Safety related factors of endotracheal intubation in patients with severe Covid‐19 pneumonia  Severe covid‐19 pneumonia with ET  COVID‐19 endotracheal intubation  120, all, 18–90  Observational  Intervention details: other: severe covid‐19 pneumonia with ET, severe covid‐19 pneumonia undergoing endotracheal intubation  –  Primary: