Category: RespirAct

Sequential Gas Delivery Provides Precise Control of Alveolar Gas Exchange

Fisher JA, Iscoe S, Duffin J. Respiratory Physiology & Neurobiology, 31 Jan 2016, 225:60-69 doi: 10.1016/j.resp.2016.01.004
 
Of the factors determining blood gases, only alveolar ventilation (VA) is amenable to manipulation. However, current physiology text books neither describe how breath-by-breath VA can be measured, nor how it can be precisely controlled in spontaneously breathing subjects. And such control must be effected independent of minute ventilation (VE) and the pattern of breathing. Control of VA requires the deliberate partition of inhaled gas between the alveoli and the anatomical deadspace.

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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.

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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.

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