Methods and apparatus for pressure therapy in the treatment of sleep disordered breathing

Abstract

A controller or processor for a respiratory pressure treatment device determines an estimate of patient respiratory flow based on a measure of pressure associated with flow generated by a flow generator and a measure of frequency of the flow generator, such as a rotational velocity of a servo-controlled blower motor. The estimate can be made without data from a flow sensor. The measure of frequency may be converted to an expected pressure based on characteristics of the flow generator and subtracted from the measured pressure to determine the flow estimate. The flow estimate can be implemented in the provision of respiratory pressure treatment with the flow generator. For example, the flow estimate may be utilized to trigger expiratory pressure relief during a patient's expiration as detected with the estimated flow signal.

1 - 34 . (canceled) 
     
     
         35 . A method of controlling pressure in a pressure treatment delivery apparatus to compensate for patient induced swing at a patient interface, the method comprising:
 determining a measure of pressure delivered by a flow generator with a pressure sensor, the pressure sensor being located proximate to the flow generator;   adjusting the measure of pressure as a function of (a) a measure of pressure drop across the flow generator, (b) a measure of impedance of a patient interface coupled to the flow generator and (c) a measure of impedance of the flow generator; and   controlling the flow generator so that the adjusted measure of pressure satisfies a target pressure setting.   
     
     
         36 . The method of  claim 35  wherein the function multiplies the measure of pressure drop with a ratio of the measure of impedance of the patient interface and the measure of impedance of the flow generator. 
     
     
         37 . The method of  claim 36  wherein a result of the function is subtracted from the measure of pressure. 
     
     
         38 . The method of  claim 37  wherein the measure of pressure drop is a difference between a measure of pressure and a derived measure of pressure that is a determined function of a frequency of the flow generator. 
     
     
         39 . A pressure treatment delivery apparatus to compensate for patient induced swing comprising:
 a patient interface to carry a flow of breathable gas to a patient;   a flow generator coupled with the patient interface to generate a flow of the breathable gas through the patient interface;   a pressure sensor to provide a pressure signal indicative of pressure associated with the flow generator; and   a processor to control the flow generator, the processor coupled with the pressure sensor to process the pressure signal, the processor being configured to control:   determining a measure of pressure delivered by a flow generator with the pressure sensor, the pressure sensor being located proximate to the flow generator;   adjusting the measure of pressure as a function of (a) a measure of pressure drop across the flow generator, (b) a measure of impedance of a patient interface and (c) a measure of impedance of the flow generator; and   controlling the flow generator so that the adjusted measure of pressure satisfies a target pressure setting.   
     
     
         40 . The apparatus of  claim 39  wherein the function multiplies the measure of pressure drop with a ratio of the measure of impedance of the patient interface and the measure of impedance of the flow generator. 
     
     
         41 . The apparatus of  claim 40  wherein a result of the function is subtracted from the measure of pressure. 
     
     
         42 . The apparatus of  claim 41  wherein the measure of pressure drop is a difference between a measure of pressure and a derived measure of pressure that is a determined function of a frequency of the flow generator. 
     
     
         43 . A pressure treatment delivery system to compensate for patient induced swing comprising:
 a patient interface means for carrying a flow of breathable gas to a patient;   a flow generation means coupled with the patient interface for generating a flow of the breathable gas through the patient interface;   a sensor means for providing a pressure signal indicative of pressure associated with the flow generator; and   a control means, coupled with the sensor means and flow generation means, for determining a measure of pressure delivered by the flow generation means, for adjusting the measure of pressure as a function of (a) a measure of pressure drop across the flow generator, (b) a measure of impedance of a patient interface and (c) a measure of impedance of the flow generator, and for controlling the flow generator so that the adjusted measure of pressure satisfies a target pressure setting.   
     
     
         44 . The system of  claim 43  wherein the function multiples the measure of pressure drop with a ratio of the measure of impedance of the patient interface and the measure of impedance of the flow generator. 
     
     
         45 . The system of  claim 44  wherein a result of the function is subtracted from the measure of pressure. 
     
     
         46 . The system of  claim 45  wherein the measure of pressure drop is a difference between a measure of pressure and a derived measure of pressure that is a determined function of a frequency of the flow generator. 
     
     
         47 . An information-bearing medium having processor-readable information thereon, the processor-readable information to control an apparatus for providing pressure treatment therapy to compensate for patient induced swing, the processor-readable information comprising control instructions to:
 determine a measure of pressure delivered by a flow generator with a pressure sensor that is located proximate to the flow generator;   adjust the measure of pressure as a function of (a) a measure of pressure drop across the flow generator, (b) a measure of impedance of a patient interface coupled to the flow generator and (c) a measure of impedance of the flow generator; and   control the flow generator so that the adjusted measure of pressure satisfies a target pressure setting.   
     
     
         48 . The medium of  claim 47  wherein the function multiplies the measure of pressure drop with a ratio of the measure of impedance of the patient interface and the measure of impedance of the flow generator. 
     
     
         49 . The medium of  claim 48  wherein a result of the function is subtracted from the measure of pressure. 
     
     
         50 . The medium of  claim 47  wherein the measure of pressure drop is a difference between a measure of pressure and a derived measure of pressure that is a determined function of a frequency of the flow generator.