The aging population, prevalence of chronic diseases, and outbreaks of infectious diseases are some of the major challenges of our present-day society. To address these unmet healthcare needs, especially for the early prediction and treatment of major diseases, health informatics, which deals with the acquisition, transmission, processing, storage, retrieval, and use of health information, has emerged as an active area of interdisciplinary research. In particular, acquisition of health-related information by unobtrusive sensing and wearable technologies is considered as a cornerstone in health informatics. Sensors can be weaved or integrated into clothing, accessories, and the living environment, such that health information can be acquired seamlessly and pervasively in daily living. Sensors can even be designed as stick-on electronic tattoos or directly printed onto human skin to enable long-term health monitoring. This paper aims to provide an overview of four emerging unobtrusive and wearable technologies, which are essential to the realization of pervasive health information acquisition, including: 1) unobtrusive sensing methods, 2) smart textile technology, 3) flexible-stretchable-printable electronics, and 4) sensor fusion, and then to identify some future directions of research.

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Unobtrusive Sensing and Wearable Devices for Health Informatics

In the past decade, there has been a resurgence in the field of unobtrusive cardiomechanical assessment, through advancing methods for measuring and interpreting ballistocardiogram (BCG) and seismocardiogram (SCG) signals. Novel instrumentation solutions have enabled BCG and SCG measurement outside of clinical settings, in the home, in the field, and even in microgravity. Customized signal processing algorithms have led to reduced measurement noise, clinically relevant feature extraction, and signal modeling. Finally, human subjects physiology studies have been conducted using these novel instruments and signal processing tools with promising results. This paper reviews the recent advances in these areas of modern BCG and SCG research.

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Ballistocardiography and Seismocardiography: A Review of Recent Advances

There is an ever-growing demand for measuring respiratory variables during a variety of applications, including monitoring in clinical and occupational settings, and during sporting activities and exercise. Special attention is devoted to the monitoring of respiratory rate because it is a vital sign, which responds to a variety of stressors. There are different methods for measuring respiratory rate, which can be classed as contact-based or contactless. The present paper provides an overview of the currently available contact-based methods for measuring respiratory rate. For these methods, the sensing element (or part of the instrument containing it) is attached to the subject’s body. Methods based upon the recording of respiratory airflow, sounds, air temperature, air humidity, air components, chest wall movements, and modulation of the cardiac activity are presented. Working principles, metrological characteristics, and applications in the respiratory monitoring field are presented to explore potential development and applicability for each method.

Contact-Based Methods for Measuring Respiratory Rate

Fiber Bragg Grating (FBG) sensors are among the most popular elements for fiber optic sensor networks used for the direct measurement of temperature and strain. Modern FBG interrogation setups measure the FBG spectrum in real-time, and determine the shift of the Bragg wavelength of the FBG in order to estimate the physical parameters. The problem of determining the peak wavelength of the FBG from a spectral measurement limited in resolution and noise, is referred as the peak-tracking problem. In this work, the several peak-tracking approaches are reviewed and classified, outlining their algorithmic implementations: the methods based on direct estimation, interpolation, correlation, resampling, transforms, and optimization are discussed in all their proposed implementations. Then, a simulation based on coupled-mode theory compares the performance of the main peak-tracking methods, in terms of accuracy and signal to noise ratio resilience.

Review and Analysis of Peak Tracking Techniques for Fiber Bragg Grating Sensors.

This article is focused on reviewing the current state-of-the-art of optical fibre pressure sensors for medical applications. Optical fibres have inherent advantages due to their small size, immunity to electromagnetic interferences and their suitability for remote monitoring and multiplexing. The small dimensions of optical fibre-based pressure sensors, together with being lightweight and flexible, mean that they are minimally invasive for many medical applications and, thus, particularly suited to in vivo measurement. This means that the sensor can be placed directly inside a patient, e.g., for urodynamic and cardiovascular assessment. This paper presents an overview of the recent developments in optical fibre-based pressure measurements with particular reference to these application areas.

