A method for monitoring patient's breathing action response to changes in a ventilator applied breathing support, where a) a desired target range for a breathing gas indication of O2-consumption for the patient is first determined, after which b) the ventilator applied breathing support is changed, and c) the breathing gas indication of O2-consumption of said patient is measured and d) compared with the desired target range. At least the steps b)-d) are repeated to maintain the measured breathing gas indication of O2-consumption of said patient within the desired target range. A system for monitoring a patient's breathing action is also provided.
