Сенсор пульоскиметрії для вимірювання часу затримки пульсової хвилі
| dc.contributor.advisor | Орлов, Анатолій Тимофійович | |
| dc.contributor.author | Тюркмен, Халіл | |
| dc.date.accessioned | 2019-08-27T12:37:20Z | |
| dc.date.available | 2019-08-27T12:37:20Z | |
| dc.date.issued | 2019-06 | |
| dc.description.abstracten | Pulse oximetry is the most affordable method for monitoring patients in many settings, especially with limited funding. It allows for a certain skill to assess several parameters of the patient's condition. After successful implementation in intensive care, wake-up wards and during anesthesia, the method began to be used in other areas of medicine, for example, in general departments where staff did not receive adequate training in the use of pulse oximetry. This method has its drawbacks and limitations, and in the hands of untrained personnel situations are possible that threaten the safety of the patient. This article is intended just for the novice user of pulse oximetry. A pulse oximeter measures hemoglobin oxygen saturation. The technology used is complex, but it has two basic physical principles. First, the absorption of two different wavelengths by hemoglobin varies depending on its oxygenation. Secondly, the light signal, passing through the tissue, becomes pulsating due to changes in the volume of the arterial bed with each contraction of the heart. This component can be separated by a microprocessor from a non-pulsating, veins, capillary, and tissue. The operation of the pulse oximeter is influenced by many factors. It can be external light, tremors, abnormal hemoglobin, pulse rate and rhythm, vasoconstriction and heart function. Pulse oximeter does not allow to judge the quality of ventilation, and shows only the degree of oxygenation, which can give a false sense of security during inhalation of oxygen. For example, it is possible to delay the onset of symptoms of hypoxia with airway obstruction. Nevertheless, oximetry is a very useful type of monitoring of the cardiorespiratory system, increasing patient safety. What does a pulse oximeter measure? Arterial hemoglobin oxygen saturation is the average amount of oxygen associated with each hemoglobin molecule. The data is given as a percentage of saturation and a sound signal, the height of which varies depending on the saturation. Pulse rate - beats per minute on average for 5-20 seconds. Pulse Oximeter does not provide information about: oxygen content in the blood; the amount of oxygen dissolved in the blood; respiratory volume, respiratory rate; cardiac output or blood pressure. About systolic blood pressure can be judged by the appearance of a wave on the plethysmogram when blowing the cuff for non-invasive pressure measurement. Principles of modern pulse oximetry Oxygen is transported by the bloodstream mainly in the form associated with hemoglobin. One hemoglobin molecule can transfer 4 oxygen molecules in which case it will be 100% saturated. The average percentage of saturation of a population of hemoglobin molecules in a certain volume of blood is the oxygen saturation of the blood. A very small amount of oxygen is transferred dissolved in the blood, but it is not measured with a pulse oximeter. The relationship between the partial pressure of oxygen in arterial blood (PaO2) and the saturation is reflected in the dissociation curve of hemoglobin (Fig. 1). The sigmoid shape of the curve reflects the oxygen unloading in peripheral tissues, where PaO2 is low. The curve can move to the left or right under various conditions, for example, after blood transfusion. A pulse oximeter consists of a peripheral sensor, a microprocessor, and a display showing the pulse curve, the saturation value, and the pulse rate. Most of the devices have a sound signal of a certain tone, the height of which is proportional to the saturation, which is very useful if the pulse oximeter display is not visible. The sensor is installed in the peripheral parts of the body, for example, on the fingers, the ear lobe or the wing of the nose. The sensor contains two LEDs, one of which emits visible light of the red spectrum (660 nm), the other in the infrared spectrum (940 nm). The light passes through the tissue to the photodetector, with some of the radiation absorbed by the blood and soft tissues depending on the concentration of hemoglobin in them. The amount of light absorbed by each of the wavelengths depends on the degree of oxygenation of hemoglobin in the tissues. The microprocessor is able to isolate the pulse component of blood from the absorption spectrum, i.e. to separate the arterial blood component from the permanent component of the venous or capillary blood. The latest generation microprocessors can reduce the effect of light scattering on the operation of the pulse oximeter. Repeated separation of the signal in time is performed using the cyclical operation of the LEDs: the red one turns on, then the infrared, then both are turned off, and so many times per second, which allows to eliminate background “noise”. The new microprocessor capability is quadratic multiple division, in which the red and infrared signals are separated in phases, and then combined again. With this option, interference from movement or