This chapter provides an overview of artificial ventilation, an intervention that has developed from a basic resuscitation technique to highly sophisticated intensive care ventilators used today. Artificial ventilation is provided to unconscious patients, whether unconsciousness was caused by a medical problem (e.g., head injury) or by anaesthesia. Ventilation is usually provided through an endotracheal tube, via a breathing system which is attached to a ventilator. A heat and moisture exchange filter is used to warm and humidify the gases that reach the patient. The healthcare professional caring for the patient will adjust various parameters to ensure the ventilation strategy is appropriate for each patient and their specific needs. Positive-pressure ventilation is used to push gases into the airways of the patient and allow gas exchange to occur. Ventilators may have several different modes for delivering breaths to patients but usually are based around limiting tidal volume or peak inspiratory pressure. Artificial ventilation can affect many different physiological systems particularly the heart and blood vessels, the brain, and the kidneys.