1) Start chloroquine as early as possible.
2) Get blood transfusions.
Virus can absolutely wreck O2/CO2 transport/exchange in red blood cells. Once your red blood cells are wrecked, the medicine may not help. Must wait for new RBCs.
This would mean if the majority of your RBCs were badly compromised, ventilators may not help. Lack of oxygen is not the real problem—it's lack of properly function red blood cells.