A serious problem of the heated thermocouple flowmeter.

In the measurement of regional blood flow with heated thermocouple flowmeter, we frequently observed puzzling phenomenon that the measured values were augmented while the flow was actually diminished and vice versa (Inversion). "Inversion" was directly attrebutable to the structure of the thermocouple probe. A countermeasure against "Inversion" was found to lie in the arrangement of the hot junction in the center of the heater, and in practical application, it must be checked by stopping the flow at each measurement. Overcoming this technical liability should pave the way for a marked improvement in the reliability of this method which, despite possessing many excellent characteristics for determining regional blood flow, is not widely used.