discharge: Mild croup after observation.
• Admit: Moderate-severe croup, epiglottitis, or uncertain diagnosis.
• ICU: Impending respiratory failure or post-intubation.

VI. Final Diagnostic Synthesis

• If the child has a barking cough, is hoarse, and looks non-toxic: Diagnosis is Viral Croup.
• If the child is drooling, mute/muffled, and toxic: Diagnosis is Epiglottitis.
• If the child has croup symptoms but high fever and poor response to nebulized epinephrine: Suspect Bacterial Tracheitis.