The threshold values of dif- ferent weaning indices and measured respiratory parameters obtained in our COPD patients could differ from those men- tioned by Esteban et al., who reported weaning success rates of 70% for PSV but their study was performed on a heteroge- neous population, and only 20% of the patients enrolled had COPD [7]. Our parameters of weaning indices in both groups were comparable with that found by Alvisi et al. [28]. A finding that helps the comparison to be fair in our study was that the mean values for all these parameters of weaning indices in both groups were found to be in the appropriate range for successful weaning and there was no significant difference between ASV and PSV when these data were compared. It is important to emphasis that both ASV and PSV are suitable methods for successful weaning of patients with COPD from MV, although ASV proved to be more successful according to the measured parameters in the current study. Brochard et al. compared syn- chronized intermittent mandatory ventilation, PSV, and T- tube weaning method, and found that PSV was superior to the other two methods of weaning from mechanical ventila- tion. Their finding of PSV group was different to our results, as we have to take into account the differences in the inclusion criteria [29].