Continuous, non-invasive volume-clamp blood pressure: Determinants of performance

Saroj K L Lal*, Anastasia S. Mihailidou, Michael Cejnar, Robyn J. Henderson, Michael Jones, Stephen N. Hunyor

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Objective: To 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. Design: The influence of these factors was determined by repeatability of finger blood pressure measurement and the relationship to contralateral arm-cuff blood pressure. Methods: Repeated 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. Results: Repeatability 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. Conclusions: Variations 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.

Original languageEnglish
Pages (from-to)1413-1422
Number of pages10
JournalJournal of Hypertension
Issue number12
Publication statusPublished - 1993
Externally publishedYes


  • Finger blood pressure
  • Peñaz method
  • Plethysmography
  • Repeatability coefficient


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