NONINVASIVE CONTINUOUS BLOOD-PRESSURE MEASUREMENT DURING ANESTHESIA -A CLINICAL-EVALUATION OF A METHOD COMMONLY USED IN MEASURING DEVICES

The objective of the study was assess the utility during anaesthesia o f noninvasive continuous blood pressure measurement techniques which u se intermittent oscillometric blood pressure measurement for their cal ibration. The assessment was performed by comparing noninvasive blood pressure with intra-arterial blood pressure. The noninvasive blood pre ssure measurement device used for evaluation was the NCAT N-500 which uses tonometry for its continuous measurements. Fifteen patients were studied. In 10 patients the intra-arterial blood pressure curve (IBP) was recorded from the radial artery (radial artery group), and in 5 pa tients it was recorded from the brachial artery (brachial artery group ). In all patients the oscillometrically calibrated tonometric blood p ressure (OTBP) was recorded from the other arm. To discriminate betwee n calibration dependent measurement error and tonometric measurement e rror, the OTBP signal was recalibrated against the IBP signal to get t he intra-arterial calibrated tonometric pressure curve (ITBP). OTBP-IB P reflected the overall measurement error, ITBP-IBP the error of the t onometric measurement, and OTBP-ITBP the calibration dependent measure ment error. According to criteria formulated in the discussion the acc uracy and agreement of the ITBP-IBP measurements were clinical accepta ble. Accuracy and agreement of OTBP-IBP and of OTBP-ITBP were not clin ical acceptable. Correlation of dynamic behavior was lower for OTBP th an for ITBP. A significant effect of site difference between calibrati on measurements and continuous measurements was not found. It is concl uded that the approach of continuous noninvasive blood pressure measur ement based on the combination of two different measurement methods, i n which the continuous method is calibrated by the oscillometric metho d, lead to clinical unacceptable accuracy and agreement in the patient group studied.