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

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

Pulse Oximeter Monitoring Bracelet for COVID-19 Patient using Seeeduino

The increase in positive cases of COVID-19 makes it grave to monitor the level of oxygen saturation in the blood (SPO2) of COVID-19 patients. The purpose is to prevent silent hypoxia, which lowers oxygen levels in the blood without symptoms. In general, a conventional pulse oximeter is a clip that is clamped on a finger to measure SPO2 levels and heart rate per minute (HR). This research aims to design a compact pulse oximeter monitoring bracelet. The main components of the pulse oximeter monitoring bracelet are the Seeeduino XIAO microcontroller, MAX30100 sensor, and OLED display. The method of collecting data on ten people using a conventional pulse oximeter and prototype device to measure SPO2 and HR levels the interval 30 seconds were a taken measurement. The results show that the Pearson correlation value for SPO2 and HR are -0.73 and 0.98, respectively. These results demonstrated that there is a strong relationship between variables and sufficient linearity. In addition, a pulse oximeter monitoring bracelet is easy to use and low-costs, which makes it an attractive option for the successful implementation of such monitoring SPO2 and HR of COVID-19 patients

The 2023 wearable photoplethysmography roadmap

Photoplethysmography is a key sensing technology which is used in wearable devices such as smartwatches and fitness trackers. Currently, photoplethysmography sensors are used to monitor physiological parameters including heart rate and heart rhythm, and to track activities like sleep and exercise. Yet, wearable photoplethysmography has potential to provide much more information on health and wellbeing, which could inform clinical decision making. This Roadmap outlines directions for research and development to realise the full potential of wearable photoplethysmography. Experts discuss key topics within the areas of sensor design, signal processing, clinical applications, and research directions. Their perspectives provide valuable guidance to researchers developing wearable photoplethysmography technology

Error Prevention in Sensors and Sensor Systems

Achievements in all fields of engineering and fabrication methods have led towards optimization and integration of multiple sensing devices into a concise system. These advances have caused significant innovation in various commercial, industrial, and research efforts. Integrations of subsystems have important applications for sensor systems in particular. The need for reporting and real time awareness of a device’s condition and surroundings have led to sensor systems being implemented in a wide variety of fields. From environmental sensors for agriculture, to object characterization and biomedical sensing, the application for sensor systems has impacted all modern facets of innovation. With these innovations, however, additional sources of errors can occur, that can cause new but exciting challenges for such integrated devices. Such challenges range from error correction and accuracy to power optimization. Researchers have invested significant time and effort to improve the applicability and accuracy of sensors and sensor systems. Efforts to reduce inherent and external noise of sensors can range from hardware to software solutions, focusing on signal processing and exploiting the integration of multiple signals and/or sensor types. My research work throughout my career has been focused on deployable and integrated sensor systems. Their integration not only in hardware and components but also in software, machine learning, pattern recognition, and overall signal processing algorithms to aid in error correction and noise tailoring in all their hardware and software components

Implementation of Accelerometer-Based Adaptive Noise Cancellation in a Wireless Wearable Pulse Oximeter Platform for Remote Physiological Monitoring and Triage

A wireless wearable battery-operated pulse oximeter has been developed in our laboratory for field triage applications. The wearable pulse oximeter, which uses a forehead-mounted sensor to provide arterial oxygen saturation (SpO2) and heart rate (HR) information, would enable field medics to monitor vital physiological information following critical injuries, thereby helping to prioritize life saving medical interventions. This study was undertaken to investigate if accelerometry (ACC)-based adaptive noise cancellation (ANC) is effective in minimizing SpO2 and HR errors induced during jogging to simulate certain motion artifacts expected to occur in the field. Preliminary tests confirmed that processing the motion corrupted photoplethysmographic (PPG) signals by simple Least-Mean-Square (LMS) and Recursive Least-Squares (RLS) ANC algorithms can help to improve the signal-to-noise ratio of motion-corrupted PPG signals, thereby reducing SpO2 and HR errors during jogging. The study showed also that the degree of improvement depends on filter order. In addition, we found that it would be more feasible to implement an LMS adaptive filter within an embedded microcontroller environment since the LMS algorithm requires significantly less operations

Wireless body sensor networks for health-monitoring applications

This is an author-created, un-copyedited version of an article accepted for publication in Physiological Measurement. The publisher is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0967-3334/29/11/R01

In vivo non-invasive monitoring of optically resonant metal nanoparticles using multi-wavelength photoplethysmography

Nanotechnology has recently emerged as a powerful modality in many biomedical applications. In particular, several classes of nanoparticles have been employed as cancer therapy and imaging contrast agents. These particles can have architecture of varying complexity, depending on their specific application. These complex architectures are achieved by various chemical techniques usually performed in specific sequences to add complexity and functionality. One such class of nanoparticle, used in tumor treatment and as contrast agents in several optical imaging techniques, is the plasmon resonant metal nanoparticle. The most common metal used for these particles is gold because of its biocompatibility, lack of cellular toxicity, and simple surface chemistry. These particles have specific optical properties in the near infrared spectrum making them ideal for modern cancer therapy and optical imaging. Two examples of these particles are gold nanoshells and gold nanorods, both of which are highly absorptive and scattering at near infrared wavelengths. It is for this reason that they are often employed in photo thermal ablation of tumors using near infrared light. In this type of tumor treatment, the particles are injected intravenously and accumulate in the tumor. After accumulation, a near infrared laser is used to heat the particles and destroy the tumor. These gold nanoparticles must be modified with biocompatible stealthing compounds before they can be injected. This is because of the high efficiency of the body\u27s reticuloendotheial system, which will quickly eliminate materials foreign through cellular phagocytosis. Although techniques for quality control in manufacturing these nanoparticles are used to confirm proper surface modification, their in vivo behavior is very difficult to predict. It is for this reason that real time feedback in nanoparticle therapy is an urgent need and will greatly improve its efficacy. This dissertation reports the development of a non-invasive optical system capable of reporting the in vivo vascular concentration of these nanoparticles in near real time. The device, termed the pulse photometer, utilizes a technique similar to that used in pulse oximetry. This technique is photoplethysmography, which has many medical applications. One of these is determining the optical characteristics of pulsatile arterial blood, which are affected after the injection of these optically resonant particles. Several prototypes of this are presented in this dissertation. The culmination of this work is the prototype III pulse photometer capable of concurrent nanoparticle monitoring and oximetry. Final testing of this prototype revealed its ability to accurately determine the vascular optical density of gold nanorods compared to ex vivo spectrophotometry, a technique also verified in this dissertation, by statistical Bland-Altman analysis

Implementation and Validation of a Real-Time Wireless Non-Invasive Physiological Monitoring in a High-G Environment

The overall purpose of this research is to develop a system capable of real-time personal positioning and physiological monitoring. The system will be composed of a shirt having non-invasive physiological sensors, Global Positioning System (GPS) receiver, wireless data transceiver, and real-time PC-based control station. The specific purpose of this research phase was to determine the performance capabilities of a modified LifeShirt™ alone (without GPS) in a high gravitational force environment with the data being sent wirelessly in real-time. The LifeShirt™ was modified with a real time wireless transmission system