Respiratory failure, often secondary to severe respiratory disease, can be divided into type I respiratory failure and type II respiratory failure according to the results of blood gas analysis. The criteria for type I respiratory failure blood gas are: partial pressure of oxygen below 60 mmHg and reduced or normal partial pressure of carbon dioxide, which are mainly seen in interstitial lung disease, pulmonary fibrosis, pulmonary embolism, etc. The criteria for type II respiratory failure blood gas analysis are: partial pressure of oxygen below 60 mmHg and partial pressure of carbon dioxide above 50 mmHg, which are mainly seen in acute exacerbation of chronic obstructive pulmonary disease, emphysema, chronic bronchitis, etc.