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Li J, Chu H, Chen Z, Yiu CK, Qu Q, Li Z, Yu X. Recent Advances in Materials, Devices and Algorithms Toward Wearable Continuous Blood Pressure Monitoring. ACS NANO 2024; 18:17407-17438. [PMID: 38923501 DOI: 10.1021/acsnano.4c04291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2024]
Abstract
Continuous blood pressure (BP) tracking provides valuable insights into the health condition and functionality of the heart, arteries, and overall circulatory system of humans. The rapid development in flexible and wearable electronics has significantly accelerated the advancement of wearable BP monitoring technologies. However, several persistent challenges, including limited sensing capabilities and stability of flexible sensors, poor interfacial stability between sensors and skin, and low accuracy in BP estimation, have hindered the progress in wearable BP monitoring. To address these challenges, comprehensive innovations in materials design, device development, system optimization, and modeling have been pursued to improve the overall performance of wearable BP monitoring systems. In this review, we highlight the latest advancements in flexible and wearable systems toward continuous noninvasive BP tracking with a primary focus on materials development, device design, system integration, and theoretical algorithms. Existing challenges, potential solutions, and further research directions are also discussed to provide theoretical and technical guidance for the development of future wearable systems in continuous ambulatory BP measurement with enhanced sensing capability, robustness, and long-term accuracy.
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Affiliation(s)
- Jian Li
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
| | - Hongwei Chu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Shenzhen Key Laboratory of Flexible Printed Electronics Technology, School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China
| | - Zhenlin Chen
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
| | - Chun Ki Yiu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
| | - Qing'ao Qu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Zhiyuan Li
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Xinge Yu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
- City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, China
- Hong Kong Institute for Clean Energy, City University of Hong Kong, Kowloon, Hong Kong, China
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Hong J, Seong D, Kang D, Kim H, Jang JH, Jeon M, Kim J. Imaging of the vascular distribution of the outer ear using optical coherence tomography angiography for highly accurate positioning of a hearable sensor. APL Bioeng 2024; 8:026113. [PMID: 38799376 PMCID: PMC11126325 DOI: 10.1063/5.0203582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/29/2024] [Indexed: 05/29/2024] Open
Abstract
Novel hearable technology is securely and comfortably positioned within the ear canal minimizing inaccuracies caused by accessory movements during activities. Despite extensive research on hearable technologies within the outer ear, there is a lack of research in the field of vascular imaging and quantitative analysis in the outer ear in vivo, which is one of the crucial factors to select the appropriate sensor position. Therefore, in this paper, we introduced optical coherence tomography angiography (OCTA)-based qualitative and quantitative analyses to visualize the inner vasculature of the outer ear to acquire vascular maps for microvascular assessments in vivo. By generating maximum amplitude projection images from three-dimensional blood vascular volume, we identified variations of blood vessel signal caused by the different biological characteristics and curvature of the ear among individuals. The performance of micro-vascular mapping using the proposed method was validated through the comparison and analysis of individual vascular parameters using extracted 20 vascular-related variables. In addition, we extracted pulsatile blood flow signals, demonstrating its potential to provide photoplethysmographic signals and ear blood maps simultaneously. Therefore, our proposed OCTA-based method for ear vascular mapping successfully provides quantitative information about ear vasculature, which is potentially used for determining the position of system-on-chip sensors for health monitoring in hearable devices.
