SOD1 and chronic obstructive pulmonary disease: By ELISA assay, we could observe that the ROS and MDA levels in patients of NIPPV, IMT and sequential NIPPV + IMT groups were obviously reduced, but the activities of SOD and GSH were upregulated, compared those in patients in OT group (Fig. 6A-D), suggesting NIPPV, IMT and sequential NIPPV + IMT treatment could alleviate the oxidative stress of COPD patients.