The co-occurrence of chronic obstructive pulmonary disease and obstructive sleep apnea hypopnea syndrome is called “overlap syndrome”. In patients with overlap syndrome, pulmonary ventilation, ventilation dysfunction and sleep apnea can occur simultaneously, which eventually leads to more severe hypoxemia and hypercapnia. As a result, patients are awakened repeatedly at night, with damaged sleep structure and nighttime respiratory stability, aggravated condition, and increased hospitalization rate and the mortality of overlap syndrome patients. Pulmonary hyperinflation in patients with chronic obstructive pulmonary disease will lead to the reduction of arousal threshold. And chronic obstructive pulmonary disease accompanied by low arousal threshold in patients is one of the main factors of the onset of overlap syndrome patients; therefore, the research about the relation between emphysema and arousal threshold and the exploration of nighttime awakening mechanism in patients with emphysema stimulus overlap syndrome can explain from another perspective, the reason why the overlap syndrome has worse sleep quality than the single disease, and provide some basis for screening patients with low arousal threshold.