Assessment of cerebral oxidative metabolism with breath holding and fMRI

Carbon dioxide inhalation can be used to map changes in cerebral metabolic rate of oxygen (CMRO2) during neuronal activation with functional MRI (fMRI). A hypercapnic stress also can be achieved with a simple breath‐holding test. Using this test as means of manipulating cerebral blood flow (CBF) independent of CMRO2, we assessed changes in CMRO2 during visual stimulation. With this task, CBF increased by 61 ± 7%, whereas CMRO2 changed by 2.43 ± 4.97%. These results are in good agreement with previous positron emission tomographic (PET) data, indicating that changes in oxidative metabolism during focal neuronal activity can potentially be determined with the breath‐holding test. This test could easily be performed during a routine MRI examination. Magn Reson Med 42:608–611, 1999. © 1999 Wiley‐Liss, Inc.