CC BY
65
Известия высших учебных заведений. Поволжский регион
УДК 681.518
A. Yu. Tychkov
DEVELOPMENT OF THE ARTERIAL PRESSURE REGISTRATION DEVICE WITH INCREASED OPERATING EFFICIENCY
Abstract.
Background. The subject of the research is the blood pressure measurement devices. The research object is the process of registration, conversion and transmission of pulse wave signals. The aim of the work is to conduct a critical analysis of the known devices for blood pressure measuring, development and research of the author's virtual device in the Labview environment.
Matherials and methods. Improvement of the blood pressure measuring devices was carried out by introduction of new registration elements and pulse wave signal conversion. The article includes the examination of the developed virtual device on real bases of pulse wave signals.
Results. The research results include the analysis of the known solutions, blood pressure measuring devices, description of advantages and disadvantages thereof. The author developed a virtual circuit device for pulse wave registration and adduced the research thereof.
Conclusions. At its microprocessor implementation the developed device can be used both in private and public clinics to enhance the accuracy of blood pressure measutrements, especially in conditions of free physical activity.
Key words: arterial pressure, cuff, automatic carpal contour, Lab View.
А. Ю. Тычков
РАЗРАБОТКА УСТРОЙСТВА РЕГИСТРАЦИИ АРТЕРИАЛЬНОГО ДАВЛЕНИЯ С ПОВЫШЕННОЙ ЭФФЕКТИВНОСТЬЮ РАБОТЫ
Аннотация.
Актуальность и цели. Предметом представленных исследований являются устройства измерения артериального давления. Объектом исследования являются процессы регистрации, преобразования и передачи сигналов пульсовой волны. Целью работы является проведение критического анализа известных устройств измерения артериального давления, разработка и исследование авторского виртуального устройства в среде Labview.
Материалы и методы. Совершенствование устройств измерения артериального давления произведено посредством введения новых элементов регистрации и преобразования сигналов пульсовой волны. Приведены исследования разработанного виртуального устройства на реальных базах сигналов пульсовой волны.
Результаты. Результаты работы заключаются в проведенном анализе известных решений, устройств измерения артериального давления, описания их достоинств и недостатков. Разработана виртуальная схема устройства регистрации пульсовой волны и приведено ее исследование.
Выводы. Разработанное устройств при его реализации в микропроцессорном исполнении может быть использовано как в частных, так и государственных клиниках для повышенной точности измерения артериального давления, особенно в условиях свободной двигательной активности.
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University proceedings. Volga region
№ 1 (33), 2015 Технические науки. Электроника, измерительная и радиотехника
Ключевые слова: артериальное давление, манжета, манжеты, автоматический кистевой контур, Lab View.
Introduction
Fast development of electronics, means of personal communication, computer facilities, passive detectors of a physiological state, and also active means of self-treatment, promotes development of health state diagnostics and monitoring devices carried out by the patient [1]. One of the most important directions in change of health providing approach is monitoring own physiology and measurement of the major indicators of activity by the person.
One of the most important indicators of the person’s health is the cardiovascular system condition [2], which can be estimated by means of determination of key parameters, such as pulse and level of arterial pressure. Processing of signals like pulse fluctuations is cornerstone of the operation principle of modern arterial pressure measurement devices - tonometers.
Tonometers represent the devices which are in total consist of the pressure sensor, the microcontroller and the regulation of pressure in the cuff mechanism , including tiny electric pump, pair of valves and a pomp [3]. Besides a basic element complete set for modern automatic tonometers essentially new decisions which promote device management process improvement are developed [4]. So, for example, additional communications for work with external peripheral devices [5] and connections with the personal computer and/or the mobile device [6] are created; they are equipped with the power unit (the network adapter) and use function of the speech guide [7], etc. All alternative options of tonometers element base change are directed on improvement of arterial pressure and pulse (frequency of heart reductions), measurement algorithm, including signal processing and its analysis.
Numerical values of pressure level indicators are defined by means of the automated mathematical processing described with application of the most convenient programming language. Today environment of visual and graphic programming of LabVIEW of the National Instruments [8, 9] company has a big popularity. The advantage of this environment is evident representation of the circuit solution of the device in the form of the developed virtual device of any complexity reflecting both internal circuit topology, and the external display panel of measurement results.
