RU121373U1 - DEVICE FOR MONITORING THE HEMODIALYSIS PROCESS - Google Patents

Abstract

A device for monitoring the hemodialysis process, containing a radiation source installed in series, an optical beam forming system, a flow cell, an optical radiation receiver and a signal processing unit with an interface, characterized in that two LEDs are used as a radiation source, the maximum of the radiation spectrum of one of which is located in the region wavelengths of 265 nm, the other in the wavelength region of 290 nm, and two photodetectors are used as a radiation detector, the spectral sensitivity regions of which overlap the emission spectra of the corresponding LEDs.

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 UV spectral region, for example, at a wavelength of 280 nm, with a specified time interval, plotting a graph reflecting a change in the dialysate absorption rate during a 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 2161791 C2, 01/10/2001), comprising a radiation source, an optical beam-forming system, a flow cell with a test fluid flowing through it, an optical radiation detector (spectrometer) ) and a signal processing unit with an 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 and 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.

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 to create a simple device for monitoring the dialysis process by measuring the concentration of uric acid in the flowing dialysate.

The problem is solved due to the fact that the proposed device, as well as the known one, contains a sequentially installed radiation source, an optical beam forming system, a flow cell, an optical radiation receiver and a signal processing unit with an interface, characterized in that it is used as a radiation source two LEDs, the maximum of the emission spectrum of one of which is located in the wavelength region of 265 nm, the other in the wavelength region of 290 nm, and two photodetectors are used as the radiation detector detector, spectral sensitivity areas which overlap the emission spectra of the respective LEDs.

The technical result is to simplify the monitoring device.

The utility model is illustrated by drawings, figure 1 shows a block diagram of a device, figure 2 - spectral absorption of the main components of the sample spent dialysate in the wavelength range of 200 ... 350 nm in figure 3 - spectral characteristics of uric acid solutions with a concentration of 0.05, 0.10, 0.15 and 0.20 mmol / L, Fig. 4 shows the spectral absorption of dialysate (sample for 15 min. Session, patient K., curve type B) and type A and C spectra obtained by changing the concentration of the pseudocomponent Nk in the dialysis fluid.

The composition of the dialysis fluid is complex and contains a large number of components with various combinations of concentrations. The results of studies of the spectral absorption of dialysis fluid during hemodialysis in the wavelength range of 200 ... 350 nm proved that the absorption of radiation is mainly due to the presence of low molecular weight components in the dialysate - urea, creatinine, uric acid, tryptophan, hippuric acid, pseudouridine, adenosine and a number of other components.

The absorption spectrum of pure dialysis fluid lies in the region of 200 ... 210 nm, urea - 200 ... 220 nm, creatinine 200 ... 250 nm, uric acid 200 ... 350 nm. The pool of other components present in small amounts in the dialysate absorbs radiation in the region of 200 ... 350 nm and can conditionally be called the pseudo-component Nk (Fig. 2).

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 Nk in this region. This circumstance significantly 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.

A device for monitoring the hemodialysis process contains (Fig. 1): a radiation source 1, including two LEDs with maxima of the radiation spectrum at wavelengths of 290 nm and 265 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 two photodetectors for detecting the radiation of the LEDs that passed 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 a 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

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

T _λ1 , T _λ2 - measured spectral transmittance of dialysis fluid at selected wavelengths;

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

, - spectral absorption of the component Nk at wavelengths λ ₁ and λ _2, respectively;

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

, - 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.

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 and 290 nm at specified times, calculation of the concentration of uric acid and pseudo-component Nk, construction of time dependences of the concentration of uric acid in dialysis fluid during 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.

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 the dialysis fluid is focused on the photodetectors 4. The signal processing unit with interface 5 consists of a registration module electrical signals from the output of each 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, registering reference signals, calculating dialysate transmittance at analytical wavelengths, storing data in an internal buffer, generating and transmitting data to a computer 6 .

Immediately before the start of the hemodialysis session, when the patient is not yet connected to the device, the extracorporeal circuit lines and the dialyzer are filled with saline. In this case, pure dialysate flows from the dialysate preparation system into the output line, which does not contain components controlled during the monitoring process and is a reference standard. At this time, using the signal processing unit with interface 5, the initial operation mode of the device is established and reference signals at the output of the photodetectors are measured, which correspond to 100% transmission. After the patient is connected to the dialyzer using a timer signal, signals at the output of photodetectors are recorded at regular intervals, and for each channel (at a wavelength of 265 nm and 290 nm), the transmittance of radiation transmitted through the cell at a given time is 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.

