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.