CLINICAL-EVALUATION OF CONTINUOUS NONINVASIVE BLOOD-PRESSURE MONITORING - ACCURACY AND TRACKING CAPABILITIES

A continuous, noninvasive device for blood pressure measurement using pulse transit time has been recently introduced. We compared blood pre ssure measurements determined using this device with simultaneous inva sive blood pressure measurements in 35 patients undergoing general end otracheal anesthesia. Data were analyzed for accuracy and tracking abi lity of the noninvasive technique, and for frequency of unavailable pr essure measurements by each method. A total of 25,133 measurements of systolic pressure, diastolic pressure, and mean arterial pressure (MAP ) by each method were collected for comparison from 35 patients. Accur acy was expressed by reporting mean bias (invasive pressure minus noni nvasive pressure) and limits of agreement between the two measurements . After correction for the offset found when measuring invasive and os cillometric methods of arterial pressure measurement, the mean biases for systolic, diastolic, and mean pressures by the pulse wave method w ere -0.37 mm Hg, -0.01 mm Hg, and -0.05 mm Hg, respectively (p < 0.001 ). The limits of agreement were: -29.0 to 28.2 mm Hg, -14.9 to 14.8 mm Hg, and -19.1 to 19.0 mm Hg, respectively (95% confidence intervals). When blood pressure measured invasively changed over time by more tha n 10 mm Hg, the noninvasive technique accurately tracked the direction of change 67% of the time. During the entire study, 3.2% of the invas ive measurements were unavailable and 12.9% of the noninvasive measure ments were unavailable. The continuous noninvasive monitoring techniqu e is not of sufficient accuracy to replace direct invasive measurement of arterial blood pressure, owing to relatively wide limits of agreem ent between the two methods. The continuous noninvasive method may ser ve as an intermediate technology between intermittent noninvasive and continuous invasive measurement of blood pressure if tracking capabili ties can be improved; but, further refinement is needed before it can be recommended for routine intraoperative use.