Management of patients difficult to wean from the ventilator is a practical challenge in which professional nurses are deeply involved.The clinical research applied over the last years has tried to describe the characteristics of weaning phenomenon and the associated factors, to find predictive outcomes to guide clinical decisions, to search new strategies to conduct the protocols and to identify the most effective modes of weaning. In this paper a critical review of the current knowledge from a nursing perspective is done. The weaning conceptual model proposed by the American Association of Critical Care Nurses (AACN) group has been used as a theoretical framework.