The feasibility and reliability of capillary blood pressure measurements in the fingernail fold

Abstract

Capillary blood pressure is an essential parameter in the study of the (patho-)physiology of microvascular perfusion. Currently, capillary pressure measurements in humans are performed using a servo-nulling micropressure system containing an oil-water interface, which suffers some drawbacks. In addition, the effect of the preparation of the skin and the presence of the tip of the pipette in the capillary during the measurement on microcirculatory perfusion has never been described. Therefore, we assessed the feasibility of capillary pressure measurements using an alternative micropressure system using an air-water interface (900 A, WPI) and examined the effect of the measurement on local microcirculation. In 19 healthy male volunteers the apex of capillaries in the eponychium of the fourth finger was punctured, after skin peeling, by a micropipette connected to a servo-nulling micropressure system. Red blood cell velocity (RBCV) was assessed after peeling during the measurement and at an adjacent area. Mean capillary pressure (in 16/19 volunteers) was 20.5 +/- 3.7 mm Hg (systolic 26.2 +/- 5.6 mm Hg, diastolic 17.6 +/- 3.9 mm Hg). RBCV was not significantly different before (0.52 mm/s) and during the measurement (0.51 mm/s) and at an adjacent area (0.51 mm/s). Capillary pressure can be measured well with the alternative setup used without hampering capillary flow, while the pressures obtained are in agreement with the results reported previously by other investigators.