Correlation between peripheral vascular resistance and time to peak flow during reactive hyperaemia

Abstract

Earlier studies have proposed that the time to reach peak hyperaemic flux recorded with laser Doppler (t_p) is a simple and accurate method of evaluating ischaemic limbs and possibly a method of estimating the peripheral vascular resistance (PR). The aim of this study was to investigate the relationship between the t_p and changes in limb vascular resistance caused by arterial stenosis. Forty postocclusive hyperaemia tests with arterial stenoses of different pressure gradients were performed in four pigs. A laser Doppler fluxmeter was used to record postocclusive hyperaemia in the skin of one hind limb. A specially designed tourniquet was used for the arterial occlusion. Proximal and distal to the occlusion level a snare was used to form different grades of stenosis. The PR (mmHgml⁻¹·-min⁻¹) was either estimated by infusion of a known blood volume into the tested limb over a given time period with simultaneous measurement of pressure or calculated on the basis of measurements of limb blood flow and blood pressure gradients. The t_p was closely related to total limb vascular resistance assessed by the blood infusion method (r = 0.83, p < 0.0003) and to the resistance calculated from volume blood flow and intraarterial pressures (r = 0.86, p < 0.0001). This study suggests that the t_p accurately reflects limb vascular resistance in an experimental model. Thus t_p may be used as a quantitative indicator of overall blood flow impairment, and should be evaluated in patients with lower-limb atherosclerosis.