Evaluation of the Daily Change in PaO2/FiO2 Ratio as a Predictor of Abnormal Chest X-rays in Intensive Care Unit Patients Post Mechanical Ventilation Weaning: A Retrospective Cohort Study

Abstract

Background and Objectives: The routine daily chest X-ray (CXR) strategy is no longer recommended in intensive care unit (ICU) patients. However, it is difficult for intensivists to collectively accept the on-demand CXR strategy because of the ambiguous clinical criteria for conducting CXRs. This study evaluated the predictive value of the change in PaO2/FiO2 (PF ratio) for abnormal CXR findings in ICU patients after mechanical ventilation (MV). Materials and Methods: A retrospective cohort study was conducted between January 2016 and March 2021 on ICU patients with MV who had at least 48 h of MV, and stayed at least 72 h in the ICU post-MV. Routine daily CXRs and daily changes in the PF ratios were investigated during the three days post-MV. Results: The 186 patients included in the study had a median age of 77 years (interquartile range: 65–82), and 116 (62.4%) were men. One hundred and eight (58.1%) patients had abnormal CXR findings, defined as one or more abnormal CXRs among the daily CXRs during the three days post-extubation. The reintubation rate was higher in the abnormal CXR group (p = 0.01). Of the 558 CXRs (normal = 418, abnormal = 140) and PF ratios, the daily change in PF ratio had a significant predictive accuracy for abnormal CXR findings (AUROC = 0.741, p < 0.01). Conclusions: The change in PF ratio (the Youden index point: ≤−23) had a sensitivity of 65.7%, and a specificity of 79.9%. Based on these results, the daily change in the PF ratio could be utilized as a predictive indicator of abnormal CXRs in ICU patients after MV treatment.