Summary of ETCO2 and MRI metrics (mean) for normocapnia and hypercapnia
| MRI/MRS and Measures | Normocapnia | Hypercapnia | P Value |
|---|---|---|---|
| 1H-MRSa | |||
| ETCO2 (mm Hg) | 44.40 ± 4.1 | 52.9 ± 2.4 | <10−4 |
| WBNAA (arb. unit) | 177.9 ± 40.5 | 178.8 ± 32.3 | .88 |
| pCASL MRI | |||
| ETCO2 (mm Hg) | 40.6 ± 4.9 | 49.4 ± 3.9 | <10−4 |
| CBF (mL/100 g/min) | 33.9 ± 6.3 | 50.2 ± 6.9 | <10−4 |
| TRUST MRI | |||
| ETCO2 (mm Hg) | 43.3 ± 4.7 | 52.5 ± 2.9 | <10−4 |
| Yv (%) | 56.4 ± 5.6 | 71.9 ± 4.8 | <10−4 |
| TRUST and pCASL | |||
| CMRO2 (μmol/100 g/min) | 120.0 ± 23.9 | 111.2 ± 18.9 | .04 |
Note:—Arb. indicates arbitrary; ETCO2, end-tidal carbon dioxide.
↵a WBNAA values measured with 1H-MRS of the posthypercapnic condition (the second normocapnia) are listed in the main text.