This analysis of our prospective RCT on using HBOT in severe COVID-19 confirmed the effectiveness of randomisation (except for IL-6), showed a clear trend towards fewer deaths in the HBOT group, confirmed the possibility of safely conducting HBOT in this patient group, showed a lower need for normobaric oxygenation in the group of patients treated with HBOT and demonstrated significant beneficial effects of HBOT on CRP, ferritin, LDH and CD3. Here, CRP is linked to COVID-19.