Dynamic Arterial Elastance: an Indirect Marker of the Critical Capillary Pressure at the Microcirculatory Level

The measurement of dynamic arterial elastance (Eadyn) was proposed as a marker of vascular tone. It is calculated by the ratio of the respiratory variation of the pulse pressure and the respiratory variation of stroke volume. Despite several clinical studies, no study has really focused on the physiological significance of Eadyn. No study demonstrates at present, if this index is a reflect of macrocirculatory parameters (systemic resistances, blood pressure, arterial elastance, ventricular elastance, ventriculo-arterial coupling) or microcirculatory tone in the capillaries and small arterioles (critical capillary pressure or capillary resistance). the physicians don't know which variables are associated with this index. One hypothesis is that Eadyn is an indirect reflection of capillary pressure (PCC). The main objective of this project is to study the correlation between the measure of Eadyn and the PCC. The study begins when the physician in charge of the patient decides a hemodynamic treatment (either volume expansion or norepinephrine). The indication of the treatment is left to the discretion of the physician in charge of the patient: volume expansion or vasopressor agent. After verification of inclusion criteria, the physician collects demographic, ventilatory, hemodynamic, cardiac ultrasound data, and the type of treatment initiated (volume expansion, norepinephrine, and their dosages). 15 minutes after the introduction of the therapy and stabilization of the hemodynamic state, a new series of measurements of the aforementioned.