Hematocrit, viscosity and blood flow velocity in men and women

A study was made on hematocrit, viscosity and blood flow velocity in men and women. Thirty three normal subjects (23 men and 10 women) with no signs or symptoms of vascular peripheral disease of the lower extremities were studied during abdominal angiography performed for evaluation of pathology of abdominal viscera. Hct was measured and a coefficient of correlation was calculated for Hct vs. flow velocity for men and women separately. The working hypothesis that the differences in flow velocity were dependent on Hct values was analyzed statistically by comparing men and women in the same Hct range. Several formulas have been suggested to describe the relationship between viscosity and Hct and these depend largely on differences in methodology. Without determining the exact relationship between the viscosity, which is a factor in the flow formula, and the Hct, the authors' results point to a good correlation between flow velocity and Hct, and thus with viscosity, in both men and women. An almost complete overlap of blood flow values in men and women in the same Hct range was found. The most likely explanation of this finding is that the differences observed in flow velocity between the sexes can be largely explained on the basis of the lower mean Hct in women. For the subject with similar Hct (six men and six women) there were not any significant differences in mean flow velocity between men and women. Statistical analysis shows that the chance for such an overlap in these two samples for populations varying in mean flow velocity by 5.4 cm/sec or more is 5%. (Szirmai - Stuttgart)