Patients with acute hypoxemic respiratory failure (AHRF) due to COVID-19 undergoing High Flow Therapy (HFT) before intubation presented an increased risk of mortality when intubation was delayed. We designed a prospective study seeking biomarkers for early prediction of HFT failure. An analytical value in blood could be more stable than the ROX index since it will not depend on the vital signs that the patient presents at that moment. We defined HFT failure as the need to scale the treatment to Non-Invasive Positive Pressure Ventilation (NPPV). The needs were respiratory rate >25, oxygen saturation of <90% despite being on flow of 60 l·min-1 and FiO2 1 or levels of PaO2/FiO2 ratio <100mmHg. The all-treatment population included all subjects enrolled in the trial. 139 patients were enrolled after starting HFT. The Pearson chi-squared test was used to compare the main study outcomes. These included the incidence of intubation, the cumulative incidence of mortality at 30 days, the cumulative incidence of mortality at 1 year, and the composite outcome of intubation or death at the end of the trial. Kaplan-Meyer plot was used to illustrate the time to HFT failure. The Cox regression model was used to estimate the hazard ratio for HFT failure for all the parameters. All were measured or collected at baseline. Lower levels of bicarbonate, thrombocytopenia, and higher levels of C-reactive protein (CRP), lactate dehydrogenase (LDH), creatinine, and glucose are early blood biomarkers independently associated with HFT failure.

SUMMARY AT A GLANCE Higher levels of C-reactive protein and lactate dehydrogenase in patients with COVID-19 pneumonia allow us to early detect patients requiring intubation with an apparent good response to high-flow oxygen therapy.

The authors have declared no competing interest.

NCT05094661

https://clinicaltrials.gov/study/NCT05094661

This study did not receive any funding

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was performed in accordance with the Declaration of Helsinki. This human study was approved by Comite Etica Investigacio Hospital Universitari Germans Trias i Pujol - approval: PI-20-372. The study's clinical trial registration number is NCT05094661 registered with https://clinicaltrials.gov. Participant registration took place from Feb-2021 to Oct-2021. All adult participants provided written informed consent to participate in this study.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.