Method and arrangement for measuring the concentration of gases

Abstract

A method and an arrangement for measuring the concentration of gases in a sample includes the generation of a monochromatic light beam having predetermined color characteristic. An indicator generates light signals indicative of the concentration of the gases in a sample to be measured and includes a light-transmissive surface positioned to be impinged by the monochromatic light beam, a diffusion membrane adapted to be placed in the proximity of a sample and being permeable to a selected gas component thereof, and an indicating substance positioned to be impinged by the monochromatic light beam penetrating the light-transmissive surface and by the gas component penetrating the diffusion membrane. The indicating substance reacts when illuminated by the incident monochromatic light by emitting a resultant light beam having an emitted component which has a color characteristic different from the predetermined color characteristic of the monochromatic light beam. The resultant light beam is conducted away from the indicating substance through the light-transmissive surface. Finally, the emitted component is discriminated from the resultant light beam so that the change in the color characteristic of the indicating substance can be measured and correlated with the concentration of gases in the sample.

Description

silicon silicone or any synthetic plastic material such as polyvinylchloride randomly mixed with the indicating substance preferably in a polymerization-type reaction. The indicating substance is so strongly embedded in the supporting foil that, even if it were placed in direct contact with the blood in flow-through chamber 6 of FIG. 1, the indicating substance would not be washed away.

Besides the planar configurations of the optodes or supporting foil, each can be adapted to conform to the particular configuration of the object being measured. Thus, the optodes may comprise a plurality of very small carrier particles having the indicating substance embedded therein and which are added to a carrier fluid containing the gas to be measured for instance to the blood.

Turning to FIG. 3, this embodiment is essentially analogous to the one described in connection with FIG. 2 except that the discrimination process is different. The resultant beam is again passed through a filter 221 which serves to screen out the reflected light component 20. The fluorescent light component 20 is then scanned by a first swinging mirror 200 in one direction, and then directed by lens 222 towards a second swinging mirror 201 whereupon another scan is taken in a mutually normal direction. Thus an areal scan is furnished. The information contained in the scanning of the optode is then conveyed to a photoelectric element 223, whereupon the information is conducted towards an amplifier 202 and coverted into an electrono-optic image or raster which can be viewed at the display screen 70 of the viewing apparatus 203.

In FIG. 4, the incident monochromatic light beam and the outgoing resultant beam are respectively directed towards and away from one or more optodes by means of light-conductive fibers 2001 and 2002 of a light-conductive cable 2000. Light-conductive fiber 2001 has its input end 2022 connected to a source of monochromatic light so that the latter is thereby brought to the optode whereupon it impinges on the indicating substance. The free end of light-conductive cable 2000 is sealingly covered with the gas-permeable membrane 8 so that the gas being measured can penetrate the membrane and react with the indicating substance. The emitted light is conducted by light-conductive cable 2003 towards its output end 2023 to a discrimination arrangement.

The light fibers may be connected to either one or more optodes and, as shown in FIG. 4, fiber 2001 is used to illuminate a pair of adjacent optodes 101 and 102 which lie behind each other as viewed in direction into the plane of FIG. 4. Moreover, each optode may be used to measure the same gas component, or preferably different gas components when their respective gas-permeable membranes are selected accordingly.

The inner surface of the gas-permeable membrane 8 can be provided with a reflective coating in case an increase in the illumination of the indicating substance by the monochromatic light is required; alternatively, the inner surface may be provided with a blackened coating in order to reduce scatter radiation. Of course, light-scattering not eliminated thereby can also be reduced and substantially eliminated by electrical means in the amplifier circuitry.

FIG. 5 shows an embodiment of a multiple analysis-type measuring device using the concept disclosed in FIG. 4. The light-conductive cable 2080 is housed in a catheter whose free end is provided with optodes 101 and 102 and covered by membrane 8. The measurement is advantageous since obtaining a plurality of separate readings, each of which is later processed to produce a final result, is more accurate as compared with a single measurement device according to Pflugers Archiv 342/41-60/1973. With this method it is possible to account for optical interferences, white light effects, single measurement errors, etc.

