Figure 3.

Distribution of none, mild, moderate or severe pre-existing conditions between treatments. Pre-existing comorbidities were scored by the treating physician. Mild disease was defined as pre-existing illnesses without any medical impairments, moderate disease as disease with mild dysfunctions and need for regular medication intake, and severe disease as requiring regular medical attention. Treatments: monitoring; insufflation of oxygen (O²); non-invasive ventilation (NIV); invasive ventilation; and extracorporeal membrane oxygenation (ECMO).