Oxygen monitoring apparatus and methods of using the apparatus

• US 20020098120A1
• Filed: 01/24/2001
• Published: 07/25/2002
• Est. Priority Date: 01/24/2001
• Status: Active Grant

• Current Assignee: RIC INVESTMENTS LLC (Koninklijke Philips N.V.)
• Original Assignee: RIC INVESTMENTS LLC (Koninklijke Philips N.V.)
• Inventors: Apperson, Jerry R., Blazewicz, Perry R., Mace, Leslie E.
• Granted Patent: US 6,632,402 B2
• Time in Patent Office: Days
• US Class Current: 422/82.07
• CPC Class Codes: G01N 2021/6432 Quenching
• CPC Class Codes: G01N 2021/7786 Fluorescence
• CPC Class Codes: G01N 21/6408 with measurement of decay time, time resolved fluorescence
• CPC Class Codes: G01N 21/783 for analysing gases
• CPC Class Codes: Y10T 436/207497 Molecular oxygen
• CPC Class Codes: Y10T 436/209163 Dissolved or trace oxygen or oxygen content of a sealed environment

Abstract

Apparatus or systems which employ luminescence quenching to produce an oxygen concentration indicative signal. Components of such systems include: (1) an airway adapter, sampling cell, or the like having a casing and a sensor which is excited into luminescence with the luminescence decaying in a manner reflecting the concentration of oxygen in gases flowing through the airway adapter or other flow device and is in intimate contact with a window in the casing; (2) a transducer with has a light source for exciting a luminescable composition in the sensor into luminescence, a light sensitive detector for converting energy emitted from the luminescing composition as that composition is quenched into an electrical signal indicative of oxygen concentration in the gases being monitored, and a casing which locates the light source and detector in close physical proximity to the window but on the side thereof opposite the sensor; and (3) subsystems for maintaining the sensor temperature constant and the temperature of the window above condensation temperature and for processing the signal generated by the light sensitive detector. Airway adapters, sampling cells, and transducers for such systems.

Claims

1. An oxygen concentration monitoring apparatus comprising:

a sensor which includes a luminescable composition;

a light source which provides light of a first wavelength capable of exciting the composition into luminescence;

a flow component for so bringing a gas to be monitored into contact with the excited, luminescing composition that the luminescence is quenched in a manner reflecting the concentration of oxygen in the gas being monitored; and

a detector impinged upon by light of a second wavelength emitted by the excited, luminescing composition for producing a signal indicative of the concentration of oxygen in the gas;

the flow component having a near wall and a far wall bounding a sampling volume for the gas being monitored;

the oxygen sensing sensor being located at the near wall of the flow component; and

the light source and the detector being located outside of the sampling volume adjacent the near wall.

2. An oxygen concentration monitoring apparatus as defined in claim 1 in which the light source and the detector are components of a transducer which can be detachably assembled to the flow component.

3. An apparatus as defined in claim 1 in which the flow component is an airway adapter.

4. An apparatus as defined in claim 1 in which the flow component is a sampling cell.

5. An oxygen concentration monitoring apparatus as defined in claim 1 which comprises a heater for maintaining the sensor at a selected temperature.

6. An oxygen concentration monitoring apparatus as defined in claim 1 which includes components for keeping from the detector extraneous visible light which is not indicative of the concentration of oxygen being monitored.

7. An oxygen concentration monitoring apparatus as defined in claim 6 wherein the components comprise:

a blue filter and an infrared blocking filter on the output side of and in alignment with the light source; and

a red dicorp filter and a red glass filter in front of the detector.

8. An oxygen concentration monitoring apparatus as defined in claim 1 in which:

the sensor comprises a luminescable composition dispersed in a polymeric membrane; and

the sensor is positioned for contact by the gas being monitored by a support made of a material which transmits electromagnetic energy of the first and second wavelengths.

9. An oxygen concentration measuring apparatus which comprises:

a sensor which includes a luminescable composition;

a source of light for exciting the composition into luminescence; and

a unitary airway adapter or sampling cell for so flowing a gas to be monitored in relation to the composition that the luminescence of the excited composition is quenched in a manner indicative of the concentration of oxygen in the gas; and

the airway adapter or sampling cell having a flow passage for the gas and a window opening onto the flow passage via which light from the source can reach the luminescable composition.

