Control of supplied pressure in assisted ventilation

A method for controlling operation of an assisted ventilation device supplying pressurised gas to a patient, the method comprising the steps of:

• measuring the currently delivered pressure;
• determining a relatively longterm average of the measured pressure;
• comparing said average against a threshold value;
• and
• if the threshold value is approached or exceeded, controlling the pressure supplied by the device.

Assisted ventilation apparatus for detecting a potential or actual overpressure condition, comprising:

• a blower to supply pressurised gas to a conduit, and in turn to a patient mask for connection with the entrance to a patient's airways;
• a pressure sensor to detect the delivered pressure of gas in the conduit or at the mask, and provide a signal thereof;
• and
• a controller, receiving the pressure signal and having control over operation of the blower, and operable to determine a relatively longterm average of the pressure signal, compare the average against a threshold value, and if the threshold value is approached or exceeded, to control the blower and thus the supplied pressure
• wherein, for the case of said longterm average exceeding said threshold, the controller operates subject to the condition that the time in excess must be greater than a minimum period of time before it is determined that a potential or actual overpressure is occurring.