Classification of patients according to the weaning process
| Group/category | Definition |
| Simple weaning | Patients who proceed from the initiation of weaning to successful extubation on the first attempt without difficulty |
| Difficult weaning | Patients who fail initial weaning and require up to three spontaneous breathing trials or as long as 7 days from the first spontaneous breathing trial to achieve successful weaning |
| Prolonged weaning | Patients who fail at least three weaning attempts or require >7 days of weaning after the first spontaneous breathing trial |