Nov 30, 1976

An isothermal flowmeter with improved frequency response for measuring tissue blood flow

Pflügers Archiv : European journal of physiology
K OlshausenH Kirchheim


An isothermal flowmeter with improved frequency response for measuring tissue blood flow was developed using thermistors. Direct heating of the thermistors allows a simple construction of small (0.5 mm outer diameter) capillary probes which do not require any additional heating coil. The changes of a feedback current necessary to keep the thermistor at a constant increment above tissue temperature indicate tissue blood flow; a second thermistor compensates variations of tissue temperature. The dynamic performance of the device shows a low-pass characteristic with a cut-off frequency higher than 5 Hz. For low flow rates the output signal was found to be proportional to the flow; for higher flow rates a linearization was necessary. Since tissue temperature can be recorded continuously, intermittent quantitative in-vivo calibration seems possibly by evaluation of "heater off" curves in the perfused and non-perfused tissue. As the flowmeter is insensitive to tissue temperature, it can be used for long-term recordings.

Mentioned in this Paper

Blood Flow Velocity
Blood Flow
Entire Capillary Blood Vessel (Organ)
Thermometer, Device
Capillary Vessel
COIL gene
Blood Capillaries

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