Figure 3.

Physiological changes in early stages of cerebrovascular disease. For increasing levels of impairment and cerebral perfusion pressure (CPP) reduction, cerebral hemodynamics adjust in a manner that depends on the adequacy of tissue-level compensation mechanisms. (A) Cerebral blood volume (CBV) can be maintained in mild stages of disease through microvascular autoregulation, which in turn (B) reduces cerebrovascular reactivity (CVR), or the further abilities of vessels to respond to a vasoactive stimulus. (C) When CVR is exhausted, cerebral blood flow (CBF) reduces if CPP reduces further. (D) Throughout these stages, microvascular atherosclerotic burden and/or damage to arteriolar smooth muscle may lead to increases in CVR_DELAY, or the time required for microvessels to vasodilate. (E) When these mechanisms become collectively inadequate to maintain sufficient oxygen delivery to tissue, the oxygen extraction fraction (OEF; ratio of oxygen consumed to oxygen delivered) will begin to increase.