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VOLUME 25 , ISSUE 8 ( August, 2021 ) > List of Articles

Original Article

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

Bhavna Gupta, Saurabh Chandrakar, Nidhi Gupta

Keywords : COVID-19 Acute Respiratory Distress Syndrome, Critically ill adults, Mortality predictors

Citation Information : Gupta B, Chandrakar S, Gupta N. 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.

DOI: 10.5005/jp-journals-10071-23917

License: CC BY-NC 4.0

Published Online: 12-08-2021

Copyright Statement:  Copyright © 2021; Jaypee Brothers Medical Publishers (P) Ltd.


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).


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  1. 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.
  2. 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.
  3. 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.
  4. Sarkar M, Niranjan N, Banyal PK. Mechanisms of hypoxemia. Lung India 2017;34(1):47–60. DOI: 10.4103/0970-2113.197116.
  5. 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.
  6. Sharma S, Hashmi M, Burns B. Alveolar gas equation. In: Treasure Island (FL); 2020.
  7. 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.
  8. 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.
  9. 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.
  10. 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/rs.3.rs-100668/v1.
  11. 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.
  12. 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.
  13. 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.
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