Figure 4.

Modelled CBF responses needed to preserve the [O₂]/[CO₂] ratio in tissue in response to increased CMRO₂ and hypercapnia. (a) With increasing O₂ metabolism, the required CBF change is shown for three different values of the baseline OEF (the red line is the typical value for the brain). Dashed lines show constant coupling ratios n of the fractional CBF change to the fractional CMRO₂ change. The shaded area between n = 1.8 and n = 4 shows the approximate range of experimental results. (b) The required CBF change for increasing arterial CO₂ shown for the same values of baseline OEF, with dashed lines indicating constant slope values, and the shaded area between slopes of 3 and 7% mmHg⁻¹ approximates the range of reported experimental values.