PHYSIOLOGICAL INFLUENCES ON CONTINUOUS FINGER AND SIMULTANEOUS INTRAARTERIAL BLOOD-PRESSURE

Because of the clinical and experimental utility of continuous finger blood pressure measurements and the need for accuracy, we tested the p erformance of a new hydraulic device in 22 consecutive hypertensive su bjects during physiological and pharmacological interventions. Ipsilat eral brachial intra-arterial pressure was monitored during rest, Valsa lva's maneuver, static handgrip, and mental arithmetic and after subli ngual glyceryl trinitrate. In excess of 40 000 blood pressure values w ere 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 m m Hg (P=NS) for diastolic pressure. Two-way ANOVA of biases with subje ct and task factors showed a subject effect (P<.001). Intersubject and intrasubject standard deviations of bias were 13.8 and 9.8 mm Hg syst olic and 8.7 and 5.7 diastolic, respectively. Linear drift (millimeter s of mercury per minute) of finger pressure was greater (P<.001) for s ystolic than diastolic pressure during static exercise and math and af ter glyceryl trinitrate. Coefficients of determination for blood press ure ranged from 0.4+/-0.3 to 0.8+/-0.3 during the tasks. We conclude t hat (1) noninvasive finger blood pressure faithfully follows intra-art erial 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 pressu re accuracy, (4) many reports of finger blood pressure measuring devic es are based on direct readings obtained with inadequate system respon se characteristics, and (5) the tested instrument falls short of the s tandards requirements (bias less than or equal to 5+/-8 mm Hg) for dev ices that measure intermittently.