Emergency complications develops in ~20% of severe/critical COVID patients.It results from excessive pathological immune response to viral pathogen.The cytokine storm that follows is a form of virus induced haemophagic lymphohistiocytosis.
ARDS causes severe oxygen diffusion impairment.The severity of ventilatory impairment can be quantified by PF Ratio; See link for PF Ratio calculation:
Mild – PF ratio 200-300mmHg
Moderate – PF ratio 100-200mmHg
Severe – PF ratio <100mmHg
Many online calculators are available online, this is one such example:
