The five commonly used parameters and normal values of the ventilator are, respiratory rate 16-20 times/minute, oxygen concentration 21%-100%, tidal volume 6-8 ml/ideal kilogram of body weight, inspiratory/expiratory ratio 1:1.5-1:2, inspiratory flow rate 40-100L/minute. 1. Respiratory rate: Normal adult respiratory rate is generally 16-20 times/minute, COPD (chronic obstructive pulmonary disease) and ARDS (acute respiratory distress syndrome) patients will be greater than this value. 2. Oxygen concentration: generally between 21%-100%, as long as the oxygenation index, i.e. PaO2 (partial pressure of arterial oxygen)/FiO2 (concentration of inhaled oxygen) is ideal, FiO2 (concentration of inhaled oxygen) should be as low as possible, and if the FiO2 is higher than 60%, then it is a high concentration of oxygen. 3. Tidal volume: the normal value is 6-8ml/ideal kilogram of body weight, which should be adjusted appropriately according to the clinical symptoms and the results of blood gas analysis in actual operation. 4. Inspiration and expiration ratio: 1:1.5-1:2.5 is the normal value; 5. Inspiratory flow rate: normal adult is generally 40-100L/min, even if long time oxygen inhalation is generally not more than 50%-60%. When the ventilator is used, the doctor needs to adjust the parameters according to the patient’s condition.