Oximeter

[0001] The invention relates to an oximeter for spectrophotometric determination of in vitro hemoglobin derivatives and at least one further analyte in a sample, preferably a hemolyzed blood sample, comprising a single measuring light source that emits measuring radiation, a sample chamber, for example a sample cuvette for receiving a sample, device detection, which records the spectrum of the measuring light after its interaction with the sample and an evaluation device attached after the detection device, which, based on the spectrum received from the detection device, determines the amount of hemoglobin derivatives and at least one further analyte.

[0002] Oximeters currently on the market mostly have incandescent lamps as the source of the measuring light. In "Technical Aspects of Bilirubin Determination in Whole Blood", Hallemann et al; Point of Care, volume 4, number 1, March 2005 describes the oximeter module of the blood gas analyzer (OMNI Blood Gas Analyzer), with which, in addition to hemoglobin derivatives, bilirubin is also determined as an additional analyte. A halogen lamp with a wide spectral range is used as the measuring light source.

[0003] From JP 2004-108781, a spectroscope is known in which the light emitted from an LED lamp / luminescent diode with white light, before irradiation of the sample is split by means of two diffraction gratings into its spectral components and through the projection gap is radiated to the sample in the purpose, for example, to determine analytes in a sample. Variants with a light-transmitting structure as well as variants with a reflective structure are described, with the intensity of transmitted or reflected light being measured each time for each wavelength. The disadvantage of this known spectroscope is the time-consuming capture of the spectrum with the help of both diffraction gratings that split the measuring light into the measuring components.

[0004] From US 2005/0154277 A1, a miniaturized "in vivo" spectroscope is known which, by means of spectral analysis, can determine possibly existing hemoglobin derivatives there, for example bleeding in the gastrointestinal tract. Among other things, LED / light-emitting diodes can be used as the light source.

[0005] In addition, from US 2005/0267346 A1 it is known to use a non-invasive oximeter in which well-blooded tissue of the finger tip or ear lobe is irradiated, with conclusions based on blood absorption, a method of transmitted light or a reflected light method. on the composition (oxygen saturation) of the blood. White light LEDs can be used as the light source, however, prior to irradiation into the tissue, filters or diffraction gratings must be used to irradiate only specific wavelengths into the tissue.

[0006] From US 6,262,798 B1, an oximetry method for measuring non-hemolyzed blood is known. In this measuring method, the sample is irradiated successively with a plurality of specific monochromatic wavelengths, using a set of LEDs of different colors or ordinary white lamps, from which monochromators are used to filter specific ranges of wavelength, which are then irradiated with the sample.

[0007] In "Blood gases and oximetry: calibration-free new dry-chemistry and optical technology for nearpatient testing"; Boalth and others; Clinica Chimica Acta 307 (2001), 225-233 describes a spectrophotometric in vitro oximetry system that works with white-light LEDs as a light source. For determination

Hemoglobin derivatives using a 128-channel linear CCD / load-coupled system, a wavelength range of 470-670 nm is prepared here and taken into account for evaluation. This wavelength range is outside the wavelength range normally used to determine hemoglobin, which makes it possible to correct hemoglobin derivatives relative to bilirubin as a possible interfering substance that overlaps with hemoglobin absorption in the partial wavelength range. This extended wavelength range is only used to correct the measured hemoglobin derivatives, but not for the determination of bilirubin as an additional analyte.

[0008] For the production of polychromatic light by means of LED, so-called luminescent conversion LEDs are known which exhibit one or more primary emission wavelengths which are modified by means of luminescent conversion layers that finally broadband polychromatic light is radiated . Such light sources are described, for example, in US 2005/0127385 A1. Radiated polychromatic light consists here of a short-wave spectral region of the primary wavelength emission that is radiated by the LED chip as the primary emitter and a long-wave spectral region which is radiated by the dye layers excited by the primary LED emission as the secondary emitter.

[0009] Next, US 6,809,347 B2 describes a white light LED, which consists of a blue light emitting LED or UV light and a phosphor layer applied thereto which absorbs part of the blue or UV light and then emits light in the long-term spectrum range so that overlap produces white light, whose spectral composition can be defined by modifying the phosphor layer.

[0010] Finally, EP 1473771 A1 describes an alternative LED construction form with white light, which consists of a number of at least partially transparent light-emitting LED layers with a variety of emission wavelengths, which are superimposed so that the individual length ranges in the direction of radiation waves overlap and white light is emitted altogether. Documents WO 2005/084 527 and US 639 3310 describe spectroscopic systems with a broadband light source for the determination of hemoglobin derivatives in the blood.

