Though individual differences in arterial carbon dioxide and oxygen levels inherently exist, the degree of their influence on cerebral vascular reactivity (CVR) is less clear. We examined the reproducibility of BOLD signal changes to an iso-oxic ramping PetCO2 protocol. CVR changes were induced by altering PetCO2 while holding PetO2 constant using a computer-controlled sequential gas delivery (SGD) device. Two MRI scans, each including a linear change in PetCO2, were performed using a 3-Tesla (3T) scanner. This ramp sequence consisted of 1 min at 30 mmHg followed by 4 min period during where PetCO2 was linearly increased from 30 to 50 mmHg, 1 min at 51 mmHg, and concluded with 4 min at baseline. The protocol was repeated at a separate visit with 3 days between visits (minimum). Intraclass correlation coefficients (ICC) and coefficients of variation (CV) were used to verify reproducibility. Eleven subjects (6 females; mean age 26.5 ± 5.7 years) completed the full testing protocol. Good reproducibility was observed for the within-visit ramp sequence (Visit 1: ICC = 0.82, CV = 6.5%; Visit 2: ICC = 0.74, CV = 6.4%). Similarly, ramp sequence were reproducible between visits (Scan 1: ICC = 0.74, CV = 6.5%; Scan 2: ICC = 0.66, CV = 6.1%). Establishing reproducible methodologies for measuring BOLD signal changes in response to PetCO2 alterations using a ramp protocol will allow researchers to study CVR functionality. Finally, adding a ramping protocol to CVR studies could provide information about changes in CVR over a broad range of PetCO2.
Bibliographical noteFunding Information:
We thank Joseph Fisher, MD, for technical collaboration. This study was partially funded by an Equipment grant from the University of Minnesota Medical Foundation and the University of Minnesota Grant‐in‐Aid (D.R.D.). This research was also supported by the NIDDK sponsored Ruth L. Kirschstein National Research Service T32 Research Training Grant (T32‐DK064584) (K.L.M.).
We thank Joseph Fisher, MD, for technical collaboration. This study was partially funded by an Equipment grant from the University of Minnesota Medical Foundation and the University of Minnesota Grant-in-Aid (D.R.D.). This research was also supported by the NIDDK sponsored Ruth L. Kirschstein National Research Service T32 Research Training Grant (T32-DK064584) (K.L.M.).
© 2020 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd
- arterial carbon dioxide changes
- sequential gas delivery