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High flow nasal oxygen therapy in COVID-19 critically ill patients with acute hypoxemic respiratory failure: A prospective observational cohort study
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  • Mohd Khan,
  • Jay Prakash,
  • Sudipto Banerjee,
  • Raman Kumar,
  • Pradip Kumar Bhattacharya
Mohd Khan
Rajendra Institute of Medical Sciences
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Jay Prakash
Rajendra Institute of Medical Sciences
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Sudipto Banerjee
Rajendra Institute of Medical Sciences
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Raman Kumar
Rajendra Institute of Medical Sciences
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Pradip Kumar Bhattacharya
Rajendra Institute of Medical Sciences
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Abstract

Background: Acute hypoxemic respiratory failure (AHRF) is common in COVID-19. Tracheal intubation in such patients is fraught with higher mortality, therefore, high flow nasal oxygen therapy (HFNOT) is being used in AHRF. In this study, we aimed to determine the impact of HFNOT on oxygenation status and also various predictors of HFNOT failure. Methods: A prospective observational cohort study was conducted in COVID-positive critically ill adult patients (aged>18 years) with AHRF, who were unable to maintain SpO2>90% on a non-rebreathing face mask at an oxygen flow ≥15 litres/minute. Respiratory variables (PaO2/FiO2, SpO2, and RR) before HFNOT (baseline), then at 1-hour, 6-hour, 7-day, and 14-day after HFNOT application, were recorded. Borg CR10 scale and visual analog scale were used to evaluate the subjective sensation of dyspnoea and comfort level respectively. Student’s t, Mann–Whitney U or Wilcoxon signed-rank tests were used as applicable. Multivariate logistic regression and Receiver-Operating Characteristic (ROC) analyses were performed to determine factors associated with HFNOT failure. Results: 114 patients were included with HFNOT failure rate of 29%. The Median PaO2/FiO2 ratio at baseline (before initiation of HFNOT) was 99.5 (80-110) which significantly increased at various time points (1-hour, 6-hour, 7-days, and 14-day) after HFNOT initiation in the successful group. Patients reported significant improvement in sensation of breathlessness (9 [8-10], 3 [2-4]; p<0.001) as well as in comfort level (2 [1-2], 8 [4-9]; p<0.001). Multivariate logistic regression analysis, SOFA>7, APACHE II>20, admission P/F ratio<100, D-dimer>2mg/L, IL-6>40 pg/mL, Random Blood Sugar (RBS)>250 mg/dL, 6-hour ROX Index<3.5, were independent prognostic factors of HFNOT failure. Conclusion: In COVID-19 patients with AHRF, the use of HFNOT significantly improved oxygenation levels at various time points after HFNOT initiation. Age, SOFA, APACHE II, and ROX scores, admission P/F ratio, IL-6, D-dimer, and RBS were independent prognostic factors of HFNOT failure in this cohort.