[0011] The object of the invention is to further modify the oximeter for spectrophotometric determination of in vitro hemoglobin derivatives in a preferably medical sample in such a way that a compact measuring module is formed, by means of which it is possible to rapidly capture measurement spectra, with further analytes being next to hemoglobin derivatives . In addition, sufficient stability (smaller trend of size changes) and longer lamp life should be secured. The oximeter should show great comfort for the user, less maintenance required due to the longer life of the light source and high accuracy of measurement results.

[0012] This task according to the invention is solved in that the measuring light source is a polychromatic LED / luminescent diode which emits measuring radiation to determine hemoglobin derivatives at least in the spectral region B, in which the hemoglobin derivatives show significant absorption and for the determination of at least one further analyte, they emit measuring radiation in the further spectral range A, in which at least one further analyte shows significant absorption. Measurement radiation must be absorbed to such a large extent that, for example, there are very different absorption values ​​of hemoglobin derivatives and further analytes for

EP 1 987 765 B1 method of multi-component analysis. Such suitable spectral ranges are, for example, the 520-670 nm range for the determination of hemoglobin derivatives and the 450-500 nm range for the determination of bilirubin.

[0013] The term polychromatic LEDs are generally understood to mean white-light LEDs, e.g., according to already cited US 2005/0127358 A1, US 6,809,347 B2 or EP 1473771 A1, whose emission wavelength range and absorption property intensity course is matched to the hemoglobin determination and optionally extended to determine additional analyte.

[0014] According to a first variant of the invention, the measuring light source can be a LED with a luminescent conversion that contains at least one primary emitter and at least one secondary emitter, wherein the primary emitter emits measuring radiation in the spectral range A and the second emitter emits radiation in the range spectral B.

In a particularly preferred solution based on LED with luminescent conversion, the spectral waveform (light intensity depending on the wavelength) is set by the type, number and amount of phosphorescent light mass / phosphor used, and by the appropriate selection of the excitation wavelength ( type and number of primary emitter) and optimally matches the determined analyte in the sample. This design form of the measuring light source has a further advantage over conventional light sources that the emitted light on the surface of the exit from the measuring light source used for measurement, or the range of radiation angle emanating from the light source used for measurement, shows a substantially uniform spectrum. Such emission properties are particularly relevant to reducing the tolerance range with respect to the position of the optical components of the oximeter measuring system. In particular, compared to a conventional halogen lamp, the size of the radiating LED surface is preferred, which allows the oximeter's optical system to be adjusted in a manner as tolerable as possible for errors.

[0016] According to a second variant of the invention, the measuring light source comprises a plurality of light-emitting layers with different emission spectra, wherein at least one of the light-emitting layers emits measuring radiation in the spectral range A and at least one further of the light-emitting layers emits measuring radiation in the spectral range B, with the light-emitting layers so arranged relative to each other within the light source, that the measuring radiation through the output surfaces of the measuring light source used for the measurement, or through the radiation angle range of the measuring light source used for the measurement, shows a substantially uniform spectrum.

[0017] According to this embodiment, single light-emitting layers or individual emitters (SMD or conventional LEDs) can also be used to generate measuring radiation as long as they are positioned in a spatially narrowed proximity so that in particular the measuring radiation used for the measurement exhibits substantially uniform spectrum across the light source output surface. The spectral course can be set by the type, number and operating parameters of individual emitting layers or individual emitters. Under the term spatially narrowed proximity it should be understood that when the light source radiates through the sample to the detector unit, the placement of optical components is insensitive to geometric tolerance. Thus, both the intensity and the spectrum of the detected light only slightly change when deviated from the ideal position (e.g., the position of the optical components set

EP 1 987 765 B1 along the optical axis) of the optically relevant components. The beneficial effect of this is much more resistant to deregulation and a less reliable optical system.

[0018] The solution according to the invention therefore consists in the use of polychromatic LEDs for spectrometric determination of all hemoglobin derivatives and at least one further substance. Such further substances also exhibit light absorption outside the absorption area of ​​hemoglobin derivatives, which can be used for spectrophotometric determination.

[0019] An example of this type of analytes is bilirubin, which, for example, can be determined on the basis of its absorption in the wavelength range 450-500 nm (corresponds to the spectral region A of the measuring radiation).

[0020] A suitable spectral range for determining hemoglobin derivatives is in particular the wavelength range 520-670 (corresponds to the spectral range B of the measuring radiation).

[0021] According to one variant, the measuring light source has a plurality of light-emitting layers with different emission spectra, which layers are at least partially transparent and are arranged one above the other in the form of a stack, such that by overlapping the emission radiation of the individual emitting layers light, resulting radiation produces emission, which, through the output surface of the measuring light source, shows substantially uniform light scattering.

