How the Method Originated and Why It Works
The method of tapping on the patient's body was first described by the Viennese physician Leopold Auenbrugger in his treatise «Inventum Novum» («A New Discovery...»). However, this diagnostic approach gained real popularity later, thanks to Napoleon I's personal physician Jean-Nicolas Corvisart, who translated the work into French and introduced percussion into global practice.
The essence of the method is based on the physics of sound generation. How a particular organ "sounds" directly depends on the elasticity of its tissues, the presence of elastic fibers in them, and the volume of air contained within.
Proper Technique: Finger-on-Finger Method
In modern clinical practice, physicians do not use instruments (unlike the historical method using a pleximeter plate and a percussion hammer). The universally accepted standard is indirect (mediate) percussion, where the physician strikes one finger with another finger placed on the patient's body.
- Left Hand (Pleximeter Finger): The working finger is the middle finger. It must be pressed firmly, but without excessive pressure, against the percussed surface. A crucial condition is that it must not touch the neighboring fingers of the hand to prevent sound dampening.
- Right Hand (Hammer Finger): The middle finger also works here. It should be slightly bent at the interphalangeal joints and isolated from the other fingers.
- Strike Biomechanics: The strike is delivered strictly to the middle phalanx of the pleximeter finger. The main mistake is striking using the entire arm (movement at the elbow) or solely from the metacarpophalangeal joint. The correct «swing» must occur exclusively at the wrist joint.
Types of Percussion: Objectives and Strike Force
Depending on the objectives of the examination, percussion is divided into two types:
- Comparative Percussion. The objective is to identify pathologies. The physician alternately taps anatomically symmetrical areas (e.g., the right and left halves of the chest) and compares the sounds between them.
- Topographic Percussion. The objective is to determine the exact boundaries of organs, their shape, and size. The physician consistently moves from top to bottom or from the center to the periphery until the character of the sound changes. Where the sound changes (e.g., from pulmonary to dull), the organ boundary lies.
Percussion also differs in strike force. Loud (deep) percussion is used to examine deeply located structures, while quiet (superficial) percussion is used for superficially lying organs.
Varieties of Percussion Sounds
Each tissue sounds differently. Sounds vary in loudness, pitch, and timbre:
- Clear Pulmonary. Loud, low-pitched, prolonged. Occurs where there is plenty of air and elastic elements (healthy lungs).
- Dull (Quiet, Femoral). Short, high-pitched, and quiet. Heard when tapping dense, inelastic, or airless tissues (muscles, liver).
- Dullness (Shortened Sound). An intermediate variant with decreased loudness. Indicates a reduction in organ aeration (e.g., pulmonary tissue consolidation).
- Tympanic. Loud, musical, higher-pitched than pulmonary. Resembles a drum beat (tympanon). Characteristic of smooth-walled gas-containing cavities (stomach, intestines).
- Boxy. Loud and low-pitched, resembling a strike on an empty box or pillow. Occurs with increased aeration against a background of decreased tissue elasticity (a classic sign of pulmonary emphysema).
Topography of Sounds in a Healthy Individual
To correctly interpret data, one must know the norm (distribution pattern over the anterior body surface):
- Clear pulmonary sound is auscultated over the main lung zone, larynx, and paranasal sinuses.
- Tympanitis prevails over the abdominal surface since the stomach and intestines contain gas (the exception is the liver area).
- Dull sound is found over parenchymatous organs: the liver, spleen, and also in the projection zone of the heart (cardiac dullness).
- Absolutely dull (femoral) sound is the standard for a quiet sound, which is normally determined over large muscles and facial areas without air-containing cavities.
Briefly: answers to topical questions
In which specific diseases is a dull (shortened) percussion sound detected?
A dull (shortened) percussion sound occurs in pathology when the air content in the percussed organ decreases, i.e., during pulmonary tissue consolidation. The following causes/conditions are confirmed from sources:
- pneumonic focus in bacterial or viral pneumonia;
- tuberculous infiltrate;
- pulmonary infarction due to PE or local thrombosis.
Also, when fluid accumulates in the pleural cavity, a dull or absolutely dull (femoral) sound is determined over the fluid; above the fluid zone — a dull-tympanic shade associated with compression atelectasis.
Along which topographic lines are the lower lung borders determined?
The determination of the lower lung borders is carried out sequentially along the conventional topographic lines of the chest. The following landmarks are used:
- Right parasternal line
- Right midclavicular line
- Anterior axillary lines (percussion of the left lung begins only from this line, since the anterior border cannot be determined due to the adjacent heart and spleen)
- Midaxillary lines
- Posterior axillary lines
- Scapular lines
- Posterior median line
Percussion is performed strictly along the ribs and intercostal spaces.
How is percussion performed to determine the borders of relative and absolute cardiac dullness?
Cardiac percussion is based on the difference in sounds: the heart as a dense muscular organ produces a dull sound, while the lungs produce a clear pulmonary sound.
- Relative cardiac dullness: first, the upper border of hepatic dullness is determined — the pleximeter finger is positioned parallel to the intercostal spaces, percussing from top to bottom from the lungs to the liver. Then, one intercostal space is moved upward, the pleximeter finger is turned parallel to the right sternal border, and percussion is performed from the lungs to the heart. Strike force is medium or slightly lower, the finger is pressed firmly. The border of relative dullness is determined by the initial dulling of the sound. The left border is determined from the anterior axillary line toward the sternum in the intercostal space where the apex beat is detected, or in its absence — in the fifth intercostal space. The upper border is determined by moving the pleximeter finger from the 2nd rib along a line parallel to the sternal border.
- Absolute cardiac dullness: threshold percussion is applied — in complete silence, very quiet strikes are delivered with the hammer finger; the sound completely disappears.
Remembering the sound distribution helps with the density rule: the more air in an organ — the louder, lower, and more prolonged the percussion sound (lungs, intestines). The denser the tissue — the quieter, shorter, and higher-pitched the sound (liver, muscles).
Class and exam questions
What is the difference between quiet and loud percussion?
They differ in the depth of sound wave penetration. Loud percussion is deep, allowing the examination of organs deep within tissues. Quiet percussion is superficial, used for superficially located structures.
Why should the pleximeter finger not touch the other fingers of the left hand?
If the working finger pressed against the body touches neighboring ones, they will dampen the vibrations. Because of this, the percussion sound will become quieter or distorted.
In what pathology does a hyperresonant (box) sound occur?
The boxy sound is characteristic of pulmonary emphysema. It occurs when the lung tissue loses its elasticity but becomes excessively aerated.
What else to study on this topic
- Detailed technique of hand positioning and wrist swing practice
- Historical research methods: use of pleximeter and percussion hammer
- Changes in percussion sound in various lung diseases (tissue consolidation)
- Diagram of the normal distribution of percussion sounds according to A.L. Myasnikov
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