A gas delivery unit and method for delivering gas for subject breathing is disclosed herein. The gas delivery unit includes a first regulating valve (33) for regulating a first gas flow and a second regulating valve (34) for regulating a second gas flow. The gas delivery unit also includes a first flow measurement device (35) for providing a signal indicative of the first gas flow, and a second flow measurement device (35) for providing a signal indicative of the second gas flow. The gas delivery unit further includes at least one anesthetic agent supply (37) for supplying in case of need an anesthetic agent and mixing with the first and/or second gas flow for delivering, and a valve unit (29) being in flow communication with at least one of the first and second flow measurement device for delivering gas in case of need for breathing bypassing the anesthetic agent supply.