[0022] According to a further variant, the measuring light source may comprise a plurality of light-emitting areas or individual emitters with different emission spectra that are arranged in such closeness to each other that by overlapping the emission of individual light-emitting areas or individual emitters in the direction of emission arises resulting radiation, which shows a substantially uniform spectrum distribution through the output surface of the measuring light source.

[0023] The emission spectrum of such a measuring light source presents a summary spectrum and is additively composed of individual emission spectra of each of the light-emitting layers, depending on the location of the individual light-emitting layers and / or the existence of light-suppressing layers within the measuring light source, prior to exit from a light source it can still be modified.

[0024] The light emitted by the measuring light source, by the output surface of the measuring light source used for the measurement, or the range of the radiation angle of the measuring light source used for the measurement, should have a substantially uniform spectrum. Under the output surface of the measuring light source or the angle of incidence of the radiation used for measurement, in particular, it is to be understood as the area of ​​the output surface of the measuring light source which is irradiated into the sample by the oximeter's optical system and is finally recorded in the detection device. In particular, in this area, the emitted measuring radiation should have as uniform a spectral composition as possible. Under a homogeneous spectral composition, one surface is understood to mean that all places inside this surface emit light that, regardless of the exact place of emission, still exhibits the same spectral composition (the same emission wavelength range and the same intensity of each emitted radiation) .

[0025] The light emitted by the measuring light source is irradiated into a sample chamber that contains the sample to be tested. There, the irradiated light interacts with the substances contained in the sample in such a way that, depending on the type and concentration of the contained substances (in particular the substance to be analyzed), the spectral composition of the light emitted by the measuring light source is changed. This is generally done by substance-specific absorption of the light emitted by the measuring light source over specific wavelength ranges. Recording of the spectrum of the measuring light radiation modified by interaction with the sample is carried out by means of a suitable detection device. This can be done both with the help of reflective optical devices as well as devices working with transmitted light. In both designs it is beneficial that the detection device, possibly also in cooperation with the attached development device, receives the light spectrum of the measuring light source modified by interacting with the sample in the measurement stage and by assessing both individual hemoglobin derivatives as well as at least one further analyte. The recording of this spectrum is preferably carried out simultaneously by means of a detector system. However, embodiments are also possible in which the spectrum is registered sequentially. In both embodiments, a single spectrum is available for evaluation as a result of the detection.

[0026] The spectrum recorded by the detection device is compiled by the subsequent device which develops in such a way that hemoglobin derivatives and at least one further analyte can be determined. Various methods are known to those skilled in the art for this purpose, such as the multi-component method, for example.

[0027] The geometrical characteristics of the emission of the measuring light source may advantageously be further modified by means of light diffusion diffuser layers in order to homogenise the radiated measuring light. Such diffuser elements can be placed both inside the measuring light source, as their integral components as well as outside the measuring light source, as separate optical elements in the optical path.

[0028] The configuration of the measuring light source according to the invention offers a favorable assumption for spectral matching of the measuring radiation in relation to the optimization of the signal / noise ratios in the entire spectral region taking into account the absorption of the analyte and harmful light depending on the wavelength in the detector unit by deliberate selection of the type, number and the amount of primary emitter and secondary emitters.

[0029] Furthermore, the oximeter may exhibit further optical components, such as filters, optical fibers, lenses, stream splitter, diffuser elements, etc., for further transmission and directing of the measuring radiation from the measuring light source to the sample chamber and / or from the sample chamber to detection device.

[0030] In particular, it is provided that the detection device consists of a polychromator and a multi-channel detection unit attached, for example a detector system that simultaneously captures all measuring wavelengths. This results in great benefits compared to the sequential measurement, which is disclosed, for example, in JP 2004-108781, cited at the beginning, while, above all, it is important to emphasize significantly shorter measurement times and to avoid mechanically moving construction parts (diffraction grating, etc.).

[0031] In addition, filters or other optically absorbing media can be used between the measuring light source and the sample chamber and / or between the sample chamber and the detection device for further spectral adjustment of the spectrum. For example, in order to avoid harmful light in the detection unit and minimize heat evolution in the sample and / or oximeter optical system, it is possible to at least partially filter out analytically defined less suitable ranges of the wavelength of light emitted by the measuring light source. Such elements can be incorporated both as integral components of the measuring light source and as a separate structural part connected to the measuring light source.