In accordance with the invention, light source 230 directs a light beam 202 towards the input end of cable 2080. Beam 202 is modulated by a rotating assembly wheel which comprises a drive 2501 which turns shaft 2500. A first set of five monochromatic filters 2502-2506 are mounted on the shaft 2500 so as to intercept beam 202 in normal direction; a second set of single frequency light filtering elements 2507-2511 is mounted on the shaft 2500 so as to subsequently intercept beam 202 at angles of approximately 45°. The second set of light elements 2507-2511 is partially mirrored and so positioned that the resultant beams returning from the optodes 101, 102 are sequentially reflected towards photocells 90-94. Each photocell converts the respective light signals into a corresponding electrical signal which is then respectively amplified in amplifiers 130-134. The plurality of electrical signals are processed together in an analyzer unit 135 which combines the separate signals in a manner disclosed by Pflugers, Archiv 342/41-60/1973. The display instruments 1361 and 1362 respectively indicate the gas concentrations detected by the optodes 101, 102. Thus, optical interference caused by the optodes or by the blood itself, white light, and additive color effects from the indicating substance are substantially eliminated.

By placing the optodes 101, 102 directly behind each other, it is possible to make the free end of the catheter-type cable very thin so that the latter can be used to measure gas components directly even in very small blood vessels.

FIG. 6 illustrates an embodiment especially useful when the optode is directly applied against the skin. Optode 1031 is comprised of two adjacent membranes 110 and 111. Membrane 110 is selected to be permeable to oxygen; and membrane 111 is selected to be permeable to carbondioxide. Then, these two gas components can be simultaneously measured.

As examples of typical indicating substances, β-methyl-umbelliferon can be used to directly measure the pH value of the blood being measured from which the carbon-dioxide value can be determined by the use of a nomograph; in addition, pyrene butyric acid can be directly used to measure the oxygen concentration of the sample.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a method and arrangement for measuring the concentration of gases, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of the prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

Claims

1. A method of measuring the concentration of gases in a sample comprising the steps of generating a monochromatic light beam having a predetermined color characteristic; generating light signals indicative of the concentration of gases in a sample to be measured by positioning an indicator having a light-transmissive surface positioned to be impinged by said monochromatic light beam, a diffusion membrane adapted to be placed in the proximity of a sample and being selectively permeable to a gas component thereof, and an indicating substance positioned to be impinged by the monochromatic light beam penetrating said light-transmissive surface and by said gas component penetrating said diffusion membrane, said indicating substance reacting when illuminated by said incident monochromatic light beam by emitting a resultant light beam having an emitted component which has a color characteristic different from said predetermined color characteristic; conducting said resultant light beam away from said indicating substance through said light-transmissive surface; and discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated with the concentration of gases in the sample.

2. In an arrangement for measuring the concentration of gases in a sample, a combination comprising means for generating a monochromatic light beam having a predetermined color characteristic; indicating means for generating light signals indicative of the concentration of gases in a sample to be measured, including a light-transmissive surface positioned to be impinged by said monochromatic light beam, a diffusion membrane adapted to be placed in proximity of a sample and being permeable to a selected gas component thereof, and an indicating substance positioned to be impinged by said monochromatic light beam penetrating said light-transmissive surface and by said gas component penetrating said diffusion membrane, said indicating substance reacting when illuminated by said incident monocrhomatic light beam by emitting a resultant light beam having an emitted component which has a color characteristic different from said predetermined color characteristic; means for conducting said resultant light beam away from said indicating substance through said light-transmissive surface; and means for discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated with the concentration of gases in the sample.

3. The arrangement of claim 2, wherein said indicating substance is sealingly embedded throughout said diffusion

membrane. 4. The arrangement of claim 2 33; and further comprising means for controlling the temperature of a sample.

5. The arrangement of claim 2, wherein the indicating substance is

β-methyl-umbelliferon. 6. The arrangement of claim 2 33, wherein the indicating substance is Pyrene-butyric

acid. 7. The arrangement of claim 2 33; and further comprising additional indicating substances intermixed with said first-mentioned indicating substance.

8. The arrangement of claim 2; and further comprising a reflecting wall located behind said membrane.

9. The arrangement of claim 2; and further comprising an absorption

wall located behind said membrane. 10. The arrangement of claim 2 33, wherein sid discriminating means comprises filtering means for permitting substantially only said emitted light to pass

through. 11. The arrangement of claim 2 33, wherein said indicating means is comprised of a plurality of particles, each

comprising said indicating substance and said diffusion membrane. 12. The arrangement of claim 2 33; and further comprising additional indicating means adjacent said first-mentioned indicating means, said additional indicating means having a diffusion membrane selectively permeable to another gas component and an indicating substance

which reacts with the latter. 13. The arrangement of claim 12, wherein the diffusion membrane of said first-mentioned indicating means is substantially permeable to oxygen; and wherein the diffusion membrane of said additional indicating means is substantially permeable to

