Wave reflection is an important contributing factor to systemic arterial compliance determination

We have previously shown with a nonlinear model that arterial compliance is pressure-dependent and thus, is affected by global alterations in pressure and flow. We hypothesize that wave reflection is an important contributing factor to total systemic arterial compliance determination and that this can be demonstrated with linear models. To investigate this, experiments were performed in anesthetized (An) and conscious (Co) dogs. Measurements of ascending aortic pressure, diameter and flow were obtained during control, dobutamine (Co;DX, 20 μg/Kg) or methoxamine (An;MTX; 20 μg/Kg) infusions. Systemic arterial compliance (C) and peripheral vascular resistance (R_s) were calculated. C was obtained from two different methods based on linear models of the arterial system (stroke volume/pulse pressure and diastolic aortic pressure decay time constant) Forward (P_f) and reflected (P_r) waves were also obtained, by a time-domain method. Results show that changes in C is closely coupled to the changes in reflected waves Systemic arterial compliance determination is significantly influenced by alterations m both ventricular inotropic state (e.g DX) and peripheral vasoactive state (e.g. MTX) under such circumstances.