[0032] Preferably, the spectral regions of the measurement radiation used for the determination of hemoglobin and at least one further analyte can in this way be separated by a region of lower intensity, in particular when the radiation information content suitable for the analytical determination in this intermediate range is low .

[0033] An oximeter as used herein is generally understood to be a spectrometer by which at least the most diverse hemoglobin derivatives, in particular hemoglobin derivatives, such as oxyhemoglobin (O2Hb), deoxygenated hemoglobin (HHb), carboxyhemoglobin (COHb) and methemoglobin ( MetHb) based on their different absorption properties. [0034] Overview of the benefits of polychromatic LEDs according to the invention over conventional incandescent bulbs:

· Better durability (smaller changes in output size over time);

· More compact design;

· Less heat;

· Lower IR intensity (consequently no IR filter is needed);

· Possible lifetime in the range of 100,000 hours (halogen lamps typically 5,000 hours) · increased degree of operation compared to incandescent lamps;

· Increased light output;

· Permanent work option due to high durability;

· No adjustment of the light source is required;

· Intensity regulation by chip temperature (thermometric sensor or contactless using an IR sensor);

· Possibility of spectral adjustment by operating current and radiation angle · possible to obtain a spectrum specific for the application.

EP 1 987 765 B1 [0035] Overview of the benefits of polychromatic LEDs according to the invention over the use of conventional LEDs (or laser diodes):

· They can be treated as a light bulb, as a light source with uniform spectral scattering throughout the entire output surface. By this you can simplify and make more economical photographic optics;

· Less sensitive to deviations;

· Possible improvement of the spectrum match;

· Compact, simpler temperature control;

· Possible simultaneous determination of additional analytes, for example bilirubin, together with hemoglobin parameters.

[0036] The oximeter according to the invention is primarily suitable for medical samples that contain blood components and optionally further analyte, such as bilirubin. These are primarily blood samples, in particular whole hemolyzed blood.

[0037] Variants for shaping the measuring light source according to the invention can also be freely combined with each other. For example, the emission spectra of individual light-emitting layers, individually or jointly, may be coated with appropriate layers of phosphors that can expand the original emission spectrum of individual light-emitting layers in the long-term range. In addition, for example, further light-emitting layers or individual emitters can also be added to LEDs with luminescent conversion to expand the spectral region of the emitted light, so that additional analytes can be determined, for example.

[0038] The invention will be explained below in more detail on the basis of drawings and diagrams. They show:

Figure 1 an oximeter according to the invention in a schematic representation;

Figure 2 absorption coefficients of hemoglobin O2Hb, HHb, COHb and MetHb derivatives as well as bilirubin depending on the wavelength in nm and

Figure 3 to Figure 6 show the emission spectra of various polychromatic LEDs.

[0039] Figure 1 shows in a schematic representation an exemplary structure of an oximeter according to the invention. In the oximeter, the polychromatic LED 1, as the measuring light source, is coupled together with the further light source 2 through the diffraction grating 3 and the lens system 4 directly to the sample chamber 5, for example a measuring cuvette with a blood sample to be analyzed. In this example, a further light source 2 is used to calibrate the oximeter's wavelength.

[0040] The polychromatic LED 1, which emits broadband measurement radiation in the spectral region from 450 to 670 nm to the chamber with sample 5, is thermally thermostated using a Peltier element and an NTC temperature sensor. The polychromatic LED is further adjustable for intensity 8

EP 1 987 765 B1 through a control circuit with a photodiode 6. The optical system is made in such a way that the setting of the polychromatic LED 1 in relation to the optical axis on the basis of a larger output surface of the measuring light source and a substantially uniform spectrum radiated by this output surface is no longer indispensable necessarily. Alternatively, a filter 7 can be used between the measuring light source 1 or the diffraction grating 3 and the sample chamber 5 to adjust the measuring radiation in the selected spectral region. The detection device, which is connected to the measuring cuvette 5 via the optical fiber 8, consists of a polychromator 9, e.g. a mesh spectrometer and a multichannel detection unit 10, e.g. a set of detectors recording all measuring wavelengths simultaneously. Figure 1 does not clearly show a value development / determination device attached after a detector device which, based on the spectrum recorded by the detection device, means hemoglobin derivatives and at least one further analyte.

[0041] The spectral requirements for measuring light source 1 are derived from a spectrometer or analyte being determined (hemoglobin derivatives and at least one further analyte). The determinations of hemoglobin and bilirubin derivatives, as an example of a further analyte, are based on the absorption coefficients shown in Figure 2. Therefore, for spectrometric determination of an analyte, a measuring light source 1 with appropriate intensity values ​​within this wavelength range is required. From a spectral point of view, the measuring light source 1 should have the following properties as appropriate for the application:

· Drooping side sides in the long-term area to reduce harmful light in the detector · maximum intensity in the spectral area B maximum absorption of hemoglobin derivatives (520-670 nm) · maximum intensity or sufficient intensity for measurement (significant) in the short-wave spectral area A (450- 500 nm) for bilirubin · reduction of intensity between these two spectral regions A and B.

