''Stealing effect'' during weaning from mechanical ventilation: The role of blood flow competition between respiratory muscles and cerebral cortex on weaning outcomes in the medical intensive care unit.

Weaning covers the entire process of liberating the patient from mechanical ventilation support and the endotracheal tube. For the majority of mechanically-ventilated patients weaning can be successfully accomplished quickly and easily, however this is not the case for 15-30% of ventilated patients. Prolonged mechanical ventilation secondary to weaning failure sacrifices a significant amount of intensive care resources, thus increasing the economic burden of public healthcare. Therefore, research needs to focus on identifying the mechanisms contributing to weaning failure. Along these lines, it has been documented that the energy cost of breathing during weaning failure can represent as much as 59% of the whole body energy requirement. Interestingly, one of the proposed mechanisms accounting for the weaning failure is the theory that during weaning the hard working respiratory muscles compromise cerebral blood flow thereby, predisposing the brain to dysfunction. Reduction in cerebral perfusion may in turn impact on the function of the respiratory muscles per se by decreasing the output of the respiratory centre thus accounting for weaning failure. Nevertheless, what we know so far in this area of interest is based on theoretical models whilst no actual data of blood flow regulation exist to support this theory. Therefore, the aim of this project is to investigate the theory of blood flow competition between respiratory muscle and brain on the prevalence of weaning failure.