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 ac curacy have suggested little systematic bias vs intra-arterial pressur e (IAP) but substantial variability. Inconsistency between studies, in respect of the magnitude, direction and variance of bias, was describ ed in the validation studies against the direct IAP. We have employed a novel resampling statistical method to combine the data from 20 publ ished 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 -2 2.6 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. +/- 18.6) with precision of 7.6 mm Hg (s.d. +/- 5.3). The calculated percentage of Finapres systolic values expect ed to fall within +/- 5 or +/- 10 of the direct intra-arterial pressur e was 35.9% and 73.1%, respectively. The calculated precision of the F inapres systolic pressure between 0-5 mm Hg was 1.6% and between 0-10 mmHg 36.4%. The comparable Values for Finapres diastolic BP for accura cy were 63.5% and 92.8% and for precision 23.1% and 79.2%. The Finapre s device can provide an accurate estimate of diastolic and mean arteri al pressure compared with the intra-arterial record; the apparent inac curacy of the Finapres systolic pressure may have a physiological expl anation. When the Finapres device is used in experimental or in clinic al situations, then calibration against a reliable reference arterial pressure is desirable to obviate the possibility of an 'offset' error.