RU133941U1 - DEVICE FOR MONITORING THE HEMODIALYSIS PROCESS - Google Patents

Abstract

A device for monitoring the hemodialysis process, containing sequentially installed radiation sources, the maximums of the emission spectrum of which are located at wavelengths of 265 nm and 290 nm, respectively, an optical beam-forming system, a flow cell, an optical radiation receiver and a signal processing unit with an interface, characterized in that an additional radiation source, the maximum of the radiation spectrum of which is located in the region of lengths 450-550 nm, and one photodetector is used as the radiation detector, the region of ktralnoy sensitivity which overlaps the emission spectra of light sources used.

Description

The utility model relates to the field of optics, namely to the study and analysis of liquid biological media using spectrophotometric methods and can be used to determine the concentration of uric acid in biological fluids, for example, samples of spent dialysate during hemodialysis in real time.

Hemodialysis therapy is the main way to maintain the life of patients suffering from chronic renal failure. The patient’s circulatory system is connected to the “Artificial kidney” apparatus, and within 3 ... 5 hours low molecular weight uremic toxins - urea, creatinine, uric acid and other components are removed from the blood through a semipermeable membrane. The problem of monitoring the adequacy of the hemodialysis process has not yet been solved, although several approaches have been proposed, the use of which involves the use of consumables and expensive equipment, the cost of which is comparable to the cost of hemodialysis machines.

Several devices are known for determining the content of metabolic products in dialysis fluid during dialysis treatment, based on a spectrophotometric method.

A device for monitoring the hemodialysis process (WO 99/62574, 12/09/1999), consisting of a light source, an optical system for generating and transmitting a light beam, a flow cell connected to the output line of the artificial kidney apparatus, a photodetector and a computer equipped with a display and a printer. The principle of operation is based on measuring the spectral transmittance of dialysate in a flow cell in the output line of the artificial kidney apparatus in the ultraviolet (UV) region of the spectrum, for example, at a wavelength of 280 nm, with a specified time interval, plotting the graph reflecting the change in the dialysate absorption rate during hemodialysis session in relative units. The UV absorbance at a wavelength of 280 nm has a direct correlation with the concentration of urea and creatinine in spent dialysate samples.

The disadvantages of such a monitoring device include the impossibility of determining the concentration of individual components of the sample, since this requires additional information and an updated methodology for the analysis and processing of spectral data.

A device is known for monitoring a liquid biological medium, for example, components of a dialysis fluid during hemodialysis (RU, Patent No. 2161791, January 10, 2001), comprising a radiation source installed in series, an optical beam forming system, a flow cell with a test fluid flowing through it, an optical radiation receiver (spectrometer) and signal processing unit with interface. The principle of operation is based on the formation of a light beam from a source of a continuous spectrum in a controlled area of a liquid biological medium, decomposition of the transmitted radiation into a spectrum, and consists in the fact that before starting monitoring, a stream of light radiation is passed through a cuvette with solutions of the studied components of known concentration, and the transmitted radiation is decomposed into a spectrum and determine the portion of the spectrum, including all absorption bands of the studied components, then in this section, determine the change in the absorption characteristics islyayut spectral absorption dynamics of the correlation coefficients for each component of the test, then the light flux passed through the cell with the liquid flowing therethrough biological medium, and then the correlation coefficients from the spectral components of the absorption study investigated the dynamics of the concentration of the components.

The disadvantages of the device include the need to use complex and expensive spectral equipment.

A device is known for monitoring the hemodialysis process (RU, Patent No. 121373, 10.20.2012), consisting of 2 radiation sources, the maximums of the emission spectrum of which are located at wavelengths of 265 nm and 290 nm, respectively, of an optical system for beam formation, a flow cell connected to the output line of the Artificial Kidney apparatus, an optical radiation receiver, and a signal processing unit with an interface. Immediately before the start of the hemodialysis session, when a clean dialysate flows in the output line and does not contain components that are monitored during the monitoring process and is a reference standard, the initial operation mode of the device is established and reference signals at the output of photodetectors corresponding to 100% transmission are measured. The principle of operation is based on measuring the spectral transmittance of dialysate in a flow cell in the output line of the artificial kidney apparatus at two wavelengths of 265 nm and 290 nm. The calculation of the concentration of uric acid in dialysis fluid by transmittance at two wavelengths is based on the Bouguer-Lambert-Beer law and the additivity principle for a binary medium.

