A NEW METHOD FOR BLOOD FLOW MEASUREMENT

A number of methods for the measurement of blood flow in the living animals have been reported so far such as Rein's thermostromuhr (1), Kolin's electromagnetic flowmeter (2), Gregg's rotameter (3) etc., and their limits in practical uses have been also discussed. However, some of them are quite expensive and requires a great deal of skill. Besides, as an indirect method, plethysmograph has been used to estimate circulatory changes in the living organs. This method was based on the volumetric change in organs due to the blood circulation. The authors (1959) (4) previously presented the new method of plethysmograph in which the volumetric change was converted to an electrical capacitance change by using a highly sensitive electric capacity measurement circuit (capacitosphygmograph), and local blood flow such as in the brain or kidney, was measured easily. However, it has the following disadvantages ; 1) the subjects should be kept in quiet, because the apparatus uses a high frequency (above 100 kc) and thus a fluctuation of leading wires causes artifacts on the pulse wave. 2) When the electrodes are applied on the surface of organs, the pulse wave detected does not indicate the circulatory change in the inner parts, but that on the surface. When the frequency below 100 kc is applied, these disadvantages have been eliminated, and this method is called “Impedance Plethysmograph.”