Category: RespirAct

Neuroimaging Assessment of Cerebrovascular Reactivity in Concussion: Current Concepts, Methodological Considerations, and Review of the Literature

Michael J. Ellis, Lawrence N. Ryner, Olivia Sobczyk,10 Jorn Fierstra, David J. Mikulis, Joseph A. Fisher, James Duffin and W. Alan C. Mutch. Front Neurol. 2016; 7: 61. Published online 2016 Apr 29. doi: 10.3389/fneur.2016.00061
Concussion is a form of traumatic brain injury (TBI) that presents with a wide spectrum of subjective symptoms and few objective clinical findings. Emerging research suggests that one of the processes that may contribute to concussion pathophysiology is dysregulation of cerebral blood flow (CBF) leading to a mismatch between CBF delivery and the metabolic needs of the injured brain. Cerebrovascular reactivity (CVR) is defined as the change in CBF in response to a measured vasoactive stimulus.

The CO2 Stimulus for Cerebrovascular Reactivity: Fixing Inspired Concentrations vs. Targeting End-tidal Partial Pressures

Joseph A Fisher. J Cereb Blood Flow Metab. 2016 Jun;36(6):1004-11. doi: 10.1177/0271678X16639326. Epub 2016 Mar 21.
Cerebrovascular reactivity (CVR) studies have elucidated the physiology and pathophysiology of cerebral blood flow regulation. A non-invasive, high spatial resolution approach uses carbon dioxide (CO2) as the vasoactive stimulus and magnetic resonance techniques to estimate the cerebral blood flow response. CVR is assessed as the ratio response change to stimulus change. Precise control of the stimulus is sought to minimize CVR variability between tests, and show functional differences.

Non-invasive Measurement of Cardiac Output Using an Iterative, Respiration-based Method

M Klein, L Minkovich, M Machina, M Selzner, V N Spetzler, J M Knaak, D Roy, J Duffin, J A Fisher. Br J Anaesth. 2015 Mar;114(3):406-13. doi: 10.1093/bja/aeu377. Epub 2014 Dec 8.
Background: Current non-invasive respiratory-based methods of measuring cardiac output [Formula: see text] make doubtful assumptions and encounter significant technical difficulties. We present a new method using an iterative approach [Formula: see text], which overcomes limitations of previous methods.