Noninvasive mechanical ventilation does not require the establishment of an invasive artificial channel, is simple and easy to perform, and has a relatively low incidence of serious complications associated with mechanical ventilation, but the patient should be awake and able to cooperate, be hemodynamically stable, and not require protection from endotracheal intubation, including that the patient is free of aspiration, has no severe gastrointestinal bleeding, has no increase in airway secretions, and has unfavorable sputum expectoration, has no facial trauma that interferes with the use of the nasal and face masks, and tolerates the use of the nasal or face mask. The patient’s unconsciousness and inability to cooperate actively are contraindications to the use of noninvasive ventilators, but in patients with chronic obstructive pulmonary disease who are unconscious due to carbon dioxide retention, noninvasive ventilators can still be used under close monitoring to see if their mental state can be turned around after the partial pressure of carbon dioxide drops.