Pulmonary percussion is a diagnostic technique used during a physical examination to evaluate the density of underlying tissues in the chest and back. The procedure involves tapping specific areas to produce sounds indicating whether the region beneath is filled primarily with air, fluid, or a solid mass. Trained medical professionals interpret these sounds to gather important information about the condition of the lungs and surrounding structures. Percussion helps narrow down potential diagnoses, though it is only one component of a comprehensive clinical assessment. This overview is educational and not intended as instruction for self-diagnosis or practice outside of a clinical setting.
Preparing for Pulmonary Percussion
The examination must take place in a quiet environment, as ambient noise can obscure subtle variations in percussion notes. To ensure accurate sound transmission and tactile feedback, the chest wall area being examined should be exposed or covered only by a very thin layer of clothing.
Patient positioning is adjusted based on the area being assessed. For percussing the posterior chest, the patient should sit, allowing the examiner full access to the back. The patient should cross their arms over their chest and place their hands on the opposite shoulders. This action rotates the scapulae laterally, exposing more of the lung field for examination.
Percussing the anterior chest can be performed with the patient sitting or lying supine. If the patient cannot sit up when examining the back, they may be gently rolled from side to side so the examiner can access the posterior chest wall. Proper positioning ensures the examiner percusses over intercostal spaces and lung tissue, avoiding bony structures which produce a naturally flat sound.
Mastering the Percussion Technique
Pulmonary percussion uses a two-finger approach: the non-dominant hand acts as the “pleximeter” and the dominant hand as the “plexor.” The middle finger of the non-dominant hand is placed firmly and flatly against the patient’s chest wall, specifically in an intercostal space. The entire pleximeter finger must maintain solid contact with the skin to prevent sound attenuation.
The dominant hand’s middle finger (the plexor) delivers a sharp, quick tap. The strike must land specifically on the distal interphalangeal joint of the pleximeter finger, avoiding the nail or the pulp. The motion is generated primarily from a quick snap of the wrist, similar to a drummer hitting a drum.
Immediately after the strike, the plexor finger must be lifted quickly from the pleximeter finger. This immediate lift-off prevents the finger from dampening the created sound wave. The procedure is repeated once or twice at each location, moving systematically across the chest in a ladder-like fashion. The systematic pattern requires comparing symmetrical points on the left and right sides of the chest.
Decoding the Sounds of Lung Percussion
The sound produced by percussion varies based on the density of the underlying tissue. Over a healthy, air-filled lung, the expected sound is termed resonance, which is a low-pitched, hollow sound. This quality is normal because the vibrating sound wave travels easily through the air and tissue of the lung parenchyma.
When the sound is louder and lower-pitched than normal resonance, it is called hyperresonance, indicating an excessive amount of air. This finding suggests conditions where air is trapped or over-inflated, such as emphysema or a pneumothorax.
Conversely, a muffled, thudding sound known as dullness occurs over tissue that is denser than normal lung. Dullness suggests that the air in the lung has been replaced by fluid or solid tissue. Examples include a pleural effusion, where fluid accumulates in the space around the lung, or consolidation, which happens when lung tissue fills with inflammatory exudate, such as in pneumonia.
An extremely dull sound, sometimes called flatness, is heard over very dense structures like bone, muscle, or a large tumor mass. A distinct, drum-like sound is known as tympany and is typically heard over air-filled structures like the stomach or a large air pocket. Finding dullness in the lower lung fields compared to the normal resonance in the upper fields helps define the extent of a fluid collection or tissue change.