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Affiliation(s)
- Juyeon Hong
- School of Electronic and Electrical Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Daewoon Seong
- School of Electronic and Electrical Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Dongwan Kang
- School of Electronic and Electrical Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Hyunmo Kim
- School of Electronic and Electrical Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Jeong Hun Jang
- Department of Otolaryngology, School of Medicine, Ajou University, 206, World cup-ro, Yeongtong-gu, Suwon 16499, South Korea
| | - Mansik Jeon
- School of Electronic and Electrical Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, South Korea
| | - Jeehyun Kim
- School of Electronic and Electrical Engineering, College of IT Engineering, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, South Korea
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Liao S, Liu H, Lin WH, Zheng D, Chen F. Filtering-induced changes of pulse transmit time across different ages: a neglected concern in photoplethysmography-based cuffless blood pressure measurement. Front Physiol 2023; 14:1172150. [PMID: 37560157 PMCID: PMC10407099 DOI: 10.3389/fphys.2023.1172150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 07/12/2023] [Indexed: 08/11/2023] Open
Abstract
Background: Pulse transit time (PTT) is a key parameter in cuffless blood pressure measurement based on photoplethysmography (PPG) signals. In wearable PPG sensors, raw PPG signals are filtered, which can change the timing of PPG waveform feature points, leading to inaccurate PTT estimation. There is a lack of comprehensive investigation of filtering-induced PTT changes in subjects with different ages. Objective: This study aimed to quantitatively investigate the effects of aging and PTT definition on the infinite impulse response (IIR) filtering-induced PTT changes. Methods: One hundred healthy subjects in five different ranges of age (i.e., 20-29, 30-39, 40-49, 50-59, and over 60 years old, 20 subjects in each) were recruited. Electrocardiogram (ECG) and PPG signals were recorded simultaneously for 120 s. PTT was calculated from the R wave of ECG and PPG waveform features. Eight PTT definitions were developed from different PPG waveform feature points. The raw PPG signals were preprocessed then further low-pass filtered. The difference between PTTs derived from preprocessed and filtered PPG signals, and the relative difference, were calculated and compared among five age groups and eight PTT definitions using the analysis of variance (ANOVA) or Scheirer-Ray-Hare test with post hoc analysis. Linear regression analysis was used to investigate the relationship between age and filtering-induced PTT changes. Results: Filtering-induced PTT difference and the relative difference were significantly influenced by age and PTT definition (p < 0.001 for both). Aging effect on filtering-induced PTT changes was consecutive with a monotonous trend under all PTT definitions. The age groups with maximum and minimum filtering-induced PTT changes depended on the definition. In all subjects, the PTT defined by maximum peak of PPG had the minimum filtering-induced PTT changes (mean: 16.16 ms and 5.65% for PTT difference and relative difference). The changes of PTT defined by maximum first PPG derivative had the strongest linear relationship with age (R-squared: 0.47 and 0.46 for PTT difference relative difference). Conclusion: The filtering-induced PTT changes are significantly influenced by age and PTT definition. These factors deserve further consideration to improve the accuracy of PPG-based cuffless blood pressure measurement using wearable sensors.
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Affiliation(s)
- Shangdi Liao
- Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, China
| | - Haipeng Liu
- Research Centre for Intelligent Healthcare, Coventry University, Coventry, United Kingdom
| | - Wan-Hua Lin
- Chinese Academy of Sciences Key Laboratory of Human-Machine Intelligence-Synergy Systems, Shenzhen Institute of Advanced Technology, Shenzhen, China
| | - Dingchang Zheng
- Research Centre for Intelligent Healthcare, Coventry University, Coventry, United Kingdom
| | - Fei Chen
- Department of Electronic and Electrical Engineering, Southern University of Science and Technology, Shenzhen, China
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Azudin K, Gan KB, Jaafar R, Ja'afar MH. The Principles of Hearable Photoplethysmography Analysis and Applications in Physiological Monitoring-A Review. SENSORS (BASEL, SWITZERLAND) 2023; 23:6484. [PMID: 37514778 PMCID: PMC10384007 DOI: 10.3390/s23146484] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/29/2023] [Accepted: 06/04/2023] [Indexed: 07/30/2023]
Abstract
Not long ago, hearables paved the way for biosensing, fitness, and healthcare monitoring. Smart earbuds today are not only producing sound but also monitoring vital signs. Reliable determination of cardiovascular and pulmonary system information can explore the use of hearables for physiological monitoring. Recent research shows that photoplethysmography (PPG) signals not only contain details on oxygen saturation level (SPO2) but also carry more physiological information including pulse rate, respiration rate, blood pressure, and arterial-related information. The analysis of the PPG signal from the ear has proven to be reliable and accurate in the research setting. (1) Background: The present integrative review explores the existing literature on an in-ear PPG signal and its application. This review aims to identify the current technology and usage of in-ear PPG and existing evidence on in-ear PPG in physiological monitoring. This review also analyzes in-ear (PPG) measurement configuration and principle, waveform characteristics, processing technology, and feature extraction characteristics. (2) Methods: We performed a comprehensive search to discover relevant in-ear PPG articles published until December 2022. The following electronic databases: Institute of Electrical and Electronics Engineers (IEEE), ScienceDirect, Scopus, Web of Science, and PubMed were utilized to conduct the studies addressing the evidence of in-ear PPG in physiological monitoring. (3) Results: Fourteen studies were identified but nine studies were finalized. Eight studies were on different principles and configurations of hearable PPG, and eight studies were on processing technology and feature extraction and its evidence in in-ear physiological monitoring. We also highlighted the limitations and challenges of using in-ear PPG in physiological monitoring. (4) Conclusions: The available evidence has revealed the future of in-ear PPG in physiological monitoring. We have also analyzed the potential limitation and challenges that in-ear PPG will face in processing the signal.
