Auscultation of the lungs is a foundational technique in medical assessment, involving the use of a stethoscope to listen to the sounds created by air moving through the respiratory system. This non-invasive practice allows professionals to evaluate airflow, identify obstructions, and detect fluid or inflammation within the lungs. Listening to the chest wall provides immediate insights into the health of the trachea, bronchi, and peripheral lung tissue. While auscultation is a powerful tool for initial diagnosis and monitoring, interpreting these sounds requires extensive training. Learning the mechanics of how to listen is valuable for understanding respiratory health, but it is not a substitute for professional medical diagnosis.
Essential Equipment and Proper Setup
The primary instrument for listening to lung sounds is the stethoscope, which features a chest piece with a diaphragm and a bell. For lung auscultation, the flat, larger diaphragm is used because it transmits the higher-frequency sounds of air movement. The bell, the smaller, concave side, detects softer, low-frequency sounds, such as heart murmurs, and is generally not used for routine respiratory assessment.
Proper preparation ensures clear sound transmission. The person being examined must be in an upright position, such as sitting, to allow for full lung expansion and access to the posterior chest. The stethoscope’s diaphragm must be placed directly against the bare skin, as listening through clothing or hair creates friction sounds that interfere with breath sounds. Furthermore, the environment must be quiet, since extraneous noise can easily mask the soft sounds produced by the lungs.
The Step-by-Step Guide to Auscultation
Listening to the lungs requires a systematic approach to ensure all areas are assessed and compared symmetrically. The standardized method follows a “ladder pattern,” moving from the top of the chest downward and comparing one side to the other at each level. This comparison of symmetrical points helps identify differences in sound intensity or quality that may indicate localized pathology.
The process begins by instructing the person to breathe deeply through their mouth, which increases the volume of the breath sounds and makes them easier to hear. Starting on the anterior chest, the stethoscope is placed just above the clavicle to listen to the lung apices. The listener moves down the chest, placing the diaphragm in the intercostal spaces (the areas between the ribs), and listening to at least one full breath cycle at each spot.
Next, assess the posterior chest, which is accessed most efficiently with the person leaning forward slightly to move the shoulder blades (scapulae) out of the way. Position the stethoscope in the triangular area between the spine and the scapula, moving from the upper back down to the bases of the lungs. The lateral areas, beneath the armpits (mid-axillary line), are also assessed, as they provide access to the lower lobes. Throughout the process, press the diaphragm firmly against the skin to create a seal and maximize sound transmission.
Understanding Normal Lung Sounds
When air moves freely through healthy lung tissue, it produces expected sounds that establish a baseline. The most common normal sound is the vesicular breath sound, heard over the majority of the peripheral lung fields. Vesicular sounds are low-pitched with a rustling quality, and inhalation is noticeably longer than exhalation.
Different sound qualities are heard over larger airways due to air turbulence. Bronchial sounds are heard best over the trachea and the manubrium (the bony upper part of the sternum). These sounds are louder and higher-pitched than vesicular sounds, and the expiratory phase is equal to or longer than the inspiratory phase. A third type, bronchovesicular sounds, are intermediate in pitch and intensity, with equal inspiratory and expiratory phases, and are heard near the main bronchi, such as between the scapulae posteriorly.
Identifying Common Abnormal Sounds
Sounds heard in addition to normal airflow noises are called adventitious sounds and indicate an issue with the airways or surrounding lung tissue.
Crackles (Rales)
Crackles, also known as rales, are brief, intermittent popping noises most often heard during inhalation. These sounds are thought to be created when small, collapsed airways or alveoli snap open, or when air bubbles move through fluid or secretions.
Wheezes
A wheeze is a continuous, high-pitched, musical sound that indicates air movement through narrowed passages. Wheezes are typically more prominent during exhalation and result from the rapid vibration of opposing airway walls that have been narrowed by bronchospasm, inflammation, or excessive secretions.
Rhonchi
Rhonchi are low-pitched, continuous sounds often described as snoring or gurgling. They occur when air passes through larger airways obstructed by thick, tenacious secretions. Hearing any of these abnormal sounds, especially when accompanied by symptoms like shortness of breath or persistent cough, warrants immediate professional medical evaluation.