Expiratory Wheezing

Airway wall fluttering results from flow limitation
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
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

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)
Chronic or Recurrent: Common
1. Asthma
2. Gastroesophageal Reflux
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

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)
Chronic or Recurrent: Common
1. Asthma
2. Allergic Rhinitis
3. Gastroesophageal Reflux disease
4. Obstructive Sleep Apnea (adenoid hypertrophy, also with craniofacial abnormalities)
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

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
Wheezing Intensity
1. Wheezing in infant heard without stethoscope suggests Congenital Anomaly
Wheezing Modifying maneuvers
1. Worse with neck flexion and better with extension suggests Vascular Ring
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)

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
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)
Consider testing for uncommon conditions
1. Cystic Fibrosis (e.g. Sweat Chloride)
2. Immunodeficiency (e.g. Serum Immunoglobulins)