Intracranial and extracranial CO2 vasomotor reactivity: assessment, approaches and clinical applications

Cerebral blood flow (CBF) describes the volume of blood flowing through the blood vessels that supply the brain. The ability to regulate CBF can have profound effects on important cognitive processes and loss of such regulation can lead to serious consequences to brain homeostasis due to susceptibility to harmful systemic blood pressure changes. Partial pressure of carbon dioxide (PaCO2) is a key mediator of CBF, causing decreased CBF in low PaCO2 and increased CBF in high PaCO2, facilitated through changes in the vasculature known as cerebrovascular reactivity (CVR). CVR is able to regulate CBF by dilating or constricting blood vessels in response to PaCO2. Extensive research has been published investigating CVR, identifying that lower CVR, is associated with an increased risk of mortality and reflects an impaired vascular system.