Non-invasive accurate measurement of arterial PCO2 in a pediatric animal model

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. We hypothesized that end-inspiratory rebreathing, previously shown to equalize PETCO2 and PaCO2 in spontaneously breathing humans, would also be effective with positive pressure ventilation. Eight newborn Yorkshire pigs were mechanically ventilated via a partial rebreathing circuit to implement end-inspiratory rebreathing. Arterial blood was sampled and tested for PaCO2. A variety of alveolar ventilations resulting in different combinations of end-tidal PCO2 (30-50 mmHg) and PO2 (35-500 mmHg) were tested for differences between PETCO2 and PaCO2 (PET-aCO2). The PET-aCO2 of all samples was (mean ± 1.96 SD) 0.4 ± 2.7 mmHg. Our study demonstrates that, in ventilated juvenile animals, end-inspiratory rebreathing maintains PET-aCO2 to what would be a clinically useful range. If verified clinically, this approach could open the way for non-invasive monitoring of arterial PCO2 in critically ill patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anesthesia / methods
  • Animals
  • Animals, Newborn
  • Arterial Pressure
  • Arteries / physiology
  • Blood Gas Analysis / instrumentation
  • Blood Gas Analysis / methods*
  • Carbon Dioxide / blood
  • Carbon Dioxide / chemistry*
  • Models, Animal
  • Monitoring, Intraoperative / methods
  • Partial Pressure
  • Pediatrics / methods
  • Pressure
  • Respiration*
  • Respiration, Artificial / methods*
  • Signal Processing, Computer-Assisted*
  • Swine


  • Carbon Dioxide