The disadvantages of such a monitoring device include the inability to register reference radiation transmission signals during the hemodialysis procedure. As a result, the measurement error associated with a possible change in the properties of pure dialysate (the solvent of the test sample) during the hemodialysis process is not taken into account. In addition, the need to register reference signals for transmitting radiation through a standard solution before connecting the patient to the "Artificial kidney" apparatus eliminates the use of a device for monitoring the hemodialysis process after the start of the procedure.

The considered device is the closest in combination of essential features to the proposed utility model.

The technical problem solved by the utility model is the creation of a simple device for monitoring the hemodialysis process by measuring the concentration of uric acid in the flowing dialysate, capable of working under conditions of changing properties of pure dialysate; the use of a device for monitoring the hemodialysis process is possible from any point in time of the procedure.

The problem is solved due to the fact that the proposed device, as well as the known one, contains sequentially installed radiation sources, an optical beam forming system, a flow cell, an optical radiation receiver and a signal processing unit with an interface, characterized in that an additional radiation source is introduced, the maximum of the emission spectrum of which is located in the region of lengths 450-550 nm, and one photodetector is used as the radiation detector, the spectral sensitivity region of which is crossed Vaeth emission spectra of light sources used.

The technical result is to reduce the measurement error and expand the conditions of use of the device for monitoring the hemodialysis process.

The utility model is illustrated by drawings, in Fig. 1 shows a block diagram of the proposed device, in Fig. 2 - transmission spectra of pure dialysate and spent dialysate samples, assigned to different types of the proposed classification in the wavelength region of 190 ... 550 nm, in Fig. 3 - spectrum absorption of one of the samples of spent dialysate, absorption spectra of uric acid, pseudocomponent Nk, their sum.

The study of the features of the shape of the absorption spectra of dialysate samples of about 300 patients made it possible to propose a classification of spectra according to informative features in the range 260 ... 290 nm (Fig. 2): absorption spectra, the shape of which in this area, are described by the function dk / dλ> 0 s maximum in the region of 290 nm; to group B, spectra for which a dependence of the type dk / dλ≈0 is characteristic without an explicit maximum; to group C - spectra, the shape of which has a falling section in the indicated region, at which dk / dλ <0.

The composition of the dialysis fluid is complex and contains a large number of components with various combinations of concentrations. An analysis of the spectral absorption shape of the spent dialysate samples in the range 260 ... 350 nm showed that in this region the dialysate absorption is determined by the absorption of only two components (Fig. 3): uric acid and the conditionally named pseudocomponent Nk. The latter is a combination of several components, which include tryptophan, hippuric acid, pseudouridine, adenosine, and a number of other, including unidentified, components. The concentration of these components is low, their combination determines the individuality and form of the spectral absorption of dialysate. The UV absorption spectrum of the pseudo-component Nk was obtained experimentally. The diversity in the shape of the spectra of patients can be characterized by a variation in the amount of the pseudocomponent Nk in the dialysate.

Thus, to determine the concentration of uric acid in the dialysate, it is necessary to limit the spectral region to a range of 260 ... 350 nm and take into account the contribution to the absorption of the dialysate of the pseudo-component in this region. This circumstance greatly simplifies the requirements for spectral equipment — the determination of two components in a binary mixture, for which it is necessary to measure the spectral transmission of the medium at two wavelengths (λ ₁ = 265 nm and λ ₂ = 290 nm).

