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Updated: Aug 2, 2026
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MRI Mapping of Cerebrovascular Reactivity via Gas Inhalation Challenges
Published on: December 17, 2014
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Variable Cerebral Blood Flow Responsiveness to Acute Hypoxic Hypoxia
Hannah R Johnson1,2, Max C Wang1,2, Rachael C Stickland2
1Department of Biomedical Engineering, McCormick School of Engineering and Applied Sciences, Northwestern University, Evanston, IL, United States.
Biorxiv : the Preprint Server for Biology
|November 28, 2024
Summary
Cerebrovascular reactivity (CVR) to hypoxia is less reliable than to hypercapnia and shows paradoxical responses, suggesting distinct vascular regulation mechanisms. This research highlights CVR
Area of Science:
- Neuroimaging
- Cardiovascular Physiology
- Medical Diagnostics
Background:
- Cerebrovascular reactivity (CVR) to carbon dioxide is a key vascular health indicator.
- Assessing CVR to oxygen, especially hypoxia, offers complementary insights but faces challenges.
- Existing methods like arterial spin labeling (ASL) MRI for hypoxic CVR show high variability and paradoxical responses.
Purpose of the Study:
- To investigate the reliability and nature of hypoxic CVR using phase-contrast MRI.
- To determine if observed paradoxical responses in hypoxic CVR are real or methodological artifacts.
- To compare the reliability of hypoxic CVR with established hypercapnic CVR.
Main Methods:
- Phase-contrast MRI was used to measure whole-brain blood flow in 21 participants.
- Participants underwent baseline, hypoxic, and hypercapnic respiratory challenges across three scan sessions.
- Intra-class correlation coefficients (ICCs) were calculated to assess CVR reliability.
Main Results:
- Hypoxic CVR demonstrated poor-to-moderate reliability (ICC=0.42-0.56), lower than hypercapnic CVR (ICC=0.67).
- Paradoxical responses in hypoxic CVR were observed even without ASL-related confounds.
- Hypoxic and hypercapnic CVR shared approximately 40% of variance, indicating distinct regulatory roles.
Conclusions:
- Hypoxic CVR is less reliable than hypercapnic CVR and exhibits genuine paradoxical responses.
- These findings suggest that hypoxic and hypercapnic CVR reflect distinct aspects of cerebrovascular regulation.
- Phase-contrast MRI provides a more reliable method for studying hypoxic CVR compared to ASL.
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