Continuous positive airway pressure (CPAP) therapy using measurements of speed and pressure

1. A respiratory assistance device, comprising:

a variable speed blower with an output;

a patient ventilation interface configured for fitment on a patient respiratory passageway, the patient ventilation interface including a ventilation mask and a piloted exhalation valve coupled to the ventilation mask;

a gas passage conduit coupling the output of the blower to the patient ventilation interface, a pilot line from the gas passage conduit being coupled to the pilot of the exhalation valve;

a pressure sensor for measuring a mask pressure in the patient ventilation interface;

a blower speed sensor for measuring a speed of the blower; and

a pressure controller, in communication with the pressure sensor and the blower speed sensor, that detects a patient inspiratory phase and a patient expiratory phase based on either or both of the measured speed of the blower and a set speed of the blower, the pressure controller adjusting an operating speed of the blower and actuating the piloted exhalation valve by selective application of fluid pressure to the pilot line from the gas passage conduit based upon the measured mask pressure.

2. The respiratory assistance device of claim 1 , wherein the pressure controller actuates the blower to induce a pressure differential at the patient ventilation interface and the blower that closes the piloted exhalation valve during the patient inspiratory phase and opens the piloted exhalation valve during the patient expiratory phase.

3. The respiratory assistance device of claim 2 , wherein the piloted exhalation valve is open to ambient pressure with the pressure differential being lower than a predefined threshold.

4. The respiratory assistance device of claim 2 , wherein the piloted exhalation valve is open to ambient pressure with the pressure differential being approximately zero to negative.

5. The respiratory assistance device of claim 4 , wherein the piloted exhalation valve is closed with the pressure differential being higher relative to the pressure differential of when the piloted exhalation valve is open.

6. The respiratory assistance device of claim 1 , wherein the pressure controller regulates therapeutic pressure at the patient ventilation interface according to a trigger limit and a cycle limit using the blower speed.

7. The respiratory assistance device of claim 6 , wherein an average blower speed over one or more patient breathing cycles defines a leak constant.

8. The respiratory assistance device of claim 7 , wherein the trigger limit is defined by the leak constant added to a trigger constant.

9. The respiratory assistance device of claim 6 , wherein the cycle limit is defined by a cycle constant fraction of a maximum blower speed.

10. The respiratory assistance device of claim 1 , wherein the pressure controller relieves mask pressure by reducing therapeutic pressure at the patient, the therapeutic pressure being a function of the blower speed.

11. The respiratory assistance device of claim 1 , wherein the pressure controller includes a first proportional-integral-derivative (PID) controller and a second proportional-integral-derivative (PID) controller, the first PID controller being part of a first control loop over the speed of the blower for minimizing error between the set speed of the blower and the measured speed of the blower, and the second PID controller, together within the first control loop, being part of a second control loop for minimizing error between the mask pressure and a set pressure.

12. The respiratory assistance device of claim 1 , further comprising:

a temperature sensor for a motor of the blower;

wherein a particular speed at which the motor is driven by the pressure controller to regulate a blower speed corresponding to delivered therapeutic pressure is a function of temperature readings from the temperature sensor.

13. A continuous positive airway pressure (CPAP) apparatus for respiratory assistance of a patient, the apparatus comprising:

a blower with an output connectible to a patient ventilation interface including a ventilation mask wearable by the patient and a piloted exhalation valve coupled to the ventilation mask, the blower having a variable speed;

a pressure sensor connected to the ventilation mask for measuring mask pressure therein;

a blower speed sensor connected to the blower for measuring the variable speed of the blower; and

a blower controller connected to the pressure sensor and the blower speed sensor, a patient inspiratory phase and a patient expiratory phase being detectable from at least one of the measured speed of the blower and a set speed of the blower to set a therapeutic pressure at the patient;

wherein the piloted exhalation valve is opened and closed by selective application of fluid pressure thereto based upon the pressure differentials between the mask pressure and a blower pressure induced by the blower controller driving the blower.

14. The respiratory assistance device of claim 13 , wherein the piloted exhalation valve is open to ambient pressure with the pressure differential being low lower than a predefined threshold.

15. The CPAP apparatus of claim 13 , wherein the piloted exhalation valve is open to ambient pressure with the pressure differential being approximately zero to negative.

16. The CPAP apparatus of claim 13 , wherein the piloted exhalation valve is closed with the pressure differential being higher relative to the pressure differential of when the piloted exhalation valve is open.

17. The CPAP apparatus of claim 13 , wherein the blower controller relieves mask pressure by reducing the blower speed.

18. The CPAP apparatus of claim 13 , further comprising:

a temperature sensor for a motor of the blower;

wherein a particular speed at which the motor is driven by the pressure controller to regulate the therapeutic pressure at the patient is a function of temperature readings from the temperature sensor.

19. The CPAP apparatus of claim 13 , wherein the blower controller regulates therapeutic pressure delivered to the patient according to a trigger limit and a cycle limit reached by the blower speed.

20. A method for administering continuous positive airway pressure (CPAP) therapy to a patient, the method comprising:

receiving a first CPAP therapeutic pressure value;

measuring a blower speed from a blower generating a therapeutic pressure to the patient;

measuring a mask pressure value at a ventilation mask worn by the patient;

evaluating a patient respiratory state from the blower speed, the patient respiratory state being one of an inspiration state and an expiration state; and

selectively adjusting the blower speed to deliver the therapeutic pressure to the patient in response to the evaluated patient respiratory state, the speed of the blower generating a quantity of the therapeutic pressure corresponding to the first CPAP therapeutic pressure value, the selectively applied quantity of the therapeutic pressure at the ventilation mask inducing a pressure differential between the output of the blower and the ventilation mask, the ventilation mask including a piloted exhalation valve being opened and closed by selective application of fluid pressure thereto in response to the induced pressure differential.

21. The method of claim 20 , further comprising:

measuring an operating speed of the blower;

measuring an operating temperature of the blower; and

modulating the blower as a function of the operating speed and the operating temperature of the blower.

22. The method of claim 20 , further comprising:

generating a leak constant value from an average blower speed value over a predetermined time period.

23. The method of claim 22 , further comprising:

generating a trigger limit value based upon the leak constant value summed with a trigger constant;

triggering the blower based upon the blower speed value reaching the trigger limit value;

wherein the selectively applying the quantity of the therapeutic pressure at the patient corresponds to the triggering the blower.

24. The method of claim 22 , further comprising:

generating a cycle limit value based upon a cycle constant fraction of a maximum blower speed value;

cycling the blower based upon the blower speed value reaching the cycle limit value;

wherein the selectively applying the quantity of therapeutic pressure at the patient corresponds to the cycling the blower.