DISTINCTION BETWEEN ARTERIAL, VENOUS AND FLOW COMPONENTS IN PHOTOELECTRIC PLETHYSMOGRAPHY IN MAN

Abstract

The possibility of making these distinctions was studied by means of photoelectric plethysmography. A technique is described for recording the vol. pulse separate from the plethysmogram, with a photoelectric plethysmograph and capacity coupled amplifier. The arterial component in the plethysmogram is distinguished by the amplitude of the vol. pulse. The flow component is indicated by the product, amplitude of the vol. pulse X heart rate. The value of this product appears to parallel flow. The analysis of the vol. changes recorded in the plethysmogram involves evaluating the arterial and flow components by these criteria, and so by a process of exclusion differentiating when possible the contr. of the venous component. Moderately heavy doses of amyl nitrite may produce prolonged loss of venous tone. The finger pad has a high venous tone as judged by the pressure required in a Gaertner capsule to produce obstruction to the venous return from the pad.