• S K Lal, A S Mihailidou, M Cejnar, R J Henderson, M Jones, and S N Hunyor.
• Department of Cardiology, Royal North Shore Hospital, Sydney, New South Wales, Australia.
• J. Hypertens. 1993 Dec 1; 11 (12): 1413-22.

ObjectiveTo test a prototype hydraulic, non-invasive, continuous finger blood pressure monitor based on the volume-clamp principle for procedure-related factors likely to influence precision.DesignThe influence of these factors was determined by repeatability of finger blood pressure measurement and the relationship to contralateral arm-cuff blood pressure.MethodsRepeated blood pressure measurements from three different fingers were made in 60 subjects following re-initialization of the device and re-insertion of the finger into the cuff. Repeatability was assessed in relation to simultaneous arm-cuff readings. Drift in arm-finger discrepancy was measured over a 1-h period. Finger diameter, drug therapy and presence of peripheral vascular disease were correlated with arm-finger blood pressure difference.ResultsRepeatability coefficients (twice the SD of the arm-finger difference) across device re-initialization were large, but similar to parallel repeated arm blood pressure determinations: 17.6 and 17.1 mmHg for systolic blood pressure (SBP) and 13.9 and 13.6 mmHg for diastolic blood pressure (DBP), respectively. Withdrawing and re-inserting the finger reduced repeatability substantially, with a 50% increase in repeatability coefficient. A trend towards a progressive 9-mmHg increase was observed in overestimation of SBP over the 1-h period. Mean +/- SD pooled arm-finger blood pressure differences were -10.8 +/- 14.6 mmHg for SBP and 4.5 +/- 9.4 mmHg for DBP. Blood pressure measured in different fingers was similar on average, with repeatability no poorer than for re-insertion of the same finger. The presence of peripheral vascular disease in 15 subjects correlated with a smaller arm-finger difference for DBP.ConclusionsVariations in positioning of the finger within the cuff influences blood pressure measurement during volume-clamp plethysmography, reducing its precision. Finger SBP exceeds brachial auscultatory readings and has similar precision.

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