Respiratory Sounds

RESPIRATORY SOUNDS (see also Amphoric breathing, Bronchial breathing and Vesicular breathing). Throughout the healthy lungs during inspiration, a uniform soft sound is heard; another sound, much shorter and weaker, is perceived during expiration. Due to the expansion of the chest, the alveolar system unfolds, expands and tenses, which leads to a rarefaction of the air layer in the lung and the influx of outside air through the trachea and bronchi. During expiration, the chest decreases in size, the elastic tissue of the alveoli collapses, and the air is as if pushed out through the bronchi, trachea, and larynx. As a result of the movement of air, oscillations occur in the laryngo-tracheo-bronchial system and in the alveolar tissue of the lung. Respiratory sounds arising in the larynx, trachea and bronchi are called bronchial breathing, in the lung parenchyma - vesicular. Air rushing in during inspiration along the trachea and bronchi encounters a series of obstacles - the narrowed lumen of the larynx at the very beginning, angles at the branching points of the bronchi. Oscillations of the air wave occur, which are transmitted through the alveolar tissue to the periphery. One of the conditions for the occurrence of bronchial breathing is a certain lumen of the bronchi: bronchi less than 4 mm in diameter cannot produce the tone characteristic of bronchial breathing. Since bronchi of larger diameter are found only starting from a depth of 4 cm from the surface in the lower lobes and at a distance of 2 cm in the upper ones, the appearance of pathological bronchial breathing requires a corresponding depth of infiltration. The pitch of bronchial breathing varies between 500 and 1,000 vibrations per second, low overtones are formed in the nasopharynx and oral cavity, high ones - in the bronchi. Recent years' research (Martini) does not confirm the theory of Boas, according to which vesicular breathing is nothing other than metamorphosed bronchial breathing passing through the alveolar tissue. Works with resonators showed that the fundamental tone and overtones of vesicular breathing are significantly lower than the tones of bronchial breathing. The laws of acoustics do not allow the possibility of a low tone being formed from a high one. Thus, the independent origin of the vesicular noise can be considered proven. It is also important to note that the fundamental tone in percussion of the lung coincides with the fundamental tone obtained when registering vesicular breathing with instruments. And this circumstance speaks in favor of the fact that during shaking (percussion) and during the tension of the alveolar system during inspiration (auscultation) there is the same source of sound - the lung parenchyma. The sudden tension of millions of alveolas creates a sound impression perceived as vesicular noise; during slow collapse, during expiration, the lung tissue produces almost no oscillations. R.S., heard on expiration and named indefinite by Skoda, is considered by most authors as a remainder of physiological bronchial breathing passed through the lung tissue. The participation of both components (bronchi and alveolar tissue) in breathing is also determined under normal conditions. The closer the bronchi are located to the periphery, the wider their lumen, the more clearly the participation of bronchial breathing appears against the background of vesicular breathing. Hence it is understandable that true full-fledged vesicular breathing is found in large masses of lung tissue in the subscapular area. Here the characteristic soft vesicular inspiration and a short, barely marked expiration are heard. Higher, in the interscapular space, a bronchial shade is mixed with inspiration; expiration in this place is longer, louder and richer in high tones. The breathing in the interscapular space is of a mixed character (Laennec). When moving toward the apices, the admixture of bronchial breathing decreases again, but not to the same degree on both apices. A sharper inspiration and a longer and louder expiration on the right apex, especially from behind, differ significantly from the softer vesicular breathing on the left. One must always keep in mind this physiological difference between both apices, due to the wider leading bronchus in the right apex. - Listening to a series of healthy individuals, one can find individual differences in vesicular breathing, which is explained by the difference in the tension of the elastic tissue of the lung, as well as the state of the chest. The pliable, flexible chest of a child and good elasticity of the lung contribute to the formation of sharp vesicular, so-called puerile breathing. The same character is acquired by vesicular breathing in perfectly healthy people during physical exertion or in a state of strong excitement, i.e., under conditions of tense breathing. Therefore, when determining pathologically intensified vesicular breathing, it is necessary to remember the differences in R.S. encountered under normal conditions (depending on how the patient breathes). Under pathological conditions, intensified vesicular breathing, sharp, harsh, is encountered in those cases when, due to an inflammatory process, tumor, pneumothorax, a significant part of the lung is excluded from the act of breathing and as a result the healthy parts of the lung compensateatorily breathe intensely (see also Vesicular breathing). Rough breathing differs, according to Turban, from normal, smooth vesicular breathing by its uneven character; it seems to consist of short, closely following one another noises. According to Sahli, rough breathing is nothing other than vesicular breathing plus undifferentiated rales. "If these additional noises can be isolated, then one speaks of rales; if they cannot be separated, then these rales give the vesicular breathing an impure rough character" (Sahli). Grancher believed that constrictions and irregularities of the small bronchi (tubercles) are the cause of such breathing. Rough breathing can be loud and quiet; more often it is heard on inspiration, less often on expiration, more often at the apices, above the clavicle and above spina scapulae, extremely rarely - in the lower lobes. Turban attaches great importance in the diagnosis of tbc to rough breathing at