If the pneumonia is central, the vocal fremitus may not be increased. It is diminished when there is an abundant pleuritic exudation over the pneumonic lung.
Percussion.—On percussion there will be marked dulness over that portion of the lung which is the seat of the pneumonia, while over the healthy portion, as well as over the opposite lung, there will be exaggerated resonance. The nearer the hepatization approaches the surface of the lung, the more marked will be the dulness. There is a peculiar sense of resistance on percussion over a completely airless hepatized lung which is not present in solidification from other causes. The exact outline of an hepatized lobe can often be traced on the chest-wall.
The tympanitic quality which is sometimes present during the stage of engorgement may continue anteriorly during the second stage, and yet posteriorly the dulness will be complete. A tympanitic percussion sound is sometimes elicited over that portion of lung which is adjacent to the consolidated lobe. When an upper lobe is consolidated, forcible percussion may elicit a tympanitic sound, for the column of air in a large bronchus will vibrate under forcible percussion. The cracked-pot sound (bruit de pot fêlé) is occasionally met with over those relaxed and permeable parts of the lung in the immediate vicinity of the consolidation. When this sound is present over the consolidated portion, it is due to the sudden expulsion of air from one of the larger bronchi. It is most frequent in young persons with thin, elastic chest-walls. The cracked-pot sound in pneumonia is not increased in intensity when the patient's mouth is open.
In basic pneumonia the subclavicular percussion note may be distinctly amphoric in character. Dulness may appear within twelve or twenty-four hours after the onset of a pneumonia, or it may be delayed until the fourth day.
Auscultation.—As soon as the air-cells are completely filled by the pneumonic exudation, the crepitant râle ceases and bronchial respiration is heard over the affected lung. The bronchial breathing is due to the fact that the vesicular element of the respiratory sound disappears on account of the complete consolidation of the vesicular structure, and the tracheal element of the respiration is conveyed to the chest-walls through the consolidated lung. It often has a metallic element, or may sound like the tearing of a piece of linen. Bronchial respiration is more intense in pneumonia than in any other disease.
Laennec taught that bronchial respiration was due to the superior conducting power of condensed lung. Skoda combats this view, and says that bronchial respiration is generated or magnified in caverns and in the bronchi of condensed lung-substance by the air in these cavities and in the bronchi vibrating in consonance with that within the trachea. The condition necessary for this consonance is provided in the circumstance that the air is pent up in confined spaces whose walls reflect the sonorous undulations.
The more complete the consolidation, the more intense is the bronchial respiration. At the commencement of this stage the tubular breathing only attends expiration, while later it accompanies both acts. Pleuritic exudation may mask or render this sound very indistinct. It may in rare instances be absent even when extensive consolidation exists and the pleura is perfectly normal. This can be accounted for in most cases by the plugging of a large bronchus. There are cases in which its absence is inexplicable.
The vocal sounds are increased in intensity and bronchophony is heard over the consolidated lung. The physical conditions of the lung which give rise to bronchophony have the same diagnostic significance as the bronchial respiration, and in all instances its occurrence, its distinctness, its temporary disappearance, and its reappearance are dependent upon precisely the same conditions as are the changes in the bronchial respiration. If the pleural cavity is partially filled with fluid, bronchophony will be indistinct or absent below the level of the fluid, while at its level the voice-sounds will be either bronchophonic or oegophonic.
During this stage the heart-sounds are transmitted to the surface over the hepatized lung with greater intensity than normal.
In children dulness is especially marked in the infra-scapular region of the affected side. Some authors44 speak of a feeling of greater solidity below than above the scapula, which can be detected before the ear can detect actual dulness on percussion. Vocal fremitus may be increased, but it is not reliable on account of the changes in the voice.