Predictors of weanability.

It is generally accepted that mechanical ventilation should be discontinued at the earliest possible time in the course of a patient's illness. An empirical weaning approach exclusively based on clinical judgement without the recognition of predictors may cause prolonged mechanical ventilation. Therefore a variety of physiologic parameters have been investigated as so called "predictors" of weaning outcome. Weaning strategies exclusively based on predictors may miss the pathophysiological complexity underlying difficult weaning. Therefore, combining measurements of physiologically based parameters--performed during prescribed spontaneous breathing trials--and clinical judgement improve weaning outcome data.