The anaesthetic machine comprises a gas flow system (6,8,10) with an inspiratory line (8), an expiratory line (10) in communication with said inspiratory line (8) and means for controlling the direction of gas flow in the gas flow system so that during inspiration, gas flows from the expiratory line (10) to the inspiratory line (8), and with a variable-volume gas container (6) for breathing gas. The anaesthetic machine comprises further a fresh gas system (24,26) for supplying a flow of fresh gas to the gas flow system (6,8,10), and a control unit (28), arranged to control the variable-volume gas container (6) during a first phase of inspiration so a flow of breathing gas is released and mixes with a flow of fresh gas from the fresh gas system (24,26). The control unit (28) is further devised to start a second phase of inspiration if the flow of breathing gas from the variable-volume gas container (6) ceases before inspiration has been completed, the control unit (28) during said second phase controlling the anaesthetic machine (2) so inspiration is maintained by a flow of fresh gas from the fresh gas system (24,26).