Measurement of spectral transmittance at a third wavelength in the range of 450-550 nm allows you to record a reference signal during the hemodialysis procedure. When using pure dialysate as a reference for comparing the spectral transmittance, it is necessary to fix the reference signal before starting the hemodialysis procedure. Given that in the wavelength range of 450-550 nm (λ ₃ ), the transmission coefficients of the samples of both pure (Fig. 2) and spent dialysate correspond to 100%, it becomes possible to register a reference signal in the specified range during the hemodialysis procedure. The introduction of the third LED allows to reduce the measurement error associated with a possible change in the properties of pure dialysate (solvent of the test sample) during the hemodialysis process. In addition, the need to register reference signals for transmitting radiation through a standard solution before connecting the patient to the "Artificial kidney" apparatus eliminates the use of a device for monitoring the hemodialysis process after the start of the procedure. The use of the proposed device for monitoring the hemodialysis process is possible from any time during the procedure

A device for monitoring the hemodialysis process contains (Fig. 1) a sequentially installed radiation source 1, including three LEDs with maxima of the radiation spectrum at wavelengths of 265 nm, 290 nm and 550 nm, respectively; optical system for forming beams 2; a flowing quartz cell 3 connected to the dialysis line of the “Artificial kidney” apparatus with a dialysis fluid flowing through it; an optical radiation receiver 4, including a photodetector for detecting the radiation of the LEDs passing through the dialysate cell; signal processing unit with interface 5 and computer 6, equipped with specialized software.

The calculation of the concentration of uric acid in the dialysis fluid by transmittance at two wavelengths is based on the Bouguer-Lambert-Behr law and the principle of additivity, according to which for a mixture of two non-interacting components the spectral absorption coefficient k _{d (λ) of a} medium layer of unit thickness at wavelengths λ ₁ and λ ₂ can be written as

,

- спектральное поглощение диализной жидкости (исследуемой среды) на выбранных длинах волн;Where:

,

- spectral absorption of dialysis fluid (test medium) at selected wavelengths;

,

- спектральное поглощение мочевой кислоты на длинах волн λ₁ и λ₂ соответственно;

,

- spectral absorption of uric acid at wavelengths λ ₁ and λ _2, respectively;

,

- спектральное поглощение компонента Nk на длинах волн λ1 и λ2 соответственно;

,

- spectral absorption of the component Nk at wavelengths λ1 and λ2, respectively;

,

- спектральные удельные коэффициенты поглощения мочевой кислоты на длинах волн λ₁ и λ₂;

,

- spectral specific absorption coefficients of uric acid at wavelengths λ ₁ and λ ₂ ;

,

- спектральные удельные коэффициенты поглощения компонента Nk на длинах волн λ₁ и λ₂;

,

- spectral specific absorption coefficients of the component Nk at wavelengths λ ₁ and λ ₂ ;

C ₁ is the concentration of uric acid in the dialysis fluid; C ₂ is the concentration of the Nk component in the dialysis fluid;

, где I_λ - интенсивность излучения на выбранной длине волны (λ₁ или λ₂), прошедшего через исследуемый объект;

- интенсивность излучения опорного сигнала на длине волны λ₃, прошедшего через исследуемый объект. λ₃ расположена в диапазоне длин волн, где интенсивность прошедшего излучения пробчистого и отработанного диализата одинакова.T _λ1 , T _λ1 - measured spectral transmittance of dialysis fluid at selected wavelengths; the spectral transmittance of the object is calculated as the ratio of the flows

where I _λ is the radiation intensity at the selected wavelength (λ ₁ or λ ₂ ) that passed through the object under study;

- the radiation intensity of the reference signal at a wavelength of λ ₃ passed through the studied object. λ ₃ is located in the wavelength range, where the intensity of the transmitted radiation from the cured and spent dialysate is the same.

The device provides automated measurement of transmission coefficients of dialysis fluid in the dialysis line of the artificial kidney apparatus at wavelengths of 265 nm, 290 nm and 550 nm at specified time points, calculation of the concentration of uric acid and pseudo-component Nk, construction of time dependences of the concentration of uric acid in dialysis fluid by the course of the session and the amount of uric acid excreted from the patient’s body, from the moment the session began, the monitoring results are displayed on a computer screen and saved as a file . Measurement of spectral transmittance at a third wavelength of 550 nm allows you to record the reference signal during the hemodialysis procedure.

The device operates as follows. The radiation of the LEDs 1 using the beam forming system 2 is directed to the selected area of the quartz flow cell 3 connected to the dialysis line of the artificial kidney apparatus and the radiation transmitted through the cell with dialysis fluid is focused on the photodetector 4. The signal processing unit with interface 5 consists of a registration module electrical signals from the output of each channel of the photodetector, followed by amplification and conversion to a digital code. In addition, the signal processing unit with interface 5 provides for setting the registration mode, controlling the operation of radiation sources using power sources, calculating the transmittance of dialysate at analytical wavelengths, storing data in an internal buffer, generating and transmitting data to computer 6.

