Change in Middle Cerebral Artery Velocity over Time to an Acute and Sustained Stimulus

Little is known of the temporal cerebral blood flow response to a chemical stimulus consisting of increased PCO2 measured over time. Currently, there is only one study suggesting multiple phases in the CBF-CO2 response. Time constants of middle cerebral artery blood velocity (MCAV) response to a change in PETCO2 have been reported to be between 3 and 99.4 s. We studied the MCAV response in 28 subjects (10 females) to a sustained +10 mmHg above baseline (10 min) acute increase of PETCO2. We found that there were three distinct MCAV response patterns among subjects. Additionally, the responses of males and females differed. These studies suggest that there are multiple overlapping mechanisms controlling the chemoresponse of cerebral blood vessels and that these mechanisms may differ between men and women.MAS