How Plaque Reduces Artery Radius: Calculating with Poiseuille's Law

[cyberdx16]

Homework Statement

When physicians diagnose arterial blockages, they quote the reduction in flow rate. If the flow rate in an artery has been reduced to 30% of its normal value due to plaque formation, and the average pressure difference has increased by 30%, by what factor has the plaque reduced the radius of the artery?

Homework Equations

Poiseuille's Law.

The Attempt at a Solution

what i used was R=(.7/1.3)^.25 and get that only 85.6% of the radius of the artery is available, and has been reduced by 14.4%

 

[denverdoc]

I think you want to use .3 in the numerator, ie

flow is now 30 percent of original, not been reduced by 30%

 

[cyberdx16]

wouldn't the presure rate be increased by .3 so from its original, which is 1 and add .3 for the increase. But yeah i just tried .3 and it didnt work

 

[denverdoc]

Its both .3 and 1.3, (.3/1.3)^.25 is that what you tried?

 

[cyberdx16]

yeah you are right denverdoc! thx

 

[denverdoc]

NP. FYI when occlusion reaches 80 percent and above, bad news. This guy has lost some exercise tolerance but still in decent shape re meeting oxygen demands.