A Thermoelectric Blood Flow Recorder in the Form of a Needle

Abstract

The needle flow recorder described here was primarily designed to measure rate of blood flow through the internal jugular vein of man. Preliminary work on animals has shown that the device possesses certain characteristics that would seem to promise it a sphere of usefulness in a variety of problems where blood flow is an important variable. The advantages of the device are as follows: Its use entails only a minimal trauma. It can be applied to the study of flow through relatively inaccessible structures. The method makes it possible to measure qualitatively the changes in blood flow through a vascular tissue without isolating or cannulizing the afferent or efferent vessels, and thus enables one to study the blood flow through a tissue or organ, the blood supply of which is not capable of being completely isolated. It also makes possible relative determinations of the blood flow through various parts of the same organ or region. This has not been possible by any method previously described. The thermoelectric methods for measurement of volume flow of blood previously reported require cannulization of a vessel and the passing of heparinized blood through a water jacket, the temperature of which is thermoelectrically determined (Bronk and Gesell 1 ); or the isolation of a vessel, the heating of the blood therein by means of a high frequency current, and the determination of the temperature gradient along the vessel (Rein²); or the insertion of an organ or region into a calorimeter.

The theory upon which the instrument operates is extremely simple. The cooling power of a stream depends, among other things, upon its velocity.