Factors influencing differences between invasive and spontaneous baroreflex estimates: distinct methods or different data?

Currently invasive BRS estimates are obtained with drug-induced data assuming a sigmoidal SBP-RR relationship, while spontaneous BRS estimates are obtained with non-sigmoidal estimators. In particular, the events (sequences) technique provides a spontaneous BRS estimate based on baroreflex events, BEs (baroreflex sequences, BSs). In this work, BRS estimates are compared considering that can be obtained with different estimators and evaluated in different conditions. All BRS estimates were found to be significantly correlated. In comparison with BS estimates, BE estimates from spontaneous data exhibited higher correlation with sigmoidal estimates and their differences were associated with differences in SBP levels from invasive to spontaneous condition. BE estimator evaluated in different conditions decreased the differences between BRS estimates, pointing out differences due to the use of distinct methods, and such differences were correlated with differences in SBP and RR levels from invasive to spontaneous conditions. Finally, sigmoid estimates were more correlated with BE estimates in invasive data in comparison with those evaluated from BS. In conclusion, BRS analysis from BEs provides an estimate that exhibits higher correlation and lower differences between BRS estimates from different conditions, and reflects properly the BRS physiology.