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Abstract

A system for measuring fluid flow within a conduit, such as blood flow from the heart, includes a heating element that is driven so as to apply heat to the fluid at an upstream position as a series of periodic heat signals. A temperature sensor located downstream measures a local temperature of the fluid and generates an electrical fluid temperature signal corresponding to the local temperature. This signal is then applied to a dispersive filter, which outputs a pulse-like signal in the presence of each periodic heat signal. Fluid flow is then calculated by a processor as a function of the area under an estimated impulse response curve for the channel in which the fluid flows. Each periodic heat signal is preferably sinusoidal and has an instantaneous frequency that varies substantially continuously between a first frequency and a second frequency over a pre-determined active input signal period. In a preferred embodiment, the frequency varies linearly between a first and a second frequency over a predetermined time period. The output signal from the filter, which is itself an estimate of the channel impulse response, is preferably integrated in order to provide a parameter estimate that is inversely proportional to flow. The corresponding method of measuring fluid flow using a frequency-swept input heat signal and matched dispersive filtering is included.

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