Clinical prediction scores predicting weaning failure from invasive mechanical ventilation: Role and limitations

Table 2 Classification of patients on the basis of weaning process

Simple weaning	Initiation of weaning to successful extubation in the first attempt without encountering any difficulty
Difficult weaning	Failed initial weaning and requirement of up to 3 SBTs or as long as 7 days from the first SBT to achieve weaning success
Prolonged weaning	Failed at least 3 weaning attempts or require 7 days or more of weaning after the first SBT

SBT: Spontaneous breathing trial.