Auscultation is a fundamental health assessment technique involving listening to breath sounds, which are generated as air moves through the bronchial tree and into the lungs. Evaluating the quality, intensity, and timing of these sounds provides important clues about the respiratory system’s health. This non-invasive process helps determine if airways are clear, narrowed, or if fluid is present. Health professionals systematically listen to specific locations on the chest and back to gather information about different lung regions.
Understanding the Anatomical Zones of the Lungs
Understanding the internal structure of the lungs, which are divided into lobes, is essential before identifying external listening points. The right lung has three lobes (superior, middle, and inferior), while the left lung has two (superior and inferior) to accommodate the heart. The placement of these lobes dictates the listening points: upper and middle lobes are accessible from the front, and lower lobes are primarily heard from the back. Proper auscultation ensures air entry is evaluated across all five lobes. The technique involves listening over the intercostal spaces (gaps between the ribs) to minimize sound blockage from bone.
Anterior Listening Points
Listening to the front of the chest focuses mainly on the upper and middle lobes. The first points are the supraclavicular areas, located just above the clavicles, which assess the lung apices (top portions). Moving down, the stethoscope is placed in the second intercostal space near the sternum to listen to the upper lobes. The right middle lobe is evaluated around the fourth intercostal space, lateral to the sternum. On the left side, this area corresponds to the left upper lobe. Standard practice involves listening in a zigzag pattern, comparing the sound on one side to the corresponding location on the opposite side to identify subtle differences.
Posterior and Lateral Listening Points
The posterior chest provides the clearest access to the large lower lobes, which occupy a significant portion of the back. Auscultation begins above the scapulae to assess the lung apices, then proceeds downward in the interscapular region. The scapulae must be avoided as they block sound transmission; having the person lean forward with arms crossed helps move them out of the way. Listening points continue down the back, generally from the third thoracic vertebra (T3) down to the tenth (T10), assessing the lower lobes. Lateral points, along the mid-axillary line (the side of the chest), are crucial for capturing the full extent of the lower lobes. This lateral placement also allows for better assessment of the right middle lobe and the left lower lobe.
Normal Versus Abnormal Sounds
After systematically listening to all locations, sounds are classified as either normal or abnormal (adventitious). Normal breath sounds, known as vesicular sounds, are soft, low-pitched, and resemble a gentle rustling. The inspiratory phase is typically longer and louder than the expiratory phase. Abnormal sounds indicate a disruption in airflow or the presence of fluid or secretions. Wheezes are continuous, high-pitched, musical sounds often heard during exhalation, suggesting narrowed airways, such as with asthma. Crackles (rales) are short, discontinuous, popping or clicking sounds, which may be fine (high-pitched) or coarse (low-pitched). These sounds suggest fluid in the small airways.