IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0974226
(2001-10-10)
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우선권정보 |
NZ-507682 (2000-10-20) |
발명자
/ 주소 |
- Seakins, Paul John
- Smith, Malcolm David
- Abeysinghe, Kaumali Prasangika
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출원인 / 주소 |
- Fisher &
- Paykel Healthcare Limited
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대리인 / 주소 |
Trexler, Bushnell, Giangiorgi, Blackstone &
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인용정보 |
피인용 횟수 :
18 인용 특허 :
5 |
초록
▼
A method and apparatus are described for sensing the absolute humidity of gases where the relative humidity of gases are measured, the humidity transducer is heated, the resulting temperature measured and the absolute humidity calculated (based on the power to heat said transducer, the temperature o
A method and apparatus are described for sensing the absolute humidity of gases where the relative humidity of gases are measured, the humidity transducer is heated, the resulting temperature measured and the absolute humidity calculated (based on the power to heat said transducer, the temperature of said transducer and the relative humidity).In further embodiments the humidity transducer may be heated to a pasteurisation temperature, to substantially kill any common pathogens present on the humidity transducer. The flow rate may be determined to estimate a more instantaneous valve of humidity. The operation of the sensor may be continually monitored for correct operation and various constructions disclosed for improving the efficiency of operation.
대표청구항
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1. A system for automatically disinfecting an absolute humidity sensing apparatus for sensing the absolute humidity of respiratory gas comprising:a humidity transducer providing a first signal, said first signal indicative of the relative humidity of said gas, a heater associated with or in substant
1. A system for automatically disinfecting an absolute humidity sensing apparatus for sensing the absolute humidity of respiratory gas comprising:a humidity transducer providing a first signal, said first signal indicative of the relative humidity of said gas, a heater associated with or in substantial thermal contact with said humidity transducer and adapted to heat at least a portion of said humidity transducer depending on energisation power supplied thereto, a temperature sensor associated with or in substantial thermal contact with said humidity transducer and providing a second signal, said second signal indicative of the temperature of said humidity transducer, and a controller or processor configured to operate in at least two modes, a first absolute humidity measurement mode configured to provide a first energisation power to said heater to heat said humidity transducer to an operating temperature and receives said first signal and said second signal and calculates an estimate of the absolute humidity of said gas based thereon, and a second disinfection mode configured to provide a second energisation power to said heater to heat said humidity transducer to a predetermined disinfection temperature, said disinfection temperature being higher than said operating temperature and adequate to substantially kill the majority of any common pathogens present on said humidity transducer. 2. A system as claimed in claim 1 wherein said disinfection temperature is above 60° C.3. A system as claimed in claim 1 or 2 wherein said operating temperature is above the temperature of said gas.4. A system for interpolating the output of an absolute humidity sensing apparatus for sensing the absolute humidity of a flow of respiratory gas comprising:a humidity transducer providing a first signal, said first signal indicative of the relative humidity of said flow of gas; a heater associated with or in substantial thermal contact with said humidity transducer and adapted to heat at least a portion of said humidity transducer depending on energisation power supplied thereto; a temperature sensor associated with or in substantial thermal contact with said humidity transducer and providing a second signal, said second signal indicative of the temperature of said humidity transducer a flow sensor configured in use to provide an indication of the flow rate of said gas and having a response tune significantly lower than said humidity transducer or said temperature sensor, and; a controller or processor configured to: (i) provide a first said energisation power to said heater to heat said humidity transducer to an operating temperature; (ii) receive said first signal and said second signal; (iii) calculate an estimate of the absolute humidity of said flow of gas based on said first signal and/or said second signal; (iv) store information on said absolute humidity over a period of time; (v) sense the flow rate of said flow of gas; (vi) store information on said flow rate of said gas over said period of time; and (vii) interpolate absolute humidity values for said flow of gas during a portion of said period of time based on said stored flow rate of gas during said portion of said period of time and said stored absolute humidity during said portion of said period of time. 5. A system as claimed in claim 4 wherein said period of time at least relates to one breathing cycle of a patient receiving respiratory therapy using said flow of gas.6. A system as claimed in claim 5 wherein said portion of said period of time relates to the inspiratory phase of said patient's breathing cycle.7. A system for automatically testing the accuracy of an absolute humidity sensing apparatus for sensing the absolute humidity of respiratory gas comprising:a humidity transducer providing a first signal, said first signal indicative of the relative humidity of said gas, a heater associated with or in substantial thermal contact with said humidity transducer and adapted to heat at least a portion of said humidity transducer depending on energisation power supplied thereto, a temperature sensor associated with or in substantial thermal contact with said humidity transducer and providing a second signal, said second signal indicative of the temperature of said humidity transducer, and a controller or processor configured to provide energisation power to said heater to heat said humidity transducer to at least two different calibration temperatures, receive said first signal and said second signal and calculate an estimate of the absolute humidity of said gas at each different calibration temperature based thereon, and detect or determine whether the apparatus is operating correctly, based on whether said absolute humidity is consistent over said temperatures. 