96 research outputs found
Remote heart rate monitoring - Assessment of the Facereader rPPg by Noldus
Remote photoplethysmography (rPPG) allows contactless monitoring of human cardiac activity through a video camera. In this study, we assessed the accuracy and precision for heart rate measurements of the only consumer product available on the market, namely the Facereaderâ„¢ rPPG by Noldus, with respect to a gold standard electrocardiograph. Twenty-four healthy participants were asked to sit in front of a computer screen and alternate two periods of rest with two stress tests (i.e. Go/No-Go task), while their heart rate was simultaneously acquired for 20 minutes using the ECG criterion measure and the Facereaderâ„¢ rPPG. Results show that the Facereaderâ„¢ rPPG tends to overestimate lower heart rates and underestimate higher heart rates compared to the ECG. The Facereaderâ„¢ rPPG revealed a mean bias of 9.8 bpm, the 95% limits of agreement (LoA) ranged from almost -30 up to +50 bpm. These results suggest that whilst the rPPG Facereaderâ„¢ technology has potential for contactless heart rate monitoring, its predictions are inaccurate for higher heart rates, with unacceptable precision across the entire range, rendering its estimates unreliable for monitoring individuals
An Empirical Study Comparing Unobtrusive Physiological Sensors for Stress Detection in Computer Work.
Several unobtrusive sensors have been tested in studies to capture physiological reactions to stress in workplace settings. Lab studies tend to focus on assessing sensors during a specific computer task, while in situ studies tend to offer a generalized view of sensors' efficacy for workplace stress monitoring, without discriminating different tasks. Given the variation in workplace computer activities, this study investigates the efficacy of unobtrusive sensors for stress measurement across a variety of tasks. We present a comparison of five physiological measurements obtained in a lab experiment, where participants completed six different computer tasks, while we measured their stress levels using a chest-band (ECG, respiration), a wristband (PPG and EDA), and an emerging thermal imaging method (perinasal perspiration). We found that thermal imaging can detect increased stress for most participants across all tasks, while wrist and chest sensors were less generalizable across tasks and participants. We summarize the costs and benefits of each sensor stream, and show how some computer use scenarios present usability and reliability challenges for stress monitoring with certain physiological sensors. We provide recommendations for researchers and system builders for measuring stress with physiological sensors during workplace computer use
Multispectral Video Fusion for Non-contact Monitoring of Respiratory Rate and Apnea
Continuous monitoring of respiratory activity is desirable in many clinical
applications to detect respiratory events. Non-contact monitoring of
respiration can be achieved with near- and far-infrared spectrum cameras.
However, current technologies are not sufficiently robust to be used in
clinical applications. For example, they fail to estimate an accurate
respiratory rate (RR) during apnea. We present a novel algorithm based on
multispectral data fusion that aims at estimating RR also during apnea. The
algorithm independently addresses the RR estimation and apnea detection tasks.
Respiratory information is extracted from multiple sources and fed into an RR
estimator and an apnea detector whose results are fused into a final
respiratory activity estimation. We evaluated the system retrospectively using
data from 30 healthy adults who performed diverse controlled breathing tasks
while lying supine in a dark room and reproduced central and obstructive apneic
events. Combining multiple respiratory information from multispectral cameras
improved the root mean square error (RMSE) accuracy of the RR estimation from
up to 4.64 monospectral data down to 1.60 breaths/min. The median F1 scores for
classifying obstructive (0.75 to 0.86) and central apnea (0.75 to 0.93) also
improved. Furthermore, the independent consideration of apnea detection led to
a more robust system (RMSE of 4.44 vs. 7.96 breaths/min). Our findings may
represent a step towards the use of cameras for vital sign monitoring in
medical applications
Sources of inaccuracy in photoplethysmography for continuous cardiovascular monitoring
Photoplethysmography (PPG) is a low-cost, noninvasive optical technique that uses change in light transmission with changes in blood volume within tissue to provide information for cardiovascular health and fitness. As remote health and wearable medical devices become more prevalent, PPG devices are being developed as part of wearable systems to monitor parameters such as heart rate (HR) that do not require complex analysis of the PPG waveform. However, complex analyses of the PPG waveform yield valuable clinical information, such as: blood pressure, respiratory information, sympathetic nervous system activity, and heart rate variability. Systems aiming to derive such complex parameters do not always account for realistic sources of noise, as testing is performed within controlled parameter spaces. A wearable monitoring tool to be used beyond fitness and heart rate must account for noise sources originating from individual patient variations (e.g., skin tone, obesity, age, and gender), physiology (e.g., respiration, venous pulsation, body site of measurement, and body temperature), and external perturbations of the device itself (e.g., motion artifact, ambient light, and applied pressure to the skin). Here, we present a comprehensive review of the literature that aims to summarize these noise sources for future PPG device development for use in health monitoring
Speckle Vibrometry for Instantaneous Heart Rate Monitoring
