Pulmonary encephalopathy is associated with respiratory insufficiency associated with various chest and lung diseases. The main cause of daytime sleepiness in pulmonary encephalopathy is abnormal central nervous system function due to hypoxia of brain tissue, carbon dioxide retention, and decreased arterial blood pH. Common causes include pulmonary disease and central nervous system lesions. 1. Lung diseases: Chronic obstructive pulmonary disease, severe lung injury, thoracic deformity, etc. lead to abnormal respiratory system function, and gas exchange in the lungs is seriously affected, which causes a significant decrease in blood oxygen saturation and carbon dioxide retention, which leads to cerebral tissue hypoxia and a decrease in arterial blood pH, resulting in daytime drowsiness. 2. Neurological lesions: Tumor, inflammation, trauma, etc. cause abnormalities in central nervous system function and affect the normal function of respiratory-related brain areas, which further leads to respiratory failure and pulmonary encephalopathy, resulting in related symptoms. When daytime sleepiness occurs in pulmonary encephalopathy, it is necessary to ensure that the respiratory tract is open, and most of them need to be treated by low-flow oxygen intake, standardized treatment under the guidance of doctors, and early control, so as to prevent irreversible damage.