the apices, provided it is constantly determined in the same place. Interrupted, saccadated breathing differs by its jerky character. The inspiratory sound does not occur continuously, but as if in separate stages, separated from each other by short pauses. According to Sahli, saccadation occurs because the stream of air penetrates into the pulmonary vesicles not continuously and unimpededly, but encounters delays on its way due to swelling of the mucous membrane of the small bronchi or due to the accumulation of secretion, which is pushed aside by the air current. Some authors believe that the cause of saccadation is the simultaneous unfolding of the alveoli due to swelling of the bronchial mucosa or compression by neighboring tuberculous foci. Turban notes the appearance of saccadated breathing in tbc of the apices at the border between healthy and diseased areas. In some cases, saccadated breathing is synchronous with the pulse. The basis of such interrupted breathing is a rhythmically pulse-intensifying pulmonary hyperemia, e.g., at the edges of a pneumonic focus, with intensified cardiac activity, in Basedow's disease and in aortic insufficiency. In dry pleurisy, pericarditis, muscular rheumatism, limited areas of interrupted breathing are also observed. In these cases, adhesions or painful sensations interfere with the smooth unfolding of the chest. In nervous individuals, interrupted breathing is sometimes heard during inspiration throughout the lungs. This is explained by the peculiar manner of the patient breathing in jerks. Weak breathing is rightly given great diagnostic significance. In individuals with a flat chest, in asthenics with hypotonia of the respiratory musculature and sluggish mobility of the diaphragm, weakening of R.S. is often observed throughout the lungs. Isolated weakening of breathing on one of the apices is often observed in diseases of the nose. In case of obstruction of a bronchus by foreign bodies, in case of narrowing of a bronchus due to a malignant neoplasm developing in its wall (bronchocarcinoma), the most characteristic auscultatory symptom will be weakened breathing in that area of the lung, which is supplied with air through this bronchus. Local weakening of breathing is an extremely valuable and early symptom of initial infiltrations in tbc; it may be an expression of sparing of the affected side, but the fixation of the lung itself by small infiltrates can also lead to a decrease in the volume oscillations of this area. In an old tuberculous process, weakening of breathing may be observed where one could expect the appearance of bronchial breathing. This, according to Sahli, is explained by the wrinkling and closure of the lumen of a large number of bronchi due to cirrhosis. Weakening of respiratory unfolding explains the weakening of R.S. in large adhesions and in all those cases when the lung is displaced by fluid, air, a neoplasm from the examining ear. In emphysema, due to the loss of elasticity of lung tissue and due to the inspiratory position of the chest, weakened breathing is observed throughout the entire extent of the lungs.

Metamorphosing breathing is a respiratory sound in which the soft vesicular beginning of inspiration suddenly transforms into a distinctly bronchial end. Expiration usually retains the same bronchial character. Seitz considered this breathing to be characteristic of a cavity. He believed that during inspiration, an obstacle at the entrance to the cavity is overcome, due to which the end of inspiration and expiration acquire a bronchial character. At the end of expiration, the obstacle at the entrance to the cavity is restored. -As for prolonged expiration, its significance is as follows. If expiration is heard throughout the lung, this indicates a loss of elasticity of lung tissue (emphysema, bronchial asthma). At the apex, prolonged expiration is sometimes also a consequence of local loss of elasticity of lung tissue. Prolonged expiration at the apices should not be given pathological significance in a flat chest, in scoliosis (on the concave side, the bronchial tree approaches the periphery). Finally, prolonged expiration at the right apex is a constant and regular phenomenon. -Often in the presence of large cavities, metallic breathing can be heard. Under particularly favorable conditions, the high tones of bronchial breathing produce highly resonant cavity tones in the cavities. In these cases, in addition to the low-sounding amphoric breathing, an additional metallic shade can be detected. Weakened metallic breathing in its pure form is clearly audible in some cases of closed pneumothorax, and it is recommended to listen to this breathing directly with the ear (Turban). -Under indefinite breathing is understood a noise that is difficult to classify as vesicular, at the same time it does not have a pronounced bronchial character. Such an indefinite character of respiratory sounds is observed in cases when it is masked by stronger noises (rales, pleural friction rub). 'The more experience the researcher has, the fewer the number of indefinite noises,' says Gerhardt. Quite often, especially in pulmonary tuberculosis, noises are encountered whose character combines features inherent in both vesicular and bronchial breathing. Salie distinguishes: 1) vesicular inspiration, bronchial expiration; 2) mixed character of inspiration, i.e., simultaneously vesicular and bronchial, and bronchial expiration. According to Salie, the mixed character occurs because each of the two respiratory sounds is conducted from different parts of the lung, e.g., in a lung penetrated by small infiltrates, at the edges of a large infiltrate with bronchial breathing, at the border of pleural exudate, above cavities surrounded by breathing lung tissue, when inspiration is formed in this tissue, and expiration in the underlying cavity. Sometimes mixed breathing, upon repeated examination, alternately transforms into vesicular and bronchial breathing. This is explained by the intermittent obstruction of bronchi, either of an infiltrated or a free area of the lung: depending on which bronchus is closed, either vesicular or bronchial breathing is obtained. For a more precise designation of mixed breathing, the terms 'vesico-bronchial' and 'broncho-vesicular breathing' are used.