Complex demodulation of baroreflex during parabolic flight

In this study we evaluated the usefulness of complex demodulation (CDM) for the assessment of baroreflex sensitivity (BRS) and time delay during dynamic changes of autonomic cardiovascular regulation induced by changing gravity during parabolic flight. BRS and time delay data assessed with CDM in the HF band are influenced by non-baroreflex coupling of heart rate and blood pressure variations. LF band estimates reflect baroreflex coupling. BRS estimates obtained with complex demodulation correlate well (r = 0.92 ; p < 0.01) with estimates obtained with power spectrum analysis. Our results show no postural differences in normo- and hypergravity. In microgravity, standing BRS estimates are higher than supine estimates. It can be concluded that CDM, applied on LF band variations of heart rate and systolic blood pressure, provides reliable estimates of baroreflex characteristics in dynamic autonomic cardiovascular control.