Utility of arterial CO2 - End-tidal CO2 gap as a mortality indicator in the surgical ICU

Published:October 20, 2022DOI:


      • The PaCO2-ETCO2 gap is defined as the absolute difference between the two values.
      • The PaCO2-ETCO2 gap is a valid predictor of mortality in SICU and is comparable to other biomarkers.
      • Patients withsustained PaCO2-ETCO2 gap above 10 after the first 24 h of SICU admission had a higher mortality rate.



      End-tidal CO2 (ETCO2) measurements have been an established tool for assessing critically ill patients. We aim to show that PaCO2-ETCO2 gap can be used as a predictor of mortality over a 7-day ICU stay.


      A retrospective chart review was performed on intubated surgical/trauma patients with documented ETCO2. We performed a univariate analysis and a receiver operating characteristic (ROC) curve.


      Thirty-four patients were included. Patients who died were found to have longer days on vasopressors, and higher lactic acid levels on days 2–5, and 7. PaCO2-ETCO2 gap was higher on days 2–4 in those that died. Using ROC, days 2 and 4 PaCO2-ETCO2 gaps had good sensitivities, comparable to lactic acid sensitivity, in predicting mortality.


      PaCO2-ETCO2 gap was shown to be comparable to lactic acid in predicating mortality. Using this surrogate may aid to predict the clinical course in the ICU.


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