A ventilation system with oxygen prefill compartment

A ventilation system for supplying oxygen-containing breathing gas to a patient via a gas delivery line comprising a flow generator for generating a flow of air from an air inlet of the gas delivery line towards the patient, the ventilation system comprising:

• an oxygen prefill compartment forming a part of the gas delivery line, arranged downstream of the air inlet such that air from the air inlet flows through the oxygen prefill compartment on its way towards the patient;
• a controllable oxygen valve for regulating a flow of oxygen through an oxygen inlet of the gas delivery line, which oxygen inlet is arranged in fluid communication with the oxygen prefill compartment, and
• a controller for controlling the oxygen valve such that a mean oxygen concentration of breathing gas delivered to the patient during inspiration substantially corresponds to a set target oxygen concentration,
• wherein the oxygen prefill compartment and the oxygen inlet are arranged upstream of the flow generator along the gas delivery line, and wherein the controller is configured to control the oxygen valve such that the oxygen prefill compartment is prefilled with a volume of oxygen prior to start of a high-flow period of an inspiration phase, during which the gas flow generated by the flow generator exceeds a maximum flow of oxygen deliverable via the oxygen valve.