By reducing the speed of blood flow profiles the dependence of Ht on the radius of the vessel becomes more elongated. However, at normal values of Ht, the effect is also insignificant. With high enough shear rates, the red blood cells become susceptible to deformation.
By decreasing the velocity of blood circulation, the dependence of Ht on the diameter of the vessel becomes more pronounced. However, at normal levels of Ht, the impact is also minimal. With sufficient shear forces, red blood cells become susceptible to stretching.