Oxygen concentration for type II respiratory failure is usually less than 35% and oxygen flow rate is 1-2 L/min. If it is an oxygen meter, the small ball should be between 1-2. If it is a home oxygen machine, the oxygen flow rate needs to be adjusted to 1-2, but long-term oxygen inhalation is required. Because type II respiratory failure is hypoxia with carbon dioxide retention, carbon dioxide inhibits the respiratory center after a long time in the body and requires low oxygen to stimulate the peripheral chemoreceptors, which then reflexively excite the respiratory center to maintain breathing. If the oxygen flow is high, the partial pressure of oxygen is normalized, the body is not hypoxic, the peripheral chemoreceptors are not working, and the respiratory center is still inhibited, so carbon dioxide retention will be further aggravated.