After connecting the patient to the “Artificial Kidney” device using a timer signal, at equal intervals of time, signals are recorded at the output of the photodetector, and for each channel (at a wavelength of 265 nm, 290 nm and 550 nm), the transmittance of radiation transmitted through the cell is calculated at a given time. The data obtained are processed, and according to the proposed method, the concentration of uric acid and the amount of uric acid excreted from the patient's body are calculated. The received data is stored in an internal buffer, and, upon request, transferred to computer 6.

Setting the monitoring mode (duration of the process, the frequency of measurements) and calculation parameters (specific absorption coefficients of the components, dry weight of the patient, dialysate flow rate, patient code), calculation of the concentration of the controlled components in the dialysis fluid, plotting the concentration and the total amount excreted from the patient’s body uric acid from time to time, saving monitoring results are implemented using specialized software running on computer 6.

It should be noted that in the spectral study of samples of spent dialysate of various types of the previously proposed classification, the concentration of the component in the dialysis fluid affects the dialysate absorption level in the uric acid absorption band. This circumstance proves that the determination of the concentration of uric acid by the classical method from the level of absorption of the dialysis fluid at one wavelength (in the region of the absorption maximum) inevitably leads to a distortion of the results.

In order to take into account the contribution of the pseudo-component Nk to the spectral absorption of dialysate and to increase the accuracy of determining the concentration of uric acid, it is necessary to measure at least two spectral regions - the region of maximum absorption of uric acid 280 ... 300 nm and the minimum absorption bands 250 ... 270 nm.

In each of these areas, it is necessary to select a narrow spectral region, for example, 265 nm and 290 nm, select the LEDs emitting in these areas, and measure the spectral transmittance of the dialysate.

The LEDs used in the inventive device emit at wavelengths of 290 nm and 265 nm and 550 nm, the use of the latter allows you to register a reference signal during the hemodialysis procedure. A quartz flow cell with an optical thickness of 5 mm is in good agreement with the sizes of the output dialysis lines of the Artificial Kidney apparatus and the dialysate flow rate. The device does not require additional power sources (semiconductor LEDs are powered by a computer via a USB port through which data exchange is organized).

The use of the proposed device for determining the concentration of uric acid in dialysis fluid in the output line of the apparatus "Artificial kidney" allows to reduce the measurement error under conditions of changing properties of pure dialysate. The use of a monitoring device is possible from any time during the hemodialysis procedure.

Example. The use of a utility model for determining the concentration of uric acid in dialysis fluid during a hemodialysis session.

The inventive device was used to determine the concentration of uric acid in the dialysis fluid of the output line of the apparatus "Artificial kidney" during one of the hemodialysis sessions. At the same time, samples were taken for spectral measurements. In each sample, the concentration of uric acid was determined in parallel with the standard biochemical method. Table 1 compares the results of calculating the concentration of uric acid in dialysis fluid according to the proposed device and the data of biochemical analysis.

Table 1. Comparison of the results of calculating the concentration of uric acid in dialysis fluid by the magnitude of the spectral absorption with the results of biochemical analysis

t min With _AcUr , μmol / L, the proposed device With _AcUr , µmol / L biochemical analysis fifteen 146 140 thirty 128 120 60 103 one hundred 90 86 80 120 72 70 150 61 60 180 54 fifty 210 44 40

The discrepancy between the results of calculating the concentration of uric acid according to the proposed device with the data of biochemical studies does not exceed 10%.

Claims (1)

A device for monitoring the hemodialysis process, containing sequentially installed radiation sources, the maximums of the emission spectrum of which are located at wavelengths of 265 nm and 290 nm, respectively, an optical beam-forming system, a flow cell, an optical radiation receiver and a signal processing unit with an interface, characterized in that an additional radiation source, the maximum of the radiation spectrum of which is located in the region of lengths 450-550 nm, and one photodetector is used as the radiation detector, the region of ktralnoy sensitivity which overlaps the emission spectra of light sources used.

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