Pulsatile gas flow in bronchi caused by the heart beat

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Abstract
Pulsatile gas flow in lobar and segmental bronchi synchronous with the heart beat has been measured during routine diagnostic bronchoscopy, using a new type of flowmeter. Pulsations were detected in three-quarters of the 60 patients examined, and occurred in all parts of the lung though they were more marked on the left side. They were seen both during inspiration and expiration, but were most obvious in the postexpiratory pauses. At a given instant in the cardiac cycle, the phase of the pulsations was sometimes different in different parts of the lung, gas going into some lobes and coming out of others. Volume flow rates up to 2.5 liter/min and displaced volumes up to 5 ml were recorded. The pulsatile flow is probably caused by changes in volume of the beating heart, and by its movements within the chest so that some parts of the lung are compressed while others expand. Because of their size and frequency, the pulsations promote mixing of the anatomical dead-space gas with alveolar gas. Submitted on October 10, 1960