ObjectiveTo compare the difference of respiratory mechanics parameters between three different spontaneous breathing trials on COPD patients in weaning process. Methods17 patients with COPD underwent mechanical ventilation for at least 48 hours who were stable and ready for weaning were enrolled. All patients underwent three spontaneous breathing trials, ie, automatic tube compensation (ATC,compensation level 100%),low level pressure support ventilation (PSV,7 cm H2O) and T-piece. Each spontaneous breathing trials continued for 10 minutes. Before each autonomous respiration experiment ended,the respiratory mechanics parameters including high airway pressure (PIP),breathing rate (RR),blood oxygen saturation (SaO2),airway occlusion pressure at 0.1 second (P0.1),maximal inspiratory mouth pressure(Pimax) and rapid shallow breathing index (RSBI) were measured. Their differences between three spontaneous breathing trials were compared. Results12 patients successfully completed three different methods of spontaneous breathing test. Compared with the T-piece,P0.1,Pimax,RSBI and RR in the COPD patients using low level PSV and ATC were significantly decreased while VT and SaO2 were increased. The difference of each parameter in the low level PSV group and the ATC group had statistical significance compared with T-piece group (P<0.05). Compared with the low PSV group,P0.1,Pimax,RSBI and RR in ATC group were elevated while PIP,VT and SaO2 were reduced. The differences of P0.1,Pimax,RSBI,PIP and RR between two groups were statistically significant (P<0.05). ConclusionFor COPD patients in weaning process with spontaneous breathing trial,both low levels of PSV and ATC are better than T-piece,and the patients are more comfortable with ATC100% than PSV.