Effect of altering vasoactivity on the measurement of finger blood pressure

Background Finapres monitors and oscillometric sphygmomanometers are widely used in blood pressure measurements on the fingers. However, the reliabili ty of finger blood pressure measurement devices still remains a matter of d ebate. Design The volume clamp and modified oscillometric methods for non-invasive beat-to-beat finger mean arterial pressure monitoring are compared during intensive spontaneous changes in vascular tone. The degree of vasoconstrict ion is established by recording the thumb pulp skin blood flow with a laser Doppler instrument. The oscillometric mean arterial pressure (MAPo) and th e Finapres mean arterial pressure (MAPf) are simultaneously recorded from a djacent fingers in eight healthy volunteers in a sitting position at room t emperature 22 - 23 degreesC. Results The changes in blood pressure were similarly tracked by the two blo od pressure monitors, except the episodes with peripheral vasoconstriction. The difference (MAPo - MAPf) for all simultaneously recorded mean blood pr essure values in episodes without vasoconstriction was (mean +/- SD) 0.7 +/ - 1.8 mmHg (P = 0.33) and in episodes with vasoconstriction 10.6 +/- 5.6 mm Hg (P < 0.01), A disagreement between the devices during vasoconstriction i s assumed to be caused mainly by the tendency of the oscillometric method t o overestimate the finger mean blood pressure, and by the tendency of the v olume clamp method (Finapres) to underestimate the finger mean blood pressu re in condition of peripheral vasoconstriction. Conclusion For both types of finger monitors (oscillometric blood pressure devices as well as Finapres or Portapres) it is recommended that intensive vasoconstriction in the subject be avoided during measurements. The presenc e of acute vasoconstrictions can be determined by simultaneous recording of finger skin blood flow. <(c)> 2001 Lippincott Williams & Wilkins.