A 37-year-old worker during a fire ended up in the area of high CO. He was delivered to a hospital in unconscious state. Objectively: the skin of his face and hands is crimson. Respiration rate is 20/min. ECG: alterations specific for hypoxic myocardium. Hourly diuresis is 40 ml. Blood test: erythrocytes – 4.5 × 1012/L, Нb- 136 g/L, color index – 0.9, ESR - 3 mm/hour, carboxyhemoglobin – 5%. What criterion allows determining the severity of the patient’s condition?