Abstract: A method and an apparatus for monitoring and controlling flows in medical equipment including an anesthetic machine and a ventilator for influencing a patient's respiratory system are disclosed. The apparatus includes a microprocessor and an airway system including drive gas conduits provided with an inhalation valve (2) and an exhalation valve (5) for gas discharging as well as a ventilator end flow sensor (3) for measuring the introduced or discharged drive gas flow through the valves. The airway system also includes patient end breathing tubing in which a patient end flow sensor (11) for measuring the patient's inspired and expired gas flow is provided. By comparing the measured values of the two flow sensors against the characteristic curve of the inhalation valve (2), the microprocessor can judge the operation states and accuracy of the respective flow sensors and the inhalation valve (2).