Measurement of Cerebrovascular Reactivity as Blood Oxygen Level-Dependent Magnetic Resonance Imaging Signal Response to a Hypercapnic Stimulus in Mechanically Ventilated Patients.

Background: Impaired cerebrovascular reactivity (CVR) is an important prognostic marker of stroke. Most measures of CVR lack (1) a reproducible vasoactive stimulus and (2) a high time and spatial resolution measure of cerebral blood flow (CBF), particularly for mechanically ventilated patients. The aim of our study was to investigate the feasibility of measuring CVR using sequential gas delivery circuit and gas blender for precise targeting of end-tidal PCO (PetCO), and blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) signal as a surrogate of CBF, in mechanically ventilated patients.