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Affiliation(s)
- Khalida Azudin
- Department of Electrical, Electronic & Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
| | - Kok Beng Gan
- Department of Electrical, Electronic & Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
| | - Rosmina Jaafar
- Department of Electrical, Electronic & Systems Engineering, Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia
| | - Mohd Hasni Ja'afar
- Department of Community Health, Faculty of Medicine, UKM Medical Centre, Universiti Kebangsaan Malaysia, Cheras 56000, Kuala Lumpur, Malaysia
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Qi Y, Zhang A, Ma Y, Chang T, Xu J. Comparison of pulse rate variability from post-auricula and heart rate variability during different body states for healthy subjects. J Med Eng Technol 2023; 47:179-188. [PMID: 36794319 DOI: 10.1080/03091902.2023.2175061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Heart rate variability (HRV) extracted from the electrocardiogram (ECG) is an essential indicator for assessing the autonomic nervous system in clinical. Some scholars have studied the feasibility of pulse rate variability (PRV) instead of HRV. However, there is little qualitative research in different body states. In this paper, the photoplethysmography (PPG) of postauricular and finger and the ECG of fifteen subjects were synchronously collected for comparative analysis. The eleven experiments were designed according to the daily living state, including the stationary state, limb movement state, and facial movement state. The substitutability of nine variables was investigated in the time, frequency, and nonlinearity domain by Passing Bablok regression and Bland Altman analysis. The results showed that the PPG of the finger was destroyed in the limb movement state. There were six variables of postauricular PRV, which showed a positive linear relationship and good agreement (p > 0.05, ratio ≤0.2) with HRV in all experiments. Our study suggests that the postauricular PPG could retain the necessary information of the pulse signal under the limb movement state and facial movement state. Therefore, postauricular PPG could be a better substitute for HRV, daily PPG detection, and mobile health than finger PPG.
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Affiliation(s)
- Yusheng Qi
- College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou, China.,Key Laboratory of Gansu Advanced Control for Industrial Processes, Lanzhou University of Technology, Lanzhou, China.,National Demonstration Center for Experimental Electrical and Control Engineering Education, Lanzhou University of Technology, Lanzhou, China
| | - Aihua Zhang
- College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou, China.,Key Laboratory of Gansu Advanced Control for Industrial Processes, Lanzhou University of Technology, Lanzhou, China.,National Demonstration Center for Experimental Electrical and Control Engineering Education, Lanzhou University of Technology, Lanzhou, China.,College of Computer and Communication, Lanzhou University of Technology, Lanzhou, China
| | - Yurun Ma
- College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou, China.,Key Laboratory of Gansu Advanced Control for Industrial Processes, Lanzhou University of Technology, Lanzhou, China.,National Demonstration Center for Experimental Electrical and Control Engineering Education, Lanzhou University of Technology, Lanzhou, China
| | - Tingting Chang
- College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou, China.,Key Laboratory of Gansu Advanced Control for Industrial Processes, Lanzhou University of Technology, Lanzhou, China.,College of Computer and Communication, Lanzhou University of Technology, Lanzhou, China
| | - Jianwen Xu
- College of Electrical and Information Engineering, Lanzhou University of Technology, Lanzhou, China.,Key Laboratory of Gansu Advanced Control for Industrial Processes, Lanzhou University of Technology, Lanzhou, China.,National Demonstration Center for Experimental Electrical and Control Engineering Education, Lanzhou University of Technology, Lanzhou, China
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Ne CKH, Muzaffar J, Amlani A, Bance M. Hearables, in-ear sensing devices for bio-signal acquisition: a narrative review. Expert Rev Med Devices 2021; 18:95-128. [PMID: 34904507 DOI: 10.1080/17434440.2021.2014321] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
INTRODUCTION Hearables are ear devices used for multiple purposes including ubiquitous/remote monitoring of vital signals. This can support early detection, prevention, and management of urgent/non-urgent healthcare needs. This review therefore seeks to analyse the challenges and capabilities of hearables used to monitor human physiological signals. AREAS COVERED Studies were identified via search (Medline, Embase, Web of Science, Cochrane Library, Scopus) and conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Bias assessment used the Mixed Methods Appraisal Tool 2018 and Quality Assessment of Diagnostic Accuracy Studies 2nd Edition. 92/631 studies met the inclusion criteria and were qualitatively analysed. The outcomes, applications, advantages and limitations were discussed according to the vital signal measured. The bias risk ranged from low to high, with most studies facing moderate to high risk in subject selection due to small sample sizes. EXPERT OPINION : Most studies reported good outcomes for ear signal acquisition compared to reference devices. To improve practicability and implementation, wireless connectivity, battery life, impact of motion/environmental artifacts and comfort need to be addressed going forward. Hearable technologies have also shown potential synergies with hearing aids. In future, multimodal ear-sensing devices opens the possibility of comprehensive health monitoring within daily life.
