Use of a hot-film velocity probe for cardiovascular studies

Constant-temperature hot-film anemometry has been developed for measuring velocities in blood vessels. Probes suitable for insertion through artery walls have been evolved, and an output filter has been employed to correct the frequency response of the DISA 55D01 anemometer when used at the very low overheat temperatures necessary in blood. It is estimated that velocities can be measured to ±5% over most of the pulse cycle, but near zero velocity the proportional errors are larger, being of the order 10 cm s −1 in the rapidly reversing flows observed in animals. Direction sensing, however, allows substantial improvement of this, the final errors being an order lower, and the use of an efficient system in an arterial flow is demonstrated.