electromagnetic radiation can be eliminated, since they cannot occur in the same phase of two LEDs. Saturation is calculated on average for 5-20 seconds. Heart rate is calculated by the number of cycles of LEDs and confident pulsating signals for a certain period of time. In proportion to the absorbed light of each frequency, the microprocessor calculates their coefficient. In memory of the pulse oximeter there is a series of oxygen saturation values obtained in experiments on volunteers with a hypoxic gas mixture. The microprocessor compares the obtained absorption coefficient of two wavelengths of light with the values stored in the memory. Because it is unethical to reduce the oxygen saturation in volunteers below 70%, it must be recognized that the saturation value below 70%, obtained by pulse oximeter, is not reliable. Reflected pulse oximetry uses reflected light, so it can be applied proximally (for example, on the forearm or anterior abdominal wall), but in this case it will be difficult to fix the sensor. The principle of operation of such a pulse oximeter is the same as that of the transmission one. Practical tips for using pulse oximetry: The pulse oximeter must be kept permanently plugged into the electrical grid to charge the batteries; turn on the pulse oximeter and wait for it to perform a self test; Select the appropriate sensor, suitable for the size and for the selected installation conditions. Nail phalanges must be clean (remove nail polish); place the sensor on the selected finger, avoiding excessive pressure; wait a few seconds while the pulse oximeter detects the pulse and calculates the saturation; look at the pulse wave curve. Without it, any values are unimportant; Look at the numbers of the pulse and saturation. Be careful with their evaluation when their values change rapidly (for example, 99% suddenly changes by 85%). This is physiologically impossible; if in doubt, evaluate the patient clinically, and do not rely on the machine; Anxiety: If the alarm "low oxygen saturation" sounds, check the patient's consciousness (if it was originally). Check the airway and the patient's breathing adequacy. Raise the chin or use other methods to restore the airway. Give oxygen. Call for help. If the “pulse not detected” alarm sounds, look at the pulse wave curve on the pulse oximeter display. Feel for a pulse in the central artery. In the absence of a pulse, call for help, begin a complex of cardiopulmonary resuscitation. If there is a pulse, change the position of the sensor. On most pulse oximeters, you can change the limits for carbonation alarms and heart rate at your discretion. However, do not change them only to silence the alarm - it can tell something important! Use of pulse oximetry In “field conditions,” a simple, all-in-one portable monitor that tracks saturation, pulse rate and rhythm regularity is best. Safe non-invasive cardio-respiratory status monitor for critical patients in the intensive care unit, as well as for all types of anesthesia. It can be used for endoscopy, when patients are sedated with midazolam. Pulse oximetry diagnoses cyanosis is more reliable than the best doctor. During transportation of the patient, especially in noisy environments, such as in an airplane, helicopter. The beep and alarm may not be heard, but the pulse wave curve and the saturation value provide general information about the cardio-respiratory status. To assess the viability of the limbs after plastic and orthopedic operations, vascular prosthetics. Pulse oximetry requires a pulsating signal, and thus helps determine whether a limb is receiving blood. Helps to reduce the frequency of blood sampling for the study of gas composition in patients in the intensive care unit, especially in pediatric practice. It helps to limit the likelihood of lung and retinal damage to oxygen in premature babies (saturation is maintained at 90%). Although pulse oximeters are calibrated for adult hemoglobin (HbA), the absorption spectrum of HbA and HbF is in most cases identical, which makes the technique equally reliable in infants. During thoracic anesthesia, when one of the lungs collapses, it helps determine the effectiveness of oxygenation in the remaining lung. Fetal oximetry is a developing technique. Used reflected oximetry, LEDs with a wavelength of 735 nm and 900 nm. The sensor is placed above the temple or cheek of the fetus. The sensor must be sterilized. It is difficult to fix, the data is not stable for physiological and technical reasons. Pulse oximetry limitation: This is not a ventilation monitor. According to the latest data, attention is drawn to the false sense of security created by the anesthesiologist using pulse oximeters. An elderly woman in the awakening unit received oxygen through a mask. She began to progressively boot, despite the fact that her saturation was 96%. The reason was that the respiration rate and minute ventilation volume were low due to residual neuromuscular block, and the oxygen concentration in expired air was very high. In the end, the concentration of carbon dioxide in arterial blood reached 280 mmHg (normal 40), and therefore the patient was transferred to the intensive care unit and stayed for 24 hours on a ventilator. Thus, pulse oximetry gave