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Affiliation(s)
| | - Jameel Muzaffar
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Aakash Amlani
- Department of Ear, Nose and Throat Surgery, Birmingham Children's Hospital, Birmingham, United Kingdom
| | - Manohar Bance
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
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Masè M, Micarelli A, Strapazzon G. Hearables: New Perspectives and Pitfalls of In-Ear Devices for Physiological Monitoring. A Scoping Review. Front Physiol 2020; 11:568886. [PMID: 33178038 PMCID: PMC7596679 DOI: 10.3389/fphys.2020.568886] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/02/2020] [Indexed: 12/31/2022] Open
Abstract
Technological advancements are opening the possibility of prolonged monitoring of physiological parameters under daily-life conditions, with potential applications in sport science and medicine, and in extreme environments. Among emerging wearable technologies, in-ear devices or hearables possess technical advantages for long-term monitoring, such as non-invasivity, unobtrusivity, good fixing, and reduced motion artifacts, as well as physiological advantages related to the proximity of the ear to the body trunk and the shared vasculature between the ear and the brain. The present scoping review was aimed at identifying and synthesizing the available evidence on the use and performance of in-ear monitoring of physiological parameters, with focus on applications in sport science, sport medicine, occupational medicine, and extreme environment settings. Pubmed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 10 years and addressing the measurement of three main physiological parameters (temperature, heart rate, and oxygen saturation) in healthy subjects. Thirty-nine studies were identified, 24 performing temperature measurement, 12 studies on heart/pulse rate, and three studies on oxygen saturation. The collected evidence supports the premise of in-ear sensors as an innovative and unobtrusive way for physiological monitoring during daily-life and physical activity, but further research and technological advancement are necessary to ameliorate measurement accuracy especially in more challenging scenarios.
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Affiliation(s)
- Michela Masè
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,Healthcare Research and Innovation Program, IRCS-HTA, Bruno Kessler Foundation, Trento, Italy
| | - Alessandro Micarelli
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy.,ITER Center for Balance and Rehabilitation Research (ICBRR), Rome, Italy
| | - Giacomo Strapazzon
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
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Nie L, Berckmans D, Wang C, Li B. Is Continuous Heart Rate Monitoring of Livestock a Dream or Is It Realistic? A Review. SENSORS 2020; 20:s20082291. [PMID: 32316511 PMCID: PMC7219037 DOI: 10.3390/s20082291] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/08/2020] [Accepted: 04/15/2020] [Indexed: 12/11/2022]
Abstract
For all homoeothermic living organisms, heart rate (HR) is a core variable to control the metabolic energy production in the body, which is crucial to realize essential bodily functions. Consequently, HR monitoring is becoming increasingly important in research of farm animals, not only for production efficiency, but also for animal welfare. Real-time HR monitoring for humans has become feasible though there are still shortcomings for continuously accurate measuring. This paper is an effort to estimate whether it is realistic to get a continuous HR sensor for livestock that can be used for long term monitoring. The review provides the reported techniques to monitor HR of living organisms by emphasizing their principles, advantages, and drawbacks. Various properties and capabilities of these techniques are compared to check the potential to transfer the mostly adequate sensor technology of humans to livestock in term of application. Based upon this review, we conclude that the photoplethysmographic (PPG) technique seems feasible for implementation in livestock. Therefore, we present the contributions to overcome challenges to evolve to better solutions. Our study indicates that it is realistic today to develop a PPG sensor able to be integrated into an ear tag for mid-sized and larger farm animals for continuously and accurately monitoring their HRs.
