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For a number of years I have from time to time noticed that in certain bronchoscopic examinations the carina, or spur dividing the left from the right main stem bronchus, underwent unusually wide to and fro excursions in a lateral direction. Such movements were always synchronous with cardiac pulsations and closely resembled the multiphasic excursions of an electrocardiographic string during recording of the heart beat. Sometimes these carinal excursions were very wide, greater than the width of the lumen of a 7 mm. bronchoscope.
At first I paid little attention to this phenomenon, simply considering it to be an exaggerated transmitted impulse of the heart beat or of the great vessels of the thorax, and attached no particular significance to it. More recently I have almost come to the conclusion that such a transmitted impulse, which reflects itself in the usually wide movement of the carina just described, takes place
JOEL J. PRESSMAN. A BRONCHOSCOPIC OBSERVATION IN CASES OF PLEURAL EFFUSION. Arch Otolaryngol. 1941;34(4):844–845. doi:10.1001/archotol.1941.00660040900020