In summary, in our study, patients with severe COVID-19 pneumonia who were not fit for invasive ventilation and treated with CPAP, had extremely high mortality which was comparable to those who were treated with high flow O2 alone. These findings were also confirmed in the prospective arm of the study. Our findings should be further validated by analysing larger datasets where available or through large-scale randomised controlled trials and may lead to a crucial change of practice and more sensible resource allocation for both staff and equipment.