PaCO 2 trajectories in mechanically ventilated patients with COVID-19: A population-based cohort study.

OBJECTIVE: To identify PaCO2 trajectories and assess their associations with mortality in critically ill patients with coronavirus disease 2019 (COVID-19) during the first and second waves of the pandemic in Denmark.

DESIGN: A population-based cohort study with retrospective data collection.

PATIENTS: All COVID-19 patients treated in eight intensive care units (ICUs) in the Capital Region of Copenhagen, Denmark, between March 1 2020 and March 31 2021.

MEASUREMENTS: Data from the electronic health records were extracted, and latent class analyses were computed based on up to the first 3 weeks of mechanical ventilation to depict trajectories of PaCO2 levels. Multivariable Cox regression analyses were used to calculate adjusted hazard ratios (aHRs) for SAPS3, sex and age with 95% confidence intervals (CIs) for death according to PaCO2 trajectories.

MAIN RESULTS: In latent class trajectory models, including 25,318 PaCO2 measurements from 244 patients, three PaCO2 latent class trajectories were identified: a low isocapnic (Class I; n = 130) a high isocapnic (Class II; n = 80), as well as a progressively hypercapnic (Class III; n = 34) trajectory. Mortality (was higher in Class II (aHR: 2.16 (1.26-3.68)) and Class III (aHR: 2.97 (1.63-5.40))) compared to Class I (reference).

CONCLUSION: Latent class analysis of arterial blood gases in mechanically ventilated COVID-19 patients identified distinct PaCO2 trajectories, which were independently associated with mortality.