The CO2‐stimulus duration and steady‐state time‐point used for data extraction alters the cerebrovascular reactivity outcome measure

Burley, Claire V.; Lucas, Rebekah A.I.; Whittaker, Anna C.; Mullinger, Karen; Lucas, Samuel J.E.

Abstract

Cerebrovascular reactivity to carbon dioxide (CVR) is a common functional test to assess brain vascular health, though conflicting age and fitness effects have been reported. Studies have used different CO2 -stimulus durations to induce CVR and extracted data from different time-points for analysis. Therefore, this study examined whether these differences alter CVR, and explain conflicting findings. Eighteen healthy volunteers (24 ± 5 years) inhaled four CO2 -stimulus durations (1, 2, 4 and 5-min) of 5% CO2 (in air) via the open-circuit Douglas bag method, in a randomised order. CVR data were derived from transcranial Doppler (TCD) measures of middle cerebral artery blood velocity (MCAv), with concurrent ventilatory sensitivity to the CO2 stimulus (VE-CO2 ). Repeated measures ANOVAs compared CVR and VE-CO2 measures between stimulus durations and steady-state time-points. An effect of stimulus duration was observed (p = 0.002, η² = 0.140), with 1-min (p = 0.010) and 2-min (p < 0.001) differing from 4-min, and 2-min differing from 5-min (p = 0.019) durations. VE-CO2 sensitivity increased ∼3-fold from 1-min to 4- and 5-min durations (p < 0.001, η² = 0.485). CVR calculated from different steady-state time-points within each stimulus duration were different (p < 0.001, η² = 0.454); specifically, for 4-min (p = 0.001) and 5-min (p < 0.001), but not 2-min stimulus durations (p = 0.273). These findings demonstrate that methodological differences alter the CVR measure. This article is protected by copyright. All rights reserved.

Citation

Burley, C. V., Lucas, R. A., Whittaker, A. C., Mullinger, K., & Lucas, S. J. (2020). The CO2‐stimulus duration and steady‐state time‐point used for data extraction alters the cerebrovascular reactivity outcome measure. Experimental Physiology, 105(5), 893-903. https://doi.org/10.1113/ep087883

• Journal Article Type: Article
• Acceptance Date: Feb 19, 2020
• Online Publication Date: Feb 21, 2020
• Publication Date: May 1, 2020
• Deposit Date: Mar 6, 2020
• Publicly Available Date: Feb 22, 2021
• Journal: Experimental Physiology
• Print ISSN: 0958-0670
• Electronic ISSN: 1469-445X
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 105
• Issue: 5
• Pages: 893-903
• DOI: https://doi.org/10.1113/ep087883
• Keywords: Physiology
• Public URL: https://nottingham-repository.worktribe.com/output/4097188
• Publisher URL: https://physoc.onlinelibrary.wiley.com/doi/abs/10.1113/EP087883
• Additional Information: This is the peer reviewed version of the following article: Burley, C.V., Lucas, R.A., Whittaker, A.C., Mullinger, K. and Lucas, S.J. (2020), The CO2‐stimulus duration and steady‐state time‐point used for data extraction alters the cerebrovascular reactivity outcome measure. Exp Physiol. Accepted Author Manuscript, which has been published in final form at https://doi.org/10.1113/EP087883. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.