The human respiratory system produces various sounds as air moves in and out of the lungs. These sounds can be heard through a stethoscope during a physical examination, a process known as auscultation. While some sounds are characteristic of healthy breathing, “adventitious breath sounds” refer to abnormal or extra noises that occur during respiration. These distinct sounds differ from the expected sounds of air flowing smoothly through the airways.
Understanding Normal Breath Sounds
Healthy, normal breath sounds are soft, clear, and rhythmic, indicating unobstructed airflow. They are categorized by their location and acoustic properties. Vesicular sounds are soft, low-pitched, and breezy, heard over most lung fields, fading during expiration. Bronchial sounds are louder, higher-pitched, and tubular, heard over the trachea or main airways, with expiration lasting longer than inspiration. Bronchovesicular sounds, with mid-range pitch and intensity, are heard over the upper anterior chest and between the shoulder blades, with inspiration and expiration being roughly equal.
Distinct Types of Adventitious Breath Sounds
Adventitious sounds are additional noises beyond normal breath sounds, often indicating an underlying issue. They are classified by their characteristics and timing within the breathing cycle.
Crackles (Rales)
Crackles, also known as rales, are discontinuous, short, explosive sounds resembling bubbling, clicking, or rattling. Heard most often during inhalation, they occur when air opens closed air spaces or small airways snap open. Fine crackles are short, high-pitched sounds, sometimes compared to hair rubbing together, while coarse crackles are lower-pitched and last longer.
Wheezes
Wheezes are continuous, high-pitched, whistling or musical sounds produced by narrowed airways. They are frequently heard during exhalation, but can also occur during inhalation if the airway narrowing is severe. The pitch and presence during inspiration or expiration can provide clues about the location and degree of airway obstruction.
Rhonchi
Rhonchi are continuous, low-pitched sounds resembling snoring or gurgling. Heard during exhalation, they are caused by air passing through larger airways obstructed by fluid, mucus, or secretions. Unlike crackles, rhonchi may sometimes clear or change after a cough as secretions shift.
Stridor
Stridor is a high-pitched, harsh, crowing sound heard predominantly during inspiration. It indicates a partial obstruction or narrowing in the upper airway, such as the larynx or trachea. Stridor is louder over the anterior neck, distinguishing it from wheezes, which originate in the lower airways.
Pleural Friction Rub
A pleural friction rub is a grating or creaking sound, sometimes described as walking on fresh snow. This non-musical sound occurs during both inspiration and expiration. It results from inflamed pleural surfaces, the two layers of tissue surrounding the lungs, rubbing against each other.
What Adventitious Sounds Can Indicate
Adventitious breath sounds provide important clues about physiological changes or medical conditions within the respiratory system. These sounds are not diagnoses, but symptoms prompting further investigation.
Crackles
Crackles, especially fine crackles, often suggest fluid in small airways or alveoli, or the sudden opening of collapsed airways. This can be observed in conditions such as pneumonia, where air sacs fill with fluid, or congestive heart failure, which can lead to fluid accumulation in the lungs. Coarse crackles indicate excessive fluid in the lungs due to conditions like pulmonary edema or chronic bronchitis.
Wheezes
Wheezes signal narrowed airways, which can restrict airflow. This narrowing occurs in conditions like asthma, where airways become swollen and constricted, or chronic obstructive pulmonary disease (COPD), which involves long-term airflow limitation. Viral infections and foreign body obstructions can also lead to wheezing.
Rhonchi
Rhonchi are associated with secretions, like mucus or fluid, in larger airways. This is a feature of conditions such as bronchitis, an inflammation of the bronchial tubes, or pneumonia, where infection and inflammation lead to mucus buildup. Chronic obstructive pulmonary disease (COPD) and cystic fibrosis can also cause rhonchi due to airway obstruction from secretions.
Stridor
Stridor indicates an obstruction or narrowing in the upper airway, which includes the throat and windpipe. Conditions like croup, a viral infection causing airway swelling, or the presence of a foreign object lodged in the airway can cause this sound. Other causes include epiglottitis or tumors affecting the voice box.
Pleural Friction Rub
A pleural friction rub points to inflammation of the pleura, the membranes that line the lungs and chest cavity. This inflammation causes the normally smooth surfaces to become rough, creating a grating sound as they rub together during breathing. Common conditions that can cause a pleural friction rub include pleurisy, which is inflammation of the pleura, pneumonia, or pulmonary embolism.
When to Consult a Healthcare Professional
Noticing any unusual breathing sounds warrants medical evaluation. Adventitious breath sounds always indicate something is impacting normal airflow. Seek prompt medical attention if abnormal breath sounds are accompanied by other concerning symptoms. These include shortness of breath, chest pain, fever, or bluish skin discoloration. A healthcare professional can perform a physical examination, including listening to lung sounds, and conduct further tests to determine the underlying cause and appropriate course of action.