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

Patent metadata

Field	Value
Publication number	US-9713690-B2
Application number	US-19224708-A
Country	US
Kind code	B2
Filing date	Aug 15, 2008
Priority date	Aug 17, 2007
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

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.

First claim

The invention claimed is:

1. A method for determining a flow in a respiratory flow generating apparatus comprising:
determining a measure of pressure produced by a respiratory flow generating apparatus;
determining a measure of a frequency of the respiratory flow generating apparatus;
deriving, with a processor, an estimate of patient respiratory flow as a function of the measure of pressure and the measure of frequency;
triggering, with the processor, an increase in pressure for inspiration by the respiratory flow generating apparatus by comparing the derived estimate of respiratory flow to a first threshold, the first threshold comprising a function of a peak value of a prior respiratory cycle of the derived estimate of respiratory flow; and
triggering, with the processor, a decrease in pressure for expiration by the respiratory flow generating apparatus by comparing the derived estimate of respiratory flow to a second threshold, the second threshold being different from the first threshold.

2. The method of claim 1 wherein the measure of frequency is a rotational velocity.

3. The method of claim 2 wherein the deriving comprises determining an expected pressure as a function of the measure of frequency.

4. The method of claim 3 wherein the deriving comprises calculating a difference between the determined expected pressure and the measure of pressure.

5. The method of claim 1 wherein the delivering of the pressure by the respiratory flow generating apparatus comprises triggering an expiratory pressure relief.

6. The method of claim 5 wherein a change in pressure is delivered in synchrony with a patient's respiratory cycle without a measure of the patient's respiratory flow from a flow sensor.

7. The method of claim 1 further comprising adjusting a pressure delivered by the respiratory flow generating apparatus to compensate for a patient induced swing at a patient interface, wherein the adjusting is based on the derived estimate of patient respiratory flow.

8. The method of claim 1 , wherein the second threshold is zero.

9. The method of claim 1 , wherein the first threshold is a predetermined fraction of the peak value of the prior respiratory cycle of the derived estimate of respiratory flow.

10. The method of claim 9 , wherein the predetermined fraction is a quarter.

11. The method of claim 1 , further comprising evaluating a predetermined period of time, wherein if the derived estimate of respiratory flow has not exceeded the first threshold within the predetermined period of time, the increase in pressure for inspiration is triggered.

12. The method of claim 11 , wherein the predetermined period of time is 15 seconds.

13. An apparatus for generating respiratory flow 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 transducer to provide a pressure signal indicative of pressure associated with the flow generator;
a tachometer to provide a velocity signal indicative of a speed of the flow generator; and
a processor to control the flow generator, the processor coupled with the pressure transducer to process the pressure signal and coupled with the tachometer to process the velocity signal, the processor being configured to control:
determining a measure of pressure with the pressure signal;
determining a measure of frequency with the velocity signal; and
deriving an estimate of patient respiratory flow as a function of the measure of pressure and the measure of frequency;
triggering an increase in pressure for inspiration by the flow generator by comparing the derived estimate of respiratory flow to a first threshold, the first threshold comprising a function of a peak value of a prior respiratory cycle of the derived estimate of respiratory flow; and
triggering a decrease in pressure for expiration by the flow generator by comparing the derived estimate of respiratory flow to a second threshold, the second threshold being different from the first threshold.

14. The apparatus of claim 13 wherein the measure of frequency is a rotational velocity.

15. The apparatus of claim 13 wherein the deriving comprises determining an expected pressure as a function of the measure of frequency.

16. The apparatus of claim 15 wherein the deriving comprises calculating a difference between the determined expected pressure and the measure of pressure.

17. The apparatus of claim 13 wherein the control of the generation of pressure with the flow generator comprises triggering an expiratory pressure relief.

18. The apparatus of claim 13 wherein changes in pressure are delivered in synchrony with a patient's respiratory cycle without a measure of the patient's respiratory flow from a flow sensor.

19. The apparatus of claim 13 wherein the processor controls adjusting a pressure delivered by the flow generator to compensate for a patient induced swing at the patient interface, wherein the adjusting is based on the derived estimate of patient respiratory flow.

20. The apparatus of claim 13 , wherein the second threshold is zero.

21. The apparatus of claim 13 , wherein the first threshold is a predetermined fraction of the peak value of the prior respiratory cycle of the derived estimate of respiratory flow.

22. The apparatus of claim 21 , wherein the predetermined fraction is a quarter.

23. The apparatus of claim 13 , wherein the processor is further configured to trigger the increase in pressure for inspiration if the derived estimate of respiratory flow has not exceeded the first threshold within a a predetermined period of time.

24. The apparatus of claim 23 , wherein the predetermined period of time is 15 seconds.

25. A system for delivering respiratory flow to a patient comprising:
an interface means to carry a flow of breathable gas;
a flow means, coupled with the interface means, for generating the breathable gas;
a pressure sensing means for measuring pressure and for generating a pressure signal representing the measured pressure of the breathable gas;
a frequency sensing means for measuring a frequency of the flow means and for generating a frequency signal representing the measured frequency;
a processing means for processing the pressure signal and the frequency signal, the processing means being configured for processing:
(a) determining a measure of pressure with the pressure signal;
(b) determining a measure of frequency with the frequency signal;
(c) deriving an estimate of patient respiratory flow as a function of the measure of pressure and the measure of frequency;
(d) controlling triggering of an increase in pressure for inspiration with the flow means by comparing the derived estimate of respiratory flow to a first threshold, the first threshold comprising a function of a peak value of a prior respiratory cycle of the derived estimate of patient respiratory flow; and
(e) controlling triggering of a decrease in pressure for expiration with the flow means by comparing the derived estimate of respiratory flow to a second threshold, the second threshold being different from the first threshold.

26. The system of claim 25 wherein the measure of frequency is a rotational velocity.

27. The system of claim 26 wherein the deriving comprises determining an expected pressure as a fun

Assignees

• Somaiya Chinmayee
• Yip Nicholas Ming Yun
• Oates John David
• Barnes Adrian
• Blunsden Christopher Kingsley
• Resmed Ltd

Inventors

• Somaiya Chinmayee
• Yip Nicholas Ming Yun
• Oates John David
• Barnes Adrian
• Blunsden Christopher Kingsley

Classifications

• A61B5/4818

  Sleep apnoea · CPC title

• A61M16/0066 Primary

  Blowers or centrifugal pumps · CPC title

• A61B5/087

  Measuring breath flow · CPC title

• A61M2205/3365

  Rotational speed · CPC title

• A61B5/4836

  Diagnosis combined with treatment in closed-loop systems or methods (A61B5/0036 takes precedence) · CPC title