FIG. 82. Auscultatory percussion. The bell of the stethoscope is placed at Band percussion is performed in gradually narrowing circles toward the heart. resonator. This tends to cause a note of lower pitch. When the costal cartilages are ossified, the thorax becomes more rigid, and less penetration of the percussion blow occurs because a greater portion of the impact is transferred laterally by the arch-like structure of the ribs, accurate topographic percussion is, therefore, more difficult. 3. Thickening of the pleura, or exudation or effusion into the pleural cavity cause both a diminished penetration of the percussion blow and a lessened resonance of sound, because the vibrations lose much of their amplitude in passing through media of different density. 4. Changes in the pulmonary tissue-the degree of tension, the amount of air, elasticity and density-produce marked and important alterations of sound. FIGS. 83 AND 84.-Showing the areas over which the percussion note is shorter, higher pitched and less resonant than normal in dextro-convex scoliosis. These changes are most marked over the area I, and least marked over the area IV. (After E. A. Gray, Jour. Am. Med. Assn., 1912, LIX, 2249.) (See Figs. 17, 34, 36.) I. Changes in pulmonary tension may be uni- or bilateral. (a) Increased tension occurs during forced inspiration and in emphy- sema. (1) General, may arise from pleural effusions, increased intra-abdominal pressure (ascites, tumors); it also occurs in senility (less elastic and more rigid thorax). Decreased tension allows the lung to vibrate as a whole. This adds a tympanitic quality to the percussion note. The high-pitched tympany which occurs above pleural effusions and around consolidations is known as Skodaic tympany. (2) Local decrease of tension occurs around consolidated areas (pneumonia, tuberculosis, etc.). II. Changes in the Amount of Air in Lung Tissue.-(a) An increase occurs in emphysema, asthma and during compensatory (forced) breathing, also in cases of cavitation. In the first case the percussion note is hyperresonant, in the last, tympanitic, provided that the cavity is sufficiently large, not too deeply placed, and that it is filled with air. In the first instance the vibrating tissues are thinner under greater tension and contain more air. In the latter the walls of the cavity vibrate in unison with the air columns it contains. During forced inspiration deep percussion yields a lower; light percussion, a higher note, than during forced expiration. (b) Decreased air bearing lung tissue occurs in consolidation (pneumonia, tuberculosis, fibrosis, atelectasis with compression, cavities filled with exudate, etc.). The percussion note becomes less resonant in proportion to the consolidation, because the vibrating tissues are thicker, less elastic and contain less air. The sound, therefore, becomes short, high-pitched and dull, and resistance is increased. Even minor degrees of spinal curvature may produce lack of resonance over certain areas of the chest. This is due to the fact that abnormal convexities of the thorax produce an increased rigidity of the more convex rib which tends to prevent penetration of the percussion blow, whereas a flattened rib has the opposite effect (Sahli) (Figs. 17, 26, 36, 83, 84). In order to detect spinal deformities the patient should be sitting, muscularly relaxed, and the examiner should note especially: the relative height of the shoulders and of the scapulae, the depth of the supraclavicular fossæ, and in women the height of the breasts. The spine itself is, of course, also inspected both from a lateral and from an anteroposterior aspect. Small degrees of scoliosis may be emphasized by marking the skin over the spinous processes of the vertebræ with a pencil. CHAPTER VII NORMAL VARIATIONS OF THE PULMONARY PERCUSSION SOUNDS INDIVIDUAL VARIATIONS There is no invariable normal standard. Actual values must be determined largely by the variation of the two sides of the chest, but the normal range must be learned by experience. Percussion sounds will vary with: (a) the soft parts overlying the lungs; (b) the flexibility of the thorax; (c) the size and shape of the lungs, and their state of tension; (d) the region percussed. FIG. 85. Showing normal areas of dulness and flatness caused by, and outlining the anatomic position of, the heart and the liver. The lower border of the heart cannot be outlined since it overlies the liver and these organs have acoustically, in so far as percussion is concerned, identical qualities. The heavy shading indicates the part of these organs which are uncovered by lung tissue and therefore yield a flat note. The arrows indicate the direction in which percussion should proceed. The light shading shows the areas over which clear pulmonary resonance is replaced by slight dulness owing to the proximity of the underlying liver and heart. (See Figs. 86, 167.) REGIONAL VARIATIONS Anteriorly. The clearest pulmonary resonance is encountered below the clavicles and at the angles of the scapulæ. In women a diminution of resonance and an elevation of pitch-owing to the mamma-begins below the second interspace. On the left side cardiac dulness begins at the upper border of the third rib, and on the right, the hepatic dulness, below the fourth interspace. The note on approaching these organs becomes progressively less resonant until absolute flatness is encountered -no lung tissue intervening between the organ and the chest wall. Diminished resonance is also encountered in the splenic region, but the spleen cannot be accurately outlined by percussion (Fig. 87). There is less resonance at the sterno-clavicular, than at the sterno-acromial angle, and less resonance over the second rib than over the second interspace. Over the upper sternum the osteal quality predominates, below the second rib more pulmonary resonance may be elicited, especially on light percussion. Shortly before the lower costal margin is reached the note becomes. slightly tympanitic owing to the underlying air-containing viscera FIG. 86.-Window dissection of the chest from in front, showing the position of the heart and liver which causes the dull areas charted in Fig. 85. The pericardium has been removed. The area of absolute (superficial) cardiac dulness is larger than normal, because the lungs were frozen in the position of expiration. The amount of heart exposed is therefore unusually large. Not infrequently the anterior pulmonary margins overlap in front, leaving very little of the heart exposed. (See Fig. 85.) stomach and intestines (Fig. 78). On this account liver dulness, especially to the right of the right para-sternal line, often does not extend to quite the lower margin of the ribs unless the organ is enlarged. On the left side near the lower costal margin a tympanitic areaTraube's semilunar space-is encountered. The tympany is caused by that area of the stomach which lies between the left lower margin of the lung, the right border of the spleen and the right border of the liver. It disappears when the stomach is filled with food and in cases of pericardial effusion. It is diagnostically of little importance (Fig. 89). Dulness over the left lateral pulmonary margin may be caused by a |
