How do you differentiate and manage inspiratory vs expiratory wheezing in patients?

Differentiating and Managing Inspiratory vs Expiratory Wheezing

Inspiratory and expiratory wheezing represent different pathophysiological processes, with expiratory wheezing typically indicating lower airway obstruction while inspiratory stridor suggests upper airway or laryngeal involvement.

Clinical Differentiation

Expiratory Wheezing

• Characteristics: High-pitched, continuous sounds heard primarily during expiration
• Location: Generated in the lower airways (bronchi, bronchioles)
• Common causes:
  • Asthma (most common)
  • COPD
  • Bronchiectasis
  • Lower airway foreign body
  • Heart failure

Inspiratory Wheezing/Stridor

• Characteristics: Loud, musical sound of constant pitch heard during inspiration
• Location: Generated in the upper airways (larynx, trachea)
• Common causes:
  • Exercise-induced laryngeal dysfunction
  • Vocal cord dysfunction
  • Tracheal stenosis
  • Upper airway foreign body
  • Tracheomalacia
  • Laryngeal tumors

Diagnostic Approach

1. Auscultation timing and characteristics:

   • Determine if wheezing is inspiratory, expiratory, or biphasic
   • Biphasic wheezing (both inspiratory and expiratory) typically indicates more severe obstruction 1
   • Note pitch, intensity, and duration of wheezing

2. Objective pulmonary function testing:

   • Spirometry with bronchodilator challenge for suspected lower airway obstruction 2
   • Flow-volume loops can help distinguish upper from lower airway obstruction

3. Imaging:

   • Chest radiograph for all patients with persistent wheezing 2
   • Consider advanced imaging for patients >40 years with tobacco history and new-onset wheezing 3

4. Additional testing based on clinical suspicion:

   • Flexible laryngoscopy for suspected upper airway/vocal cord dysfunction 2
   • Exercise challenge testing for exercise-induced bronchoconstriction

Management Algorithm

For Expiratory Wheezing (Lower Airway)

1. Acute management:

   • Short-acting β2-agonists (e.g., albuterol) via nebulizer or MDI with spacer 2, 4
   • Systemic corticosteroids for moderate-severe obstruction (prednisolone 30-60mg) 2
   • Oxygen therapy if hypoxemic
   • Consider ipratropium bromide for severe episodes 2

2. Chronic management:

   • Identify and treat underlying cause (asthma, COPD)
   • Controller medications based on diagnosis
   • For asthma: inhaled corticosteroids, long-acting bronchodilators
   • For COPD: long-acting bronchodilators, pulmonary rehabilitation 5

For Inspiratory Wheezing/Stridor (Upper Airway)

1. Acute management:

   • Maintain airway patency
   • Heliox (helium-oxygen mixture) may reduce work of breathing
   • Racemic epinephrine nebulization for laryngeal edema
   • Urgent ENT consultation for severe cases

2. Chronic management:

   • Speech therapy for vocal cord dysfunction
   • Treatment of underlying cause (e.g., surgical intervention for stenosis)
   • Breathing exercises and behavioral therapy for exercise-induced laryngeal dysfunction 2

Special Considerations

Exercise-Induced Bronchoconstriction vs. Laryngeal Dysfunction

• Exercise-induced bronchoconstriction (lower airway): predominantly expiratory wheezing, responds to bronchodilators
• Exercise-induced laryngeal dysfunction (upper airway): predominantly inspiratory stridor, does not respond to bronchodilators 2

Combined Presentations

• Some patients may have both inspiratory and expiratory components (biphasic wheezing)
• Patients with asthma may develop vocal cord dysfunction as a comorbidity 6
• Treat both components appropriately

Common Pitfalls

1. Misdiagnosis: Mistaking vocal cord dysfunction for asthma, leading to inappropriate treatment 2

2. Underestimation of severity: Failure to recognize that biphasic wheezing typically indicates more severe obstruction 1

3. Inadequate assessment: Relying solely on auscultation without objective pulmonary function testing 2, 1

4. Missing upper airway pathology: Not considering tracheal stenosis or other fixed upper airway obstructions in patients with persistent "difficult asthma" 6

5. Overreliance on bronchodilators: Using bronchodilators for inspiratory stridor caused by vocal cord dysfunction, which will not respond to this therapy

By carefully distinguishing between inspiratory and expiratory wheezing and applying the appropriate diagnostic and management strategies, clinicians can provide targeted treatment that addresses the underlying pathophysiology and improves patient outcomes.