A novel sensor for wrist based optical heart rate monitor

Sensors and Functionalities of Non-Invasive Wrist-Wearable Devices: A Review

Abstract: Wearable devices have recently received considerable interest due to their great promise for a plethora of applications. Increased research efforts are oriented towards a non-invasive monitoring of human health as well as activity parameters. A wide range of wearable sensors are being developed for real-time non-invasive monitoring. This paper provides a comprehensive review of sensors used in wrist-wearable devices, methods used for the visualization of parameters measured as well as methods used for intelligent analysis of data obtained from wrist-wearable devices. In line with this, the main features of commercial wrist-wearable devices are presented. As a result of this review, a taxonomy of sensors, functionalities, and methods used in non-invasive wrist-wearable devices was assembled.

Preliminary results for measurement and classification of overnight wandering by dementia patient using multi-sensors

Abstract: The measurement and detection of overnight wandering is a significant issue for dementia patients and their caregivers such as a spouse The wandering places the patient at risk of injury or even death if they fall or leave their residence without being detected While it also causes stress and reduced sleep for the caregiver as they try to remain alert to the actions of their partner This paper presents initial data for the first participant from an ongoing study of dementia patients where a wander detection and diversion system based on low-cost commercial sensors has been deployed into the residence The paper shows that over a 3-week period, the analysis and classification of the sensor data is able to measure the behavior of the patient In this period, the patient only used the washroom overnight and did not wander into other parts of the residence These early results show that an off the shelf system targeted for residential security and home automation applications based on low-cost sensors supported with automated analysis and classification has the potential to be used to assist caregivers and dementia patients

Evaluation of the signal quality of wrist-based photoplethysmography

Abstract: Objective Wearable devices with embedded photoplethysmography (PPG) sensors enable continuous monitoring of cardiovascular activity, allowing for the detection cardiovascular problems, such as arrhythmias. However, the quality of wrist-based PPG is highly variable, and is subject to artifacts from motion and other interferences. The goal of this paper is to evaluate the signal quality obtained from wrist-based PPG when used in an ambulatory setting. Approach Ambulatory data were collected over a 24 h period for 10 elderly, and 16 non-elderly participants. Visual assessment is used as the gold standard for PPG signal quality, with inter-rater agreement evaluated using Fleiss' Kappa. With this gold standard, 5 classifiers were evaluated using a modified 13-fold cross-validation approach. Main results A Random Forest quality classification algorithm showed the best performance, with an accuracy of 74.5%, and was then used to evaluate 24 h long ambulatory wrist-based PPG measurements. Significance In general, data quality was high at night, and low during the day. Our results suggest wrist-based PPG may be best for continuous cardiovascular monitoring applications during the night, but less useful during the day unless methods can be identified to improve low quality signal segments.

A Yellow–Orange Wavelength-Based Short-Term Heart Rate Variability Measurement Scheme for Wrist-Based Wearables

Abstract: Heart rate variability (HRV) is one of the important biomarkers of physical and psychological well-being. Hence, a convenient and minimally intrusive method for HRV measurement is advantageous. Although high levels of surrogacy of short-term HRV estimates obtained from the measurements of blood volume changes to traditional electrocardiographic (ECG) measurements have been reported, no detailed account on extraction of such parameters from a wrist-based optical monitor is found in the literature. In this paper, a yellow–orange wavelength-based optical scheme is incorporated into a wearable device for HRV estimation from dorsal side of the wrist. This design is pivotal in catering to a wider span of population with varied skin tones. The developed wearable in alliance with a gateway device is capable of picking up photoplethysmography from the measurement site, allowing estimation of HRV-indices within a confidence of 5% from ECG-derived parameters. The HRV measurement ecosystem is validated under the setting of three postural loads for 20 subjects, generating 60 data sets. Study results show statistically significant positive correlation and nonsignificant bias in Bland–Altman analysis, for the HRV-indices derived from either method. In most of the extracted HRV features, the observations in supine position showed minimum deviation from the reference. Estimation of short-term HRV-indices from wrist-based photoplethysmography under stationary conditions shows promising results from the study. Electrical and biological noninterference and ease of usage of the proposed design simplify stationary and ambulatory monitoring of HRV.

Photoplethysmography and its application in clinical physiological measurement.

