The Point of Origin of the Bronchial Breath Sounds

Abstract

A tracheotomy was performed on a patient who had a carcinoma of the larynx, and a pneumonia developed in the left lower lobe. With the patient's nose closed firmly by the fingers of the doctor and the mouth closed firmly by the patient, bronchial breath sounds which sounded typical were heard over the left lower lobe. The breath sounds over the other lower lobe were normal. This would seem to show that the vocal cords play no very large rôle in the formation of the bronchial breath sounds, but that the bronchial breath sounds are formed by the passage of air through the bronchial tubes much after the manner of the formation of sound in lip pipes. A patient who had loud bronchial breath sounds over the right lower lobe came to autopsy. A rubber tube was passed through the vocal cords and air was periodically allowed to enter the lungs from an oxygen tank. There was a side tube for allowing the egress of air and by alternately closing the outflow and inflow tubes, artificial inspiration and expiration could be produced. Auscultation over the right lower lobe produced bronchial breath sounds resembling fairly closely those heard over the same area by the intern and resident physician before the death of the patient. The trachea was now cut off below the larynx and the same rubber tube was inserted down just beyond the bifurcation. On auscultation the breath sounds were still bronchial and apparently were a little higher pitched than when the tube was passed just beyond the vocal cords. This experiment shows that the components of the bronchial breath sounds are formed largely in the bronchial tubes below the vocal cords and that some of the bronchial breath sound is formed apparently beyond the primary bronchus.