THE PULSATILE NATURE OF THE PULMONARY CAPILLARY BLOOD FLOW*

Abstract

The nature of the pulmonary capillary blood flow is fundamental for the understanding both of pulmonary hemodynamics and of respiratory gas exchange. Direct examinations of the surface of the lung in the cat, rabbit, dog and rat (1-5) have indicated that pulmonary capillary blood flow is basically non-pulsatile. On the other hand, ex- perimental studies by Lee and DuBois (6), using the body plethysmograph in man, have suggested that pulmonary capillary blood flow is consistently pulsatile. Their experimental evidence consisted of a rhythmic distortion of the record, synchronous with the heart beat, obtained during breathholding with open glottis, after a single inspiration of nitrous oxide.