Breathing anesthesia circuit is a medical device. It is used to deliver oxygen, remove carbon dioxide, and deliver inhalational anaesthetic agents to a patient. Therefore, it is originally developed for use in anaesthesiology. A typical breathing circuit comprise a breathing tubing, an adjustable pressure valve, and a reservoir bag. In order to meet different surgical application, there are several types of breathing anesthesia circuits, like duo limbo circuit and caoxial circuit.