Indirect Measurement of Arterial Pressure, Blood Flow and Volume Elastic Modulus in Human Fingers Using Electric Impedance-Cuff

Abstract

A new Plethysmograph, the electric impedance-cuff, was designed for the indirect measurement of blood pressure and flow, volume elastic modulus (Ev) and compliance (C) in human finger arteries. The device comprises a compression chamber filled with electrolyte solution and a tetrapolar electric impedance Plethysmograph whose electrodes are embedded inside the chamber; the compression chamber for controlling transmural arterial pressure (Pt) and the impedance Plethysmograph for detecting total finger volume (Vo), mean arterial volume (Va) and its variations (Av). Systolic (Pas) and mean (Pam) arterial pressures in fingers were determined by detecting pulsatile impedance variations during the gradual increase (or decrease) in Pc using volume oscillometric technique. Diastolic pressure (Pad) and pulse pressure (AP) were calculated using the equations: Pad = (3Pam -_Pas)/2 and ΔP = Pas — Pad. Ev and C defined as Ev = ΔP/(ΔV/Va) and C = ΔVa/ΔP were measured at various Pt levels controlled by Pc. Arterial pressures, blood flow and Ev were measured in 171 healthy subjects. In some subjects, the change in pressure, blood flow and Ev of finger arteries were detected during acupuncture.