a good assessment of oxygenation, but did not give direct information about progressive respiratory disorders. Critical patients. In critical patients, the effectiveness of the method is low, since the tissue perfusion is poor and the pulse oximeter cannot determine the pulsating signal. The presence of a pulse wave. If there is no visible pulse wave on the pulse oximeter, any figures for the percentage of saturation are of little significance. Inaccuracy. Bright external light, shaking, movements can create a pulsatile curve and non-pulse saturation values. Abnormal hemoglobin types (for example, methemoglobin in case of an overdose of prilocain) can give a saturation level of 85%. Carboxyhemoglobin, which appears when carbon monoxide poisoning, can give a saturation value of about 100%. Pulse oximeter gives false values for this pathology, therefore it should not be used. Dyes, including nail polish, can provoke a low saturation value. Vasoconstriction and hypothermia cause a weakening of tissue perfusion and impair the registration of the signal. Tricuspid regurgitation causes venous pulsation and a pulse oximeter can record venous saturation. The saturation value below 70% is not accurate, because There are no control values to compare. Cardiac arrhythmias can interfere with the pulse pulse perception by the pulse oximeter. NB! Age, sex, anemia, jaundice and dark-colored skin have practically no effect on the operation of the pulse oximeter. Lagging monitor. This means that the partial pressure of oxygen in the blood can decrease much faster than the saturation begins to decrease. If a healthy adult patient breathes 100% oxygen for a minute, and then the ventilation stops for any reason, it may take several minutes before the saturation begins to decrease. Under these conditions, a pulse oximeter will warn of a potentially fatal complication only a few minutes after it has happened. Therefore, a pulse oximeter is called "the clock, standing on the edge of the abyss of desaturation." The explanation of this fact is in the sigmoid form of the oxyhemoglobin dissociation curve (Fig. 1). The delay of the reaction is due to the fact that the signal is averaged. This means that there is a delay of 5–20 seconds between how real oxygen saturation begins to fall and the values on the pulse oximeter display change. Patient safety. There are one or two reports of burns and overpressure damage when using pulse oximeters. This is due to the fact that in early models, a heater was used in the sensors to improve local tissue perfusion. The sensor must be the correct size and must not exert excessive pressure. Now there are sensors for pediatrics. Especially you need to stay on the correct position of the sensor. It is necessary that both parts of the sensor are symmetrical, otherwise the path between the photodetector and the LEDs will be unequal and one of the wavelengths will be “overloaded”. Changing the position of the sensor often leads to a sudden "improvement" of saturation. This effect may be associated with unstable blood flow through pulsating skin venules. Please note that the waveform may be normal, because measurement is carried out only on one of the wavelengths. Alternatives to Pulse Oximetry CO-oximetry is the gold standard and the classic method for calibrating a pulse oximeter. A CO-oximeter calculates the actual concentration of hemoglobin, deoxyhemoglobin, carboxyhemoglobin, methemoglobin in the blood sample, and then calculates the actual oxygen saturation. CO-oximeters are more accurate than pulse oximeters (within 1%). However, they give saturation at a certain point (“snapshot”), are bulky, expensive, and require arterial blood sampling. They need constant maintenance. Analysis of blood gases - requires an invasive sampling of a patient’s arterial blood. It gives a “complete picture”, including the partial pressure of oxygen and carbon dioxide in arterial blood, its pH, actual bicarbonate and its deficiency, standardized concentration of bicarbonate. Many gas analyzers calculate the saturation, which is less accurate than that calculated by pulse oximeters. Finally A pulse oximeter provides a non-invasive assessment of the saturation of arterial hemoglobin with oxygen. Used in anaesthesiology, block awakening, intensive care (including neonatal), when transporting the patient. Two principles are used: u separate absorption of light by hemoglobin and oxyhemoglobin; u extraction from the signal of the pulsating component. Does not give direct instructions on the patient's ventilation, only on his oxygenation. Delayed monitor - there is a time delay between the onset of potential hypoxia and the reaction of the pulse oximeter. Inaccuracy in strong external light, tremors, vasoconstriction, pathological hemoglobin, changes in pulse and rhythm. In new microprocessors, signal processing is improved. | uk |
