The concentration of inhaled oxygen is related to the way of oxygen inhalation and should not be generalized. There are three ways of oxygen administration for clinical treatment: first, low-flow oxygen administration; second, medium-flow oxygen administration; third, high-flow oxygen administration. The concentration of low-flow oxygen administration is 29%-33%, which is routinely used for chronic lung diseases, such as chronic bronchitis, emphysema, pulmonary heart disease decompensation, etc. The oxygen concentration should not be too high if the body is hypoxic, too high will lead to an increase in partial pressure of blood oxygen, which will reduce the reflex stimulation of the carotid sinus to the respiratory center leading to a decrease in ventilation, which will easily lead to the aggravation of carbon dioxide retention and aggravate the disease. The concentration of medium-flow oxygen administration is 37%-47%, which is commonly used in diseases such as bronchiectasis, severe pneumonia, pneumothorax and bronchial asthma. The concentration of high-flow oxygen administration is 50% or more, mostly used for critical or respiratory depression diseases, such as respiratory and cardiac arrest or acute respiratory distress syndrome, inhalation of toxic gases, which should be immediately resuscitated with high concentration or pure oxygen, but the use time should not be too long to avoid oxygen toxicity.