Model based processing of cardiovascular variability applied to bed-rest case studies

The cardio-vascular (CV) deconditioning observed in CV diseases or in weightlessness conditions can be reproduced by experimental maneuvers such as head down tilt bed rest (HDTBR) study. This maneuver can elicit CV regulation and control mechanisms. Three healthy subjects were studied during an exercise session before and after a sustained bed rest study. The CV, baroreflex response, and identification of the components of diastolic arterial pressure (DAP) and sources of variability were studied. Tachycardia and hypotension were observed after HDTBR. Changes were noticed in the baroreflex control of heart rate (HR) after HDTBR, whereas no clear difference in the diastolic time constant was found. Spectral power of DAP and of its tachogram-dependent component were lower after HDTBR.. The present work suggested the feasibility of the multiparametric analysis and gave preliminary indications of reflex mechanisms reset.