Increased CO₂ leads to increased [H⁺], which activates voltage gated K⁺ channels. The resulting hyperpolarization of endothelial cells reduces intracellular calcium, which leads to vascular relaxation and hence vasodilatation (Kitazono et al. 1995; Nelson & Quayle, 1995).

Why does hypercapnia cause cerebral vasodilation?

Carbon dioxide (CO₂) has a profound and reversible effect on cerebral blood flow, such that hypercapnia causes marked dilation of cerebral arteries and arterioles and increased blood flow, whereas hypocapnia causes constriction and decreased blood flow [167,168].

Does hypercapnia cause vasodilation?

Hypercapnia induces cerebral vasodilation and increases cerebral blood flow (CBF), and hypocapnia induces cerebral vasoconstriction and decreases CBF. ... The increase in CBF was greater than that in CBV during hypercapnia, indicating an increase in vascular blood velocity.