Instantaneous versus average wave speed calculation in large mammals under acute hemorrhage

Arterial blood pressure and velocity pulse wave speed are important biomarkers of arterial stiffness and cardiovascular disease risk in man. Arterial wave speed is usually assessed using pulse wavefront movement over a known finite portion of the arterial tree. In our pilot study we assess a new technique for determining instantaneous wave speed using "wave intensity analysis" of simultaneously recorded high fidelity pressure and velocity waveforms at a single point in the porcine aorta during acute changes in hemodynamic status (hemorrhage). The results, when compared with a traditional wavefront approach over a length of aorta, suggest that the two techniques produce different results that could be explained by the varying properties along the aorta from heart to periphery. We show that instantaneous wave speed can be determined and monitored during acute hemodynamic change using "wave intensity analysis" at one point in the aorta. Furthermore, we uncovered discrepancies between instantaneous and averaged wave speed, which will be important in understanding the integrative physiology of acute cardiovascular perturbations and could have important application in monitoring the progression of chronic cardiovascular diseases.