The invention relates to respiration systems (10) comprising a flow sensor (20) and a ventilator (30) for delivering gas to the patient (5) via the flow sensor (20). More particularly, the invention relates to calibrating the flow sensor (20) of such respiration system (10) in an automated manner, substantially improving the workflow, decreasing risk of human error and enhancing the quality of the obtained calibration data, including subsequent control and information capturing. A fully automated manner is further provided by not disconnecting the patient (5) while continuing ventilation.