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Affiliation(s)
- Luwei Nie
- Department of Agricultural Structure and Bioenvironmental Engineering, College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; (L.N.); (B.L.)
- Key Laboratory of Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, Beijing 100083, China
| | - Daniel Berckmans
- M3-BIORES KU Leuven, Department BioSystems, Kasteelpark Arenberg 30, 3001 Leuven, Belgium;
| | - Chaoyuan Wang
- Department of Agricultural Structure and Bioenvironmental Engineering, College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; (L.N.); (B.L.)
- Key Laboratory of Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, Beijing 100083, China
- Correspondence: ; Tel.: +86-10-6273-8635
| | - Baoming Li
- Department of Agricultural Structure and Bioenvironmental Engineering, College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; (L.N.); (B.L.)
- Key Laboratory of Agricultural Engineering in Structure and Environment, Ministry of Agriculture and Rural Affairs, Beijing 100083, China
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9
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Passler S, Müller N, Senner V. In-Ear Pulse Rate Measurement: A Valid Alternative to Heart Rate Derived from Electrocardiography? SENSORS 2019; 19:s19173641. [PMID: 31438600 PMCID: PMC6749408 DOI: 10.3390/s19173641] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 07/31/2019] [Accepted: 08/19/2019] [Indexed: 11/16/2022]
Abstract
Heart rate measurement has become one of the most widely used methods of monitoring the intensity of physical activity. The purpose of this study was to assess whether in-ear photoplethysmographic (PPG) pulse rate (PR) measurement devices represent a valid alternative to heart rate derived from electrocardiography (ECG), which is considered a gold standard. Twenty subjects (6 women, 14 men) completed one trial of graded cycling under laboratory conditions. In the trial, PR was recorded by two commercially available in-ear devices, the Dash Pro and the Cosinuss°One. They were compared to HR measured by a Bodyguard2 ECG. Validity of the in-ear PR measurement devices was tested by ANOVA, mean absolute percentage errors (MAPE), intra-class correlation coefficient (ICC), and Bland–Altman plots. Both devices achieved a MAPE ≤5%. Despite excellent to good levels of agreement, Bland–Altman plots showed that both in-ear devices tend to slightly underestimate the ECG’s HR values. It may be concluded that in-ear PPG PR measurement is a promising technique that shows accurate but imprecise results under controlled conditions. However, PPG PR measurement in the ear is sensitive to motion artefacts. Thus, accuracy and precision of the measured PR depend highly on measurement site, stress situation, and exercise.
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Affiliation(s)
- Stefanie Passler
- Technical University of Munich, Department of Mechanical Engineering, Professorship of Sport Equipment and Materials, Boltzmannstraße 15, D-85747 Garching, Germany.
| | - Niklas Müller
- Technical University of Munich, Department of Mechanical Engineering, Professorship of Sport Equipment and Materials, Boltzmannstraße 15, D-85747 Garching, Germany
| | - Veit Senner
- Technical University of Munich, Department of Mechanical Engineering, Professorship of Sport Equipment and Materials, Boltzmannstraße 15, D-85747 Garching, Germany
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Tamura T. Current progress of photoplethysmography and SPO 2 for health monitoring. Biomed Eng Lett 2019; 9:21-36. [PMID: 30956878 PMCID: PMC6431353 DOI: 10.1007/s13534-019-00097-w] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 01/05/2019] [Accepted: 01/15/2019] [Indexed: 11/28/2022] Open
Abstract
A photoplethysmograph (PPG) is a simple medical device for monitoring blood flow and transportation of substances in the blood. It consists of a light source and a photodetector for measuring transmitted and reflected light signals. Clinically, PPGs are used to monitor the pulse rate, oxygen saturation, blood pressure, and blood vessel stiffness. Wearable unobtrusive PPG monitors are commercially available. Here, we review the principle issues and clinical applications of PPG for monitoring oxygen saturation.