| dc.description.abstractru | Оценка сердечно-сосудистых параметров с использованием бесконтактной видеоплетизмографии на основе видео или визуализации (IPPG) обычно считается неточной из-за сильного влияния артефактов движения. Чтобы оптимизировать эту технику, мы выполнили одновременную запись электрокардиограммы и видеокадров лица для 36 здоровых добровольцев. Мы обнаружили, что сигнальные нарушения происходят в основном из стохастически усиленного дихроичного выреза, вызванного эндогенными сердечно-сосудистыми механизмами, с меньшим вкладом артефактов движения. Наш правильно разработанный алгоритм позволил нам повысить точность измерения времени прохождения импульса и визуализировать распространение пульсовой волны в области лица. Таким образом, точное измерение параметров пульсовой волны с помощью этой методики предполагает чувствительный подход к оценке локальной регуляции микроциркуляции при различных физиологических и патологических состояниях.1. Введение Частота сердечных сокращений человека, вариабельность сердечного ритма (ВСР) и время прохождения импульса (РТТ) являются важными жизненно важными показателями для медицинской диагностики и оценки состояния здоровья человека. ВСР часто используется для количественной оценки активности автономной нервной системы при различных физиологических состояниях и заболеваниях [1–3]. PTT определяет скорость пульсовой волны, которая может служить прогностическим маркером для различных заболеваний, таких как гипертония, диабет и периферический атеросклероз [4,5]. Как HRV, так и PTT полагаются на измерения положения каждого сердечного цикла в шкале времени. В настоящее время электрокардиография (ЭКГ) является золотым стандартом для измерения ВСР на основе анализа интервалов R-R. Альтернативой ЭКГ при оценке периодов сердечного цикла является регистрация пульсовой волны артериального давления. Эти записи могут быть предоставлены пьезоэлектрическим преобразователем [5,6], доплеровским ультразвуком [7,8] и фотоплетизмографическими (ППГ) датчиками [9–11]. PTT обычно определяется как интервал времени между отрицательной зубцом Q ЭКГ и приходом стопы артериальной крови на периферическую область измерений [9,12]. Однако все эти методы (включая ЭКГ) требуют контактов с телом, что часто неудобно, что мотивирует исследователей искать более простые методы мониторинга пульсаций крови. Недавно в качестве метода дистанционного измерения и мониторинга сердечно-сосудистых функций была внедрена видеоплетизмография на основе видео или изображений (IPPG) [13–16]. Этот метод стал очень популярным среди исследователей из-за его простоты использования и потенциально низкой стоимости. Одним из главных преимуществ IPPG является то, что он может применяться в различных частях тела, включая легкодоступные, такие как лицо человека [17–20]. Подобно форме волны PPG, сигналы IPPG следуют за изменениями артериального кровяного давления [21], но в отличие от контактных датчиков PPG эти изменения измеряются одновременно во многих физически различных областях тела. Однако широкое использование систем IPPG ограничено низким отношением сигнал / шум (SNR). Большинство исследователей связывают возмущения сигнала, которые приводят к низкому SNR, с артефактами движения. Для восстановления сигнала, связанного с сердечной деятельностью, было предложено несколько алгоритмов обработки данных IPPG [17,22–25]. Эти алгоритмы основаны на анализе независимых компонентов [17,22], анализе основных компонентов [23], вейвлет-преобразовании [24] и средневзвешенном значении различных каналов [25]. Все они были направлены на поиск оптимальной формы волны PPG, которая предполагается уникальной для всей исследуемой области. Эта идея вытекает из предположения, что сердце является единственным источником волны кровяного давления. Однако параметры волны кровяного давления на периферическом участке (например, на лице или конечностях) отличаются от исходных (в сердце) [6] и могут варьироваться даже в небольших прилегающих областях из-за распространения пульсовой волны через сосудистая система. В этой работе мы использовали изготовленную на заказ систему IPPG, синхронизированную с электрокардиографом, для оценки PTT от сердца до каждой небольшой области на лице субъекта. Учитывая наши экспериментальные данные о том, что нарушения формы волны PPG происходят главным образом из-за переменных физиологических параметров сердечно-сосудистой системы, вызванных стохастически усиленной дикротической насечкой, был предложен новый надежный алгоритм обработки данных IPPG. В отличие от предыдущих алгоритмов, в основном предназначенных для визуализации амплитуды пульсаций крови, он позволяет точно оценить анакротическую волну, начиная с высокого временного и пространственного разрешения. Таким образом, мы впервые демонстрируем, насколько нам известно, что предложенный алгоритм позволяет точно отображать PTT в области лица. Это открывает новые возможности для визуализации распространения пульсовой волны в различных частях тела при различных физиологических состояниях и заболеваниях. | uk |
| dc.format.page | 60 c. | uk |
| dc.identifier.citation | Тюркмен, Х. Сенсор пульоскиметрії для вимірювання часу затримки пульсової хвилі : дипломна робота … бакалавра : 6.050801 Мікро- та наноелектроніка / Тюркмен Халіл. – Київ, 2019. – 60 с. | uk |
| dc.identifier.uri | https://ela.kpi.ua/handle/123456789/28894 | |
| dc.language.iso | ru | uk |
| dc.publisher | КПІ ім. Ігоря Сікорського | uk |
| dc.publisher.place | Київ | uk |
| dc.title | Сенсор пульоскиметрії для вимірювання часу затримки пульсової хвилі | uk |
| dc.type | Bachelor Thesis | uk |
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