Adventitious breath sounds are extra or abnormal noises heard over the chest during breathing. These sounds are not part of the normal airflow acoustics within the respiratory system and serve as important indicators of underlying issues. Understanding these sounds helps recognize that changes in breathing noises can signal various conditions requiring medical attention. This information explains what these sounds are, how they differ from normal breathing, and what they might suggest about respiratory health.
Distinguishing Normal from Adventitious Breath Sounds
Normal breath sounds serve as the baseline for evaluating lung health and are categorized into two main types: vesicular and bronchial. Vesicular sounds are soft, low-pitched, and resemble a gentle rustling, primarily heard over the lung periphery where air moves into the small air sacs. The inspiratory phase of vesicular sounds is typically longer and louder than the expiratory phase, with no pause between them.
Bronchial sounds are louder, higher-pitched, and have a harsh, hollow quality, normally heard only over the trachea and main airways. Unlike vesicular sounds, the inspiratory and expiratory phases of bronchial sounds are roughly equal in length, with a distinct pause between them. Adventitious sounds are defined as any sounds that replace these normal acoustic patterns, indicating some alteration in the airflow or lung structure.
The Major Categories of Adventitious Sounds
Adventitious sounds are categorized based on their distinct acoustic characteristics, including pitch, timing, and whether they are continuous or intermittent. One common type is crackles, also known as rales, which are short, discontinuous, popping or clicking sounds typically heard during inhalation. Crackles are further differentiated into fine crackles (high-pitched and brief) and coarse crackles (low-pitched and moist).
Wheezes are continuous, high-pitched, musical sounds that are usually more prominent during exhalation. They are produced when air is forced through severely narrowed or constricted airways. A related sound is rhonchi, which are low-pitched, continuous, rumbling, or snoring-like sounds originating in the larger airways. Rhonchi sometimes clear significantly after a person coughs.
Stridor is a distinct, harsh, high-pitched, crowing sound typically heard during the inspiratory phase. It is a continuous sound that is usually louder over the neck than the chest, which helps to distinguish it from a wheeze. This sound signifies a partial obstruction of the upper airway, specifically the larynx or trachea.
What Adventitious Sounds Indicate
The presence of adventitious sounds signifies a physiological alteration in the movement of air or the structure of the respiratory system. Crackles are generated by the sudden opening of small, collapsed airways or by the bubbling of air through fluid and secretions. Fine crackles are often associated with conditions like heart failure and pulmonary fibrosis, while coarse crackles may indicate pulmonary edema or bronchitis.
Wheezes and rhonchi both indicate that air is passing through narrowed or partially obstructed airways, causing turbulent flow. Wheezes are generally caused by diffuse narrowing, such as bronchospasm in asthma or inflammation from bronchitis. Rhonchi, which are lower-pitched, are primarily caused by thick secretions or mucus in the larger bronchial passages. The tendency of rhonchi to clear with a cough helps confirm that secretions are the likely cause.
Stridor is a severe and urgent sign because it implies a significant obstruction in the main windpipe or throat. Conditions such as a foreign body lodged in the airway or severe swelling from an infection, like epiglottitis, can cause this sound. The severity of stridor is related to the degree of upper airway narrowing, making it a sound that requires immediate professional medical evaluation.