Dynamic cerebral autoregulation and cerebrovascular carbon dioxide reactivity in middle and posterior cerebral arteries in young endurance-trained women

Abstract

The integrated responses regulating cerebral blood flow are understudied in women, particularly in relation to potential regional differences. In this study, we compared dynamic cerebral autoregulation (dCA) and cerebrovascular reactivity to carbon dioxide (CVRco₂) in the middle (MCA) and posterior cerebral arteries (PCA) in 11 young endurance-trained women (age, 25 ± 4 yr; maximal oxygen uptake, 48.1 ± 4.1 mL·kg^-1·min^-1). dCA was characterized using a multimodal approach including a sit-to-stand and a transfer function analysis (TFA) of forced blood pressure oscillations (repeated squat-stands executed at 0.05 Hz and 0.10 Hz). The hyperoxic rebreathing test was utilized to characterize CVRco₂. Upon standing, the percent reduction in blood velocity per percent reduction in mean arterial pressure during initial orthostatic stress (0-15 s after sit-to-stand), the onset of the regulatory response, and the rate of regulation did not differ between MCA and PCA (all P > 0.05). There was an ANOVA effect of anatomical location for TFA gain (P < 0.001) and a frequency effect for TFA phase (P < 0.001). However, normalized gain was not different between arteries (P = 0.18). Absolute CVRco₂ was not different between MCA and PCA (1.55 ± 0.81 vs. 1.30 ± 0.49 cm·s^-1/Torr, P = 0.26). Relative CVRco₂ was 39% lower in the MCA (2.16 ± 1.02 vs. 3.00 ± 1.09%/Torr, P < 0.01). These findings indicate that the cerebral pressure-flow relationship appears to be similar between the MCA and the PCA in young endurance-trained women. The absence of regional differences in absolute CVRco₂ could be women specific, although a direct comparison with a group of men will be necessary to address that issue.NEW & NOTEWORTHY Herein, we describe responses from two major mechanisms regulating cerebral blood flow with a special attention on regional differences in young endurance-trained women. The novel findings are that dynamic cerebral autoregulation and absolute cerebrovascular reactivity to carbon dioxide appear similar between the middle and posterior cerebral arteries of these young women.

Keywords: cerebral blood velocity; cerebrovascular reactivity; dynamic cerebral autoregulation; regional differences; women.