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Second year medical student asking.
Does the blood pressure at the root of aorta equal the blood pressure in the brachial artery?
I've heard it does but it doesn't quite seem to make sense as I'd think the blood pressure would be lowered the further it travels? Research indicates[1] that there is not the same pressure but I can't seem to find a "why".
The mean pressure has to be lower peripherally for blood to flow in that direction. However, it is well known that there is an amplification of systolic blood pressure in the limbs due to reflection of pressure wave from periphery (see http://hyper.ahajournals.org/content/51/1/112.full). Vascular stiffness also affects this phenomenon. See figure 4 of this article in American Journal of Physiology: http://ajpheart.physiology.org/content/299/3/H584
The phenomenon of pressure wave reflection is shown clearly in figure 5 of this article in Advances in Physiology Education http://advan.physiology.org/content/37/4/321
This phenomenon is also exaggerated in aortic regurgitation, where it is called the Hill's sign: http://www.learntheheart.com/cardiology-review/hills-sign/
