A flexible organic reflectance oximeter array.

Transmission-mode pulse oximetry, the optical method for determining oxygen saturation in blood, is limited to only tissues that can be transilluminated, such as the earlobes and the fingers. The existing sensor configuration provides only single-point measurements, lacking 2D oxygenation mapping capability. Here, we demonstrate a flexible and printed sensor array composed of organic light-emitting diodes and organic photodiodes, which senses reflected light from tissue to determine the oxygen saturation. We use the reflectance oximeter array beyond the conventional sensing locations. The sensor is implemented to measure oxygen saturation on the forehead with 1.1% mean error and to create 2D oxygenation maps of adult forearms under pressure-cuff-induced ischemia. In addition, we present mathematical models to determine oxygenation in the presence and absence of a pulsatile arterial blood signal. The mechanical flexibility, 2D oxygenation mapping capability, and the ability to place the sensor in various locations make the reflectance oximeter array promising for medical sensing applications such as monitoring of real-time chronic medical conditions as well as postsurgery recovery management of tissues, organs, and wounds

Reflectance Photoplethysmography as Non-Invasive Monitoring of Tissue Blood Perfusion.

In the last decades Photoplethysmography (PPG) has been used as noninvasive technique for monitoring arterial oxygen saturation by Pulse Oximetry (PO), whereas Near Infrared Spectroscopy (NIRS) has been employed for monitoring tissue blood perfusion. While NIRS offers more parameters to evaluate oxygen delivery and consumption in deep tissues, PO only assesses the state of oxygen delivery. For a broader assessment of blood perfusion, this paper explores the utilization of dual-wavelength PPG by using the pulsatile (AC) and continuous (DC) PPG for the estimation of arterial oxygen saturation (SpO2) by conventional PO. Additionally, the Beer-Lambert law is applied to the DC components only for the estimation of changes in deoxy-hemoglobin (HHb), oxy-hemoglobin (HbO2) and total hemoglobin (tHb) as in NIRS. The system was evaluated on the forearm of 21 healthy volunteers during induction of venous occlusion (VO) and total occlusion (TO). A reflectance PPG probe and NIRS sensor were applied above the brachioradialis, PO sensors were applied on the fingers, and all the signals were acquired simultaneously. While NIRS and forearm SpO2 indicated VO, SpO2 from the finger did not exhibit any significant drop from baseline. During TO all the indexes indicated the change in blood perfusion. HHb, HbO2 and tHb changes estimated by PPG presented high correlation with the same parameters obtained by NIRS during VO (r2=0.960, r2=0.821 and r2 =0.974 respectively) and during TO (r2=0.988, r2=0.940 and r2=0.938 respectively). The system demonstrated the ability to extract valuable information from PPG signals for a broader assessment of tissue blood perfusion

