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Can we improve the estimate of arterial PCO2 from end-tidal PCO2?

Published online by Cambridge University Press:  16 August 2006

R. Fletcher  and
F. Boris-Möller
R. Fletcher
Affiliation:
Directorate of Anaesthesia, Central Manchester Hospitals NHS Trust, Manchester, UK
F. Boris-Möller
Affiliation:
Directorate of Anaesthesia, Central Manchester Hospitals NHS Trust, Manchester, UK
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Abstract

To use end-tidal PCO2 as a non-invasive estimate of arterial PCO2, one adds a nominal value, representing the arterial–end-tidal PCO2 difference. How much does one add? We hypothesized that, halving the ventilator rate and simultaneously doubling tidal volume, the immediate change in end-tidal PCO2 would be proportional to the original arterial-end-tidal PCO2 difference. We ventilated 31 patients at 20 breaths per minute (bpm), sampled arterial blood, and changed the rate to 10 bpm. The change in end-tidal PCO2 was, as hypothesized, positively correlated to the original arterial–end-tidal difference at 20 bpm (r = 0.64). End-tidal PCO2 increased in 23 patients. Thus, in theory, this method could offer some improvement in the estimate of arterial PCO2 from end-tidal. However, because of the considerable spread of values, a separate study is needed for verification

Keywords

carbon dioxidetensionarterialgradientsanaesthesiageneralrespirationartificialintermittent positive-pressure ventilation
Type
Original Article
Information
European Journal of Anaesthesiology , Volume 17 , Issue 5 , May 2000 , pp. 306 - 310
Copyright
2000 European Society of Anaesthesiology

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