Outcomes
The primary outcome of the study was a composite of all-cause death or
invasive mechanical ventilation, whereas the secondary outcomes were in
hospital all-cause mortality and the requirement for invasive mechanical
ventilation. The mortality rates in patients with COVID-19 depend
largely on the need to start oxygen supply and the level of respiratory
support [14]. Therefore, patients were divided into two groups
according to oxygen saturation and the requirement for oxygen supply at
enrolment, that is, with oxygen saturation at rest ≤93% (group 1) and
>93% (group 2). The study outcomes were evaluated
separately in the two groups. Primary and secondary end-points, if met,
were determined prospectively for treated patients and retrospectively
by chart review for control patients.