What lung sound is associated with constricted bronchioles?

Wheezing is the Characteristic Lung Sound Heard in Constricted Bronchioles

Wheezing is the primary lung sound that can be heard when bronchioles are constricted. This high-pitched, continuous, musical sound is produced by the oscillation of opposing airway walls whose lumen is narrowed 1.

Characteristics of Wheezes from Constricted Bronchioles

• Definition: Wheezes are high-pitched continuous adventitious lung sounds with a dominant frequency of 400 Hz or more 2
• Mechanism: Produced by fluttering of the airways walls and fluid together, induced when airflow reaches a critical velocity through narrowed airways 2
• Clinical significance: Wheezes are usual clinical signs in patients with obstructive airway diseases, particularly during acute episodes of asthma 2

Physiological Basis

Wheezing occurs when:

1. Bronchioles become constricted due to:

   • Bronchoconstriction (bronchial smooth muscle contraction)
   • Airway edema
   • Mucus hypersecretion
   • Airway inflammation 3

2. Air passing through these narrowed airways creates vibrations in the airway walls, generating the characteristic high-pitched sound 2

Clinical Correlation with Airway Obstruction

• Wheezing is strongly associated with airway obstruction - in a study of patients with wheezing, at least one parameter of lung function was always found to be pathological 4
• For asthmatic patients, significant differences were found in MEF(50), R(tot), and Tiffeneau values compared to non-wheezing patients 4
• In COPD patients, significant differences were found in FEV1 and MEF(50) 4
• Importantly, wheezing was never found in healthy persons with normal lung function 4

Clinical Assessment

When examining a patient with suspected bronchiolar constriction:

• Listen for high-pitched, musical sounds during expiration (most common) or both inspiration and expiration
• Note that wheezing may not be as sensitive as changes in basic lung sounds in acute airway narrowing 5
• The narrower the airways are, the higher the frequency of breathing sounds 5
• Forced expiratory wheeze (FEW) may be an early sign of airway obstruction in patients with bronchial asthma 5

Important Clinical Considerations

• While wheezing is characteristic of constricted bronchioles, its absence does not rule out significant airway obstruction, especially in very severe cases where airflow may be too limited to generate wheezes 3
• Wheezing can be heard in several diseases, not only asthma 2
• The relationship between wheeze characteristics and degree of obstruction is not precise enough to predict FEV1 from wheeze duration 2
• In severe airway obstruction, patients may have diminished breath sounds rather than wheezing due to severely limited airflow 3

Differential Considerations

• Rhonchi: Lower-pitched continuous sounds (dominant frequency about 200 Hz or less) 2
• Stridor: A special kind of wheeze described as a loud musical sound of constant pitch, heard in patients with tracheal or laryngeal obstruction (upper airway) 1

Understanding these characteristic sounds helps in the clinical assessment of patients with respiratory conditions involving bronchiolar constriction, such as asthma and COPD.