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ORIGINAL RESEARCH article

Front. Physiol.

Sec. Vascular Physiology

Volume 16 - 2025 | doi: 10.3389/fphys.2025.1562582

This article is part of the Research Topic Physiological and Pathological Responses to Hypoxia and High Altitude, Volume III View all 7 articles

Variable Cerebral Blood Flow Responsiveness to Acute Hypoxic Hypoxia

Provisionally accepted
  • 1 Department of Biomedical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, Illinois, United States
  • 2 Physical Therapy & Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
  • 3 Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
  • 4 Division of Stroke and Neurocritical Care, The Ken & Ruth Davee Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States

The final, formatted version of the article will be published soon.

    Cerebrovascular reactivity (CVR) to changes in blood carbon dioxide and oxygen levels is a robust indicator of vascular health. Although CVR is typically assessed with hypercapnia, the interplay between carbon dioxide and oxygen, and their ultimate roles in dictating vascular tone, can vary with pathology. Methods to characterize vasoreactivity to oxygen changes, particularly hypoxia, would provide important complementary information to established hypercapnia techniques. However, existing methods to study hypoxic CVR, typically with arterial spin labeling (ASL) MRI, demonstrate high variability and paradoxical responses. To understand whether these responses are real or due to methodological confounds of ASL, we used phase-contrast MRI to quantify wholebrain blood flow in 21 participants during baseline, hypoxic, and hypercapnic respiratory states in three scan sessions. Hypoxic CVR reliability was poor-to-moderate (ICC=0.42 for CVR relative to PETO2 changes, ICC=0.56 relative to SpO2 changes) and was less reliable than hypercapnic CVR (ICC=0.67). Without the uncertainty from ASL-related confounds, we still observed paradoxical responses at each timepoint. Concurrent changes in blood carbon dioxide levels did not account for paradoxical responses. Hypoxic CVR and hypercapnic CVR shared approximately 40% of variance across the dataset, indicating that the two effects may indeed reflect distinct, complementary elements of vascular regulation.

    Keywords: cerebral blood flow, cerebrovascular reactivity, hypoxia, phase contrast MRI, Hypercapnia

    Received: 17 Jan 2025; Accepted: 24 Feb 2025.

    Copyright: © 2025 Johnson, Wang, Stickland, Chen, Parrish, Sorond and Bright. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Hannah R Johnson, Department of Biomedical Engineering, McCormick School of Engineering and Applied Science, Northwestern University, Evanston, IL 60208, Illinois, United States

    Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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