carbondioxide. 14. The arrangement of claim 2 33; wherein said means for generating said monochromatic light beam includes a light-conductive cable for directing said monochromatic light beam towards said indicating means; and wherein said conducting means comprises another light-conductive cable for directing said resultant light beam away from

said indicating means. 15. The arrangement of claim 14; and further comprising additional indicating means located adjacent said first-mentioned indicating means; and wherein said monochromatic light beam comprises two monochromatic components, each being directed by said

one light-conductive cable towards said respective indicating means. 16. The arrangement of claim 15, and wherein both said indicating means respectively emit emitted light components, each being conducted by said other light-conductive cable towards said discrimination means so that

each emitted light component is individually measured. 17. The arrangement of claim 2 33; and further comprising a portable housing containing said means for generating a monochromatic light beam and said discrimination means for transporting the measuring arrangement

to a sample. 18. The arrangement of claim 17, wherein said indicating

means is interchangeably mounted in said housing. 19. The arrangement of claim 17; and further comprising additional measuring electrodes mounted

in said housing. 20. The arrangement of claim 2 34, wherein said light-transmissive surface is planar and constitutes an upper layer, and wherein said indicating substance is generally located in a

plane intermediate said upper layer and said diffusion membrane. 21. The arrangement of claim 20 34, wherein said indicating substance is arranged in a dichroic layer having one side which absorbs said monochromatic light beam.

22. The arrangement of claim 20, wherein said membrane has a reflective layer on its side facing said indicating substance.

23. The arrangement of claim 20 wherein said membrane has

an absorbing layer on its side facing said indicating substance. 24. The arrangement of claim 2 33, wherein said means for generating a monochromatic light beam includes means for modifying the latter into a plurality of separate monochromatic components, each monochromatic component being directed towards said indicating substance.

5. The arrangement of claim 24, wherein said modifying means comprises a plurality of monochromatic filters, each positioned to be impinged by said

monochromatic light beam. 26. The arrangement of claim 24, wherein said conducting means comprises a plurality of light-reflective elements, each

positioned to be impinged by said emitted light component. 27. The arrangement of claim 26, wherein said discriminating means processes each

of said emitted light components. 28. A method of measuring at least the pH value of a sample comprising the steps of generating a light beam having a predetermined color characteristic; generating light signals indicative of the pH value of a sample to be measured by positioning an indicator having a light-transmissive surface positioned to be impinged by said light beam, a diffusion membrane adapted to be placed in the proximity of a sample and being selectively permeable to a component of the sample which will allow a pH measurement of the sample to be made, and a pH indicating substance which is capable of fluorescing positioned to be impinged by the light beam penetrating said light-transmissive surface and by said component penetrating said diffusion membrane, said pH indicating substance responding when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a color characteristic different from said predetermined color characteristic and is related to the pH value of the sample; conducting said resultant light beam away from said indicating substance through said light-transmissive surface; and discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated with the pH

value of the sample. 29. A method as defined in claim 28 wherein said sample is blood. 30. A method as defined in claim 28 wherein the pH indicating substance is beta-methyl-umbelliferon. 31. A method of measuring the concentration of carbon dioxide in a sample comprising the steps of generating a light beam having a predetermined color characteristic; generating light signals from which the concentration of carbon dioxide in a sample to be measured can be determined by positioning an indicator having a light-transmissive surface positioned to be impinged by said light beam, a diffusion membrane adapted to be placed in the proximity of a sample and being selectively permeable to at least a carbon dioxide component thereof, and an indicating substance which is capable of fluorescing positioned to be impinged by the light beam penetrating said light-transmissive surface and by said carbon dioxide component penetrating said diffusion membrane, said indicating substance responding when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a color characteristic different from said predetermined color characteristic and is related to the concentration of carbon dioxide in the sample; conducting said resultant light beam away from said indicating substance through said light-transmissive surface; discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be ascertained; and correlating the changes in the color characteristic with the concentration