10. An apparatus as defined in claim 9:

wherein the component for flowing gas into contact with the sensor is an airway adapter;

the apparatus further comprising a transducer to which the airway adapter can be detachably coupled, the transducer comprising source of light, a detector sensitive to electromagnetic energy emitted from the luminescable composition for producing a signal which is a function of the oxygen concentration in the gas flowing through the airway adapter, and a casing in which the source of light and the detector are mounted.

11. An oxygen concentration monitoring apparatus as defined in claim 9 in which the transducer further comprises a platform housed in the casing, the light source and the detector being mounted to and thereby integrated with the platform.

12. An oxygen concentration monitoring apparatus as defined in claim 9 in which the source of light is an LED which emits electromagnetic energy in the 300-600 nm band.

13. An oxygen concentration monitoring apparatus as defined in claim 12 in which the source of light is a blue or green LED.

14. An oxygen concentration monitoring apparatus as defined in claim 9 in which the luminescable composition is a phosphorescent organometallic complex having a 400-700 mn absorption band and a 500-1100 nm emission band.

15. An oxygen concentration monitoring apparatus as defined in claim 14 in which the luminescable composition is a fluorinated porphyrin.

16. An oxygen concentration monitoring apparatus as defined in claim 15 in which the luminescable composition is selected from the group consisting of palladium meso-tetraphenyl porphine, platinum meso-tetraphenyl porphine, palladium meso-tetra (perfluoro) phenyl porphine, and platinum meso-tetra (perfluoro) porphine.

17. An oxygen concentration monitoring apparatus as defined in claim 9 in which the luminescable composition is embedded in a matrix, the matrix being a microporous hydrophobic polymer having a thickness in the range of 5 to 20 μ

m and a pore size in the range of 0.10 to 10.0 μ

m.

18. An oxygen concentration monitoring apparatus as defined in claim 17 in which the polymer is:

a silicone, a polycarbonate, a polystyrene, a polymethyl methacrylate, a polyvinyl chloride, a polypropylene, a polyester, or an acrylic copolymer.

19. An oxygen concentration monitoring apparatus as defined in claim 18 in which the polymer is a track etched polycarbonate.

27. An oxygen concentration monitoring apparatus as defined in claim 9 which comprises means for processing the detector generated signal into an oxygen concentration signal.

28. An oxygen concentration monitoring apparatus as defined in claim 9 in which the sensor comprises a luminescable composition embedded in a porous polymer.

29. An apparatus as defined in claim 9:

wherein the sampling unit is a cell;

the apparatus further comprising a pump for effecting a flow of the gas to be monitored to the cell.

30. An apparatus as defined in claim 9 in which the sampling unit is an online airway adapter.

20. An oxygen concentration monitoring apparatus which comprises:

a sampling unit which has a wall bounding a sampling volume;

an optical window in the wall;

a sensor which comprises a luminescable composition distributed in a porous matrix, the sensor being supported in the sampling volume for contact by gas therein by the window;

a light source for transmitting through the window to the sensor energy of a wavelength capable of exciting the composition into luminescence; and

a detector for energy of excitation emitted by the sensor and transmitted through the window to the detector.

21. An apparatus as defined in claim 20 which comprises a heater unit for heating the window to a temperature high enough to keep condensate from forming on the window.

22. An apparatus as defined in claim 20 which comprises a heater unit for so heating the window as to keep the sensor at a specified temperature by the transfer of heat from the window to the sensor.

23. An apparatus as defined in claim 20:

which includes a transducer comprising the light source, the detector, and a monolithic mount for the light source and the detector.

24. An apparatus as defined in claim 20 in which:

there is an aperture in the near wall;

a light transmitting window in the aperture; and

the sensor is mounted to the window.

25. An oxygen concentration monitoring apparatus as defined in claim 20:

wherein the detector is responsive to energy in the visible light range;

wherein the energy emitted by the sensor and indicative of the concentration of oxygen in the gases being monitored is in the visible light range; and

wherein the apparatus includes means for keeping from the detector extraneous visible light which is not indicative of the oxygen concentration.

26. An oxygen concentration monitoring apparatus as defined in claim 25 in which the means for keeping extraneous visible light from the detector comprises a filter in an optical path between the sensor and the detector.

