Patent ID: 6439229
Filing Date: 2002-08-27
Classification: A61M

Abstract:
A pressure support ventilation system, comprising:a ventilator unit having an input for connection to a source of breathing gases, an inspiration line for connection to a patient, a gas delivery unit for controlling gas delivery from the source to the inspiration line, an expiratory line for exhausting gases from the patient, and an expiratory unit for controlling removal of gases during expiration; at least one flow sensor for sensing the level of gas flow in the system; a pressure sensor for sensing pressure in the system; and a control unit connected to the gas delivery unit, expiratory unit, and the flow and pressure sensors for controlling the gas delivery and expiratory units to provide an inspiration phase in which gases are supplied to the patient through the gas delivery unit and an expiratory phase in which gases are removed from the patient; the control unit calculating, for each breath, a patient respiratory time constant based on the outputs of the flow and pressure sensors, and including an expiratory trigger sensitivity controller for varying an expiratory trigger sensitivity in response to variations in the calculated patient respiratory time constant, such that the expiratory trigger sensitivity at which the ventilator unit switches from gas delivery to gas removal is increased with increase in the patient respiratory time constant.