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hi folks. new on here so hope question is the sort of thing you talk about.
We use the tri , bi and mono classification of pulse all the time to indicate the state of Patient's peripheral circulation at various points but something bothers me about this. As I understand it the 1st part is the forward flow from the contracting ventricle, the second the rebound from the arterioles or capillary beds and the 3rd is due to the elasticity of the aorta. sending out another forward pulse. If I am correct in this assumption then that 3rd aorta pulse either happens or it doesn't. I don't see how it can happen in one leg but not the other. This would mean that it would be impossible to have triphasic at one pulse and monophasic at another which is clearly not the case.
Please explain in simple language to a simpleton!
Many thanks

 

Hi Len,

Interesting question. I don't think the answer is very simple and would seem to lie in the physics of fluid flow dynamics in elastic verses inelastic vessels.

My (simple) understanding of it would be that inelastic vessels offer greater resistance to flow than elastic vessels - if you push a bolus off fluid down an inelastic vessel local pressure will increase, pushing back against the driving force; hence we have elastic arteries. As each phase has progressively less power than the last the tri and then bi phasic wave forms will be attenuated sooner than the initial systolic wave. This effect will be more severe in sclerotic vessels and particularly those with a stenosis. Additionally we don't have a simple single vessel system; there are multiple branches (arterioles) each offering their own different and variable resistance to flow and thus influencing the wave form in the pedal pulses. Both of these effects will tend to lead to different wave forms presenting in different legs or arteries.

For more on this try here

http://hyper.ahajournals.org/content/56/5/926.full

and here

https://www.quora.com/As-I-understa...-cause-the-different-sounds-that-are-produced

Ben

 

Thanks Ben,
That Hashimoto study is fascinating. Will have to read it a couple more times to really get it though. Interesting that there are so many factors that affect the pulse in different ways. Also interesting that it seems that even now it is not fully understood even by the experts (which gives me hope)! But I definitely have more of a handle on it now. Thanks once again.
Len

 

It seems that the only simple answer is that it's complicated.

There are probably also effects caused by more laminar flow in healthy arteries and more turbulent flow in more sclerotic and stenosed arteries and the ratios of laminar to turbulent flow and transition from one to the other.

Some good diags here

https://www.uio.no/studier/emner/ma...rvisningsmateriale/modul-5/Pipeflow_intro.pdf


Ben