The normal value of co2 partial pressure is 35-45 mmHg in normal people. If the patient’s partial pressure of oxygen is lower than 60 mmHg and partial pressure of carbon dioxide is higher than 50 mmHg, the clinical diagnosis of type II respiratory failure is confirmed. If the partial pressure of carbon dioxide is lower than 35 mmHg, the clinical consideration is respiratory alkalosis. Clinically, chronic obstructive pulmonary disease and chronic pulmonary heart disease can present with elevated partial pressure of carbon dioxide, and hyperventilation, such as bronchial asthma and pulmonary embolism, can present with respiratory alkalosis. When patients have abnormal partial pressure of carbon dioxide, we should actively search for the cause of the disease and take targeted treatment according to the cause.