Patent ID: 9526852
Filing Date: 2016-12-27
CPC Classification: A61M

Claim Text:
1. A method of controlling pressure in a patient interface of a CPAP apparatus, the CPAP apparatus having a flow generator, the patient interface, an air delivery conduit for delivering air from the flow generator to the patient interface, a pressure sensor for determining a pressure from the flow generator, a flow sensor for determining a flow from the flow generator, and a control mechanism that causes air to be delivered through the air delivery conduit at a desired pressure at the patient interface, the method of controlling pressure in the patient interface comprising: sensing the pressure at the pressure sensor; sensing the flow at the flow sensor; estimating a pressure loss in the air delivery conduit based on the sensed flow; determining an estimated mask pressure based on the sensed pressure at the pressure sensor and the estimated pressure loss in the air delivery conduit; calculating a derivative of the flow at run time; setting a converted derivative of flow value by converting the calculated derivative of the flow based on whether the calculated derivative of the flow is positive or negative, wherein the calculated derivative is converted based on a comparison of the calculated derivative to a threshold; calculating a pressure discrepancy value indicative of a discrepancy of the estimated mask pressure based on the converted derivative of flow value; determining an adjusted mask pressure at the patient interface based on the estimated mask pressure and the pressure discrepancy value; and controlling the flow generator by maintaining the adjusted mask pressure substantially equal to the desired pressure.