Predictors of prolonged weaning and survival during ventilator weaning in a respiratory ICU

An International Consensus Conference proposed classifying weaning into simple, difficult, and prolonged weaning. However, the usefulness of this classification in a respiratory intensive care unit (ICU) is unknown. The aims of the study were: (1) to compare the clinical characteristics and outcomes of patients from the three weaning groups in a respiratory ICU; and (2) to assess predictors for prolonged weaning and survival.

We prospectively studied 181 mechanically ventilated patients (131, 72% with chronic respiratory disorders) in whom weaning had been initiated, divided into simple (78, 43%), difficult (70, 39%), and prolonged (33, 18%) weaning. We compared the characteristics and outcomes among the three groups and determined the factors associated with prolonged weaning and survival in multivariate analysis.

Patients with simple and difficult weaning had similar characteristics and outcomes. A higher proportion of patients with prolonged weaning had chronic obstructive pulmonary disease, and these patients also had more complications, a longer stay and lower survival. Increased heart rate (≥105 min(-1), p < 0.001) and PaCO(2) (≥ 54 mmHg, p = 0.001) during the spontaneous breathing trial independently predicted prolonged weaning. In addition, the need for reintubation (p < 0.001) and hypercapnia during the spontaneous breathing trial (p = 0.003) independently predicted a decreased 90-day survival.

Because of the similar characteristics and outcomes, the differentiation between simple and difficult weaning had no relevant clinical consequences in a respiratory ICU. Patients with prolonged weaning had the worst outcomes. For the overall population, hypercapnia at the end of spontaneous breathing predicts prolonged weaning and a worse survival, and clinicians should implement measures aimed at improving weaning outcome.