222 PATHOLOGICAL RESPIRATORY SOUNDS. 



During forced respiration rustling sounds often arise at the mouth 

 and nostrils; with these sounds the primary tone of the oral cavity 

 (usually the vowel-sound ah) is often mingled in mouth-breathing. 



PATHOLOGICAL RESPIRATORY SOUNDS. 



The recognition of the succussion-sound, the friction-sound, and many catar- 

 rhal sounds dates back to Hippocrates (460-377 B. C.). The actual foundation of 

 auscultation on a physical basis was laid by Laennec (1816), and its classical 

 development is due to Skoda (1839). 



Bronchial breathing arises over the entire area of the lungs, either when the 

 air-vesicles have become airless (through exudation) or when the lungs are com- 

 pressed from without. In both cases the condensed pulmonary tissue conducts 

 the bronchial respiration to the walls of the thorax. Bronchial breathing will 

 also be heard over pathological cavities of considerable size that communicate with 

 a large bronchus, provided the cavities lie sufficiently near the thoracic wall and 

 have walls of considerable resistance. If there is no movement of air in the cavity, 

 the sounds may be wholly conducted out through the trachea ; or during expiration 

 a stenosis-sound (like that at the glottis) may arise in the communicating bronchus, 

 and may be rendered amphoric by the resonant cavity. 



Amphoric breathing resembles the sound produced by blowing across the 

 mouth of a bottle. It may arise when there occurs in the lungs a cavity at least 

 the size of a fist, through which the air passes in such a manner that there is pro- 

 duced the characteristic sound with a peculiar metallic echo. If the lung is 

 partly expansible and contains air, and the pleural cavity also contains air, the 

 resonance of the latter, together with the exchange of air in the lung, will also 

 produce the amphoric sound. 



If the respiratory sounds have no definite character, so that they oscillate 

 between vesicular and bronchial breathing, they are termed indefinite respiratory 

 sounds. Frequently a deep respiration or expectoration of mucus will make the 

 character of the sound more evident. 



If the air meets with resistance in its passage through the lungs, various 

 phenomena may result: (a) At times the air- vesicles are not all filled simultane- 

 ously, but intermittently. This occurs (especially at the apices) when partial 

 swelling of the walls of the air-passages obstructs the steady interchange of air; 

 cogwheel respiration is the result. Occasionally this is heard in perfectly normal 

 lungs, when the muscles of the chest contract in an intermittent fashion, (b) If a 

 bronchus leading to a pulmonary cavity is narrowed in such manner that the air 

 meets with a temporary resistance, the inspiratory sound is at first like that of 

 a loud G, and then goes over during the latter two-thirds of inspiration into a 

 bronchial or amphoric sound. This is termed a metamorphosing sound, (c) Rales 

 are produced in the larger air-passages when the air causes bubbling of the con- 

 tained mucus. In the smaller air-spaces rales arise either when the walls of the 

 latter are separated from the fluid contents during inspiration, or when their walls 

 are in contact and are suddenly separated from each other. Rales are distinguished 

 as moist (arising in watery contents) or as dry (in tough, tenacious contents) ; 

 further, as inspiratory or expiratory, or continuous; also coarse, fine, or irregular 

 rales, the high-pitched crepitant rales, and finally the metallic tinkling rales produced 

 by the resonance of large cavities, (d) If the mucous membrane of the bronchi is 

 so swollen or so covered with mucus that the air must force its way through, 

 there arises frequently in the larger passages a deep humming purr sonorous 

 rhonchus; and in the smaller tubes a clear whistling sound sibilant rhonchus. 

 In cases of widespread bronchial catarrh a thrill may often be felt in the chest- 

 wall bronchial fremitus caused by the numerous rales. 



When the lung is collapsed and the pleural cavity contains fluid and air, 

 a sound may be heard on shaking the chest, similar to that produced by shaking 

 a large bottle containing water and air the succussion-splash of Hippocrates. 

 Rarely a higher-pitched similar sound may be heard in pulmonary cavities the 

 size of a fist. 



When the opposed layers of the pleura are roughened by inflammatory 

 processes, and rub against each other in the act of respiration, a friction- phenomenon 

 is produced. This may be partly felt (often by the patient himself) and partly 

 heard. The sound is usually creaking, and may be compared to that produced 

 by bending new leather. Friction-sounds are produced also by the heart's action 

 between the two layers of the diseased roughened pericardium. 



