Method for rejecting electrical interference from physiological measurements

摘要

Methods and apparatus for eliminating the effects of electrosurgical interference on continuous, heat-based cardiac output measurements employing several procedures, including the steps of (1) supplying power via an isolation transformer and carrier frequency to a catheter-mounted heating element; (2) measuring the voltage and current on the primary side of the isolation transformer; (3) determining the voltage and current on the secondary side of the transformer on the basis of the measured primary side voltage and current; and (4) calculating the power delivered to and resistance of the catheter-mounted heater on the basis of the secondary voltage and current. A heater power waveform generated with this process will be substantially free of electrical interference due to electrosurgical devices. Then, a system transfer function may be produced via signal processing techniques which involve cross-correlating the heater power waveform with the blood temperature waveform. The system transfer function will be uncorrupted, even if the blood temperature waveform contains moderate electrical interference, since the heater power waveform is free of any correlated electrical interference.