Abstract: A device and method for improving the stability of a ventilation pattern of a patient (1) uses a sensor (4) for sensing a parameter which reflects a level of lung gas in a patient, such as oxygen or carbon dioxide. The output signal of the sensor is received by a processor (3) which assesses the level of lung gas of the patient and activates means (18,20) for increasing the lung gas level of the patient beyond what it would otherwise have been without treatment in response to a decreasing level or a predicted decreasing level of the lung gas. Thus the device can be used to retard a decrease in said lung gas level, thereby reducing oscillations in the respiration.