On age dependence of peripheral augmentation index

Sir: The possibility to continuously assess changes in blood pressure dictates the need to find proper ways of obtaining clinically relevant information from such signals. In the simplest linear case scenario pressure changes are directly proportional to volume changes. This could give some theoretical soundness to the use of photoplethysmographic signals for similar purposes1. Even when the PPG signal is not a "purely volumetric" signal, the fact that it is at least partially related to volume, can justify , in the sense of the Takens theorem, its use as a surrogate of continuous pressure signal. If this will work in practice, the amount of resources saved and the number of patients potentially evaluated can increase substantially.