Percussion

Percussion is one of the fundamental examination techniques, along with inspection, palpation and auscultation. After more than two centuries of its use in modern medicine it still has invaluable place in diagnosis of chest disorders, pleural effusion in particular. The main goal is to generate percussion sound that is specific for surrounding tissues, detecting disease, in other times to elicit pain.

History

Percussion was known to physicians in ancient times, including Hippocrates. However, it was Leopold Auenbrugger, an Austrian physician, who first described its role in lung diseases. He observed the technique from his father who by percussing wine barrels was measuring their fluid level. In 1761, after a decade of post-mortem experiments Auenbrugger published the first monography about percussion.

It gained on popularity only because Napoleon’s court physician Jean-Nicolas Corvisart translated it to French in 1808. Many physicians started to investigate its role in diagnosing diseases even more, most notably René Laennec, the student of Corvisart and the inventor of stethoscope, Josef Škoda, the first physician to apply principles of physics in percussion, and Adolph Piorry, the inventor of pleximeter and indirect percussion technique known today.

Until the discovery of x-ray in 1895, percussion and auscultation were the only chest investigation methods.

Clinical Vignette

30-year old male was admitted to the cardiology department after an episode of ventricular fibrillation, necessitating ICD implantation. Subclavian vein was used as a way to insert electrodes. During the procedure, electrode was misplaced as a rare complication outside of the pericardium. Chest x-ray detected iatrogenic pneumohemothorax. Had he been examined properly, asymmetrical apical tympanic and basal dull note would had been appreciated.

Physical Examination

Percussion is relatively simple examination skill, yet to be mastered it needs to be practiced properly. Based on observational studies percussion has relatively low kappa coefficient (κ) which means there is high interobserver disagreement. This may be due to inconsistent technique.

Percussion Methods

There are two main methods for percussion – direct and indirect.

Direct Method. It’s the original method of Auenbrugger and Laennec. In this method physician is striking the body wall directly with the plexor. Most of the time physicians use their right middle finger. In early days, percussion hammers were used.

Indirect Method. This method was developed by Piorry and Škoda. It replaced direct method partly because percussion blows were so hard it caused patients great pain and put them at risk of trauma. In this method percussion blows are conveyed to body wall indirectly through pleximeter which is placed firmly on the body wall. Nowadays physicians use their left middle finger. In early days, wooden or ivory plates or coins were used.

  1. Place hyperextended left middle finger (pleximeter) on the body wall. Make sure it’s pressed firmly as light touch changes sound intensity. Other fingers should be spread apart and not touching the body as it dampens the vibrations and changes percussion note.
  2. With the tip of the right middle finger (plexor) strike the left middle phalanx bone. Use quick, hard but relaxed motion of the wrist, not the finger itself.
  3. After the blow, quickly withdraw the plexor finger or let it rest lightly on the pleximeter.
  4. Repeat steps 2 and 3 with the same force and same technique to elicit valid percussion sound.

Percussion Types & Special Techniques

Based on clinical use there are three types of percussion – comparative, topographic and auscultatory.

Comparative Percussion. In this method physician is comparing percussion sounds at identical places on both sides of the chest. It’s usefulness lies in detecting asymmetrical finding indicating underlying pathologic process rather than the sound or note itself. From the definition, it is impossible to detect symmetrical bilateral process.

Topographic Percussion. It’s useful for outlining the borders of the organs like liver or spleen. Although traditionally taught, studies have shown there is high interobserver variability in the absolute findings, questioning its validity.

Auscultatory Percussion. This less known technique combines percussion and auscultation with stethoscope. Physician places stethoscope over the body wall and percuss it, listening to the changes of the sound through the stethoscope. The technique itself varies greatly in different authors. Moreover, its usefulness lacks scientific support. One of the example is scratch test of the liver.

Threshold Percussion. This special technique is based on the principle that resonant percussion sound has higher intensity that dull one. The lighter the percussion blow is the lower the sound intensity. Therefore physician strikes the pleximeter so lightly the normally resonant sound is barely audible. When over normally dull sound, the percussion blow is not audible at all. As Adolph Weil said, it is much easier to distinguish “something from nothing” than “more from less.”

Interpretation

Although modern textbooks describe up to five different percussion sounds, based on clinical studies there are only three percussion sounds that have high interobserver agreement,  the dullness, resonance and tympany. Each of them are different in duration, frequency content and intensity.

Tympany can normally be elicited over air-filled intestines or pathologically over pneumothorax. It’s the only percussion sound that has musical quality. The resonant percussion note is normally heard over healthy lung tissue. Dullness is normally heard over solid tissue like liver, spleen or thigh, pathologically in pleural effusion, ascites or lung consolidation.

Tympany Resonance Dullness
Normal finding Air-filled intestines Healthy lungs Solid tissue (liver, spleen, thigh)
Pathologic finding Pneumothorax Chronic bronchitis Pleural effusion, ascites, lung consolidation
Quality Musical Noise Noise
Duration >40 ms 15 ms <3 ms
Frequency content Single dominant frequency Lower frequency than dull Higher frequency than dull

Based on McGee, S. R. (2018).

Clinical Significance

To be added at later date.

 

Caveats and Errors

Several Centimeter Rule

One of the most common misconceptions about percussion is the several centimeter rule proposed by Adolf Weil in 1880 stating that percussion blow penetrates tissues only 6 cm deep at most.

It’s the main dogma of topographic percussion theory (only underlying tissue generates the sound) that tried to explain physical principles of percussion. However, unlike cage resonance theory (all the the tissues regardless of depth and proximity generate the sound) proposed by J. F. Mazoon, it lacks scientific evidence.

Percussion Blow & Pressure

The technique as well as blows themselves have high variability amongst the physicians. Therefore consistency is the key to valid examination findings.

Lighter strokes can generate sound that is duller. Lifting pleximeter even lightly off the body wall will generate duller sound as well. Quick withdrawal of plexor after striking the pleximeter was never proven to change the percussion note.

References

Chi, J., Artandi, M., Kugler, J., Ozdalga, E., Hosamani, P., & Koehler, E. et al. (2016). The Five-Minute Moment. The American Journal Of Medicine, 129(8), 792-795. doi: 10.1016/j.amjmed.2016.02.020

McGee, S. R. (2018). Evidence-based physical diagnosis. Philadelphia, PA: Elsevier.

Bates, B., Bickley, L. S., & Szilagyi, P. G. (2013). Bates guide to physical examination and history taking. Philadelphia: Wolters Kluwer, Lippincott Williams et Wilkins.

Soiferman, E., & Rackow, E. (1998). A brief history of the Practice of Percussion. Retrieved May 12, 2018, from http://www.antiquemed.com/percus.html