Examples:

[0042] The following examples are based on the oximeter of Figure 1. For this purpose, a mesh spectrometer 9 with a resolution of 1.5 nm and a row sensor 10 with a pixel number 512 was used. The measuring cuvette 5 forms a flow channel 1 mm wide and thick layers 100 mm. The spectral measurement of polychromatic LED 1 was carried out on an air-filled measuring cuvette. The coupling of the LED measuring radiation in the measuring cuvette 5 and consequently in the optical fiber 8 is carried out through the lens 7 (magnification factor of about 1.6). The optical fiber 8 is made as a bundle of fibers so that a small radius of curvature of the optical fiber can be created between the measuring cuvette and the spectrometer. The active diameter of the fiber at the input is about 0.7 mm. At the light output, the individual fibers are made as fiber strands and thereby simultaneously form the spectrometer input gap. Photodiode 6 is used to adjust the intensity of LED 1. In this example, LED 1 is connected together with the further light source 2 (neon bulb) by means of diffraction grating 3, 9

EP 1 987 765 B1 so that changes can be made between two different types of lighting (measuring radiation and calibration radiation). Alternatively, as already mentioned, it is possible to introduce in the construction a filter element 7 for further spectral adjustment of the measuring light source 1.

Example 1:

[0043] On the basis of the measurement structure presented above, a market LED white light from Seoul Semiconductor (type: N32180 400 mA 3.5 V) was used. The broadband spectrum (see Figure 3) enabled technical measurement of the determination of hemoglobin and bilirubin derivatives. The ratio between excitation intensity and luminescence intensity as well as a decrease in intensity above 600 nm are suitable for the application.

Example 2:

[0044] In this example, Luxeon white light LED (type: LXHL 1 watt) was used (see spectrum according to Figure 4). This LED also allows technical measurement of the determination of hemoglobin and bilirubin derivatives, however, to reduce harmful light in the spectrometer requires the use of additional filters in the long-term region. Figure 4 shows the unfiltered and filter spectrum (BG38 Schott, 2 mm). This light source is therefore suitable for use in particular in combination with this type of filter.

Example 3 [0045] As a preferred variant, a polychromatic LED with two phosphors and a color temperature of 4000 is used^aboutK. The required spectrum is obtained by a LED chip with a dominant wavelength of 460-462.5 in combination with two phosphors (phosphor 1: green, CIE coordinates: x = 0.195 +/- 0.004 y = 0.651 + / 0.004 and phosphor 2: orange , CIE coordinates: x = 0.450 +/- 0.002 y = 0.537 +/- 0.002). This LED is set to 350 mA operating current. In this example, the operating current is 100 mA. The spectrum obtained is shown in Figure 5 with the analytes absorption coefficients. This light source meets all the requirements for measuring light sources (1). Additional spectrum adjustment by means of filters is not required here.

[0046] Figure 6 shows the resulting spectrum of such a LED with luminescent conversion based on examples with two phosphors (510 nm and 590 nm) as secondary emitter and primary 460 nm emitter. LED chips, blue or UV emitting with luminescent dyes are combined here. These dyes are contained in the paste that is applied to the LED chip. Short-wave and therefore richer blue light stimulates dye or dyes to glow. At the same time, long-term light is rendered, which is more energy-poor. Because not all blue light is transformed, the resulting additive mixture of spectral colors is obtained (see the result spectrum according to a smooth line) of polychromatic light with the first narrowband maximum spectrum in the spectral range A around 460 nm and the second broadband spectrum maximum in the spectral region B 510-590 nm . These two spectral regions are separated by a minimum spectral region of around 485 nm. It is particularly advantageous here that, due to the narrowband emission radiation of the original emitter, there is a short-wave range of measurement waves for determining bilirubin per 10

Based on its absorption maximum at about 460 nm and by the broadband emission radiation of the secondary emitter there is a wide long-term area in which all hemoglobin derivatives for determination exhibit significant absorption and absorption maxima.

[0047] The spectrum of this kind of polychromatic LED with luminescent conversion according to the invention, by selecting the primary emitter (LED chip that emits in the spectral region A) and choosing a combination of different phosphors (secondary emitters that emit in the spectral range B) can be specifically focused on further analytes sought.