Measuring oxygen extraction fraction (OEF) may prove a useful clinical tool for assessing brain oxygen consumption. Dual-calibrated fMRI is used to map voxel-wise OEF across grey-matter and requires respiratory challenge (hypercapnia and hyperoxia). However, this method presents challenges to clinical implementation. Conversely, OxFlow provides a global estimate of OEF, has a shorter acquisition time and does not require respiratory challenge. Here we examine the relationship between both approaches for measuring OEF, revealing a significant association between methods. While further investigation is required, OxFlow may offer additional clinical utility for measuring cerebral oxygen consumption.