Instantaneous heart rate (IHR) has been investigated for sleep applications, such as sleep apnea detection and sleep staging. To ensure the comfort of the patient during sleep, it is desirable for IHR to be measured in a contact-free fashion. In this work, we use speckle vibrometry (SV) to perform on-skin and on-textile IHR monitoring in a sleep setting. Minute motions on the laser-illuminated surface can be captured by a defocused camera, enabling the detection of cardiac motions even on textiles. We investigate supine, lateral, and prone sleeping positions. Based on Bland–Altman analysis between SV cardiac measurements and electrocardiogram (ECG), with respect to each position, we achieve the best limits of agreement with ECG values of [−8.65, 7.79] bpm, [−9.79, 9.25] bpm, and [−10.81, 10.23] bpm, respectively. The results indicate the potential of using speckle vibrometry as a contact-free monitoring method for instantaneous heart rate in a setting where the participant is allowed to rest in a spontaneous position while covered by textile layers
Recent development of respiratory rate measurement technologies
Respiratory rate (RR) is an important physiological parameter whose abnormity has been regarded as an important indicator of serious illness. In order to make RR monitoring simple to do, reliable and accurate, many different methods have been proposed for such automatic monitoring. According to the theory of respiratory rate extraction, methods are categorized into three modalities: extracting RR from other physiological signals, RR measurement based on respiratory movements, and RR measurement based on airflow. The merits and limitations of each method are highlighted and discussed. In addition, current works are summarized to suggest key directions for the development of future RR monitoring methodologies
The Role of Edge Robotics As-a-Service in Monitoring COVID-19 Infection
Deep learning technology has been widely used in edge computing. However,
pandemics like covid-19 require deep learning capabilities at mobile devices
(detect respiratory rate using mobile robotics or conduct CT scan using a
mobile scanner), which are severely constrained by the limited storage and
computation resources at the device level. To solve this problem, we propose a
three-tier architecture, including robot layers, edge layers, and cloud layers.
We adopt this architecture to design a non-contact respiratory monitoring
system to break down respiratory rate calculation tasks. Experimental results
of respiratory rate monitoring show that the proposed approach in this paper
significantly outperforms other approaches. It is supported by computation time
costs with 2.26 ms per frame, 27.48 ms per frame, 0.78 seconds for convolution
operation, similarity calculation, processing one-minute length respiratory
signals, respectively. And the computation time costs of our three-tier
architecture are less than that of edge+cloud architecture and cloud
architecture. Moreover, we use our three-tire architecture for CT image
diagnosis task decomposition. The evaluation of a CT image dataset of COVID-19
proves that our three-tire architecture is useful for resolving tasks on deep
learning networks by edge equipment. There are broad application scenarios in
smart hospitals in the future
Wearable in-ear pulse oximetry: theory and applications
Wearable health technology, most commonly in the form of the smart watch, is employed by millions of users worldwide. These devices generally exploit photoplethysmography (PPG), the non-invasive use of light to measure blood volume, in order to track physiological metrics such as pulse and respiration. Moreover, PPG is commonly used in hospitals in the form of pulse oximetry, which measures light absorbance by the blood at different wavelengths of light to estimate blood oxygen levels (SpO2). This thesis aims to demonstrate that despite its widespread usage over many decades, this sensor still possesses a wealth of untapped value. Through a combination of advanced signal processing and harnessing the ear as a location for wearable sensing, this thesis introduces several novel high impact applications of in-ear pulse oximetry and photoplethysmography. The aims of this thesis are accomplished through a three pronged approach: rapid detection of hypoxia, tracking of cognitive workload and fatigue, and detection of respiratory disease.
By means of the simultaneous recording of in-ear and finger pulse oximetry at rest and during breath hold tests, it was found that in-ear SpO2 responds on average 12.4 seconds faster than the finger SpO2. This is likely due in part to the ear being in close proximity to the brain, making it a priority for oxygenation and thus making wearable in-ear SpO2 a good proxy for core blood oxygen. Next, the low latency of in-ear SpO2 was further exploited in the novel application of classifying cognitive workload. It was found that in-ear pulse oximetry was able to robustly detect tiny decreases in blood oxygen during increased cognitive workload, likely caused by increased brain metabolism. This thesis demonstrates that in-ear SpO2 can be used to accurately distinguish between different levels of an N-back memory task, representing different levels of mental effort. This concept was further validated through its application to gaming and then extended to the detection of driver related fatigue. It was found that features derived from SpO2 and PPG were predictive of absolute steering wheel angle, which acts as a proxy for fatigue.
The strength of in-ear PPG for the monitoring of respiration was investigated with respect to the finger, with the conclusion that in-ear PPG exhibits far stronger respiration induced intensity variations and pulse amplitude variations than the finger. All three respiratory modes were harnessed through multivariate empirical mode decomposition (MEMD) to produce spirometry-like respiratory waveforms from PPG. It was discovered that these PPG derived respiratory waveforms can be used to detect obstruction to breathing, both through a novel apparatus for the simulation of breathing disorders and through the classification of chronic obstructive pulmonary disease (COPD) in the real world.
This thesis establishes in-ear pulse oximetry as a wearable technology with the potential for immense societal impact, with applications from the classification of cognitive workload and the prediction of driver fatigue, through to the detection of chronic obstructive pulmonary disease. The experiments and analysis in this thesis conclusively demonstrate that widely used pulse oximetry and photoplethysmography possess a wealth of untapped value, in essence teaching the old PPG sensor new tricks.Open Acces
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