Resmed Limited

Shane Darren Finn

Gregory Alan Colla

Hary Soesanto Surjadi

Steven Paul Farrugia

A flow generator having use in the provision of CPAP or assisted ventilation treatment is disclosed The flow generator has a turbine for the supply of breathable gas which is driven by an electric motor and an associated motor power supply. The power supply in turn is controlled by a controller. A pressure sensing port measures delivery pressure that is passed to a pressure transducer, the output signal of which is passed to the motor controller. The zero offset of the pressure transducer is automatically calibrated on occurrence of the conditions where the turbine is not operating and no pressure activity is sensed by the transducer. The turbine not operating condition can be determined from Hall-effect sensors integral to the motor.

Auto-calibration of pressure transducer offset

A CPAP treatment apparatus has a patient mask is coupled to an air delivery conduit. The air delivery conduit is coupled to an impeller and motor, collectively forming a blower arrangement for providing a positive pressure of air to the conduit. A controller receives a signal representing respiratory flow. The controller is operable to cause the blower to supply an inspiratory phase pressure and an expiratory phase pressure. The controller selectively triggers generation of a pressure intermediate of the inspiratory phase and expiratory phase pressures for a period of time as a transitional state upon the first flow threshold being crossed. The controller also selectively triggers generation of a pressure intermediate of the expiratory phase and inspiratory phase pressures for a period of time as a transitional state upon the second flow threshold being crossed.

Control of the administration of continuous positive airway pressure treatment

A method of flow estimation during CPAP treatment is disclosed and involves measuring turbine (,) speed by means of the motor's Hall-effect sensors (,). The equivalent pressure, p,, that would be developed by the turbine (,) for the measured speed if the flow were zero is estimated using a predetermined mathematical function. Coincidentally with the speed measurement and pressure estimation, the delivery tube pressure, p,, is measured by the pressure transducer (,), and from p,together with p,, the difference between the two pressures is calculated, representing an estimation of flow, f,. The flow estimation value can be linearised by the square root device (,), and then filtered by the combination of low pass and high pass filters (,) to derive a filtered flow estimate value, that has the non-respiratory components removed. A method of flow compensation of flow-induced pressure swings also is disclosed.

Flow estimation and compensation of flow-induced pressure swings in CPAP treatment and assisted respiration

A flow generator for the supply of breathable gas, which includes an electric motor driving a turbine, control circuitry, a pressure transducer to sense delivery pressure at or remote from said flow generator and whose electrical output is connected to the control circuitry, and sensing means connected to the control circuitry, and wherein the control circuitry is operable to determine from the sensing means whether the electric motor or the turbine are operating and from the pressure transducer whether there is no pressure activity, and if both determinations are satisfied, to accept the output of the transducer as a calibrated pressure offset value representative of atmospheric pressure.

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North Rocks, Australia

Shane Darren Finn