Abstract: Photoplethysmography (PPG) is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is often used non-invasively to make measurements at the skin surface. The PPG waveform comprises a pulsatile ('AC') physiological waveform attributed to cardiac synchronous changes in the blood volume with each heart beat, and is superimposed on a slowly varying ('DC') baseline with various lower frequency components attributed to respiration, sympathetic nervous system activity and thermoregulation. Although the origins of the components of the PPG signal are not fully understood, it is generally accepted that they can provide valuable information about the cardiovascular system. There has been a resurgence of interest in the technique in recent years, driven by the demand for low cost, simple and portable technology for the primary care and community based clinical settings, the wide availability of low cost and small semiconductor components, and the advancement of computer-based pulse wave analysis techniques. The PPG technology has been used in a wide range of commercially available medical devices for measuring oxygen saturation, blood pressure and cardiac output, assessing autonomic function and also detecting peripheral vascular disease. The introductory sections of the topical review describe the basic principle of operation and interaction of light with tissue, early and recent history of PPG, instrumentation, measurement protocol, and pulse wave analysis. The review then focuses on the applications of PPG in clinical physiological measurements, including clinical physiological monitoring, vascular assessment and autonomic function.

The Optics of Human Skin

Abstract: An integrated review of the transfer of optical radiation into human skin is presented, aimed at developing useful models for photomedicine. The component chromophores of epidermis and stratum corneum in general determine the attenuation of radiation in these layers, moreso than does optical scattering. Epidermal thickness and melanization are important factors for UV wavelengths less than 300 nm, whereas the attenuation of UVA (320-400 nm) and visible radiation is primarily via melanin. The selective penetration of all optical wavelengths into psoriatic skin can be maximized by application of clear lipophilic liquids, which decrease regular reflectance by a refractive-index matching mechanism. Sensitivity to wavelengths less than 320 nm can be enhanced by prolonged aqueous bathing, which extracts urocanic acid and other diffusible epidermal chromophores. Optical properties of the dermis are modelled using the Kubelka-Munk approach, and calculations of scattering and absorption coefficients are presented. This simple approach allows estimates of the penetration of radiation in vivo using noninvasive measurements of cutaneous spectral remittance (diffuse reflectance). Although the blood chromophores Hb, HbO2, and bilirubin determine dermal absorption of wavelengths longer than 320 nm, scattering by collagen fibers largely determines the depths to which these wavelengths penetrate the dermis, and profoundly modifies skin colors. An optical "window" exists between 600 and 1300 nm, which offers the possibility of treating large tissue volumes with certain long-wavelength photosensitizers. Moreover, whenever photosensitized action spectra extend across the near UV and/or visible spectrum, judicious choice of wavelengths allows some selection of the tissue layers directly affected.

Evaluation of wearable consumer heart rate monitors based on photopletysmography.

Abstract: Wearable monitoring of heart rate (HR) during physical activity and exercising allows real time control of exercise intensity and training effect. Recently, technologies based on pulse plethysmography (PPG) have become available for personal health management for consumers. However, the accuracy of these monitors is poorly known which limits their application. In this study, we evaluated accuracy of two PPG based (wrist i.e. Mio Alpha vs forearm i.e. Schosche Rhythm) commercially available HR monitors during exercise. 21 healthy volunteers (15 male and 6 female) completed an exercise protocol which included sitting, lying, walking, running, cycling, and some daily activities involving hand movements. HR estimation was compared against values from the reference electrocardiogram (ECG) signal. The heart rate estimation reliability scores for <;5% accuracy against reference were following: mio Alpha 77,83% and Scosche Rhytm 76,29%. The estimated results indicate that performance of devices depends on various parameters, including specified activity, sensor type and device placement.

Wearable sensors : fundamentals, implementation and applications

Abstract: Written by industry experts, this book aims to provide you with an understanding of how to design and work with wearable sensors. Together these insights provide the first single source of information on wearable sensors that would be a valuable addition to the library of any engineer interested in this field. Wearable Sensors covers a wide variety of topics associated with the development and application of various wearable sensors. It also provides an overview and coherent summary of many aspects of current wearable sensor technology. Both industry professionals and academic researchers will benefit from this comprehensive reference which contains the most up-to-date information on the advancement of lightweight hardware, energy harvesting, signal processing, and wireless communications and networks. Practical problems with smart fabrics, biomonitoring and health informatics are all addressed, plus end user centric design, ethical and safety issues. * Provides the first comprehensive resource of all currently used wearable devices in an accessible and structured manner.* Helps engineers manufacture wearable devices with information on current technologies, with a focus on end user needs and recycling requirements.* Combines the expertise of professionals and academics in one practical and applied source.