Category: RespirAct

Magnetic Resonance Imaging–Based Cerebrovascular Reactivity and Hemodynamic Reserve: A Review of Method Optimization and Data Interpretation

Joseph A. Fisher, Lashmi Venkatraghavan and David J. Mikulis. Stroke. 2018;49:2011–2018.
Physiological Control of Cerebral Blood Flow
Given adequate perfusion pressure and nonlimiting intracranial or venous pressure, cerebral blood flow (CBF) is regulated to match cerebral metabolic rate of oxygen (CMRO2). Variations in perfusion pressure are addressed by adjusting downstream vascular resistance, termed autoregulation.

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Non-invasive Prospective Targeting of Arterial P(CO2) in Subjects at Rest

Shoji Ito, Alexandra Mardimae, Jay Han, James Duffin, Greg Wells, Ludwik Fedorko, Leonid Minkovich, Rita Katznelson, Massimiliano Meineri, Tamara Arenovich, Cathie Kessler, Joseph A Fisher. J Physiol. 2008 Aug 1;586(15):3675-82. doi: 10.1113/jphysiol.2008.154716. Epub 2008 Jun 19.
Accurate measurements of arterial P(CO2) (P(a,CO2)) currently require blood sampling because the end-tidal P(CO2) (P(ET,CO2)) of the expired gas often does not accurately reflect the mean alveolar P(CO2) and P(a,CO2). Differences between P(ET,CO2) and P(a,CO2) result from regional inhomogeneities in perfusion and gas exchange.

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Effects of Carbonic Anhydrase Inhibition on Ventilation-perfusion Matching in the Dog Lung

E R Swenson, H T Robertson, M P Hlastala. J Clin Invest. 1993 Aug;92(2):702-9. doi: 10.1172/JCI116640.
Lung carbonic anhydrase (CA) permits rapid pH responses when changes in regional ventilation or perfusion alter airway and alveolar PCO2. These pH changes affect airway and vascular resistances and lung compliance to optimize the balance of regional ventilation (VA) and perfusion (Q) in the lung. To test the hypothesis that these or other CA-dependent mechanisms contribute to VA/Q matching, we administered acetazolamide (25 mg/kg intravenously) to six anesthetized and paralyzed dogs and measured VA/Q relationships before and after CA inhibition by the multiple inert gas elimination technique.

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