Reproducibility and diurnal variation of the directional sensitivity of the cerebral pressure-flow relationship in men and women

J Appl Physiol (1985). 2022 Jan 1;132(1):154-166. doi: 10.1152/japplphysiol.00653.2021. Epub 2021 Dec 2.

Abstract

The cerebral pressure-flow relationship has directional sensitivity, meaning the augmentation in cerebral blood flow is attenuated when mean arterial pressure (MAP) increases versus MAP decreases. We used repeated squat-stands (RSS) to quantify it using a novel metric. However, its within-day reproducibility and the impacts of diurnal variation and biological sex are unknown. Study aims were to evaluate this metric for: 1) within-day reproducibility and diurnal variation in middle cerebral artery (MCA; ΔMCAvT/ΔMAPT) and posterior cerebral artery (PCA; ΔPCAvT/ΔMAPT) and 2) sex differences. ΔMCAvT/ΔMAPT and ΔPCAvT/ΔMAPT were calculated at 7 timepoints (08:00-17:00) in 18 participants (8 women; 24 ± 3 yr) using the minimum-to-maximum MCAv or PCAv and MAP for each RSS at 0.05 Hz and 0.10 Hz. Relative metric values were also calculated (%MCAvT/%MAPT, %PCAvT/%MAPT). Intraclass correlation coefficient (ICC) evaluated reproducibility, which was good (0.75-0.90) to excellent (>0.90). Time-of-day impacted ΔMCAvT/ΔMAPT (0.05 Hz: P = 0.002; 0.10 Hz: P = 0.001), %MCAvT/%MAPT (0.05 Hz: P = 0.035; 0.10 Hz: P = 0.009), and ΔPCAvT/ΔMAPT (0.05 Hz: P = 0.024), albeit with small/negligible effect sizes. MAP direction impacted both arteries' metric at 0.10 Hz (all P < 0.024). Sex differences in the MCA only (P = 0.003) vanished when reported in relative terms. These findings demonstrate that this metric is reproducible throughout the day in the MCA and PCA and is not impacted by biological sex.NEW & NOTEWORTHY The findings of the current study indicate that our time-adjusted metric to evaluate the directional sensitivity of the cerebral pressure-flow relationship is reproducible throughout the day in both the anterior and posterior cerebral circulations. Although a diurnal variation was noted across the day within this metric, this appeared to be of minimal physiological relevance. Finally, the metric is not impacted by biological sex.

Keywords: hysteresis; mean arterial pressure; middle cerebral artery blood velocity; reproducibility; squat-stand.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arterial Pressure
  • Blood Flow Velocity
  • Blood Pressure
  • Cerebrovascular Circulation*
  • Female
  • Humans
  • Male
  • Middle Cerebral Artery*
  • Posterior Cerebral Artery
  • Reproducibility of Results

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