Percussion

Source: Jaideep S. Talwalkar, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT

Simply stated, percussion refers to the striking of one object against another to produce sound. In the early 1700s, an Austrian inn-keeper's son, named Leopold Auenbrugger, discovered that he could take inventory by tapping his father's beer barrels with his fingers. Years later, while practicing medicine in Vienna, he applied this technique to his patients and published the first description of the diagnostic utility of percussion in 1761. His findings faded into obscurity until the prominent French physician Jean-Nicolas Corvisart rediscovered his writings in 1808, during an era in which great attention was focused on diagnostic accuracy at the bedside.¹

There are three types of percussion. Auenbrugger and Corvisart relied on direct percussion, in which the plexor (i.e. tapping) finger strikes directly against the patient's body. An indirect method is used more commonly today. In indirect percussion, the plexor finger strikes a pleximeter, which is typically the middle finger of the non-dominant hand placed against the patient's body. As the examiner's finger strikes the pleximeter (or directly against the surface of the patient's body), sound waves are generated. If using indirect percussion, important information is gained from the vibration in the pleximeter finger, as well.² The third type of percussion, auscultatory percussion, relies on the clinician using a stethoscope to discern differences in sounds created by the plexor finger.

The density of the structure underlying the site of percussion determines the tone of the percussion note; the denser the structure, the quieter the note. Notes differ in relative intensity, pitch, and duration, and help the examiner determine what lies below the skin surface. Knowledge of what particular locations on the body should sound like, in conjunction with the particulars of a specific clinical situation, can help a clinician determine if percussion notes in a particular patient are normal or not.