of carbon dioxide in the sample. 32. A method as defined in claim 31 wherein said indicating substance includes a pH indicating substance. 33. In an arrangement for measuring the concentration of gases in a sample, a combination comprising means for generating a monochromatic light beam having a predetermined color characteristic; indicating means for generating light signals indicative of the concentration of gases in a sample to be measured, including a light transmissive surface positioned to be impinged by said monochromatic light beam, a diffusion membrane of silicone adapted to be placed in proximity of a sample and being permeable to a selected gas component thereof, and an indicating substance sealingly embedded throughout said diffusion membrane and positioned to be impinged by said monochromatic light beam penetrating said light-transmissive surface and by said gas component penetrating said diffusion membrane, said indicating substance reacting when illuminated by said incident monochromatic light beam by emitting a resultant light beam having an emitted component which has a color characteristic different from said predetermined color characteristic; means for conducting said resulting light beam away from said indicating substance through said light transmissive surface; and means for discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated with the concentration of gases

in the sample. 34. In an arrangement for measuring the concentration of carbon dioxide in a sample, a combination comprising means for generating a light beam having a predetermined color characteristic; indicating means for generating light signals from which the concentration of carbon dioxide in a sample to be measured can be determined, including a light transmissive surface positioned to be impinged by said light beam, a diffusion membrane adapted to be placed in proximity of a sample and being permeable to at least a carbon dioxide component thereof, and an indicating substance which is capable of fluorescing positioned to be impinged by said light beam penetrating said light-transmissive surface and by said carbon dioxide component penetrating said diffusion membrane, said indicating substance responding when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a color characteristic different from said predetermined color characteristic and is related to the concentration of carbon dioxide in the sample; means for conducting said resulting light beam away from said indicating substance through said light transmissive surface; means for discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be ascertained and means for correlating the change in the color characteristic with the concentration of carbon dioxide in the sample. 35. A method as defined in claim 34 wherein said indicating substance includes a

pH indicating substance. 36. In an arrangement for measuring at least one of the characteristics of a sample wherein the sample characteristics consist essentially of the pH value and the concentration of gases in the sample, a combination comprising means for generating a light beam having a predetermined color characteristic; indicating means for generating light signals indicative of the sample characteristic to be measured, including a light transmissive surface positioned to be impinged by said light beam, a selectively permeable diffusion membrane of silicone adapted to be placed in proximity of a sample and being permeable to a component thereof, and an indicating substance in said diffusion membrane and positioned to be impinged by said light beam penetrating said light-transmissive surface and by said component penetrating said diffusion membrane, said indicating substance being capable of fluorescing and reacting when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a color characteristic different from said predetermined color characteristic; means for conducting said resultant light beam away from said indicating substance through said light transmissive surface; and means for discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated

with the sample characteristic to be measured. 37. An arrangement as defined in claim 36 wherein the indicating substance is mixed with the membrane. 38. An arrangement as defined in claim 36 including an absorption surface facing said indicating substance and being between the indicating substance and the sample. 39. An arrangement as defined in claim 36 including a reflective surface facing said indicating substance and being between the indicating substance and the sample. 40. An arrangement as defined in claim 36 wherein said indicating substance is sealingly embedded throughout said diffusion membrane. 41. An arrangement as defined in claim 40 wherein the membrane includes a polymer and said polymer is mixed with the indicating substance. 42. An arrangement as defined in claim 36 wherein said membrane is permeable to a component of the sample which will allow a pH measurement of the blood to be made and said indicating substance is a pH indicating substance.

43. An arrangement as defined in claim 42 wherein said indicating substance is sealingly embedded throughout said diffusion membrane and said membrane includes a polymer and said polymer is mixed with the indicating substance. 44. An arrangement as defined in claim 36 wherein said membrane is permeable to at least a carbon dioxide component of the sample and said predetermined color characteristic is related to the concentration of carbon dioxide in the sample. 45. An arrangement as defined in claim 44 wherein said indicating substance is sealingly embedded throughout said diffusion membrane and said membrane includes a polymer and said polymer is mixed

with the indicating substance. 46. In an arrangement for measuring the concentration of gases in a sample, a combination comprising means for generating a monochromatic light beam having a predetermined color characteristic; indicating means for generating light signals indicative of the concentration of gases in a sample to be measured, including a light transmissive surface positioned to be impinged by said monochromatic light beam, a diffusion membrane adapted to be placed in proximity of a sample and being permeable to a selected gas component thereof, and an indicating substance sealingly embedded throughout said diffusion membrane and positioned to be impinged by said monochromatic light beam penetrating said light-transmissive surface and by said gas component penetrating said diffusion membrane, said indicating substance reacting when illuminated by said incident monochromatic light beam by emitting a resultant light beam having an emitted component which has a color characteristic different from said predetermined color characteristic; means for conducting said resulting light beam away from said indicating substance through said light transmissive surface; and means for discriminating said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated with the concentration of gases in the sample, said indicating substance being betamethyl-umbelliferone.

