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In Reply.—The observations made by Drs Merrill and Finseth that there are various arbitrary ways to look at the data presented by us (Arch Surg 112:679-683, 1977) are correct. In trying to categorize clinical results, a two-dimensional graph is one of the easier ways to visualize a condition defined by two variables. While Dr Merrill is correct in the purest mathematical sense in suggesting the analogy between the product of the pressure and the flow being power as in electricity (E X I), this does not pertain in the clinical setting. The product of P and PFz is a function of the compliance of the system, ie, P X PFz ∝ 1/R ∝ compliance. However, the compliance of this vascular system is a function of many conditions (ie, age, diabetes) so that there is no simple way to enter it in the above relationship. Currently, we are
WATER JMVD. Noninvasive Assessment of the Peripheral Vascular System-Reply. Arch Surg. 1978;113(1):111-112. doi:10.1001/archsurg.1978.01370130113024