P2). - e - Blood viscosity. - r - Radius. - L - Tube length.* If parameter values remain constant, - Blood flow is directly propoional to 4th power of radius.* Resistance of vessel to blood flow can be calculated by combining Ohm's law with Poiseuille's equation. - By substituting values of Q from Poiseuille's law in Ohm's law. - Implying, resistance is mainly affected by, 1. Blood vessel radius, 2. Vasodilatation/vasoconstriction.* Thus ultimately, if parameter values remain constant, - Resistance to blood flow is inversely propoional to the 4th power of radius.">