Finger arterial pressure measurement with Finapres.

Finger arterial pressure measurement with Finapres has been available since a decade. Its availability has promoted at least 300 methodological and research papers over these years, outlining the usefulness and the limitations of the method and the device. Finapres is based on the volume clamp method of Peñáz and the Physiocal criteria of Wesseling. Tracking of intraarterial pressure is usually satisfactory even under conditions of strongly changing hemodynamics and high and very low blood pressures. Finapres accuracy is similar to that of other non-invasive methods. Systolic pressure levels scatter more than mean and diastolic levels. One source of error is physiologic and determined by the peripheral measurement site of the finger, causing pulse waveform distortion and a pressure gradient. The Finapres waveform can be filtered, however, to obtain a brachial pressure wave. This decreases systolic scatter under vaso-constrictive drug infusion and dynamic exercise to exhaustion, conditions where precision of systolic tracking has been criticized in the literature. Recently, level correction techniques were found which shift finger pressure up or down based on a regression equation with finger systolic and diastolic pressures. This procedure requires no additional measurements yet improves systolic, diastolic and mean level accuracy and precision remarkably. Finally, we show how to judge the quality of a Finapres recording from the behavior of Physiocal.