Physiological Influences on Continuous Finger and Simultaneous Intra-arterial Blood Pressure

Abstract

Because of the clinical and experimental utility of continuous finger blood pressure measurements and the need for accuracy, we tested the performance of a new hydraulic device in 22 consecutive hypertensive subjects during physiological and pharmacological interventions. Ipsilateral brachial intra-arterial pressure was monitored during rest, Valsalva's maneuver, static handgrip, and mental arithmetic and after sublingual glyceryl trinitrate. In excess of 40,000 blood pressure values were analyzed. Average bias (intra-arterial minus finger blood pressure) was 8.2 +/- 17.0 mm Hg (mean +/- SD, P = NS) for systolic and 2.8 +/- 10.4 mm Hg (P = NS) for diastolic pressure. Two-way ANOVA of biases with subject and task factors showed a subject effect (P < .001). Intersubject and intrasubject standard deviations of bias were 13.8 and 9.8 mm Hg systolic and 8.7 and 5.7 diastolic, respectively. Linear drift (millimeters of mercury per minute) of finger pressure was greater (P < .001) for systolic than diastolic pressure during static exercise and math and after glyceryl trinitrate. Coefficients of determination for blood pressure ranged from 0.4 +/- 0.3 to 0.8 +/- 0.3 during the tasks. We conclude that (1) noninvasive finger blood pressure faithfully follows intra-arterial changes but with clinically relevant offsets, (2) this technique is best suited for assessing pressure changes, (3) physiological and pharmacological interventions do not consistently affect finger pressure accuracy, (4) many reports of finger blood pressure measuring devices are based on direct readings obtained with inadequate system response characteristics, and (5) the tested instrument falls short of the standard requirements (bias < or = 5 +/- 8 mm Hg) for devices that measure intermittently.

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

“…23 However, under resting conditions the relationship between the central and peripheral estimates of arterial pressure is sufficiently robust under most conditions for the Finapres to be useful in tracking pressure changes in man under a variety of clinical conditions and physiological circumstances. 10,26,29 There are no defined standards against which a continuous non-invasive BP monitor, such as the Finapres, can be assessed. Suggested evaluation protocols, such as those of AAMI and subsequent revision, 30,31 are intended to cover the situations when a non-invasive BP monitor (NIBM) is assessed either using a standard mercury reference sphygmomanometer (measuring at the same level in the circulation), or against the directly recorded arterial pressure.…”

“…Clearly the accuracy of the method is very dependent on the finger positioning within the cuff and the extent to which the device has been correctly calibrated during the initial set up. 10,23 In 50 coronary patients undergoing diagnostic angiography, we previously accessed its accuracy and variability; the Finapres systolic pressure was higher than the aortic pressure (mean difference +7.2 mm Hg (s.d. 13.7), but the diastolic −1.0 mm Hg (s.d.…”

“…Re-sample 3: re-sampling of eight robust studies and 186 patients: Of the various studies reported, only nine documented the frequency response and damping ratio of the IABP system; 3,[8][9][10]16,17,22,23 one was an exercise study and was therefore excluded. 27 A total of 186 patient-grouped data, with average IAPFinapres bias and s.d.…”

“…Studies with the Finapres suggest small average bias but large variability [4][5][6][7][8][9] ; additionally the published data show inconsistent magnitude, polarity and variance of discrepancies between the method and direct intra-arterial recordings. 10 Central and peripheral arterial pressures are dissimilar due to interaction of incident and reflected waveforms;…”

“…12 Therefore any periheral BP method such as the Finapres requires rigorous validation to understand its strengths and limitations. The accuracy of the Finapres compared with intra-arterial reference pressure has now been assessed in many studies [3][4][5][6][7][8][9][10][13][14][15][16][17][18][19][20][21][22][23] without any clear consensus emerging on the average performance of the method; precision data has been infrequently reported. 20,24 This paper is a synthesis of these literature data; a novel statistical method of re-sampling allowed a global overview of the performance of the system to be derived.…”