CPAP systems

Patent metadata

Field	Value
Publication number	US-9802015-B2
Application number	US-201013505564-A
Country	US
Kind code	B2
Filing date	Nov 3, 2010
Priority date	Nov 3, 2009
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

A CPAP system includes a flow generator ( 10 ), a patient interface ( 50 ), an air delivery conduit ( 20 ) that interconnects the flow generator and the patient interface, wherein the air delivery conduit has an internal diameter of less than 19 mm. Preferably the air delivery conduit has an internal diameter of between about 10 mm and about 18 mm. The CPAP system may also include a controller for compensating for pressure swings and/or increased impedance within the system. Preferably the blower includes a low inertia blower.

First claim

What is claimed is:

1. A continuous positive airway pressure (CPAP) system comprising:
a flow generator including a low inertia blower that supplies breathable gas at pressure and a pressure sensor for determining a measured pressure of the gas supplied from the blower, the flow generator configured for coupling with a patient interface and an air delivery conduit interconnecting the flow generator and the patient interface, the air delivery conduit including a conduit portion having an internal diameter less than 19 mm; and
a controller adapted to control pressure delivered to the patient interface based on speed of the blower and a pressure compensation calculation, wherein the pressure compensation is based on the equation:
P 1− P 2= K 1 Q 2 ,

where P 1 is the pressure of the breathable gas supplied from the blower, P 2 is the pressure delivered to the patient interface, K 1 is a constant related to the length and diameter of the air delivery conduit and Q is flow, and
wherein the controller includes a feedforward control system to predict pressure disturbances expected to occur within the CPAP system and reduce pressure swings pre-emptively based on a predicted level of pressure disturbance,
in which the feedforward control system generates, based on detected changes in flow, a feedforward output which is summed with a feedback output that is a signal generated by a feedback control system of the controller from a comparison of the measured pressure of the gas supplied from the blower and a set pressure for patient delivery.

2. The CPAP system according to claim 1 wherein the blower supplies said breathable gas at a pressure of 3-25cmH 2 O.

3. The CPAP system according to claim 2 wherein the blower supplies said breathable gas at a pressure of 3-20cmH 2 O.

4. The CPAP system according to claim 1 wherein K 1 is determined by conduit length/conduit diameter 4 .

5. The CPAP system according to claim 1 wherein K 1 is empirically determined by experiment as co-efficient of a second order polynomial term of a flow versus pressure drop plot.

6. The CPAP system according to claim 1 wherein the controller includes a two-quadrant controller.

7. The CPAP system according to claim 1 , wherein the pressure compensation is based on the equation:
P 1− P 2= K 1 Q 2 +K 2 Q,

where K 2 is a constant based on flow versus pressure drop.

8. The CPAP system of claim 7 wherein K 2 is determined as co-efficient of a linear component of a polynomial of a flow versus pressure drop plot.

9. The CPAP system according to claim 1 , wherein the conduit portion has an internal diameter of between about 10 mm to about 18 mm.

10. The CPAP system according to claim 1 wherein the conduit portion has an internal diameter of between about 13 mm to about 16 mm.

11. The CPAP system according to claim 1 , wherein the conduit portion has an internal diameter of about 15 mm.

12. The CPAP system of claim 1 wherein the feedforward control system includes a sensor adapted to measure and detect the changes in the flow, and
when the changes in the flow are detected, the controller adjusts the pressure supplied from the blower to reduce a second level of pressure disturbance delivered to the patient interface.

13. The CPAP system of claim 12 wherein the pressure supplied is adjusted by the feedforward output calculated by multiplying change in the flow by a coefficient K f .

14. A positive airway pressure (PAP) system comprising:
a flow generator including a blower that supplies breathable gas at pressure and a pressure sensor for determining a measured pressure of the gas supplied, the flow generator configured for coupling with a patient interface and an air delivery conduit interconnecting the flow generator and the patient interface, the air delivery conduit including a conduit portion having an internal diameter less than 19 mm;
a flow sensor; and
a controller adapted to control pressure delivered to the patient interface based on speed of the blower and measured flow, the controller including a feedforward control system configured to predict pressure disturbances expected to occur within the PAP system and reduce pressure swings pre-emptively based on a predicted level of pressure disturbance, in which the feedforward control system generates, based on detected changes in flow, a feedforward output which is summed with a feedback output that is a signal generated by a feedback control system of the controller from a comparison of the measured pressure of the gas supplied from the blower and a set pressure for patient delivery.

15. The PAP system according to claim 14 wherein the blower supplies said breathable gas at a pressure of 3-25cmH 2 O.

16. The PAP system according to claim 15 wherein the blower supplies said breathable gas at a pressure of 3-20cmH 2 O.

17. The PAP system of claim 14 wherein the feedforward control system is configured to monitor the changes in the flow based on flow measurements from the flow sensor and predict the pressure disturbances expected to occur in response to any changes in the flow by calculating the feedforward output and adjusting the pressure supplied in accordance with the calculated feedforward output.

18. The PAP system of claim 17 wherein the feedforward output is calculated based on a gain factor, K F , multiplied by a change in flow.

19. The PAP system of claim 18 further comprising a high pass filter to filter the changes in the flow before calculating the feedforward output.

20. The PAP system according to claim 17 , wherein the feedforward output is fed to a Proportional Integral Derivative (PID) controller for adjusting the pressure supplied.

21. The PAP system according to claim 14 wherein the flow sensor is a high resolution flow sensor.

22. The PAP system according to claim 14 wherein the pressure sensor is configured to measure the pressure delivered and the feedback control is configured to compare measured pressure with the set pressure.

Assignees

• Virr Alexander
• Tarakci Cem
• Oates John David
• Kenyon Barton John
• Cutcliffe Graham Stephen
• Row Nathan John
• Resmed Ltd

Inventors

• Virr Alexander
• Tarakci Cem
• Oates John David
• Kenyon Barton John
• Cutcliffe Graham Stephen
• Row Nathan John

Classifications

• A61M16/1095

  in the connecting tubes · CPC title

• A61M2205/3368

  Temperature · CPC title

• A61M2016/0027

  pressure meter · CPC title

• A61M2205/3653

  by Joule effect, i.e. electric resistance · CPC title

• A61M2205/3365

  Rotational speed · CPC title