Basic value in operation of arterial pressure measurement devices has a cuff design on which qualitative characteristics in particular efficiency and reliability of measurement results [10] depend.
Methods
The arterial blood pressure (AP) is one of the most important indicators of a person health state. AP - the magnitude showing force value and blood pressure in heart [11].
Various interpretations of the AP measurement methods are known [12]. However, despite variety of existing approaches to the AP measurement process, all of them are used in modern tonometers for control and diagnostics of a person’s condition in the medical or sports purposes or for the prevention of physical or emotional human body overloads in various conditions of its activity.
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Today there is a huge number of various devices allowing to carry out AP measurement [4-7, 13, 14]. The block diagram of the known AP measurement devices [14] is provided on the fig.
Pressure sensor
Oscillatory contour
Pump drive chain
Valve of operating scheme
Micro count roller
Fig. 1. Block diagram of the AP measurement devices
Display
Memory
Console
The cuff containing an air bag, by means of rubber tubes is connected to entrances of the pressure sensor, the pump and the valve. The pressure sensor exit is connected to an oscillatory contour. The exit of the pump is connected with a pump drive chain, and a valve exit with the valve of the operating scheme. The oscillatory contour, pump drive chain and the valve of the operating scheme are directly connected with the microcontroller. The timer, the block of indication (display), memory and the console connected with the power unit are connected to the corresponding exits of the microcontroller. The power unit is also connected to one of microcontroller exits.
The presented devices don't reflect the full list of existing tonometers [4-7, 13, 14], however they show the opportunities, allowing to improve characteristics of AP measurement devices for process efficiency and speed increase.
Results
The carried-out critical analysis of existing AP measurement devices and the development of own solution of the modern AP measurement device allowing to increase AP measurement efficiency and speed by the patient, both in case of limited physical capacities (disabled people), and under control of the expert [15] is result of the authors work.
The developed AP measurement device includes a cuff with an automatic carpal contour, pressure sensor, the tiny electric pump with the valve, the microcontroller, and also the built-in sound signaling device. The entrance of a cuff is connected with the tiny electric pump and the valve which entrances are connected to one of microcontroller exits, and an exit - with pressure sensor which exit is connected to a microcontroller conclusion. The built-in sound signaling device, the display and the keyboard are also connected to the microcontroller.
Feature of the developed device is new circuitry solution of a cuff with an automatic carpal contour application at AP measurement developed by authors [16]. The developed cuff used in the device, is "adapted" under a hand of the patient that allows to carry out uniform pumping and an air etching in it, thereby providing high accuracy and reliability of carried-out AP measurements , and also to provide it’s comfortable and safe use by patients at operation.
The rating and air pumping in a cuff is made through rubber connecting tubes or other special means built in the device.
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All pulsations and changes of pressure are fixed by pressure sensor, being primary converter information with which already directly arrives on the microcontroller and then is displayed on the digital display. Received information can be written down also for Flash-memory, to betray on the personal computer by means of USB port and to make result listing on the printer.
The device is equipped with a sound signaling device which allows to control critical (emergency) device operation conditions, signals about the beginning and the end of measurement process.
At the expense of the built-in sound guide (speech "navigator") the device allows to simplify work with it at independent operation and makes it available for patients with limited opportunities (visually impaired). Also sound alarm system gives additional control and diagnostics possibility for critical conditions of patient’s health that allows to secure them against various accidents and in time to inform on arising danger of surrounding people or the expert (doctor).
Built-in memory of the device allows to remember and store data on several consistently carried out measurements and the calculated average normal pressure of the patient, and at the subsequent pressure measurements and it’s value change for the worse the device by means of a sound signaling device notifies on the danger menacing to a state of the patient’s health [1].
For a quality and quantitative possibilities estimation of the suggested by authors device AP measurement device with a cuff with an automatic carpal contour is offered to realize the device model in the environment of graphic programming of LabView, with use of National Instruments laboratory of the Penza state university [9, 17].
The virtual device of the AP measurement device developed by authors in the environment of LabView is given in fig. 2.
