Hemodynamic and metabolic changes during hypercapnia with normoxia and hyperoxia using pCASL and TRUST MRI in healthy adults

Pieter T. Deckers*, Alex A. Bhogal*, Mathijs B. J. Dijsselhof, Carlos C. Faraco, Peiying Liu, Hanzhang Lu, Manus J. Donahue, Jeroen C. W. Siero

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Blood oxygenation level-dependent (BOLD) or arterial spin labeling (ASL) MRI with hypercapnic stimuli allow for measuring cerebrovascular reactivity (CVR). Hypercapnic stimuli are also employed in calibrated BOLD functional MRI for quantifying neuronally-evoked changes in cerebral oxygen metabolism (CMRO 2). It is often assumed that hypercapnic stimuli (with or without hyperoxia) are iso-metabolic; increasing arterial CO 2 or O 2 does not affect CMRO 2. We evaluated the null hypothesis that two common hypercapnic stimuli, ‘CO 2 in air’ and carbogen, are iso-metabolic. TRUST and ASL MRI were used to measure the cerebral venous oxygenation and cerebral blood flow (CBF), from which the oxygen extraction fraction (OEF) and CMRO 2 were calculated for room-air, ‘CO 2 in air’ and carbogen. As expected, CBF significantly increased (9.9% ± 9.3% and 12.1% ± 8.8% for ‘CO 2 in air’ and carbogen, respectively). CMRO 2 decreased for ‘CO 2 in air’ (−13.4% ± 13.0%, p < 0.01) compared to room-air, while the CMRO 2 during carbogen did not significantly change. Our findings indicate that ‘CO 2 in air’ is not iso-metabolic, while carbogen appears to elicit a mixed effect; the CMRO 2 reduction during hypercapnia is mitigated when including hyperoxia. These findings can be important for interpreting measurements using hypercapnic or hypercapnic-hyperoxic (carbogen) stimuli.

Original languageEnglish
JournalJournal of Cerebral Blood Flow and Metabolism
Early online date2021
Publication statusE-pub ahead of print - 2021
Externally publishedYes

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