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Affiliation(s)
- Toshiyo Tamura
- Future Robotics Institute, Wadeda University, Tokyo, Japan
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11
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Saritas T, Greber R, Venema B, Puelles VG, Ernst S, Blazek V, Floege J, Leonhardt S, Schlieper G. Non-invasive evaluation of coronary heart disease in patients with chronic kidney disease using photoplethysmography. Clin Kidney J 2019; 12:538-545. [PMID: 31384446 PMCID: PMC6671527 DOI: 10.1093/ckj/sfy135] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Indexed: 12/16/2022] Open
Abstract
Background Chronic kidney disease (CKD) patients have an increased risk for coronary artery disease (CAD) and myocardial infarction. Therefore, there is a need to identify CKD patients at high risk of CAD. Coronary angiography, the gold standard for detecting CAD, carries a risk of serious adverse events. Methods Here, we assessed the validity of a novel non-invasive reflectance mode photoplethysmography (PPG) sensor for the evaluation of CAD in patients with advanced CKD. PPG signals were generated using green and infrared wavelengths and recorded from fingers of 98 patients. The detected signal has the shape of the pulse wave contour carrying information about the vascular system, that is, arterial stiffness. We studied four patient groups: (i) controls—patients without CKD or CAD; (ii) CKD alone; (iii) CAD alone (confirmed by coronary angiography); and (iv) CKD and CAD combined. Results With advancing age, we observed a steeper ascending signal during systole and greater signal decline during diastole (infrared wavelength: Slopes 4–6, P = 0.002, P = 0.003 and P = 0.014, respectively; green wavelength: Slopes 2–3, P = 0.006 and P = 0.005, respectively). Presence of CAD was associated with a slower signal decline during diastole in CKD patients compared with those without CAD (infrared wavelength: Slope 1, P = 0.012). CKD was associated with lower blood volume amplitude during each cardiac cycle compared with those without CKD (R-value, P = 0.022). Conclusions PPG signal analyses showed significant differences between our groups, and it may be a potentially useful tool for the detection of CAD in CKD patients.
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Affiliation(s)
- Turgay Saritas
- Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Germany
| | - Ruth Greber
- Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Germany
| | - Boudewijn Venema
- Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany
| | - Victor G Puelles
- Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Germany.,Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia.,III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Sabine Ernst
- Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Germany
| | - Vladimir Blazek
- Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany
| | - Jürgen Floege
- Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Germany
| | - Steffen Leonhardt
- Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany
| | - Georg Schlieper
- Nephrology and Clinical Immunology, University Hospital RWTH Aachen, Germany.,Center for Nephrology, Hypertension, and Metabolic Diseases, Hannover, Germany
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12
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Martin A, Voix J. In-Ear Audio Wearable: Measurement of Heart and Breathing Rates for Health and Safety Monitoring. IEEE Trans Biomed Eng 2018; 65:1256-1263. [DOI: 10.1109/tbme.2017.2720463] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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13
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Lin ST, Chen WH, Lin YH. A Pulse Rate Detection Method for Mouse Application Based on Multi-PPG Sensors. SENSORS (BASEL, SWITZERLAND) 2017; 17:E1628. [PMID: 28708112 PMCID: PMC5539748 DOI: 10.3390/s17071628] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Revised: 06/26/2017] [Accepted: 07/11/2017] [Indexed: 11/16/2022]
Abstract
Heart rate is an important physiological parameter for healthcare. Among measurement methods, photoplethysmography (PPG) is an easy and convenient method for pulse rate detection. However, as the PPG signal faces the challenge of motion artifacts and is constrained by the position chosen, the purpose of this paper is to implement a comfortable and easy-to-use multi-PPG sensor module combined with a stable and accurate real-time pulse rate detection method on a computer mouse. A weighted average method for multi-PPG sensors is used to adjust the weight of each signal channel in order to raise the accuracy and stability of the detected signal, therefore reducing the disturbance of noise under the environment of moving effectively and efficiently. According to the experiment results, the proposed method can increase the usability and probability of PPG signal detection on palms.
