Effectness of Treatment With Mechanical Insufflation-Exsufflation

Patients defined with impaired cough function as maximum expiratory pressure (MEP) \< 60cmH2O. Collected the patients in our surgical ICU who are able to reach 6-8CC/IBW under pressure support mode for 24 hours and MEP \< 60cmH2O. Then the patients will be allocated to 3 groups to receive (1) conventional CPT (control group) (2) MI-E (study group A) (3) MI-E plus CPT (study group B) until 48 hours after extubation. Reintubation rates, ICU mortality and post-extubation ICU length of stay will be analyzed to evaluate its effects.