8. A system as claimed in claim 7 wherein said correct operation of said apparatus at least relates to whether said estimate of the absolute humidity of said gas is accurate within predetermined limits.9. A system as claimed in claim 8 wherein said accuracy of said absolute humidity is monitored in at least one aspect by detecting the presence of liquid water on said humidity transducer.10. A system as claimed in 9 wherein said detection of liquid water comprises the steps:a) storing absolute humidity values during normal operation; b) providing a third said energisation power to said heater to heat said humidity transducer to the dewpoint of said gas (where the relative humidity just reaches 100%); c) comparing the absolute humidity reading at dew point with that during normal operating (stored in step (a)); and if there is a substantial difference providing a fourth signal indicative of incorrect or faulty operation. 11. A system as claimed in 9 wherein said detection of liquid water comprises the steps of:a) determining whether said first signal indicates 100% relative humidity, b) providing a fourth said energisation power to said heater to heat said humidity transducer to a substantially higher temperature; c) if the relative humidity does not reduce from 100% providing a fourth signal indicative of incorrect or faulty operation. 12. A system as claimed in claim 10 or 11 wherein if said fourth signal indicates incorrect or faulty operation said controller or processor provides a fifth said energisation power to said heater to heat said humidity transducer to substantially evaporate said liquid water therefrom.13. A system as claimed in claim 10 or 11 wherein, if said fourth signal indicates incorrect or faulty operation said controller or processor discontinuing said energisation power to said heater, and using said second signal to estimate an upper limit for the absolute humidity of said flow of gas.14. A system for locating an absolute humidity sensor within a gas delivery apparatus for suppling a flow of respiratory gas to a patient comprising:a gas supply adapted to provide a flow of gas at a desired pressure, a humidifier having an inlet and an outlet, said inlet adapted to be in fluid communication with said gas supply and said humidifier thereby providing water vapour to humidify said flow of gas as they pass through said humidifier, a conduit in use adapted to be connected to said outlet and accepting said flow of gas there from, said conduit including an interior and an exterior, said conduit in use conveying said flow of gas through said interior, in use a portion of said conduit adjacent said outlet being substantially vertical and including a protrusion within the interior of said substantially vertical portion, and a humidity sensor adapted to be located in said interior providing an estimate of the absolute humidity of said flow of gas, said humidity sensor juxtapositioned below said protrusion, said protrusion thereby substantially preventing any liquid water from flowing down said conduit onto said humidity sensor. 15. A system as claimed in claim 14 wherein said gas conduit having an aperture including a keyway, said humidity sensor comprising a humidity transducer provided in a sensor housing, said housing adapted to engage with said aperture and having a key which engages with said keyway in said aperture such that said housing can only be installed in said aperture in a single orientation.16. A system as claimed in claim 14 wherein said humidity sensor is permanently housed within said conduit.17. A method of automatically disinfecting an absolute humidity sensor for respiratory gas comprising the steps:operating in an absolute humidity measurement mode comprising the steps of using a humidity transducer to sense the relative humidity of said gas; heating at least a portion of said humidity transducer to an operating temperature and sensing the temperature of said humidity transducer, and determining an estimate of the absolute humidity of said gas based on said temperature and said relative humidity; operating in a disinfecting mode comprising the step of heating said humidity transducer to a predetermined disinfection temperature, said disinfection temperature being higher than said operating temperature and adequate to substantially kill the majority of any common pathogens present on said humidity transducer. 18. A method of interpolating the output of an absolute humidity sensor of respiratory gas comprising the steps:using a humidity sensor to sense the relative humidity of said gas, heating at least a portion of said humidity sensor to an operating temperature, determining an estimate of the absolute humidity of said flow of gas based on said relative humidity and temperature, said absolute humidity determination having a response time, storing said relative or absolute humidity over a period of time, sensing the flow rate of said gas, said flow rate having a response time significantly lower than said humidity, storing said flow rate over said period of time, and interpolating values for absolute humidity during a portion of said period of time based on said stored flow rate and said stored absolute humidity. 19. A method of automatically testing the accuracy of an absolute humidity sensor for respiratory gas comprising the steps:using a humidity sensor to sense the relative humidity of said gas at each temperature, heating at least a portion of said humidity sensor to at least two different calibration temperatures, calculating an estimate of the absolute humidity of said gas at each temperature based on said relative humidities and said temperatures, detecting or determining whether the apparatus is operating correctly, based on whether said absolute humidity is substantially consistent over said temperatures. 20. A method of locating an absolute humidity sensor for respiratory gas comprising the steps:providing a flow of gas at a desired pressure, humidifying said flow of gas, conveying said flow of gas through the said interior of a conduit and providing at least a portion of said conduit substantially vertical with a protrusion in said interior of said substantially vertical portion, positioning a humidity sensor within the flow of gas below said protrusion, said protrusion thereby substantially preventing any liquid water from flowing down said interior onto said humidity sensor, and providing an estimate of the absolute humidity of said flow of gas, based on the temperature and relative humidity of said gas from said humidity sensor.
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