The science of weaning: when and how?

Weaning patients from long-term mechanical ventilation continues to be a goal of clinicians and scientists and the hospitals charged with their care. This article describes the science of the "wean" and the "how" of weaning. A goal of scientists has been to develop predictors that determine accurately the optimal time to initiate weaning. Unfortunately to date none has emerged as superior. Quite simply, predictors do not predict. In contrast, methods that decrease variation in care practices have demonstrated positive outcomes. The methods include protocols for weaning trials and sedation and other system initiatives inclusive of a multidisciplinary plan of care or clinical pathway.