The determination of respiratory failure in advanced stage of lung cancer is based on the results of blood gas analysis, which can be diagnosed as respiratory failure when the characteristics of blood gas analysis reach arterial blood oxygen partial pressure <60mmHg with or without carbon dioxide partial pressure >50mmHg. Respiratory failure is divided into type I and type II. Type I respiratory failure is simple hypoxia, with arterial oxygen partial pressure <60mmHg and arterial carbon dioxide partial pressure reduced or normal in blood gas analysis. type II respiratory failure is hypercapnic respiratory failure, with arterial oxygen partial pressure <60mmHg accompanied by carbon dioxide partial pressure >50mmHg in blood gas analysis. Patients with advanced lung cancer may have insufficient ventilation due to airway obstruction by inflammation and mass, and airway pathology, as well as reduced lung compliance or poor lung blood supply due to lung parenchyma or interstitial involvement, and disproportionate ventilation and blood flow, leading to hypoxia, with or without carbon dioxide retention, resulting in respiratory failure. Clinical manifestations of respiratory failure may include dyspnea, low blood pressure, cyanosis due to hypoxia, drowsiness, apathy, and other mental states.