Journal of clinical monitoring
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Comparative Study
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 pressure measurement determined using this device with simultaneous invasive blood pressure measurements in 35 patients undergoing general endotracheal anesthesia. Data were analyzed for accuracy and tracking ability of the noninvasive technique, and for frequency of unavailable pressure measurements by each method. ⋯ When blood pressure measured invasively changed over time by more than 10 mm Hg, the noninvasive technique accurately tracked the direction of change 67% of the time. During the entire study, 3.2% of the invasive measurements were unavailable and 12.9% of the noninvasive measurements were unavailable. The continuous noninvasive monitoring technique is not of sufficient accuracy to replace direct invasive measurement of arterial blood pressure, owing to relatively wide limits of agreement between the two methods.(ABSTRACT TRUNCATED AT 250 WORDS)
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During initial clinical tests to calibrate our reflectance pulse oximetry system, we observed serious physiologic limitations to the use of pulse oximetry in the forehead region. We present a case of simultaneous reflectance and transmission mode pulse oximetry monitoring in a child undergoing cardiac surgery for congenital cyanotic heart disease with a large intracardiac shunt. ⋯ We suggest that the difference was caused by vasodilatation and pooling of venous blood due to compromised venous return to the heart, and a combination of arterial and venous pulsations in the forehead region. This means that the reflectance pulse oximeter measured a mixed arterial-venous oxygen saturation.