What is rhonchi in patients with a history of respiratory issues, such as asthma, chronic obstructive pulmonary disease (COPD), or chronic bronchitis?

What is Rhonchi?

Rhonchi are continuous, low-pitched adventitious lung sounds with a dominant frequency of approximately 200 Hz or less, characterized by rumbling noises that are most prominent during forced expiration and may clear or change after coughing as secretions move. 1, 2

Acoustic Characteristics

• Frequency and pitch: Rhonchi have a dominant frequency of about 200 Hz or less, distinguishing them from wheezes which have higher frequencies (400 Hz or more) 2
• Timing: These sounds are especially prominent during forced expiration 1
• Dynamic nature: Unlike some other adventitious sounds, rhonchi may clear or change after coughing as airway secretions move 1

Clinical Significance in Respiratory Disease

Common Associated Conditions

Rhonchi are commonly found in patients with conditions causing airway secretions or obstruction, including: 1, 3

• Chronic Obstructive Pulmonary Disease (COPD): Rhonchi reflect underlying chronic obstructive lung disease pathology, though physical findings are nonspecific 3
• Chronic bronchitis: Frequently present due to excessive mucous secretion in the bronchial tree 4
• Bronchiectasis: Physical examination commonly reveals variable degrees of rhonchi and crackles, though findings may be entirely normal 3
• Acute and chronic bronchitis: Present in both acute and chronic forms 1, 3
• Pneumonia: May be present but alone do not significantly increase likelihood of pneumonia on chest radiograph in pediatric patients 3

Diagnostic Limitations

• Non-specific finding: Rhonchi are not sufficiently diagnostic to determine the specific underlying condition and require correlation with other clinical findings 1, 3
• Poor predictive value: The presence of rhonchi does not reliably predict the severity of airway obstruction 1, 3
• Variable correlation: In bronchiectasis, the presence or absence of rhonchi on auscultation does not reliably correlate with high-resolution CT findings 3

Clinical Approach When Rhonchi Are Detected

Initial Evaluation

When rhonchi are detected, the following assessment should be performed: 3

• Imaging studies: Obtain chest radiograph initially; consider high-resolution CT if bronchiectasis is suspected 3
• Associated findings to assess: 3
  • Sputum production volume and character
  • Presence of digital clubbing
  • Other adventitious sounds (crackles, wheezes)

Further Workup

• Pulmonary function testing: Consider to assess degree of obstruction 3
• Sputum cultures: Obtain if chronic productive cough is present 3
• Spirometry: Essential objective measure when asthma or COPD is suspected, as physical examination alone is unreliable 4

Pathophysiologic Context

Mechanism in Chronic Bronchitis

In chronic bronchitis, rhonchi result from: 4

• Mucociliary abnormalities: Formation of a continuous sheet or blanket of mucus lining the airways instead of discrete deposits
• Pooling of secretions: Provides substrate for bacterial growth and further airway damage
• Airway inflammation: Excessive bronchial secretions activate the afferent limb of the cough reflex 4

Clinical Pitfalls

• Do not rely on rhonchi alone: The absence of rhonchi does not rule out significant respiratory disease, as findings may be absent between episodes in conditions like asthma 4
• Consider upper airway obstruction: Negative frequency dependence of respiratory resistance (characteristic of bronchial obstruction) has also been observed in patients with upper airway obstruction without intrapulmonary disease 4
• Distinguish from wheezes: While both are continuous sounds, wheezes are higher-pitched (≥400 Hz) and have different clinical implications 2