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Early detection of cardiac ischemia using a conductometric pCO2 sensor: real-time drift correction and parameterization

For detection of cardiac ischemia based on regional pCO2 measurement, sensor drift becomes a problem when monitoring over several hours. A real-time drift correction algorithm was developed based on utilization of the time-derivative to distinguish between physiological responses and the drift, customized by measurements from a myocardial infarction porcine model (6 pigs, 23 sensors). IscAlert™ conductometric pCO2 sensors were placed in the myocardial regions supplied by the left anterior descending coronary artery (LAD) and the left circumflex artery (LCX) while the LAD artery was fully occluded for 1, 3, 5 and 15 min leading to ischemia in the LAD-dependent region. The measured pCO2, the drift-corrected pCO2 (ΔpCO2) and its time-derivative (TDpCO2) were compared with respect to detection ability. Baseline stability in the ΔpCO2 led to earlier, more accurate detection. The TDpCO2 featured the earliest sensitivity, but with a lower specificity. Combining ΔpCO2 and TDpCO2 enables increased accuracy. Suggestions are given for the utilization of the parameters for an automated early warning and alarming system. In conclusion, early detection of cardiac ischemia is feasible using the conductometric pCO2 sensor together with parameterization methods.