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Affiliation(s)
- Shu-Tyng Lin
- Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
| | - Wei-Hao Chen
- Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
| | - Yuan-Hsiang Lin
- Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
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14
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Aboughaly AA, Abd El Ghany MA. Unobtrusive Wearable Health Monitoring System. 2017 IEEE COMPUTER SOCIETY ANNUAL SYMPOSIUM ON VLSI (ISVLSI) 2017. [DOI: 10.1109/isvlsi.2017.52] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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15
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Sun Y, Thakor N. Photoplethysmography Revisited: From Contact to Noncontact, From Point to Imaging. IEEE Trans Biomed Eng 2015; 63:463-77. [PMID: 26390439 DOI: 10.1109/tbme.2015.2476337] [Citation(s) in RCA: 191] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Photoplethysmography (PPG) is a noninvasive optical technique for detecting microvascular blood volume changes in tissues. Its ease of use, low cost and convenience make it an attractive area of research in the biomedical and clinical communities. Nevertheless, its single spot monitoring and the need to apply a PPG sensor directly to the skin limit its practicality in situations such as perfusion mapping and healing assessments or when free movement is required. The introduction of fast digital cameras into clinical imaging monitoring and diagnosis systems, the desire to reduce the physical restrictions, and the possible new insights that might come from perfusion imaging and mapping inspired the evolution of the conventional PPG technology to imaging PPG (IPPG). IPPG is a noncontact method that can detect heart-generated pulse waves by means of peripheral blood perfusion measurements. Since its inception, IPPG has attracted significant public interest and provided opportunities to improve personal healthcare. This study presents an overview of the wide range of IPPG systems currently being introduced along with examples of their application in various physiological assessments. We believe that the widespread acceptance of IPPG is happening, and it will dramatically accelerate the promotion of this healthcare model in the near future.
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16
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Budidha K, Kyriacou PA. Devepopment of an optical probe to investigate the suitability of measuring photoplethysmographs and blood oxygen saturation from the human auditory canal. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2015; 2013:1736-9. [PMID: 24110042 DOI: 10.1109/embc.2013.6609855] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Pulse oximetry has become a standard for patient monitoring in the operating room, and the finger is the most common site used for monitoring blood oxygen saturation (SpO2). However, SpO2 measurements made from extremities such as the finger, ear lobe and toes become susceptible to inaccuracies, when patients become hypothermic, hypovolemic and vasoconstrictive. This is due to the week arterial pulsations detected in these conditions. To overcome this limitation, the external auditory canal has been proposed as an alternative monitoring site for estimating SpO2, on the hypothesis that this central site will be better perfused. A dual wavelength optoelectronic sensor along with a processing system was developed to investigate the suitability of measuring photoplethysmographic (PPG) signals and SpO2 values in the human auditory canal. A pilot study was conducted on 12 healthy volunteers to validate the developed sensor. The red and infrared PPG signals obtained from all the volunteers were of very good quality. The SpO2 values recorded from the ear canal were compared with simultaneously acquired data from a commercial finger pulse oximeter. The results show good correlation between the commercial pulse oximeter and the custom made ear canal sensor (r(2) = 0.825).
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17
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Zheng YL, Ding XR, Poon CCY, Lo BPL, Zhang H, Zhou XL, Yang GZ, Zhao N, Zhang YT. Unobtrusive sensing and wearable devices for health informatics. IEEE Trans Biomed Eng 2015; 61:1538-54. [PMID: 24759283 PMCID: PMC7176476 DOI: 10.1109/tbme.2014.2309951] [Citation(s) in RCA: 247] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
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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18
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Venema B, Gehring H, Michelsen I, Blanik N, Blazek V, Leonhardt S. Robustness, Specificity, and Reliability of an In-Ear Pulse Oximetric Sensor in Surgical Patients. IEEE J Biomed Health Inform 2014; 18:1178-85. [DOI: 10.1109/jbhi.2013.2292118] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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19
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20
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Budidha K, Kyriacou PA. The human ear canal: investigation of its suitability for monitoring photoplethysmographs and arterial oxygen saturation. Physiol Meas 2014; 35:111-28. [PMID: 24399082 DOI: 10.1088/0967-3334/35/2/111] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
