Abbott Laboratories Corporation

David N Swingler

Timothy J Hughes

A method and apparatus for correcting thermal drift in cardiac output measurements based upon a temperature signal indicative of the change in temperature of blood leaving the heart is disclosed. In a first preferred embodiment of a cardiac output monitoring system(10), the catheter(14) is provided with an electrical resistance heater (22). An electrical current having a sinusoidal waveform with a period of from 30 to 60 seconds is applied to the heater, causing power to be dissipated into the blood within a patient's heart (12). A temperature sensor (24) disposed near a distal end of the catheter produces a signal indicative of the temperature of blood leaving the heart. The temperature signal and the signal corresponding to the electrical power dissipated in the heater (an input signal) are filtered at a frequency .omega. corresponding to the frequency of the applied electrical current, i.e., the frequency of the input signal. An output signal indicative of the temperature of the blood leaving the heart, corrected for the effects of thermal drift, is then determined. The corrected cardiac output signal is determined by first determining a drift slope of the blood temperature signal due to thermal drift. The drift slope is then used to produce a signal corrected for thermal drift. Cardiac output is determined as a function of the amplitude of the input power, the amplitude of the signal corrected for thermal drift, and their phase difference.

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Halifax, Canada

David N Swingler