Listening to the sounds produced by the lungs, a process called auscultation, provides important information about the state of the respiratory system. Healthcare professionals use a stethoscope to listen for normal breath sounds and abnormal sounds that may indicate an underlying issue. Among these adventitious sounds are rhonchi, which are low-pitched, coarse noises suggesting a partial obstruction in the airways. Understanding the source and location of rhonchi helps identify respiratory problems that require attention.
What Rhonchi Are and How They Are Produced
Rhonchi are continuous, low-pitched sounds often described as resembling snoring, gurgling, or rumbling. They are typically more prominent during exhalation (expiration), but can also be heard during inhalation.
The physiological mechanism involves air attempting to pass through larger airways, such as the trachea and main bronchi, that are partially blocked. This obstruction is usually caused by thick secretions, like mucus or fluid, accumulated in the airways. The sound is created as air encounters the narrowed passage, causing the airway walls or the secretions themselves to vibrate.
Because the sound originates in the larger, central air passages, rhonchi are considered a feature of obstructive lung disease. These large airways are supported by cartilage, unlike the smaller air sacs (alveoli). This structural difference contributes to the low-pitched, continuous nature of rhonchi, distinguishing them from the finer, high-pitched crackles (rales) that occur in smaller air spaces.
The Specific Areas Where Rhonchi Are Heard
Rhonchi are heard over the chest wall where the larger airways, the bronchi, are located. They are most audible over the central chest fields, particularly near the sternum (breastbone) and over the trachea in the neck. Since the sounds are produced in large, central passages, they are often widely conducted across the entire front and back of the chest.
When listening to the back, the sounds may be loudest over the upper and mid-back, corresponding to the location of the mainstem bronchi. The sound’s intensity can be quite loud because the secretions causing the vibration are in the main respiratory passages. If the obstruction is significant, the sounds can sometimes even be heard without a stethoscope.
A defining characteristic of rhonchi is that the sound often changes, decreases, or clears entirely after the patient coughs. A forceful cough can temporarily shift or mobilize the thick secretions causing the partial blockage. This temporary clearing confirms the obstruction is due to movable fluid or mucus in the larger airways. The ability to clear with coughing helps distinguish rhonchi from other abnormal lung sounds.
Medical Conditions Associated with Rhonchi
The presence of rhonchi signals an underlying respiratory issue causing excessive secretion or partial airway obstruction. Common conditions include acute and chronic bronchitis, which involve inflammation and increased mucus production in the bronchial tubes. Chronic Obstructive Pulmonary Disease (COPD), which includes chronic bronchitis, is a frequent cause of persistent rhonchi.
Rhonchi are also found in patients with cystic fibrosis, a genetic condition causing the body to produce thick, sticky mucus that clogs the airways. Pneumonia, an infection causing fluid and pus accumulation, can also result in rhonchi, especially as secretions move into the larger airways during earlier or resolving stages. The presence of rhonchi indicates a need for treatments, such as bronchodilators or antibiotics, aimed at clearing the airways and addressing the underlying congestion.