We have reported that CPAP treatment improved the walking capacity of overlap syndrome patients.

However, the previous study was not randomized, double blinded study. Therefore, we design a prospective, randomized, double blinded, controlled, cross-over trial to confirm this finding.

inclusion criteria :

• COPD : FEV1/FVC < 70%, no response to bronchodilator (FEV1 change <12% and <200ml)
• OSA : AHI > 15/h, obstructive type predominant

exclusion criteria :

• any malignancy
• pregnancy
• claustrophobia
• age<18

primary outcome : exercise capacity (walking distance (meter), measured by incremental shuttle walking test)

Method : For those fit in criteria. CPAP titration will be performed to determine the optimal pressure Baseline measurement : incremental shuttle walking test, urine catecholamine, heart rate variability, muscle power and other baseline characteristics Randomized those patients to group A and group B group A : CPAP treatment with optimal pressure for 1 month, repeat measurement change CPAP treatment to sham pressure 5cm H2O for 1 month, repeat measurement group B : CPAP treatment with sham pressure for 1 month, repeat measurement change CPAP treatment with optimal pressure for 1 month, repeat measurement

Inclusion Criteria:

• FEV1/FVC < 70%, no response to bronchodilator (FEV1 change <12% and <200ml)
• OSA : AHI > 15/h, obstructive type predominant

Exclusion Criteria:

• any malignancy
• pregnancy
• claustrophobia
• age<18