Arterial Blood Gas as a Predictor of Mortality in COVID Pneumonia Patients Initiated on Noninvasive Mechanical Ventilation: A Retrospective Analysis

Abstract

Background: The alveolar–arterial oxygen (A–a) gradient measures the difference between the oxygen concentration in alveoli and the arterial system, which has considerable clinical utility. Materials and methods: It was a retrospective, observational cohort study involving the analysis of patients diagnosed with acute COVID pneumonia and required noninvasive mechanical ventilation (NIV) over a period of 3 months. The primary objective was to investigate the utility of the A–a gradient (pre-NIV) as a predictor of 28-day mortality in COVID pneumonia. The secondary objective included the utility of other arterial blood gas (ABG) parameters (pre-NIV) as a predictor of 28-day mortality. The outcome was also compared between survivors and nonsurvivors. The outcome variables were analyzed by receiver-operating characteristic (ROC) curve, Youden index, and regression analysis. Results: The optimal criterion for A–a gradient to predict 28-day mortality was calculated as ≤430.43 at a Youden index of 0.5029, with the highest area under the curve (AUC) of 0.755 ( p <0.0001). On regression analysis, the odds ratio for the A–a gradient was 0.99. A significant difference was observed in ABG predictors, including PaO 2 , PaCO 2 , A–a gradient, AO 2 , and arterial–alveolar (a–A) (%) among nonsurvivors vs survivors ( p -value <0.001). The vasopressor requirement, need for renal replacement therapy, total parenteral requirement, and blood transfusion were higher among nonsurvivors; however, a significant difference was achieved with the vasopressor need ( p <0.001). Conclusion: This study demonstrated that the A–a gradient is a significant predictor of mortality in patients initiated on NIV for worsening respiratory distress in COVID pneumonia. All other ABG parameters also showed a significant AUC for predicting 28-day mortality, although with variable sensitivity and specificity. Key messages: COVID-19 pneumonia shows an initial presentation with type 1 respiratory failure with increased A–a gradient, while a subsequent impending type 2 respiratory failure requires invasive ventilation. A significant difference was observed in ABG predictors, including PaO 2 , PaCO 2 , A–a gradient, AO 2 , and a–A (%) among nonsurvivors vs survivors. ( p -value <0.001). The vasopressor requirement, need for renal replacement therapy, total parenteral requirement, and blood transfusion need were higher among nonsurvivors than survivors; however, a significant difference was achieved with the vasopressor need ( p <0.001). How to cite this article: Gupta B, Jain G, Chandrakar S, Gupta N, Agarwal A. Arterial Blood Gas as a P...

Hypocapnia as a predictor of the need for non-invasive mechanical ventilation in subjects with SARS-CoV-2 related pneumonia

“…14 More directly a retrospective study on 165 covid subjects requiring NIMV showed that PaCO 2 levels are significantly lower in nonsurvivors. 15 Similarly, in a previous study we showed that the ratio between PaCO 2 levels and the fraction of inspired oxygen was able to predict the need for invasive mechanical ventilation independently from several already known predictors of severe disease. 16 In line with these studies, that indirectly demonstrated the predictive role of clinical worsening of hypocapnia, our data prospectively highlight its potential role in predicting the need for NIMV in a patient population entering the emergency department for acute respiratory failure related to SARS-CoV-2 infection, independently of a number of confounding factors.…”

Risk Factors for COVID-19 Adverse Outcomes in ICU Settings of Various Types Repurposed Hospitals

“…Для Анализ КОС и газов крови является важным способом оценки состояния пациента в ОРИТ. В нескольких исследованиях подтверждено, что рО₂ и рСО₂ в артериальной крови могут быть предикторами летального исхода в той или иной степени [11]. Вместе с тем они, как и значения рН, не вошли в мета-анализы значимых предикторов исхода COVID-19 [12,13].…”