Cerebrovascular reactivity (CVR) is assessed by dynamic MRI scanning, such as BOLD-fMRI during a hypercapnia gas challenge. Conventional CVR metrics do not account for individual vasoactive challenges in series. We study the relationship between vasoconstriction after the 1st hypercapnia challenge and CVR during the 2nd challenge, using a non-parametric method, Sen’s Slope, to estimate BOLD change. We show that vasoconstriction is directly proportional to the amplitude of CVR across a range of adult ages, as assessed by linear regression analysis. These results support our hypothesis that temporal features of a cerebrovascular challenge can provide additional insight on cerebrovascular physiology.