Agreement between Arterial and End-tidal Carbon Dioxide in Adult Patients Admitted With Serious Traumatic Brain Injury

Neil Sardesai, Owen Hibberd, James Price, Ari Ercole, Ed B. G. Barnard


Low-normal levels of arterial carbon dioxide (PaCO2) are recommended in the acute phase of traumatic brain injury (TBI) to optimize oxygen and CO2 tension, and to maintain cerebral perfusion. End-tidal CO2 (ETCO2) may be used as a surrogate for PaCO2 when arterial sampling is less readily available. ETCO2 may not be an adequate proxy to guide ventilation and the effects on concomitant injury, time, and the impact of ventilatory strategies on the PaCO2-ETCO2 gradient are not well understood. The primary objective of this study was to describe the correlation and agreement between PaCO2 and ETCO2 in intubated adult trauma patients with TBI.

Materials and method

This study was a retrospective analysis of prospectively-collected data of intubated adult major trauma patients with TBI, admitted to the East of England regional major trauma centre (MTC), 2015–2019. This study was undertaken at Cambridge University Hospitals NHS Foundation Trust (CUH), United Kingdom—the MTC for the East of England Trauma Network, covering a population of 6.3 million people over 20,000km2.


During the study period 1746 patients were eligible for inclusion. 1051 patients met predefined exclusion criteria and n = 695 patients were included in the final analysis; per protocol (Fig 1).


This study demonstrates poor correlation between the PaCO2 and ETCO2 gradient for intubated adult patients with serious or more severe TBI. The presence of concomitant injuries was associated with a larger gradient. The magnitude of the gradient reduced during the first 120 hours of admission, particularly in patients with moderate-severe lung injury. A larger PaCO2 and ETCO2 gradient on admission was associated with increased mortality.


Amongst adult patients with TBI, the PaCO2-ETCO2 gradient was greater than previously reported values, particularly early in the patient journey, and when associated with concomitant injury. An increased PaCO2-ETCO2 gradient was associated with increased mortality.


The authors would like to thank Junli Awit and Jakub Jaworski for their help in creating the EMR data extract. We would also like to acknowledge the assistance of Assiah Mahmood and Jacques Bowman of the CUH Trauma Office in compiling the original data.

Citation: Sardesai N, Hibberd O, Price J, Ercole A, Barnard EBG (2024) Agreement between arterial and end-tidal carbon dioxide in adult patients admitted with serious traumatic brain injury. PLoS ONE 19(2): e0297113.

Editor: Wan-Jie Gu, Jinan University First Affiliated Hospital, CHINA

Received: September 7, 2023; Accepted: December 27, 2023; Published: February 2, 2024

Copyright: © 2024 Sardesai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: Subject to the terms of the HRA approval and Cambridge University Hospitals NHS Foundation Trust policy, data cannot be shared by the authors. Researchers with appropriate may apply for permission to access from [email protected] subject to HRA approval and Trust guidelines and review.

Funding: This research was supported by data analysts from the NIHR Cambridge Biomedical Centre (BRC 121520014).

Competing interests: The authors have declared that no competing interests exist.



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