Over the past 2 decades, anesthesia machines have become increasingly more complex. These anesthesia machines present many challenges to anesthetists in terms of their increased complexity, changed layout and function, and integration of new technologies.

The basic function of the anesthesia machine is to prepare a gas mixture of known and variable composition, and then deliver that gas to the patient. The machine regulates a controlled flow of oxygen, nitrous oxide, and air, to which anesthetic vapors are added. These gases flow into a breathing system. The breathing system can provide positive pressure ventilation via a mechanical ventilator or manual bag ventilation, and also allow a patient to breathe the gases spontaneously. The breathing system incorporates means for warming and humidification of gases, and for removal of CO₂ from the exhaled gases. Anesthesia machines also provide a scavenger system to allow removal of waste gases from the immediate environment.

The anesthesia breathing system is unique among mechanical ventilators in that it is explicitly designed to allow patients to rebreathe exhaled gases, so that anesthetic agents can be conserved. To facilitate rebreathing, machine features are incorporated to ensure that the gas mixture delivered to the patient is safe. At a minimum, anesthesia machines incorporate an oxygen sensor, to measure the oxygen concentration in the gas mixture. Many anesthesia machines also incorporate a sophisticated gas analysis system, capable of measuring oxygen, carbon dioxide, and anesthetic agents. Anesthesia machines also comply with a complex set of standards, with built-in monitors and sensors used to survey the functioning of the ventilation system, and detect equipment malfunctions.