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 (Delta MCAvT/Delta MAPT) 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 Delta MCAvT/Delta MAPT during OLBNP-induced MAP increases (INC) (Delta MCAvT/ Delta MAP T INC ) and decreases (DEC) (Delta MCAvT/ Delta MAP T DEC ). Nineteen healthy participants [9 females; 30 +/- 6 years] were included. There were no differences in Delta MCAvT/Delta MAPT between INC and DEC at 0.05 Hz. Delta MCAvT/ Delta MAP T INC (1.06 +/- 0.35 vs. 1.33 +/- 0.60 cm & sdot;s-1/mmHg; p = 0.0076) was lower than Delta MCAvT/ Delta MAP T DEC at 0.10 Hz. These results support OLBNP as a model to evaluate the directional sensitivity of the cerebral pressure-flow relationship.