Wheezing

Basics

Description

  • Result of turbulent airflow:
    • High-pitched sound with dominant frequency at 400 Hz:
      • Gas flowing through constricted airways analogous to a vibrating reed
    • Resonant vibration of the bronchial walls when airflow velocity reaches critical values
  • Caused by airway narrowing between 2–5 mm:
    • Wheezing is very low pitched with airway diameters of 5 mm
    • Airways of <2 mm are unable to transmit sound because the energy is lost as friction heat
  • Airway narrowing is caused by a combination of ≥1 of the following:
    • Constriction (as with reactive airway disease)
    • Peribronchial interstitial edema
    • Inflammation
    • Obstruction

Etiology

  • Pulmonary (small airway):
    • Asthma
    • Acute respiratory distress syndrome
    • Anaphylaxis
    • Aspiration pneumonia:
      • Wheezing occurs early in the disease due to intense bronchospasm following the event
    • Byssinosis:
      • Occupational lung disease of textile workers exposed to cotton dust
    • Drugs:
      • Can precipitate angioedema or allergic reaction
      • ACE inhibitors
      • β-Blockers
      • Aspirin and NSAIDs
    • Forced exhalation in normal patients
    • Hyperventilation
    • Chronic obstructive pulmonary disease
    • Chronic cor pulmonale
    • Chemical pneumonitis
    • Carcinoid tumors
    • Paroxysmal nocturnal dyspnea
    • Pulmonary edema
    • Pulmonary embolism:
      • Rarely associated with wheezing
      • Focal
    • Pneumonia
    • Sleep apnea
  • Pulmonary (large airway):
    • Vocal cord dysfunction (paralysis, paradoxical movement)
    • Foreign body
    • Epiglottitis:
      • Wheezing associated with stridor in 10% of cases
    • Diphtheria
    • Smoke inhalation
    • Bronchial tumor
    • Tracheal tumor

Pediatric Considerations
  • Viral bronchiolitis in patients <3 yr of age
  • Asthma
  • Infection:
    • Croup
    • Rhinovirus
  • Epiglottitis
  • Gastroesophageal reflux
  • Foreign-body aspiration
  • Congenital abnormalities:
    • Tracheomalacia
    • Tracheal stenosis
    • Vascular ring
  • Cystic fibrosis
  • Cardiac disease
  • Psychogenic respiratory distress
    • Paradoxical vocal cord dysfunction characterized by abnormal vocal cord adduction during inspiration

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