Percussion to which I have alluded, and the resonance of the vesicular structure is quite different from that which would be caused by the same quantity of air contained in a single bag, or large vesicle. If the air contained in a large number of scattered vesicles were collected together, and percussion were made upon the sac which contains it, the sound would be drum-like, or tympanitic. This character is actually observed in certain morbid conditions of the chest, but it is never similar to the healthy sound, which is more deep and hollow, but at the same time less gaseous. The difference between the two varieties of the clear sound will be appreciated at once if we examine the chest, and then percuss downwards until we come to the hollow viscera of the abdomen, which yield the tympanitic resonance very different from the hollow sound, which is caused by percussion on the lungs, and which is called vesicular. After we have gained a general idea of the resonance of the chest, we should proceed to a more thorough examination of the various portions of it, one by one. For this purpose, it is convenient to divide the chest into regions or parts. These may be the anatomical divisions corresponding to the exterior of the chest; as the clavicular, scapular regions, etc.; or we may use terms expressive merely of the fractional parts into which the surface is divided, such as thirds, fourths, etc. For most purposes, the latter method has seemed to me to be the most convenient. When we wish to be more exact, we may subdivide these regions, or we may, in addition, designate them by a reference to their anatomical relations; but if we divide the anterior and posterior surfaces into three parts, and the axillary into two, it will be sufficiently minute for most purposes. The anterior surface may be divided, therefore, first, into an upper third, extending from the summit of the lung to the lower margin of the second rib, and of course including the anatomical subdivisions of post-clavicular, or to the space above the clavicle; clavicular, that corresponding directly to this bone; and sub-clavicular, or the region found immediately beneath it. This portion, in general terms, may be said to correspond with the summit of the lung, and is of great interest to the physician; for it is the ordinary seat of tuberculous diseases, which of course render the sound dull; and occasionally of pneumonia, which produces the same effect in a more marked degree; and, thirdly, of emphysema, which renders the sound preternaturally clear. The middle third extends from the lower margin of the upper division to the space between the fourth and fifth ribs; it is less interesting for practical study, for its diseases are, for the most part, rather such as begin in the upper or in the lower third, and extend themselves to the middle, than those which commence in it. Emphysema, however, is often more developed about the middle of the lung than in any other part of this surface. The lower third extends from the boundary of the second to the lower margin of the chest; it is the usual seat of pleuritic effusions and of hydrothorax; in both of these diseases the liquid extends itself gradually from the posterior parts of the chest, towards its anterior margin, rendering the lower portion dull. In the healthy condition the sounds of percussion are not equally sonorous in all parts of the anterior surface of the chest; in children the lower third is decidedly the most sonorous; in adults the middle is generally the clearest. In women we shall find it difficult to compare these various portions together, for the mamme interfere so much with percussion that it is extremely difficult to examine the middle third in a satisfactory way. The heart is another cause of dulness of sound at the internal part of the lower third on the left side. The precordial dullness extends from the space between the fourth and fifth ribs at the sternum to the nipple, generally passing a little within this part. On the right the dullness is bounded by a line which follows the middle of the sternum; the lower part of the heart rests upon the diaphragm, and the percussion is therefore dull to the base of the thorax.<Callout type="important" title="Key Areas for Examination">The upper third of the anterior chest surface is crucial for identifying tuberculous diseases, while the middle third is often affected by emphysema. The lower third is typically where pleuritic effusions and hydrothorax occur.</Callout>
Key Takeaways
- Understanding resonance patterns helps in diagnosing various diseases.
- Dividing the chest into thirds aids in precise localization of disease.
- The heart and mammary glands can interfere with percussion results.
Practical Tips
- Use a stethoscope to enhance your ability to hear subtle differences in sound.
- Practice on healthy individuals to familiarize yourself with normal sounds.
Warnings & Risks
- Be cautious of interference from the heart and mammary glands when percussing.
- Ensure you are trained properly before attempting diagnosis on others.
Modern Application
While modern imaging techniques have advanced significantly, understanding percussion remains valuable for initial assessments in remote or resource-limited settings. It can quickly identify potential issues like pneumonia or pleurisy without the need for sophisticated equipment.
Frequently Asked Questions
Q: What is the significance of tympanitic resonance observed during chest examination?
Tympanitic resonance, which sounds drum-like, indicates a condition where air or fluid has accumulated in the lungs or pleural cavity, often due to diseases such as pneumonia or hydrothorax.
Q: Why is it important to divide the chest into thirds during examination?
Dividing the chest into thirds helps in precisely localizing and identifying specific areas affected by disease. Each third has its own common conditions, making this method crucial for accurate diagnosis.
Q: How does the heart affect percussion results on the left side of the chest?
The presence of the heart causes a dull sound in the lower third on the left side due to its resting position on the diaphragm, which can interfere with normal percussive sounds.