Optical Fibre Pressure Sensors in Medical Applications

This paper shows the design of a fiber-based sensor for living activities in human body and the results of a laboratory evaluation carried out on it. The authors have developed a device that allows for monitoring the vibrations of human body evoked by living activities-breathing and cardiac rhythm. The device consists of a Bragg grating inscribed into a single mode optical fiber and operating on a wavelength of around 1550 nm. The fiber Bragg grating (FBG) is mounted inside a pneumatic cushion to be placed between the backrest of the seat and the back of the monitored person. Deformations of the cushion, involving deformations of the FBG, are proportional to the vibrations of the body leaning on the cushion. Laboratory studies have shown that the sensor allows for obtaining dynamic strains on the sensing FBG in the range of 50-124 μ strain caused by breathing and approximately 8.3 μstrain induced by heartbeat, which are fully measurable by today's FBG interrogation systems. The maximum relative measurement error of the presented sensor is 12%. The sensor's simple design enables it to be easily implemented in pilot's and driver's seats for monitoring the physiological condition of pilots and drivers.

Monitoring Respiration and Cardiac Activity Using Fiber Bragg Grating-Based Sensor

Fibre-optic Sensor for Respiration and Heart Rate Monitoring in the MRI Environment

The article presents the first attempt for design of an autonomous measurement system to aid assessment and to determine the psychological profile of soldiers. A method for ascertaining the psychological profile is presented including the physiological signals being generated by the monitored subject as an important element thereof. The measurement system used in the preliminary experiments and the design of a new, extended-functionality system, are presented. The new version of the measurement system facilitates determination of physiological parameters, environmental conditions and physical activity. In addition, it allows introduction of data on the psychological profile of the soldier to determine the degree of a soldier's adaptation to task-related situation at given point in time. The main element of the measurement system has been designed using an application-specific integrated circuit.

First approach for design of an autonomous measurement system to aid determination of the psychological profile of soldiers

This article shows the design of a fiber-based sensor for living activities in human body and the results of laboratory evaluation carried out on it. The authors have developed a device that allows for monitoring the vibrations of human body evoked by living activities - breathing and cardiac rhythm. The device consists of a Bragg grating inscribed into a single-mode optical fiber and operating on a wavelength of around 1550 nm. The fiber Bragg grating (FBG) is mounted inside a pneumatic cushion to be placed between the backrest of the seat and the back of the monitored person. Deformations of the cushion, involving deformations of the FBG, are proportional to the vibrations of the body leaning on the cushion. Laboratory studies have shown that the sensor allows for obtaining dynamic strains on the sensing FBG in the range of 16.5–24.8 µstrain caused by breathing and approx. 8.3 µstrain induced by heartbeat, which are fully measurable by today's FBG interrogation systems.

Fiber-optic sensor for monitoring respiration and cardiac activity

The paper concerns recording biomedical signals for the purpose of monitoring psychophysiological parameters in extreme conditions, using a microwave glucose sensor. The intended project involves a modern system for monitoring the psychophysiological activity, integrated with a personal microcomputer system monitoring the human efficiency. The elements of the monitoring system are applicable in the newest trends connected with health care called telemedicine. The elaborated set of micro sensors and algorithms of data processing will allow elaborating proper indicators of the psychomotor state estimation. The interference-resistant technology developed for the military sector enables the proposed solutions to be used also in civilian applications.

J. Lewandowski

Papers

Monitoring Respiration and Cardiac Activity Using Fiber Bragg Grating-Based Sensor

Fibre-optic Sensor for Respiration and Heart Rate Monitoring in the MRI Environment

First approach for design of an autonomous measurement system to aid determination of the psychological profile of soldiers

Fiber-optic sensor for monitoring respiration and cardiac activity

Multisensor system for monitoring human psychophysiologic state in extreme conditions with the use of microwave sensor