Different responses of Finapres and the oscillometric finger blood pressure monitor during intensive vasomotion

Two different techniques for non-invasive beat-to-beat finger arterial blood pressure monitoring are compared in six healthy volunteers during local hand heating from 21 to 38 degrees C. The degree of peripheral vasoconstriction was established by recording the thumb pulp skin blood flow with a laser Doppler instrument. For time episodes without vasoconstriction no systematic difference in the readings of beat-to-beat mean blood pressure of the two monitors was found (the oscillometric device UT9201 minus Finapres difference was 0.3 mm Hg, SD 0.3). For the episodes with vasoconstriction the difference was statistically significant (6.7 mm Hg, SD 2.0). The oscillometric device minus Finapres difference and the laser Doppler signal were found to be inversely correlated, the correlation coefficient varying from -0.28 to -0.67. A disagreement between the readings of the instruments during intensive vasomotion is assumed to be caused mainly by the tendency of the oscillometric method to overestimate the finger mean blood pressure under the condition of peripheral vasoconstriction.