Blood viscosity as a chronic contributing factor of vasodilatation in humans

Publisher Website
Google Scholar
Abstract
Since resistance to flow is theoretically determined by arteriolar geometry and blood viscosity, we studied these two factors in 44 normal and 106 hypertensive subjects. Brachial bed vascular resistance was calculated as the ratio between mean pressure and brachial artery flow. Systemic blood viscosity in vitro was determined at 96 pers, while microvessel blood viscosity in vivo was estimated from the haematocrit—viscosity relationship at 240 pers. A resistive radius index was calculated which was only related to the microvessel viscosity: resistance ratio. Compared to normal subjects, hypertensive subjects had higher systemic in vitro blood viscosity (4.75 ± 0.47 versus 4.50 ± 0.43 mPa.s; PPPPPPPPP<0.001), showing that, at the highest viscosities, arterial radius increased less in hypertensive than in normal subjects. Thus, the level of blood viscosity might influence arterial diameter. However, the dilatory effects of the small arteries appeared to be less efficient in hypertensive than in normotensive subjects, possibly suggesting some impairment due to hypertension.