47. In an apparatus for measuring at least one of the characteristics of blood within a body wherein the sample characteristics consist essentially of the pH value and the concentration of gases in the blood, a combination comprising:

means for generating a light beam having a predetermined color characteristic;

a catheter receivable in a vein or artery and having a distal end, said catheter including indicating means for generating light signals indicative of the sample characteristic to be measured and a light-conductive cable means having an input end for conducting the light beam from the input end to the indicating means;

said indicating means including a light-transmissive surface positioned to be impinged by said light beam, a diffusion membrane permeable to a selected component of the blood, and an indicating substance which fluoresces positioned to be impinged by said light beam penetrating said light-transmissive surface and by said component penetrating said diffusion membrane, each of said light-transmissive surface, diffusion membrane and indicating substance being near said distal end of said catheter, said indicating substance being in said diffusion membrane and responding when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a predetermined color characteristic different from said predetermined color characteristic, said catheter including light conductive cable means for conducting said resulting light beam away from said indicating substance; and

means for discriminating said emitted component from said resultant light beam received from said last-mentioned light conductive cable means so that the change in the predetermined color characteristic of said indicating substance can be measured and correlated with the sample characteristic to be measured. 48. An apparatus as defined in claim 47 wherein the membrane includes a polymer and said polymer is

mixed with the indicating substance. 49. An apparatus as defined in claim 47 wherein the membrane includes silicone. 50. In an apparatus for measuring at least one of the characteristics of blood within a body wherein the sample characteristics consist essentially of the pH value and the concentration of gases in the blood, a combination comprising:

means for generating a light beam having a predetermined color characteristic;

a catheter receivable in a vein or artery and having a distal end, said catheter including indicating means for generating light signals indicative of the sample characteristic to be measured and a light-conductive cable means having an input end for conducting the light beam from the input end to the indicating means;

said indicating means including a light-transmissive surface positioned to be impinged by said light beam, a diffusion membrane permeable to a selected component of the blood, and an indicating substance which fluoresces positioned to be impinged by said light beam penetrating said light-transmissive surface and by said component penetrating said diffusion membrane, each of said light-transmissive surface, diffusion membrane and indicating substance being near said distal end of said catheter, said indicating substance responding when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a predetermined color characteristic different from said predetermined color characteristic, said catheter including light conductive cable means for conducting said resulting light beam away from said indicating substance; and

means for discriminating said emitted component from said resultant light beam received from said last-mentioned light conductive cable means so that the change in the predetermined color characteristic of said indicating substance can be measured and correlated with the sample characteristic to be measured. 51. An apparatus for measuring at least one of the characteristics of blood within a body wherein the sample characteristics consist essentially of the pH value and the concentration of gases in the blood, the apparatus is adapted to receive a light beam having a predetermined color characteristic and is coupled to provide an optical signal to discriminating means, said apparatus comprising:

indicating means for generating light signals indicative of the sample characteristic to be measured;

a light-conductive cable means having an input end for receiving the light beam and conducting the light beam to the indicating means;

said indicating means including a light-transmissive surface positioned to be impinged by said light beam, a diffusion membrane permeable to a selected component of the blood, an indicating substance which fluoresces positioned to be impinged by said light beam penetrating said light-transmissive surface and by said component penetrating said diffusion membrane, said apparatus being receivable in a vein or artery and having a distal end, each of said light-transmissive surface, diffusion membrane and indicating substance being near said distal end of said apparatus, said indicating substance responding when illuminated by said incident light beam by emitting a resultant light beam having a fluorescent emitted component which has a color characteristic different from said predetermined color characteristic; and

1ight conductive cable means for conducting said resulting light beam away from said indicating substance to the light discriminating means whereby the light discriminating means can discriminate said emitted component from said resultant light beam so that the change in the color characteristic of said indicating substance can be measured and correlated with the sample characteristic to be measured. 52. An apparatus as defined in claim 51 wherein said membrane is permeable to a component of the blood which will allow a pH measurement of the blood to be made and said indicating substance is a pH indicating substance. 53. An apparatus as defined in claim 51 wherein said membrane is permeable to at least a carbon dioxide component of the blood and said predetermined color characteristic is related to the concentration of carbon dioxide in the blood. 54. An apparatus as defined in claim 51 including an absorption surface facing said indicating substance and being between the indicating substance and the blood. 55. An apparatus as defined in claim 51 including a reflective surface facing said indicating substance and being between the indicating substance and the blood.