What are rhonchi?

Definition of Rhonchi

Rhonchi are continuous adventitious lung sounds characterized by low-pitched rumbling noises with a dominant frequency of about 200 Hz or less, typically heard during auscultation of the chest, especially on forced expiration. 1

Characteristics of Rhonchi

• Rhonchi are classified as continuous adventitious lung sounds, distinguishing them from discontinuous sounds like crackles 2
• They are low-pitched sounds with a dominant frequency of approximately 200 Hz or less, in contrast to wheezes which are higher-pitched (>400 Hz) 2
• Rhonchi are especially prominent during forced expiration 1
• They may be heard in various respiratory conditions and are not specific to any single disease 1
• The sound is produced by air passing through airways that are partially obstructed by secretions, mucus, or inflammation 3

Clinical Significance

• Rhonchi are commonly found in patients with conditions causing airway secretions or obstruction 1
• They may be present in various respiratory disorders including:
  • Chronic Obstructive Pulmonary Disease (COPD) 1
  • Bronchiectasis 1
  • Bronchitis 1
  • Pneumonia 1
  • Airway obstruction from various causes 1
• The presence of rhonchi on physical examination is not sufficiently diagnostic to determine the specific underlying condition and requires correlation with other clinical findings 1

Differentiation from Other Lung Sounds

• Rhonchi differ from wheezes in their frequency (rhonchi <200 Hz vs. wheezes >400 Hz) 2
• Unlike crackles which are discontinuous sounds, rhonchi are continuous throughout the respiratory cycle 4
• While rhonchi are typically low-pitched, wheezes are high-pitched 2
• Rhonchi may clear or change after coughing as secretions move, unlike some other adventitious sounds 1

Detection and Monitoring

• Auscultation with a stethoscope is the traditional method for detecting rhonchi 5
• Modern technologies including electronic stethoscopes and acoustic sensors can aid in more objective identification 4, 6
• Deep learning algorithms have been developed to automatically classify respiratory sounds including rhonchi with accuracy rates of approximately 85.7% 4
• Experienced clinicians (fellows) demonstrate higher accuracy (80.1%) in identifying rhonchi compared to medical students (60.3%), interns (53.4%), and residents (68.8%) 4

Clinical Implications

• The presence of rhonchi should prompt further evaluation for underlying respiratory conditions 1
• Rhonchi may be present in both acute and chronic respiratory diseases 1
• While rhonchi can indicate airway obstruction, they do not reliably predict the severity of obstruction 1
• The detection of rhonchi during physical examination may guide diagnostic testing such as imaging studies or pulmonary function tests 1