Respiratory device measurement system

• US 20060283450A1
• Filed: 06/08/2006
• Published: 12/21/2006
• Est. Priority Date: 06/21/2005
• Status: Active Grant

• Current Assignee: Philips RS North America LLC (Koninklijke Philips N.V.)
• Original Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Inventors: Truschel, William A., Shissler, Andrew L., Truitt, Patrick W.
• Granted Patent: US 8,561,611 B2
• Time in Patent Office: Days
• US Class Current: 128/204.210
• CPC Class Codes: A61B 2560/0228 using calibration standards
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/097 Devices for facilitating collection of breath or for directing breath into or through measuring devices
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61M 16/0063 Compressors
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/0072 Tidal volume piston pumps
• CPC Class Codes: A61M 16/0075 Bellows-type
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/142 with semi-permeable walls separating the liquid from the respiratory gas
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0033 electrical
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2202/025 Helium
• CPC Class Codes: A61M 2202/0275 Nitric oxide [NO]
• CPC Class Codes: A61M 2205/3358 Measuring barometric pressure, e.g. for compensation
• CPC Class Codes: A61M 2205/3365 : Rotational speed
• CPC Class Codes: A61M 2205/3368 : Temperature
• CPC Class Codes: A61M 2205/3569 : sublocal, e.g. between console and disposable
• CPC Class Codes: A61M 2205/52 : with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2230/432 : partial CO2 pressure (P-CO2)
• CPC Class Codes: G01F 15/005 : Valves valves in general F16K
• CPC Class Codes: G01F 15/046 : involving digital counting
• CPC Class Codes: G01F 25/10 : of flowmeters

Abstract

A gas delivery system comprising a pressure generator, a pressure sensor, a control valve, and a processor. The pressure generator pressurizes breathable gas for delivery to a patient. The pressure sensor measures a pressure difference between the pressurized breathable gas and atmospheric pressure. The control valve is disposed downstream from the pressure generator and is constructed and arranged to control a flow rate of the pressurized breathable gas. The processor controls the control valve to bring the flow rate of the pressurized breathable gas to substantially zero while the pressure generator is operating and, when the flow rate is substantially zero, determines at least one of atmospheric pressure, an atmospheric air density, or a density correction factor based at least in part on the pressure difference between the pressurized breathable gas and the atmospheric pressure.

Claims

1. A gas delivery system comprising:

a pressure generator that pressurizes breathable gas for delivery to a patient;

a pressure sensor that measures a pressure difference between the pressurized breathable gas and atmospheric pressure;

a flow sensor that measures a standard flow rate of the pressurized breathable gas output by the pressure generator; and

a processor that determines at least one of atmospheric pressure, an atmospheric air density, or a density correction factor based at least in part on the pressure difference and the measured standard flow rate.

2. The system of claim 1, wherein the flow sensor is a hot wire anemometer.

3. The system of claim 2, wherein the processor is triggered to determine at least one of the atmospheric pressure, the atmospheric air density, and the density correction factor upon a detection of a predetermined triggering event.

4. The system of claim 3, wherein the predetermined triggering event comprises the pressurized breathable gas having a standard flow rate of substantially zero.

5. The system of claim 1, further comprising a valve downstream from the pressure generator, the valve being controlled by the processor.

6. The system of claim 1, wherein the processor determines the density correction factor and multiplies the standard flow rate of the pressurized breathable gas by the density correction factor to determine a volumetric flow rate of the pressurized breathable gas.

7. The system of claim 1, further comprising a temperature monitor that monitors the temperature of the pressurized breathable gas.

8. The system of claim 7, wherein the processor determines the at least one of the atmospheric pressure, the atmospheric air density, or the density correction factor also based at least in part on the temperature of the pressurized breathable gas.

9. The system of claim 1, wherein the pressure generator comprises a blower, the blower further comprising:

a motor associated with the blower; and

an impeller associated with the blower, the impeller being rotatably driven by the motor to pressurize the breathable gas, wherein the processor determines the at least one of the atmospheric pressure, the atmospheric air density, and the density correction factor also based at least in part on a dimension of the impeller and a rotational velocity at which the impeller is driven.

10. The system of claim 9, further comprising a tachometer that monitors the rotational velocity at which the impeller is driven.

11. The system of claim 1, wherein the processor assumes that the pressurization of the breathable gas is an incompressible, isothermal process.

12. A gas delivery system comprising:

a pressure generator that pressurizes breathable gas for delivery to a patient;

a pressure sensor that measures a pressure difference between the pressurized breathable gas and atmospheric pressure;

a control valve disposed downstream from the pressure generator, the control valve constructed and arranged to control a flow rate of the pressurized breathable gas; and

a processor that controls the control valve to bring the flow rate of the pressurized breathable gas to substantially zero while the pressure generator is operating and, when the flow rate is substantially zero, determines at least one of atmospheric pressure, an atmospheric air density, or a density correction factor based at least in part on the pressure difference between the pressurized breathable gas and the atmospheric pressure.

13. The system of claim 12, further comprising a flow sensor disposed downstream from the pressure generator, the flow sensor measuring a standard flow rate of the pressurized breathable gas.

14. The system of claim 13, wherein the processor determines the density correction factor and multiplies the standard flow rate of the pressurized breathable gas by the density correction factor to determine a volumetric flow rate of the pressurized breathable gas.

15. The system of claim 12, wherein the processor assumes that the pressurization of the breathable gas is an incompressible, isothermal process.

16. The system of claim 12, wherein the processor controls operation of the pressure generator based on at least one of the atmospheric pressure, the atmospheric air density, or the density correction factor.

17. A method of monitoring a pressurized breathable gas that is delivered to a patient, the method comprising:

(a) pressurizing a breathable gas with a pressure generator;

(b) determining a pressure imparted to the breathable gas by the pressure generator; and

(c) determining at least one of atmospheric pressure, an atmospheric air density, or a density correction factor based at least in part on the pressure imparted to the breathable gas by the pressure generator.

18. The method of claim 17, further comprising:

determining a standard flow rate of the pressurized breathable gas, and wherein the determining step (c) is also based at least in part on the standard flow rate.

19. The method of claim 18, wherein the standard flow rate of the pressurized breathable gas is determined by measuring the standard flow rate with a flow sensor.

20. The method of claim 19, wherein the flow sensor is a hot wire anemometer.

21. The method of claim 19, further comprising detecting a predetermined triggering event, and wherein the step of determining at least one of an atmospheric pressure, an air density, or a density correction factor is triggered by the detection of the predetermined triggering event.

22. The method of claim 21, wherein the predetermined triggering event comprises determining that the pressurized breathable gas has a standard flow of substantially zero.

23. The method of claim 17, further comprising:

bringing the flow rate of the pressurized breathable gas to substantially zero, and wherein the determining step (c) is also based at least in part on an assumption that the standard flow rate is zero.

24. The method of claim 23, wherein bringing the standard flow rate of the pressurized breathable gas to substantially zero comprises closing a valve.

25. The method of claim 17, further comprising determining a temperature of the pressurized breathable gas.

26. The method of claim 25, wherein the determination of at least one of the atmospheric pressure, the atmospheric air density, or the density correction factor is based at least in part on the pressure imparted to the breathable gas by the pressure generator, and the temperature of the pressurized breathable gas.

27. The method of claim 17, further comprising:

controlling the pressure generator based at least in part on at least one of the atmospheric pressure, the atmospheric air density, or the density correction factor.

28. The method of claim 17, further comprising:

controlling the control valve based at least in part on at least one of the atmospheric pressure, the atmospheric air density, or the density correction factor.