Bronchial Breathing

BRONCHIAL BREATHING, transmitted to the surface of the lung through the bronchi, is laryngo-tracheal breathing. It is artificially reproduced by strong mouth breathing, with the lips shaped to pronounce the letter 'h'. Physiologically, it is formed by the passage of air through a narrow glottis into an expanded larynx. The expiration is heard more strongly and lasts longer than the inspiration, depending on the greater narrowing of the glottis during expiration and its longer duration. Normally, bronchial breathing is heard over the larynx, trachea, and at the site of bifurcation of the bronchi at the level of the seventh cervical vertebra. Pathologically, it is observed in cases of lung infiltration (pneumonia, tuberculosis, infarction), in atelectasis (tumors, etc.), in compression (pleuritic exudate)—provided that air passes freely through the conducting bronchus—and in the formation of pathological cavities in the lung that communicate with a bronchus (cavity), or in the dilation of a bronchus (bronchiectasis). The occurrence of bronchial breathing is explained by the better conductivity of laryngeal noise from its place of origin through the consolidated or compressed lung (Laennec), by the increased resonance of the bronchial walls surrounded by dense tissue (Scoda), and by the amplification of the noise (Sahli). In the presence of a cavity communicating with a bronchus, in addition to the free conduction and resonating effect of the infiltrated tissue around the cavity, the cause of the formation of B. d. is sometimes the passage of air from a relatively narrow bronchus into the wide cavity of a cavern. The pitch of bronchial breathing depends on the conditions of resonance.