A six fold increase in blood flow through a major coronary a

A six fold increase in blood flow through a major coronary artery is typically observed following an occlusion of about 10 seconds. This phenomenon is known as reactive hyperemia. It occurs without significant changes in pressure and is due to dilation of arteries distal to the occlusion. What fractional change in resistance is necessary to explain this result? If the relative increase in vessel diameters is uniform throughout this arterial tree, what is the r/r_0 where r_0 is the artery radius in the control state (before occlusion) and r is the radius during the reactive hyperemia? Assume Poiseuille flow. Assume that the resistance in the coronary artery equals the resistance in the distal arteries prior to occlusion.

Solution

resistance =increase in blood flow/ time=>6/10=0.6

   r->artery radius in the control state=r

ro->radousm during reactive hyperemia=>6r(6 timestheoriginal radius)

the ratio=r/r0=>r/6r=>1/6