Directional sensitivity of the cerebral pressure-flow relationship during forced oscillations induced by oscillatory lower body negative pressure.

A directional sensitivity of the cerebral pressure-flow relationship has been described using repeated squat-stands. Oscillatory lower body negative pressure (OLBNP) is a reproducible method to characterize dynamic cerebral autoregulation (dCA). It could represent a safer method to examine the directional sensitivity of the cerebral pressure-flow relationship within clinical populations and/or during pharmaceutical administration. Therefore, examining the cerebral pressure-flow directional sensitivity during an OLBNP-induced cyclic physiological stress is crucial. We calculated changes in middle cerebral artery mean blood velocity (MCAv) per alterations to mean arterial pressure (MAP) to compute ratios adjusted for time intervals (ΔMCAv/ΔMAP) with respect to the minimum-to-maximum MCAv and MAP, for each OLBNP transition (0 to -90 Torr), during 0.05 Hz and 0.10 Hz OLBNP. We then compared averaged ΔMCAv/ΔMAP during OLBNP-induced MAP increases (INC) (ΔMCAv/) and decreases (DEC) (ΔMCAv/). Nineteen healthy participants [9 females; 30 ± 6 years] were included. There were no differences in ΔMCAv/ΔMAP between INC and DEC at 0.05 Hz. ΔMCAv/ (1.06 ± 0.35 vs. 1.33 ± 0.60 cm⋅s/mmHg; p = 0.0076) was lower than ΔMCAv/ at 0.10 Hz. These results support OLBNP as a model to evaluate the directional sensitivity of the cerebral pressure-flow relationship.