The gas anesthesia machine mixes the anesthetic gas with oxygen and delivers it to your dog via the endotracheal tube. The gas then moves across the lungs until it reaches the alveoli. The gas is then transferred through the alveoli into the bloodstream and onward to the brain, where the state of anesthesia is achieved. To decrease the depth of anesthesia during the procedure or to awaken your dog, the process is reversed.Gas anaesthesia is generally safe in older animals so that we can reduce the anaesthetic risk.