Invasive mechanical ventilation, one of the defining interventions in critical care medicine, is received by more than 20 million patients annually in intensive care units (ICUs) worldwide. In any given ICU, usually half or more of patients require invasive ventilatory support. Among those needing at least 2 days of mechanical ventilation, the ICU mortality rate is high (>30%), as is the proportion of patients with difficult or prolonged weaning (>35%).
