2.7. Sample Size
Since the primary outcome was number of days spent on respiratory support, a difference of two days was set arbitrarily as a difference that would mean significant clinical effect. Considering that, the calculated sample size to detect a 2-day difference in number of days on respiratory support was 274 (137 patients in each group). However, the number of severe COVID-19 patients treated in the ICU in the study period was large; almost half of them did not meet inclusion criteria. Furthermore, the number of patients admitted to the ICU declined during the study period, so we were not able to include the planned number of patients.