Baroreflex sensitivity analysis: spontaneous methodology vs. Valsalva's maneuver.

INTRODUCTION: Spontaneous analysis techniques and Valsalva's maneuver (VM) are often used as a non-pharamcological approach to assess both sympathetic (sBRS) and cardiovagal (cBRS) baroreflex sensitivity. Despite their wide utilization, no studies have assessed the intra-individual reliability between these analysis techniques. Accordingly, we hypothesized that spontaneous BRS would be positively correlated to VM BRS.
METHODS: Heart rate (HR), blood pressure (BP), and muscle sympathetic nerve activity (MSNA) were measured in 26 healthy subjects (age, 22 ± 1 year; 14 men and 12 women) during 10 min supine rest and 3 VM at 40 mmHg expiratory pressure (15 s, 1 min recoveries). For spontaneous BRS, relations between diastolic BP and MSNA were used to determine sBRS, while relations between systolic BP and R-R interval were used to determine cBRS. During VM, sBRS was the ratio of MSNA and the maximum diastolic BP reduction during early phase II, and cBRS was derived from linear relations between systolic BP and R-R interval during early phase II (i.e., hypotensive stimulus) and phase IV (i.e., hypertensive stimulus).
RESULTS: Spontaneous sBRS was significantly correlated to VM sBRS (r = 0.516, p = 0.036). In contrast, spontaneous cBRS from up-up sequence was not correlated to VM phase IV cBRS (r = 0.274, p = 0.109). Similarly, spontaneous cBRS from down-down sequence was not correlated to VM phase II cBRS (r = 0.199, p = 0.207).
CONCLUSION: In conclusion, our findings demonstrate positive association between spontaneous sBRS and VM sBRS, but there is no correlation between spontaneous and VM cBRS.