Fig. 2. Virtual AP measurement device
Operation of the AP measurement device can be described as follows. The signal source is selected by means of the “ Load the File” button. Depending on the chosen operating mode a source of a signal of arterial pressure will be the signal generator, or the file of data of the .tdms format which can be written down by means of the data collection device. At a choice of a signal loading from the file the dialog box in which it is necessary to choose the file of data opens. Further the loaded or generated signal arrives on the elliptic filter of the low frequencies of the third order in which the signal is filtered from noise. Further the signal of arterial pressure is brought to the device front panel. Then the filtered signal is given on the processing block in which informative parameters of a studied signal are allo-
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cated - magnitudes of two levels of arterial pressure, value of average arterial pressure, value of pulse which are displayed on the front panel in the form of the diagram with the levels of arterial pressure specified on it.
The received values of arterial pressure are compared to norms: for systolic pressure from 140 to 90, for diastolic pressure from 110 to 70. If both measured values are included in norm the green indicator if at least one of values doesn't enter norm lights up the red indicator.
The developed virtual device allows to work in two modes, to carry out comparison of informative parameters magnitudes of the filtered signal of an arterial pulsation of blood depending on the established age category and to display the corresponding result by means of indicator illumination. Thus the developed device of AP change in the environment of graphic programming of LabView can be used for development of the final device on the element National Instruments base and its introductions in production.
Discussion
For comparison estimation and AP measurement results confirmation with use of the developed device and a cuff with an automatic carpal contour we will define pros and con of existing analogs and prototypes of AP measurement devices.
Authors of the known offered device [13], prove high precision of AP measurement by means:
- estimates of the maximum amplitudes of an oscillation and fixing of pressure value corresponding to the decompression moment and dependence of systolic and diastolic pressure calculation from signal processing algorithm;
- distortion exceptions of a nature of a cuff surface fluctuations registration and pressure sensors indications caused by liquid compressibility and distortion of pressure value transfer to the sensor;
- eliminations of the noise caused by work of heart, lungs, movement of joints and external acoustic noise.
The main shortcomings of this device are:
- use as a compressor cuff - the working body filled with liquid (water). This shortcoming is connected with absence of completely formulated chemical and biological requirements of liquid use as a cuff filler;
- tank use with water which increases overall dimensions of the device, its weight and worsens consumer properties;
- complexity of the device realization, consisting in full immobilization of inspection object and connected with big measurement errors.
Shortcomings of other known device [14] are:
- the used cuff with the air bag, not allowing "to adapt" under specific features of a patient hand can cause inconveniences at its operation;
- lack of the sound signaling device, allowing to trace critical (emergency) device operation conditions, to signal about the beginning and the end of the measurement process, and also to control for critical conditions of patients at pressure measurement and to signal in time about arising dangers to surrounding people;
- lack of ports for connection of external peripherals (Flash-memory, USB port for connection with the personal computer, the printer), providing long-term storage and processing of the received measurement results and other information, and also possibility of its transfer on other devices or data carriers;
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- impossibility of wireless data and information transmission on external peripherals;
- ambiguity of the use of the external power supply or its absence at all, ensuring continuous functioning.
Conclusions
Use of the developed AP measurement device provides high accuracy, reliability and stability of reproduced results of arterial pressure measurement.
For the first time the applied cuff with an automatic carpal contour possesses a number of advantages that allows to provide:
- high accuracy of selection and determination of a cuff diameter on specific features of a structure and the hand size for each user;
- high accuracy for fast and correct cuff imposing on a hand of the patient (superficial a material and/or a cone-shaped form of air bags);
- dense pressing of a cuff to a patient’s hand o (mainly cone-shaped form of air bags).
- the increased speed and high precision of measurement with more comfortable conditions of AP measurement to patients.
The developed device can be applied in medical institutions, as the independent device and in the complex exercising complete control and diagnostics patient condition.
References
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Тычков Александр Юрьевич кандидат технических наук, заместитель директора научно-исследовательского института фундаментальных и прикладных исследований, Пензенский государственный университет (Россия, г. Пенза, ул. Красная, 40)
E-mail: [email protected]
Tychkov Aleksandr Yur'evich Candidate of engineering sciences, vice-director of the research institute of fundamental and applied research, Penza State University (40 Krasnaya street, Penza, Russia)
УДК 681.518 Tychkov, A. Yu.
The development of the arterial pressure registration device with the increased efficiency of work / A. Yu. Tychkov // Известия высших учебных заведений. Поволжский регион. Технические науки. - 2015. - № 1 (33). -С. 92-98.
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