Page 18, hemodynamics, Dr. D. Penney


Usefulness of the Poiseuille Equation (continued..)

When distensible versus rigid tubes are used, an increase in perfusion pressure produces an increase in transmural pressure which in turn increases vessel caliber, resulting in more than proportional increases in fluid flow. Thus a non-linear relationship develops which violates the Poiseuille equation.

It might be asked why the Poiseuille equation is even used. Despite its limitations, it can be useful in predicting flow just as long as we are mindful of its limitations when applying it to living systems. An equation that would be an exact representation of living systems is probably beyond the capability of today's science, and even if it could be written it would be so complex and cumbersome as to be inconvenient to work with.




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