II. Pathophysiology

  1. Airway wall fluttering results from flow limitation
  2. Expiration typically occurs passively with elastic recoil of the chest wall
    1. Obstruction to outflow requires active expulsion of air
    2. Resulting positive intrapleural pressure worsens the obstruction
  3. Wheezing is more common in children than adults
    1. Inflammation of a child's smaller Bronchi has a greater impact on airway resistance
    2. Obstruction is more likely in a child's airway due to less chest elastic recoil
    3. A child's compliant airway walls collapse more easily under negative pressure

III. Causes: Infants

  1. Acute
    1. RSV or other Bronchiolitis (most common cause in infants)
    2. Asthma Exacerbation
    3. Other respiratory infection (Acute Bronchitis, Pneumonia)
    4. Foreign Body Aspiration (uncommon under age 1 year)
  2. Chronic or Recurrent: Common
    1. Asthma
    2. Gastroesophageal Reflux
  3. Chronic or Recurrent: Uncommon or Rare
    1. Aspiration Pneumonitis
    2. Anomalous innominate artery
    3. Anomalous left common Carotid Artery
    4. Bronchopulmonary Dysplasia
    5. Bronchomalacia
    6. Choanal Atresia
    7. Congenital Lobar Emphysema
    8. Congestive Heart Failure
    9. Cystic Fibrosis or ciliary Dyskinesia
    10. Double aortic arch
    11. Diaphragmatic Hernia
    12. Extrinsic compression by tumor (Neuroblastoma)
    13. Hemosiderosis
    14. Tracheal Stenosis
    15. Tracheomalacia
    16. Tracheoesophageal Fistula
    17. Vascular Ring
    18. Visceral larval migrans

IV. Causes: Children and Adolescents

  1. Acute
    1. Asthma Exacerbation (most common cause in children)
    2. RSV or other Bronchiolitis
    3. Acute Bronchitis
    4. Pneumonia
    5. Foreign Body Aspiration (uncommon after preschool age, if no Developmental Delay)
  2. Chronic or Recurrent: Common
    1. Asthma
    2. Allergic Rhinitis
    3. Gastroesophageal Reflux disease
    4. Obstructive Sleep Apnea (adenoid hypertrophy, also with craniofacial abnormalities)
  3. Chronic or Recurrent: Uncommon or rare
    1. a1-antitrypsin Deficiency
    2. Aspergillosis
    3. Cystic Fibrosis
    4. Ciliary Dysmotility Syndrome
    5. Sarcoidosis
    6. Tumors or Lymph Node compression
    7. Vocal Cord Dysfunction

V. History

  1. Onset
    1. Onset as an infant: Congenital cause
    2. Sudden onset: Foreign Body Aspiration
    3. Winter onset with upper respiratory symptoms and with cluster of cases
      1. Respiratory Syncytial Virus (fall to spring)
      2. Croup (fall and winter)
      3. Human Metapneumovirus (winter to spring)
  2. Pattern
    1. Seasonal pattern
      1. Asthma
      2. Allergic Rhinitis
    2. Persistent or recurrent respiratory illnesses with Wheezing
      1. Cystic Fibrosis
      2. Bronchopulmonary Dysplasia
      3. Laryngomalacia
      4. Immunodeficiency (e.g. Primary ciliary Dyskinesia, Agammaglobulinemia)
    3. Associated cough
      1. Cough After feeding: Gastroesophageal Reflux
      2. Dry, nighttime cough
        1. Gastroesophageal Reflux
        2. Allergic Rhinitis
        3. Asthma
        4. Obstructive Sleep Apnea
  3. Modifying Factors
    1. Wheezing after feeding
      1. Gastroesophageal Reflux (most common)
      2. Tracheoesophageal fistula
      3. Laryngeal cleft
    2. Positional change
      1. Tracheomalacia
      2. Great Vessel anomalies

VI. Signs

  1. General: Signs of chronic systemic illness (e.g. Cystic Fibrosis, Immunodeficiency)
    1. Observe for ill, wan, tired appearance
    2. Review growth charts for fall in Growth Velocity
  2. Wheezing Intensity
    1. Wheezing in infant heard without stethoscope suggests Congenital Anomaly
  3. Wheezing Modifying maneuvers
    1. Worse with neck flexion and better with extension suggests Vascular Ring
  4. Severity: Asseess for outpatient versus inpatient management
    1. Observe for critical or ominous signs
      1. Altered Mental Status
      2. Diaphoresis
    2. Observe for respiratory distress
      1. Neck or intercostal retractions
      2. Tachypnea
      3. Grunting (Auto-PEEP)

VII. Imaging: Chest XRay

  1. Consider inspiratory and expiratory films (detects airway foreign bodies)

VIII. Evaluation

  1. Full Vital Signs including Oxygen Saturation, Respiratory Rate and Peak Flows (if possible)
    1. V-Q Mismatch in Asthma or Bronchiolitis is typically mild to moderate
    2. Severe V-Q Mismatch with significant Hypoxemia (O2 Sat <90%) suggests other underlying cause
      1. Example: Pneumonia
  2. Consider specific testing or empiric therapy in common conditions
    1. Asthma (e.g. Spirometry)
    2. Allergic Rhinitis (e.g. Allergy Testing)
    3. Gastroesophageal Reflux (e.g. barium swallow)
  3. Consider testing for uncommon conditions
    1. Cystic Fibrosis (e.g. Sweat Chloride)
    2. Immunodeficiency (e.g. Serum Immunoglobulins)

IX. References

  1. Claudius and Brown (2017) Crit Dec Emerg Med 31(12): 13-20
  2. Majoewsky (2012) EM:Rap-C3 2(5):2
  3. Bush (2007) Prim Care Respir J 16:7-15 [PubMed]
  4. Martinati (1995) Allergy 50:701-10 [PubMed]
  5. Weiss (2008) Am Fam Physician 77: 1109-14 [PubMed]

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