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

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.