Pulsatility Index quantification in the human precapillary arterioles of the eye.

The Pulsatility Index (PI) was quantified for the first time in the human conjunctival pre-capillary arterioles in vivo. In 30 arterioles with diameters ranging between 6 and 12μm, from 15 healthy humans, peak to peak velocity ranged from 0.2 up to 4.8mm/s with a mean value equal to 1.4±0.2 (SE) mm/s. The PI ranged from 0.4 to 1.5 and the overall mean value was 0.8±0.1 (SE). The linear correlation between PI and diameter was practically zero (Spearman's correlation coefficient, rs≈0) for the range of arteriolar diameters examined here. In this work a first step was made towards the complete PI mapping of the human carotid arterial tree.