Accuracy and precision of blood pressure determination with the Finapres: an overview using re-sampling statistics.

The Finapres non-invasive blood pressure (BP) monitor uses the method of Penaz to indirectly record the arterial waveform; studies on its accuracy have suggested little systematic bias vs intra-arterial pressure (IAP) but substantial variability. Inconsistency between studies, in respect of the magnitude, direction and variance of bias, was described in the validation studies against the direct IAP. We have employed a novel re-sampling statistical method to combine the data from 20 published studies; a robust overall estimate of the accuracy and precision of the Finapres was thereby obtained. Based on 449 patients and 4490 re-samples, the average Finapres systolic bias (IAP- Finapres) was 2.2 mm Hg (s.d.+/-12.4) with limits of agreement (bias+/-2 s.d.) of -22.6 and 26.9 mm Hg. The average precision was 12.1 mm Hg (s.d.+/-8.4). The Finapres diastolic bias was -0.3 mm Hg (s.d.+/-7.9) with the limits of agreement of -16.1 and 15.5 mm Hg. The average precision was 7.6 mm Hg (s.d.+/-5.3). The average Finapres mean arterial pressure bias was 2.1 mm Hg (s.d.+/-8.6) with precision of 7.6 mm Hg (s.d.+/-5.3). The calculated percentage of Finapres systolic values expected to fall within +/-5 or +/-10 of the direct intra-arterial pressure was 35.9% and 73.1%, respectively. The calculated precision of the Finapres systolic pressure between 0-5 mm Hg was 1.6% and between 0-10 mm Hg 36.4%. The comparable values for Finapres diastolic BP for accuracy were 63.5% and 92.8% and for precision 23.1% and 79.2%. The Finapres device can provide an accurate estimate of diastolic and mean arterial pressure compared with the intra-arterial record; the apparent inaccuracy of the Finapres systolic pressure may have a physiological explanation. When the Finapres device is used in experimental or in clinical situations, then calibration against a reliable reference arterial pressure is desirable to obviate the possibility of an 'offset' error.