Psychophysiological Factors Analysis in Unpressurized Aircraft Cabins

In the versatile aviation environment, the pilot’s well-being is a crucial and demanding factor which is directly related to his good performance. Adding the fact that most of the aircraft that belong to the light aviation do not have pressurized cabins, this type of aviation can become a dangerous activity for the safety of pilots and passengers. The change in pilot’s performance during the changing of psychological and physiological parameters has proved to be a very significant factor in terms of flight safety. Also the increasing of altitude in different phases of flight corresponds to a reduction in oxygen partial pressure. This occurrence may lead to early symptoms of hypoxia which may become an even greater danger if the pilots do not have time to feel, or recognize their symptoms. A review of international legislation indicates a high tolerance to establish safety limits in this matter, taking into account the unpredictability of reactions of the human body of each pilot for the same flight conditions. This work is generally focused in acquired data during different flight situations, with different pilots and respective processing of data obtained during different tasks of flight. To achieve the proposed objectives the acquired data contain parameters such as altitude, absolute pressure and temperature inside the cabin; as well as registration oximetry, peripheral and cerebral, to study the phenomenon hypoxia. Also comprises electrocardiogram (ECG) and electroencephalogram (EEG) in order to establish a correlation between the influence of mental workload and other physiological parameters during different phases of flight. The specific objective of this research is the acquisition and processing of data collected directly from the aircraft and the pilot, performing flight simulation tests in different scenarios, contributing to trying to define the physiological limits of each individual with the purpose of creating an alert system on board to avoid possible incidents or accidents. This study also aims to suggest a restriction in the legislation on licensing of light aviation, within physiological limits of each individual, thus contributing to a safer flight environment.No ambiente versátil da aviação, o bem-estar do piloto é um factor crucial e exigente que está directamente relacionado com o seu desempenho. Adicionando o facto da maioria das aeronaves que pertencem á aviação ligeira não possuírem cabines pressurizadas, este tipo de aviação pode tornar-se numa actividade perigosa para a segurança de pilotos e passageiros. A mudança de desempenho dos pilotos aquando da alteração de parâmetros psicológicos e fisiológicos tem-se revelado um fator bastante significativo em termos de segurança de voo. Também o aumento da altitude nas diferentes fases de voo corresponde a uma diminuição da pressão parcial de oxigénio. Esta ocorrência pode levar a sintomas iniciais de hipoxia o que se pode tornar um perigo ainda maior se os pilotos não possuírem tempo para sentir, ou reconhecer, os seus sintomas. Uma revisão da legislação internacional indica uma grande tolerância a estabelecer limites de segurança neste tema, tendo em conta a imprevisibilidade de reacções do corpo humano de cada piloto para as mesmas condições de voo. O objectivo geral deste trabalho consiste na aquisição de dados durante distintas situações de voo, com diferentes pilotos, e o respectivo processamento dos dados obtidos durante as diferentes tarefas de voo. Para realizar os objectivos propostos os dados adquiridos contêm parâmetros como altitude, pressão absoluta e temperatura no interior da cabina, bem como o registo de oximetrias, periférica e cerebral, para estudar o fenómeno hipoxia. Também compreende electrocardiogramas (ECG) e electroencefalogramas (EEG) de modo a estabelecer uma correlação entre a influência da carga de trabalho mental e outros parâmetros fisiológicos durante as diferentes fases de voo. O objectivo específico desta investigação é a aquisição e processamento de dados recolhidos directamente da aeronave e do piloto, realizando testes de simulação de voo em diferentes cenários, contribuindo para tentar definir os limites fisiológicos de cada individuo com a finalidade de criar um sistema de alerta a bordo para evitar possíveis incidentes ou acidentes. Com este estudo pretende-se também sugerir uma restrição na legislação no licenciamento da aviação ligeira, dentro dos limites fisiológicos de cada individuo, contribuindo assim para um ambiente de voo mais seguro

Pulse Oximeter Design for SpO2 and BPM Recording on External Memory to Support the Covid-19 Diagnosis

COVID-19 (coronavirus disease) is an acute respiratory illness induced by exposure to coronavirus 2 in 2019 (SARS-CoV-2). WHO confirms that there were 1.8 million registered deaths in 2020 and that there were 3.5 million recorded deaths in 2021. People who are infected with SARS-CoV-2 without symptoms should have a pulse oximeter. Early detection of low oxygen levels in the blood can lead to fewer complications. Continuously decreasing oxygen saturation, if not controlled, will cause hypoxia (an abnormal respiratory circulation system condition that causes breathlessness). In normal conditions, oxygen levels and heart rate are related. When a person has a shortage of oxygen (breathlessness), their heart rate increases to supply the oxygen. Regulating heart rate can aid in the prevention of disorders such as arrhythmia, coronary heart disease, and hypertension. A pulse oximeter is used to measure the oxygen saturation in the blood and the patient's heart rate (BPM) with non-invasive methods. Conventional pulse oximeters do not support users by not having features such as medical records, which are required for further examination by a doctor. The purpose of this research is to make a pulse oximeter with external storage capability. The difference in wavelength between the red and infrared LED lights that will be captured by the photodiode is measured. SpO2 and HR values will be generated as a result of comparative measurements. Using a MAX30102 sensor to detect SpO2 and heart rate, and an Arduino Mega256 to process data for display on the TFT Nextion with Memory Card storage. By comparing the module to a conventional pulse oximeter, data was collected 10 times for each respondent. The maximum SpO2 error value is 0.43%, whereas the BPM parameter has the largest error value of 2.02% and the smallest error value of 0.01% based on the data collected. A significant error value is caused by finger movement. The module is usable, based on the results, because the maximum error tolerance for a pulse oximeter is 1% SpO2 and 5% BPM, according to the 2001 Ministry of Health Ministry's Guidelines for Testing and Calibrating Medical Devices

Investigation of Photodetector Optimization in Reducing Power Consumption by a Noninvasive Pulse Oximeter Sensor

