Model-based assessment of baroreflex and cardiopulmonary couplings during graded head-up tilt

We propose a multivariate dynamical adjustment (MDA) modeling approach to assess the strength of baroreflex and cardiopulmonary couplings from spontaneous cardiovascular variabilities. Open loop MDA (OLMDA) and closed loop MDA (CLMDA) models were compared. The coupling strength was assessed during progressive sympathetic activation induced by graded head-up tilt. Both OLMDA and CLMDA models suggested that baroreflex coupling progressively increased with tilt table inclination. Only CLMDA model indicated that cardiopulmonary coupling due to the direct link from respiration to heart period gradually decreased with tilt table angles, while that due to the indirect link mediated by systolic arterial pressure progressively increased.