Oxygen debt as a predictor of high-flow nasal cannula therapy failure in SARS-CoV-2 patients with acute respiratory failure: A retrospective cohort study

Background: Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is known for its rapid progression to acute hypoxemic respiratory failure (AHRF). The increased use of oxygen therapy during the pandemic and the progression of AHRF have highlighted the need to promptly determine the need for orotracheal intubation (OTI). Objetive: To determine the validity of quantitative measurement of oxygen debt (DEOx) according to arterial gases compared to the use of iROX in patients with high-flow nasal cannula (HFNC) therapy requirement, presenting with acute respiratory failure as a consequence of SARS-CoV-2 infection. In addition, we aimed to identify the factors associated with the need for orotracheal intubation (OTI). Methods: A retrospective observational cohort study of a database collected from patients with SARS-CoV-2 infection admitted to intensive care units with AHRF and had received HFNC upon admission during the Covid-19 pandemic (March 23, 2020 through August 02, 2021). The variables of interest were factors determining the predictive ability of DEOx and iROX. We used a multiple logarithmic regression model to correct for confounding and mixed-effects variables, and validated for OTI in patients treated with HFNC. Results: From a total of 373 patients treated with HFNC, 317 patients (84.9%) required invasive mechanical ventilation. APACHE II (AOR 1.44; 95% CI: 1.14–1.83, p 0,032), vasopressor use (AOR 27.7; 95% CI: 1.83 – 420,63, p 0,017), and DEOx (AOR 1.26; 95% CI: 1.10 – 1.44, p 0,001) were associated with the need for intubation. The predictive model between iROX and DEOx evidenced an AUC of 0.535 vs. 0.606, respectively, with a DEOx cut off point of 7.14 (±10.16, p < 0.01). DEOx as an independent factor of OTI presents an OR 2,48 with cut point 4.5 mlO2/kg (AUC 0.780, CI 95%, 0.753 – 0.808, p < 0.01). Conclusions: DEOx is a valuable measurment to identify the need for OTI in patients with SARS-CoV-2 who were under management with HFNC with a predictive value superior to iROX, being a reproducible and valid quantitative method for the need OTI that can be implemented in other critically illconditions. Further studies are required to characterize the usefulness of DEOx more precisely.