Pulmonary percussion is a diagnostic tool used during a physical examination. The technique involves tapping on the body surface to produce vibrations and sounds, which helps the clinician assess the density of the underlying lung tissue. This method determines if an area beneath the chest wall contains air, fluid, or solid material, offering insight into the condition of the lungs and surrounding structures. By listening to the pitch and duration of the resulting sound, a healthcare provider can evaluate the state of the respiratory system.
The Mechanics of Chest Percussion
The standard approach for pulmonary assessment is the indirect percussion method, which utilizes both hands to generate the sound. The non-dominant hand’s middle finger, called the pleximeter, is placed firmly against the patient’s skin between the ribs. It is important to hyperextend this finger slightly and ensure no other part of the hand touches the chest wall, as contact can dampen the resulting vibrations.
The middle finger of the dominant hand, known as the plexor, acts as the striking tool. The plexor finger strikes the pleximeter finger with a short, sharp motion originating from the wrist, not the elbow. The tip of the plexor finger should aim for the distal interphalangeal joint of the pleximeter finger.
Immediately after the strike, the plexor finger is quickly withdrawn to avoid muffling the sound. This technique ensures a clear, distinct vibration. The force used is typically light for the lungs, as heavy percussion is reserved for assessing deeper, denser organs.
Key Anatomical Landmarks for Pulmonary Assessment
Percussion of the lungs is always performed in a comparative manner, moving systematically from one side of the chest to the corresponding location on the other side. This systematic approach helps identify differences in sound that may indicate pathology. The procedure covers the back (posterior), front (anterior), and sides (lateral) of the chest.
The assessment usually begins on the patient’s back, starting above the scapulae, which is the apex of the lung. The examiner then proceeds downward in a consistent ladder-like pattern, tapping across the intercostal spaces. Avoid percussing directly over the scapulae and the bony vertebrae, as dense bone naturally produces a flat sound that obscures lung findings.
On the anterior chest, percussion starts above the clavicles, then moves down the chest wall between the ribs. Percussion follows the midclavicular lines, moving symmetrically down the chest until the limits of the lung are reached. The assessment is limited by solid organs, such as the heart on the left and the liver on the right, which naturally produce a dull sound.
Finally, the sides of the chest, or the axillary areas, are percussed with the patient’s arms raised. This lateral assessment follows the mid-axillary line, moving from the armpit downward. This area is useful for evaluating the middle lobe of the right lung and the lingula section of the left lung.
Understanding the Percussion Sounds
The sounds generated by percussion vary based on the density of the underlying tissue, providing distinct clues about the lung’s condition. Resonance is the normal, expected sound heard over healthy, air-filled lung tissue. This sound is described as low-pitched and hollow, indicating a normal balance of air and tissue.
An abnormally loud, booming sound is known as hyperresonance, which suggests an excess amount of air. Hyperresonance is typically associated with conditions that cause hyperinflation, such as a large air pocket in the pleural space (pneumothorax) or generalized air trapping (emphysema). This finding indicates that the lung or chest cavity contains more air than expected.
Conversely, sounds described as dullness or flatness indicate denser tissue beneath the percussion site. Dullness is a quiet, high-pitched thudding sound that occurs when air in the lung is replaced by fluid or solid material. Examples include fluid in the pleural space (pleural effusion) or consolidated tissue from an infection (pneumonia). Dullness is also the normal sound heard when percussing over solid organs.