What are the typical lung sounds associated with bronchitis?

Typical Lung Sounds in Bronchitis

In bronchitis, the most characteristic lung sounds are wheezes and rhonchi (continuous adventitious sounds), often accompanied by crackles/rales, which reflect airway inflammation, mucus accumulation, and airway narrowing.

Primary Auscultatory Findings

Wheezes

• Wheezes are high-pitched continuous sounds (≥400 Hz) produced by airway narrowing and turbulent airflow through inflamed, narrowed bronchi 1, 2
• The mechanism involves fluttering of airway walls at critical flow velocities, with pitch dependent on airway wall elasticity and flow velocity 2
• Wheezes can occur during both inspiration and expiration, though expiratory wheezes are more common in obstructive conditions 2
• The duration of wheeze relative to the respiratory cycle (tw/ttot) correlates with degree of bronchial obstruction, though the relationship is too scattered to predict specific lung function values 2

Rhonchi

• Rhonchi are low-pitched continuous sounds (<200 Hz) that reflect secretions in larger airways and are particularly common in chronic bronchitis 1, 2
• These sounds result from excessive bronchial secretions and mucus accumulation in central airways 1
• Rhonchi may clear or change with coughing as secretions mobilize 1

Crackles (Rales)

• Crackles are discontinuous adventitious sounds heard in bronchiolitis and bronchitis, reflecting small airway inflammation and fluid 1
• In acute bronchitis, crackles may be present alongside wheezes, indicating involvement of smaller airways 1
• These sounds are produced by sudden opening of previously closed small airways during inspiration 1

Clinical Context and Interpretation

Acute Bronchitis

• Lung sounds in acute bronchitis typically include scattered wheezes and/or rhonchi, with or without crackles, in the setting of acute cough without focal consolidation 3, 4
• Normal breath sounds may be present early in the disease course before significant airway inflammation develops 3
• The absence of focal chest findings (asymmetric sounds, dullness to percussion, egophony) helps distinguish acute bronchitis from pneumonia 5, 4

Chronic Bronchitis

• Chronic bronchitis is characterized by persistent rhonchi and wheezes due to chronic mucus hypersecretion and airway inflammation 1
• Airway inflammation and excessive bronchial secretions activate cough receptors, with heightened capsaicin-induced cough sensitivity 1
• When airflow obstruction is present, breath sounds may be diminished with prolonged expiratory phase 1

Diagnostic Implications

Differentiating from Other Conditions

• Focal findings (localized crackles, bronchial breath sounds, dullness) suggest pneumonia rather than bronchitis and warrant chest radiography 5, 4
• Diffuse polyphonic wheezes throughout both lung fields suggest asthma rather than simple bronchitis 3
• Transient airflow obstruction with wheezing occurs in approximately 40% of patients with acute respiratory infections and typically resolves within 6 weeks 3

Clinical Pitfalls

• Approximately one-third of patients diagnosed with acute bronchitis actually have asthma, which presents with more prominent wheezing and bronchial hyperresponsiveness 3
• The presence of adventitious sounds does not indicate bacterial infection or need for antibiotics, as viral infections cause identical inflammatory changes 5, 4
• Lung sound analysis combined with spirometry increases sensitivity for detecting pulmonary disease from 71% to 87% compared to spirometry alone, particularly in chronic bronchitis patients with normal spirometry 6

Auscultation Technique Considerations

• Breath sounds should be assessed at multiple locations over the chest wall, including trachea and bilateral anterior, lateral, and posterior chest 7
• Both inspiratory and expiratory phases should be evaluated, as some adventitious sounds are phase-specific 6, 7
• Electronic stethoscopes can capture high-quality recordings for documentation and analysis, with frequency filters emphasizing different sound characteristics 7