Closed-circle systems--a new direction in the practice of anaesthesia

Closed-circuit anaesthesia is the most scientific method of anaesthesology. A fresh gas flow of at least 10 l/min is used for wash-in of the desired alveolar concentrations. In practice, maintenance of closed-circuit anaesthesia has been found remarkably easy, safe and logistically feasible by the administration of constant quantities of approximately 240 ml oxygen, 100 ml of nitrous oxide, 12 ml halothan evapour or 23 ml enflurane vapour per minute (both with 70% nitrous oxide). The only prerequisites are low-flow rotameters, an oxygen monitor and a ventilator designed specifically for anaesthetic use in the operating theatre.