Noninvasive pulse oximetry represents an area of potential interest to the army, because it could provide cost-effective, safe, fast and real-time physiological assessment in a combat injured soldier. Consequently, there is a need to develop a reliable, battery-powered, wearable pulse oximeter to acquire and process photoplethysmographic (PPG) signals using an optimized sensor configuration. A key requirement in the optimal design of a wearable wireless pulse oximeter is low power management without compromising signal quality. This research investigated the advantage gained by increasing the area of the photodetector and decreasing the light emitting diode (LED) driving currents to reduce the overall power requirement of a reflectance mode pulse oximeter sensor. In vitro and preliminary in vivo experiments were conducted to evaluate a multiple photodetector reflectance sensor setup to simulate a varying detection area. It was concluded that a reflection pulse oximeter sensor employing a large area photodetector is preferred over a similar transmission type sensor for extending the battery life of a wireless pulse oximeter intended for future telemedicine applications

The Use of Pulse Oximetry in the Assessment of Acclimatization to High Altitude

Background: Finger pulse oximeters are widely used to monitor physiological responses to high-altitude exposure, the progress of acclimatization, and/or the potential development of high-altitude related diseases. Although there is increasing evidence for its invaluable support at high altitude, some controversy remains, largely due to differences in individual preconditions, evaluation purposes, measurement methods, the use of different devices, and the lacking ability to interpret data correctly. Therefore, this review is aimed at providing information on the functioning of pulse oximeters, appropriate measurement methods and published time courses of pulse oximetry data (peripheral oxygen saturation, (SpO2) and heart rate (HR), recorded at rest and submaximal exercise during exposure to various altitudes. Results: The presented findings from the literature review confirm rather large variations of pulse oximetry measures (SpO2 and HR) during acute exposure and acclimatization to high altitude, related to the varying conditions between studies mentioned above. It turned out that particularly SpO2 levels decrease with acute altitude/hypoxia exposure and partly recover during acclimatization, with an opposite trend of HR. Moreover, the development of acute mountain sickness (AMS) was consistently associated with lower SpO2 values compared to individuals free from AMS. Conclusions: The use of finger pulse oximetry at high altitude is considered as a valuable tool in the evaluation of individual acclimatization to high altitude but also to monitor AMS progression and treatment efficacy

Investigating the Effects of Sensor Mass, Applied Heat, and Applied Pressure on Motion Artifact in Photoplethysmography within a Military Transport Environment

Despite the wide use of pulse oximetry as a clinical monitoring device for non-invasive measurement of hemoglobin oxygen saturation and heart rate, reports have shown its high sensitivity to motion artifact, rendering the device less accurate and reliable during field applications such as in military environments or ambulatory transport. This paper investigates the effects of sensor weight, localized heating and locally applied pressure on measurement accuracy of a prototype forehead pulse oximeter during a simulated military transport environment. The results yielded that increased sensor weight led to measurement errors and more severe signal corruption, while increased heat (up to 42oC) and pressure (up to 60mmHg) decreased errors and improved signal fidelity

BIOTEX-biosensing textiles for personalised healthcare management.

Textile-based sensors offer an unobtrusive method of continually monitoring physiological parameters during daily activities. Chemical analysis of body fluids, noninvasively, is a novel and exciting area of personalized wearable healthcare systems. BIOTEX was an EU-funded project that aimed to develop textile sensors to measure physiological parameters and the chemical composition of body fluids, with a particular interest in sweat. A wearable sensing system has been developed that integrates a textile-based fluid handling system for sample collection and transport with a number of sensors including sodium, conductivity, and pH sensors. Sensors for sweat rate, ECG, respiration, and blood oxygenation were also developed. For the first time, it has been possible to monitor a number of physiological parameters together with sweat composition in real time. This has been carried out via a network of wearable sensors distributed around the body of a subject user. This has huge implications for the field of sports and human performance and opens a whole new field of research in the clinical setting

Principles, Utility and Limitations of Pulse Oximetry in Management of COVID-19

Pulse oximetry is an essential component of the standard care of COVID-19 patients. In the context of the spreading COVID-19 pandemic for which no targeted therapy or vaccines are yet available, early identification of the severe cases or cases with high risk of severe disease and appropriate supportive treatment are of paramount importance to save lives. Pulse oximetry is a cheap, fast, easy to use, noninvasive, painless and accurate tool that allows real-time monitoring of hypoxemia. As the primary target of the disease is the respiratory system pulse oximetry provides an unparalleled way to assess the severity of the disease, guide supportive therapies and monitor the clinical status and response to treatment with greater benefits in the low-resource settings. All settings from the quarantine facilities at the ground level to the ICUs in the highest level hospitals can utilize it to achieve their goals. To get the best of this tool, it needs to be used properly and the findings interpreted carefully. Role of basic understanding of the physiological principles and technology behind its use and awareness of its limitations cannot be overemphasized. The pulse oximetry readings are interpreted in the context of blood hemoglobin concentration, tissue perfusion, arterial blood carbon dioxide concentration and oxygen supplementation status