The adverse effects and complications of mechanical ventilation may arise from the artificial airway or from positive pressure ventilation and the drugs required to facilitate this. The occurrence of complications cannot be completely eliminated, but an appropriately managed intensive care unit will monitor the occurrence of complications and use this information to look for trends, to learn from the lessons that each complication can teach and as a quality assessment and quality assurance tool. Airway management and intubation in the operating department are performed under ideal circumstances with anaesthetists working in familiar, well-equipped surroundings supported by competent assistants on patients who, in the vast majority of cases, have been assessed and prepared for the procedure. Ventilator-induced diaphragmatic damage (VIDD) may contribute to the many factors causing failure to wean in patients undergoing mechanical ventilation. This chapter also talks about neurological function.