The application of hot-film anemometer to blood flow velocity measurements

The application of constant-temperature hot-film anemometry to blood flow velocity measurements, is discussed. There are several difficulties in calibration and use of this apparatus in liquids, which are, not encountered in its use in gases. The calibration of the hot-film probes for several homogeneous liquids and the bovine, blood with various hematocrit values was performed by a modified Seed's and Wood's method. The stability of calibration seems to depend upon the stability of rotation of the tank. The disturbances induced by the hot-film probe into liquids also have some extent of influence on the stability of the calibration. Preliminary animal experiments were designed to study the characteristics of intracardiac and intravascular blood flows. Flow velocity patterns in the left ventricle and the ascending aorta are demonstrated, showing almost similar character to those of other authors. Although the constant-temperature hot-film anemometry has not been used widely in physiological research, this method will be very useful in this area, for example, for identifying the complex nature of flows in cardiovascular chambers and canals because of, its excellent frequency response and position resolution.