31. An oxygen concentration monitoring apparatus which comprises:

a sensor which comprises a luminescable composition dispersed in a porous matrix;

a light source for providing to the sensor light of a wavelength capable of exciting the composition into luminescence;

an arrangement for so bringing a gas to be monitored into contact with the sensor that the excited, luminescing composition is quenched in a manner reflecting the concentration of oxygen in the gas being monitored;

a detector for intercepting light emanating from the excited, luminescing sensor composition and for outputting a signal reflecting parameters of the intercepted light; and

a signal processor for making a phase-sensitive measurement of the signal, the signal being indicative of the concentration of oxygen in the gas being monitored.

32. An apparatus as defined in claim 31 which has a digital signal processor for the signal outputted from the detector.

33. A sampling device for an oxygen concentration monitoring apparatus comprising:

a casing defining a volume for a gas being monitored;

an optical window mounted in an aperture in the casing;

an oxygen sensor film comprising a compound which can be excited into luminescence by light transmitted through the window to the sensor film; and

a device for fixing the sensor film to the window, the device comprising;

a ring surrounding the window and mounting the window in the casing aperture; and

a mesh overlying the sensor film and pressing the sensor against and into intimate contact with the window.

35. A sampling device as defined in claim 33 which comprises:

a windowed aperture on one side of the casing for transmitting electromagnetic energy emitted by luminescence from the sensor;

the sensor being located on the same side of the passage as the windowed aperture.

36. A sampling device as defined in claim 33 in which the sensor film comprises a luminescable composition embedded in a porous polymeric film.

37. A sampling device as defined in claim 36 in which the polymeric film is stretched over the window and has an edge portion trapped between the window and the edge of the aperture.

38. A sampling device as defined in claim 33 in which the casing has integral misalignment prevention means.

39. A sampling device as defined in claim 33 in which the casing has integral end sections configured to provide connections for coupling the sampling device to components of an airway circuit.

40. A sampling device as defined in claim 33 wherein

the casing comprises:

a center section and two end sections;

the end sections being aligned with the center section defining a flow passage extending seriatim through one of the end sections, the center section, and the other of the end sections.

34. A replaceable airway adapter for oxygen concentration monitoring apparatus, the airway adapter comprising:

a flow passage-defining casing;

a luminescable, oxygen quenchable sensor exposed to the flow passage; and

an optical window mounting the sensor to the casing.

41. A sidestream sampling system for monitoring the concentration of gases flowing through the system, the sampling system comprising:

a sampling cell comprising a sensor which has an oxygen sensitive, luminescable composition, the sampling cell being located in the system flow path;

a complementary transducer which includes casing which houses a light source for exciting the composition into luminescence and a detector for intercepting energy emitted by the excited, luminescing composition for producing a signal indicative of the concentration of oxygen in the gases; and

a pump for so effecting a flow of the gases being monitored through the sampling cell and into contact with the luminescing composition that the luminescence is quenched in a manner indicative of the concentration of oxygen in the gases;

the sampling cell including a windowed aperture;

the sensor being in intimate contact with a first side of a window in the aperture; and

the light emitter and the detector being located by the transducer casing on a second, opposite side of and in close physical proximity to the window.

42. A system as defined in claim 41 in which:

the sampling cell has a casing;

the sampling cell casing has a flow passage therethrough; and

the system comprises a port providing communication between the passage and the ambient surroundings to bring the system to atmospheric pressure and thereby establish a baseline pressure in the system.

43. A system as defined in claim 41 which includes an arrangement active during the operation of the system to identify occlusions in the system by comparing the actual pressure in the system with the baseline pressure.

44. A system as defined in claim 42 in which:

the casing provides a flow path from a source of gases to be monitored through the sampling cell and to the pump;

a motor for the pump;

components for so controlling the speed of the motor as to maintain a constant pressure in the system; and

a differential pressure transducer for providing to the motor speed control signals reflecting the rate-of-flow in the system flow path;

there being a flow restrictor in the flow path and means providing fluid communication between;

(a) the flow path and the transducer, and (b) the flow restrictor and the transducer.

45. A system as defined in claim 41 which comprises:

an absolute pressure transducer;

a differential pressure transducer; and

a valve which is selectively operable to;

(a) provide communication between the system flow path and the absolute pressure transducer;

(b) the flow path and the ambient surroundings; and

(c) the flow path and the differential pressure transducer.

46. A system as defined in claim 41 in which there is an accumulator in the system flow path to dampen the pressure pulses generated by the operation of the system pump.

47. A system as defined in claim 45 in which there is a flow restrictor in the flow path that further dampens pressure pulses attributable to the cyclic operation of the pump.

48. A system as defined in claim 41 in which the sampling cell is replaceably removable from the system.