Related Experiment Video
Updated: Jul 9, 2025
Expired CO2 Measurement in Intubated or Spontaneously Breathing Patients from the Emergency Department
Published on: January 29, 2011
Correlation and Agreement Between the CO2 Gap Obtained From Peripheral Venous Blood and From Mixed Venous Blood in
Daniele Orso1, Chiara Molinari1, Giacomo Bacchetti1
1Anaesthesia and Intensive Care Medicine Department, ASUFC University Hospital of Udine and Department of Medical Science (DAME), University of Udine, Udine, Italy.
Background:
Venous-arterial CO2 difference (Pv-aCO2) is a valuable marker that can identify a subset of patients in shock with inadequate cardiac output to meet tissue metabolic requirements. Some authors have found that Pv-aCO2 levels calculated from mixed vs central venous blood demonstrate a linear relationship. The purpose of this study is to determine whether there is a linear relationship between Pv-aCO2 obtained with peripheral venous blood (Pv-aCO2p) and with mixed venous blood, and the agreement between the 2 measures.
Methods:
This was a prospective, single-center, observational clinical study enrolling mechanically ventilated patients in septic shock during the first 24 hours following admission to the intensive care unit.
Results:
The Bravais-Pearson r-coefficient between Pv-aCO2 and Pv-aCO2p was .70 in 38 determinations (95%CI .48-.83; P-value = 1.25 x 10^-6). The Bland-Altman bias was 4.11 mmHg (95%CI 2.82-5.39), and the repeatability coefficient was 11.05. Using the Taffe approach, the differential and proportional biases were 2.81 (95%CI .52-5.11) and 1.29 (95%CI .86-1.72), respectively.
Conclusion:
There was linear correlation between Pv-aCO2p and Pv-aCO2 in mechanically ventilated patients with septic shock. The bias showed a gradual increase in high Pv-aCO2 values in an upward trend.
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