Analysis of the transmission and absorption spectra of solutions of uric acid of various concentrations (Fig. 3) shows that for the quantitative assessment of the concentration of uric acid in solutions, one of the absorption bands can be used, which are described by the following characteristics: λ _max = 235 nm, δλ = 14 nm; λ _max = 290 nm, δλ = 12 nm.

Spectral studies of the dialysis fluid of a large group of patients (sample - 81 patients, more than 250 hemodialysis sessions) showed that the spectral absorption spectra can be divided into groups A, B and C and allowed us to experimentally determine the shape of the absorption spectrum of the pseudo-component Nk. may be characterized by a variation in the amount of the pseudocomponent Nk in the dialysate.

In figure 4. the absorption spectrum of a type B dialysate sample (patient K.) is presented taken at 15 minutes from the beginning of the dialysis session, as well as the absorption spectra of type A and C obtained by changing the amount of the pseudo-component Nk.

Obviously, the shape of the absorption curve of the dialysate assigned to type A in the region of 290 nm is mainly determined by the relative content of uric acid (band λ _max = 290 nm, Fig. 3). In the wavelength range of 250 ... 290 nm, the shape of the absorption curve is determined by the presence of both uric acid and the pseudocomponent Nk in the dialysis fluid.

It should be noted that when switching from type A to type C (increasing the concentration of the Nk component in the dialysis fluid), the dialysate absorption level in the uric acid absorption band changes, although the concentration of uric acid remains unchanged. This circumstance proves that the determination of uric acid concentration by the classical method from the level of absorption of dialysis fluid at one wavelength (in the region of 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. They emit in a narrow spectral region, are compact, inexpensive. 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" when using flow cells allows you to solve the following tasks:

- determine the concentration of uric acid in the dialysis fluid during hemodialysis in real time;

- determine the spectral absorption of dialysis fluid at two wavelengths;

- determine, if necessary, the concentration of the pseudo-component Nk (in relative units);

- implement monitoring of the hemodialysis procedure in the on-line mode;

- quantify the rate of change in the concentration of uric acid in the flowing dialysate;

- determine the amount of uric acid excreted from the patient’s body from the moment the hemodialysis session begins in real time.

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 k ₂₆₅ , 1 / cm k ₂₉₀ , 1 / cm C _AcUr , mmol / l proposed device C _AcUr , mmol / L biochemical analysis fifteen 5.466 5.466 0.146 0.14 thirty 4.906 4.884 0.128 0.12 60 3.99 3.946 0.103 0.10 90 3.396 3.322 0.086 0.08 120 2.914 2.8 0.072 0.07 150 2.56 2.42 0.061 0.06 180 2.292 2.14 0.054 0.05 210 1.984 1.822 0.046 0.04

Note that the contribution of the second unidentified component to the absorption of dialysis fluid at a wavelength of 290 nm reaches 25%. 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 12%.

Figure captions:

Figure 1. A device for monitoring the hemodialysis process contains: a radiation source 1, including two LEDs with maxima of the radiation spectrum at wavelengths of 290 nm and 265 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 two photodetectors for detecting the radiation of the LEDs that passed through the dialysate cell; signal processing unit with interface 5 and computer 6, equipped with specialized software.

Figure 2. Spectral absorption of the main components of the spent dialysate sample in the wavelength range of 200 ... 350 nm. The absorption spectrum of pure dialysis fluid lies in the region of 200 ... 210 nm, urea - 200 ... 220 nm, creatinine 200 ... 250 nm, uric acid 200 ... 350 nm, the pool of the remaining components (pseudo-component) 200 ... 350 nm.

Figure 3. The spectral characteristics of uric acid solutions with a concentration of 0.05, 0.10, 0.15 and 0.20 mmol / l: a - spectral transmittance; b - spectral absorption.

Figure 4. Spectral absorption of dialysate (sample for 15 min. Session, patient K., curve type B) and spectra of type A and C obtained by changing the concentration of the pseudocomponent Nk in the dialysis fluid.

Claims (1)

A device for monitoring the hemodialysis process, which contains a sequentially installed radiation source, an optical system for beam formation, a flow cell, an optical radiation receiver and a signal processing unit with an interface, characterized in that two LEDs are used as the radiation source, the maximum of the radiation spectrum of one of which is located in the region wavelengths of 265 nm, the other in the wavelength region of 290 nm, and two photodetectors, spectral sensitivity regions, are used as a radiation detector which overlap the emission spectra of the respective LEDs.