Arterial Blood Gas as a Predictor of Mortality in COVID Pneumonia Patients Initiated on Noninvasive Mechanical Ventilation: A Retrospective Analysis
Bhavna Gupta, Gaurav Jain, Saurabh Chandrakar, Nidhi Gupta, Ankit Agarwal, Bhavna Gupta, Gaurav Jain, Saurabh Chandrakar, Nidhi Gupta, Ankit Agarwal
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 PaO2, PaCO2, A-a gradient, AO2, 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 PaO2, PaCO2, A-a gradient, AO2, 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 Predictor of Mortality in COVID Pneumonia Patients Initiated on Noninvasive Mechanical Ventilation: A Retrospective Analysis. Indian J Crit Care Med 2021;25(8):866-871.
Keywords: COVID-19 Acute Respiratory Distress Syndrome; Critically ill adults; Mortality predictors.
Conflict of interest statement
Source of support: Nil Conflict of interest: None
Copyright © 2021; Jaypee Brothers Medical Publishers (P) Ltd.
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References
- Li X, Ma X. Acute respiratory failure in COVID-19: is it “typical” ARDS? Crit Care. 2020;;24((1):):198.. doi: 10.1186/s13054-020-02911-9.. DOI:
- Armstrong RA, Kane AD, Cook TM. Outcomes from intensive care in patients with COVID-19: a systematic review and meta-analysis of observational studies. Anaesthesia. 2020;;75((10):):1340––1349.. doi: 10.1111/anae.15201.. DOI:
- Grasselli G, Greco M, Zanella A, Albano G, Antonelli M, Bellani G, et al. Risk factors associated with mortality among patients with COVID-19 in intensive care units in Lombardy, Italy. JAMA Intern Med. 2020;;180((10):):1345––1355.. doi: 10.1001/jamainternmed.2020.3539.. DOI:
- Sarkar M, Niranjan N, Banyal PK. Mechanisms of hypoxemia. Lung India. 2017;;34((1):):47––60.. doi: 10.4103/0970-2113.197116.. DOI:
- Dhont S, Derom E, Braeckel E, Depuydt P, Lambrecht BN. The pathophysiology of ‘happy’ hypoxemia in COVID-19. Respir Res. 2020;;21((1):):198.. doi: 10.1186/s12931-020-01462-5.. DOI:
- Sharma S, Hashmi M, Burns B. Alveolar gas equation. Treasure Island (FL); 2020.. In:
- Brosnahan S, Jonkman A, Kugler M, Munger J, Kaufman D. COVID-19 and respiratory system disorders. Arterioscler Thromb Vasc Biol. 2020;;40((11):):2586––2597.. doi: 10.1161/ATVBAHA.120.314515.. DOI:
- Burnham EL, Janssen WJ, Riches DH, Moss M, Downey GP. The fibroproliferative response in acute respiratory distress syndrome: mechanisms and clinical significance. Eur Respir J. 2014;;43((1):):276––285.. doi: 10.1183/09031936.00196412.. DOI:
- Avci S, Perincek G. The alveolar-arterial gradient, pneumonia severity scores and inflammatory markers to predict 30-day mortality in pneumonia. Am J Emerg Med. 2020;;38((9):):1796––1801.. doi: 10.1016/j.ajem.2020.05.048.. DOI:
- Farina G, Gianstefani A, Salvatore V, Anziati M, Baldassarri F, Beleffi M, et al. Alveolar-to-arterial oxygen gradient: role in the management of COVID-19 infection mild population. Res Sq [Internet] 2021. doi: 10.21203/-100668/v1.. DOI:
- Gilbert R, Keighley JF. The arterial-alveolar oxygen tension ratio. An index of gas exchange applicable to varying inspired oxygen concentrations. Am Rev Respir Dis. 1974;;109((1):):142––145.. doi: 10.1164/arrd.1974.109.1.142.. DOI:
- Xie J, Tong Z, Guan X, Du B, Qiu H. Clinical characteristics of patients who died of coronavirus disease 2019 in China. JAMA Netw Open. 2020;;3((4):):e205619.. doi: 10.1001/jamanetworkopen.2020.5619.. DOI:
- Garciá-Tardón N, Abbes AP, Gerrits A, Slingerland RJ, Den Besten G. Laboratory parameters as predictors of mortality in COVID-19 patients on hospital admission. J Lab Med. 2020;;44((6):):357––359.. doi: 10.1515/labmed-2020-0087.. DOI:
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