Continuous monitoring of end-tidal carbon dioxide (PETCO2) is a long-established standard of care in the operating room (OR). Carbon dioxide can be useful to monitor the mechanically ventilated patient when used in conjunction with other monitors of the patient's clinical status. CO2 monitoring is affected by changes in metabolism or CO2 production, cardiovascular function, and respiratory function. Comparison of the gradient between arterial and end-tidal CO2 (PaCO2-PetCO2) can offer valuable information regarding a patient's clinical status. In newborns, the therapeutic administration of CO2 in the ventilator circuit has been used in the preoperative management of hypoplastic left heart syndrome. Volumetric capnography or volumetric CO2 (VCO2) is the measurement of CO2 as a function of volume as opposed to time. When CO2 production increases with constant minute ventilation, PaCO2 will increase. Alveolar minute ventilation can be used as a guide for predicting the PaCO2 that may result from adjusting ventilation parameters.

A supraglottic airway is an airway that does not pass across the vocal cords, such as an oropharyngeal airway or a laryngeal mask. Intubation of the trachea with a cuffed tube is the only way to simultaneously provide a secure airway, repeated access to the trachea and ventilatory support. Unfortunately, the placement of an artificial airway, be it a supraglottic airway or an endotracheal or tracheostomy tube, bypasses many of the patient's natural defences and thus increases the risk of upper and lower airway colonization, aspiration and infection. For anything other than immediate life support, however, the airway needs to be secured with a cuffed endotracheal tube, or in some circumstances, a tracheostomy endotracheal intubation in the critically ill patient carries challenges over and above those encountered during routine anaesthesia airway management because of a number of additional complicating factors. A primary goal of airway management is oxygenation.

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.