To investigate the factors and mechanisms which may affect the sleep and cognitive function of patients with chronic obstructive pulmonary disease(COPD)and respiratory failure. To improve the clinical understanding and to find the evidences in order to intervene and treat in time.

The Pittsburgh sleep quality index(PSQI) scale. Montreal cognitive function (MoCA) and mini-mental state examination (MMSE) were used to evaluate the sleep and cognitive function in COPD groups and the healthy adult control group. The baseline data, sleep, and cognitive functions were then compared and analyzed.

The PSQI scores of COPD patients in respiratory failure group were higher than those in Non respiratory failure group and normal control group, but the total scores of MoCA and MMSE was obviously lower. The differences of total scores between each groups were statistically significant (P<0.05) . The spatial execution, nomenclature, concentration of attention, language calculation, abstract thinking and recall scores were significantly lower in patients with COPD combined with respiratory failure, especially combined with type Ⅱ respiratory failure. By contrast, there were no significant differences in short-term recall between the groups, but the differences in delayed recall were statistically significant(P<0.05). MoCA score and MMSE score were negatively correlated with PaCO₂, lactic acid, mMRC and CAT scores, and positively correlated with PaO₂ and FEV₁%pred. These correlations are statistically significant(P<0.05).

Patients with COPD have extensive cognitive impairment. And as the disease worsens, cognitive impairment is more pronounced. Respiratory failure may be one of the most important factors that aggravate the abnormal sleep and cognitive dysfunction in COPD patients. Its mechanism is related to hypoxemia, hypercapnia, lactic acidosis and so on.