Alterations in Cardiovascular Regulation and Function Assessed Using Cardiovascular System Identification

Cardiovascular System Identification (CSI), a novel technique for the noninvasive and quantitative characterization of short-term cardiovascular regulation, was applied to determine the effects of simulated microgravity environments on cardiovascular deconditioning in general and orthostatic intolerance in particular. Preliminary results indicate that simulated micro-gravity environments significantly alter the autonomic mediation of short-term cardiovascular reflexes, including the heart-rate baroreflex. Furthermore, CSI was applied to determine the effects of visual pathway stimulation on short-term autonomic regulation. The results indicate that visually induced virtual tilt does elicit changes in short-term cardiovascular regulation, correlating positively with individual measures of tilt perception. Finally, to provide a reference point with existing cardiovascular analysis, three quantitative models were created to estimate the Smyth heart-rate baroreflex sensitivity coefficient from CSI analysis. Using these models, we were able to non-invasively estimate heart-rate baroreflex sensitivity without the use of pharmaceuticals. Thesis Supervisor: Richard J. Cohen Title: Whitaker Professor in Biomedical Engineering