Rhonchi are adventitious, or abnormal, breath sounds identified by medical professionals listening to the lungs. They are defined as coarse, low-pitched, continuous sounds originating in the larger airways of the respiratory tract. These sounds indicate that the normal flow of air is being disrupted by a partial obstruction within the main bronchi or trachea. This blockage is most commonly caused by the accumulation of thick secretions, such as mucus, or by the narrowing of the airway diameter.
The Distinctive Sound of Rhonchi
The acoustic quality of rhonchi is low-pitched and continuous, meaning the sound lasts longer than the brief, popping noises heard in other lung sounds. Rhonchi are often compared to a deep, coarse snoring, gurgling, or rumbling noise. This low pitch is directly related to the sound’s origin within the relatively wide, large-caliber air passages.
The physical mechanism involves air passing through an airway that has been narrowed or partially blocked. As air flows across thick, tenacious secretions or a constricted bronchial wall, it causes the walls of the airway to vibrate. This vibration generates the characteristic low-frequency rumbling heard during auscultation.
Rhonchi are often heard most clearly during expiration, but they can be present during both phases of the breathing cycle. A defining feature that helps distinguish rhonchi is their transient nature. The sound may change in intensity, or even disappear entirely, after a person coughs effectively, as the mechanical force temporarily shifts or clears the obstructing mucus.
Conditions That Cause Rhonchi
The underlying conditions that cause rhonchi lead to either excessive fluid accumulation or narrowing within the large airways. One of the most frequent causes is acute or chronic bronchitis, where inflammation of the bronchial tubes leads to increased production of thick mucus. This mucus sits within the bronchi, creating the obstruction necessary to produce the rumbling sound.
Chronic Obstructive Pulmonary Disease (COPD) frequently presents with rhonchi due to the long-term inflammation and excessive mucus production that characterize the disease. The airways become chronically narrowed and prone to obstruction. Similarly, bronchiectasis involves the permanent widening and damage of the bronchi, resulting in poor clearance of secretions and subsequent pooling of mucus that produces rhonchi.
Infectious processes, such as pneumonia, can also cause rhonchi, particularly when the infection affects the larger conducting airways, leading to an increase in inflammatory exudates and fluid. While pneumonia is more often associated with crackles in the smaller air sacs, the involvement of the main bronchi will generate the lower-pitched rhonchi. Cystic fibrosis, an inherited disease, also causes rhonchi because it results in the production of abnormally thick, sticky mucus that consistently clogs the airways.
Clinical Detection and Management
Rhonchi are detected during a physical examination when a healthcare provider uses a stethoscope to listen to the patient’s lungs (auscultation). The sound is typically listened for over the chest and back, and its presence helps the clinician narrow down the location and nature of the respiratory problem. To accurately differentiate rhonchi, providers must distinguish them from high-pitched wheezes, which occur in smaller airways, or fine crackles, which are brief popping sounds from the smallest air sacs.
Once rhonchi are identified, the management strategy focuses on addressing the root cause of the airway obstruction. If the rhonchi are due to excessive secretions, treatment includes promoting airway clearance to mobilize the mucus. This may involve encouraging the patient to cough, ensuring adequate hydration to thin the secretions, or using specialized techniques like chest physiotherapy.
When the underlying cause is an infection, such as bacterial bronchitis or pneumonia, a course of antibiotics is often prescribed to treat the pathogen and reduce the inflammatory fluid production. For conditions involving chronic inflammation and airway narrowing, like COPD, treatment may include bronchodilator medications to relax and widen the bronchial muscles. Medical evaluation is always recommended to ensure proper diagnosis and targeted treatment of the underlying condition.