Category: RespirAct

Carbon Dioxide added late in Inspiration Reduces Ventilation-perfusion Heterogeneity without causing Respiratory Acidosis

Thomas V Brogan, H Thomas Robertson, Wayne J E Lamm, Jennifer E Souders, Erik R Swenson. J Appl Physiol (1985). 2004 May;96(5):1894-8. doi: 10.1152/japplphysiol.00160.2003. Epub 2003 Dec 5.
We have shown previously that inspired CO2 (3-5%) improves ventilation-perfusion (Va/Q) matching but with the consequence of mild arterial hypercapnia and respiratory acidosis. We hypothesized that adding CO2 only late in inspiration to limit its effects to the conducting airways would enhance Va/Q matching and improve oxygenation without arterial hypercapnia. CO2 was added in the latter half of inspiration in a volume aimed to reach a concentration of 5% in the conducting airways throughout the respiratory cycle.

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End-inspiratory Rebreathing Reduces the End-tidal to Arterial PCO2 Gradient in Mechanically Ventilated Pigs

Jorn Fierstra, Matthew Machina, Anne Battisti-Charbonney, James Duffin, Joseph Arnold Fisher, Leonid Minkovich. Intensive Care Med. 2011 Sep;37(9):1543-50. doi: 10.1007/s00134-011-2260-y. Epub 2011 Jun 7.
Purpose: Noninvasive monitoring of the arterial partial pressures of CO2 (PaCO2) of critically ill patients by measuring their end-tidal partial pressures of CO2 (PETCO2) would be of great clinical value. However, the gradient between PETCO2 and PaCO2 (PET-aCO2) in such patients typically varies over a wide range. A reduction of the PET-aCO2 gradient can be achieved in spontaneously breathing healthy humans using an end-inspiratory rebreathing technique.

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Non-invasive Accurate Measurement of Arterial PCO2 in a Pediatric Animal Model

Jorn Fierstra, Jeff D Winter, Matthew Machina, Jelena Lukovic, James Duffin, Andrea Kassner, Joseph A Fisher. J Clin Monit Comput. 2013 Apr;27(2):147-55. doi: 10.1007/s10877-012-9403-8. Epub 2012 Oct 26.
The PCO2 in arterial blood (PaCO2) is a good parameter for monitoring ventilation and acid-base changes in ventilated patients, but its measurement is invasive and difficult to obtain in small children. Attempts have been made to use the partial pressure of CO2 in end-tidal gas (PETCO2), as a noninvasive surrogate for PaCO2. Studies have revealed that, unfortunately, the differences between PETCO2 and PaCO2 are too variable to be clinically useful.

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