Category: RespirAct

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.

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.

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.