Model-based estimation of radial artery blood pressure from recordings of the Nexfin monitor.

We propose a model-based reconstruction technique to estimate radial artery blood pressure from measurements obtained by the Nexfin noninvasive blood pressure monitor. The Nexfin monitor provides brachial artery pressure estimates by transforming a pressure measured at the finger. The estimated brachial pressure differs significantly from the radial artery pressure commonly measured in intensive care applications. Our reconstruction method is based on a transmission line model of the arterial network and transforms brachial to radial pressure estimates. Applying the method to 22 records from six patients reduced mean pulse pressure differences between reconstructed and measured radial artery pressures from -17.9 (s.d. 12.1) mmHg to 1.8 (12.0) mmHg. Mean systolic and diastolic pressure differences changed from -18.7 (10.5) and -0.7 (6.2) to -0.8 (10.5) and -2.6 (6.9) mmHg, respectively. Our method can be applied to more general problems of estimating pressure waveforms downstream from an upstream measurement location.