Predictive Value of P۵۰ in the Clinical Outcome of the Patients with Severe COVID-۱۹ Pneumonia: A Retrospective Cohort Study

Background: The oxygen tension at half-saturation (P۵۰) was found to be increased in patients with respiratory distress. However, the roles of P۵۰ calculated upon hospital admission in predicting the prognosis of severe COVID-۱۹ patients are not well-investigated. Thus, this study aimed to investigate whether P۵۰ values obtained from hypoxic severe COVID-۱۹ patients upon admission were associated with a later need of invasive mechanical ventilation (IMV). This study also aimed at finding independent predictors of IMV. Materials and Methods: ۱۵۱ patients with confirmed severe COVID-۱۹ were enrolled in this study between August and December ۲۰۲۰. Overall, ۶۳ (۴۱.۷%) progressed to IMV, and ۸۸(۵۸.۲%) did not need IMV. Demographic data, clinical outcome, and laboratory measurements were recorded, and P۵۰ was calculated. P۵۰ that discriminated patients required IMV and patients did not require IMV was determined using the ROC curve. The risk factors for the need for IMV were identified through logistic regression. Results: The calculated P۵۰ of all patients was higher than the normal value (P<۰.۰۰۵). Moreover, P۵۰ was significantly higher in patients who required IMV (P=۰.۰۰۲). ROC curve verified the discriminatory ability of P۵۰, providing an area under the ROC curve of ۰.۶۴۷(۹۵%CI ۰.۵۵۸-۰.۷۳۶; P=۰.۰۰۲) for a cutoff of ۲۹.۲۹mmHg. Calculated P۵۰≥۲۹.۲۹mmHg was a risk factor for the need of IMV (OR=۳.۳۰۶, ۹۵%CI ۱.۶۷۶-۶.۵۲۵; P=۰.۰۰۱). In multivariate analysis, the independent predictors of the need for IMV were older age, male sex, high P۵۰, high aspartate transaminase, and low PO۲ (P<۰.۰۵). Conclusion: Calculated P۵۰ on hospital admission might serve as a promising predictor of IMV in severe COVID-۱۹.

Keywords:

COVID-۱۹ , Mechanical ventilation , P۵۰ , Pneumonia