Inhalational anesthetics are often used to maintain general anesthesia. However, it is known that volatile anesthetics are greenhouse gases and some can damage the earth's ozone layer. To lower the use of these anesthetic agents, a low flow anesthesia technique can be applied. This technique is based on re-inhaling expired anesthetic agent by reducing fresh gas flow (mixture of administered oxygen, air and anesthetic agent) below the set minute ventilation. Lowering fresh gas flow increases rebr