For the last two decades, pulse oximetry has been used as a standard procedure for monitoring arterial oxygen saturation (SpO2). However, SpO2 measurements made from extremities such as the finger, ear lobe and toes become susceptible to inaccuracies when peripheral perfusion is compromised. To overcome these limitations, the external auditory canal has been proposed as an alternative monitoring site for estimating SpO2, on the hypothesis that this central site will be better perfused. Therefore, a dual wavelength optoelectronic probe along with a processing system was developed to investigate the suitability of measuring photoplethysmographic (PPG) signals and SpO2 in the human auditory canal. A pilot study was carried out in 15 healthy volunteers to validate the feasibility of measuring PPGs and SpO2 from the ear canal (EC), and comparative studies were performed by acquiring the same signals from the left index finger (LIF) and the right index finger (RIF) in conditions of induced peripheral vasoconstriction (right hand immersion in ice water). Good quality baseline PPG signals with high signal-to-noise ratio were obtained from the EC, the LIF and the RIF sensors. During the ice water immersion, significant differences in the amplitude of the red and infrared PPG signals were observed from the RIF and the LIF sensors. The average drop in amplitude of red and infrared PPG signals from the RIF was 52.7% and 58.3%. Similarly, the LIF PPG signal amplitudes have reduced by 47.52% and 46.8% respectively. In contrast, no significant changes were seen in the red and infrared EC PPG amplitude measurements, which changed by +2.5% and -1.2% respectively. The RIF and LIF pulse oximeters have failed to estimate accurate SpO2 in seven and four volunteers respectively, while the EC pulse oximeter has only failed in one volunteer. These results suggest that the EC may be a suitable site for reliable monitoring of PPGs and SpO2s even in the presence of peripheral vasoconstriction.
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Affiliation(s)
- K Budidha
- School of Engineering and Mathematical Sciences, City University, London, EC1V 0HB, UK
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21
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Venema B, Schiefer J, Blazek V, Blanik N, Leonhardt S. Evaluating Innovative In-Ear Pulse Oximetry for Unobtrusive Cardiovascular and Pulmonary Monitoring During Sleep. IEEE JOURNAL OF TRANSLATIONAL ENGINEERING IN HEALTH AND MEDICINE-JTEHM 2013; 1:2700208. [PMID: 27170855 PMCID: PMC4819232 DOI: 10.1109/jtehm.2013.2277870] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 05/24/2013] [Accepted: 07/14/2013] [Indexed: 11/06/2022]
Abstract
Homecare is healthcare based on the principle "outpatient before inpatient," with the aim of moving at least some care-delivery to the home. But reliable determination of vital signs at home requires new, smart sensors, which can be used by the patients themselves. We present a novel pulse oximetry sensor worn in the ear channel. It was previously shown that measurement of heart rate, arterial oxygen saturation and related respiratory information can be performed with reliable accuracy under laboratory conditions. The present study explores the clinical feasibility of the sensor system for cardiovascular monitoring during sleep, with the aim to diagnose sleep apnea. For this, human trials were performed in a sleep laboratory including patients with a clinical suspicion of sleep apnea. Besides a general analysis of the sensor's signal quality during sleep, the evaluation focuses on heart rate dynamics and time-variant oxygen saturation. In addition, several methods to derive respiration rate from photoplethysmographic signals are examined and discussed. Results from the in-ear sensor are compared with standard polysomnography monitoring and demonstrate that this novel system allows long-term nocturnal measurement of heart rate, oxygen saturation and respiratory rate with sufficient accuracy.
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Affiliation(s)
- Boudewijn Venema
- RWTH Aachen University Philips Chair for Medical Information Technology (MedIT) Aachen Germany 52074
| | - Johannes Schiefer
- RWTH Aachen University Hospital Department of Neurology Aachen Germany 52074
| | - Vladimir Blazek
- RWTH Aachen University Philips Chair for Medical Information Technology (MedIT) Aachen Germany 52074
| | - Nikolai Blanik
- RWTH Aachen University Philips Chair for Medical Information Technology (MedIT) Aachen Germany 52074
| | - Steffen Leonhardt
- RWTH Aachen University Philips Chair for Medical Information Technology (MedIT) Aachen Germany 52074
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22
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Goy CB, Dominguez JM, Gómez López MA, Madrid RE, Herrera MC. Electrical characterization of conductive textile materials and its evaluation as electrodes for venous occlusion plethysmography. J Med Eng Technol 2013; 37:359-67. [DOI: 10.3109/03091902.2013.812689] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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23
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Lee J, Matsumura K, Yamakoshi T, Rolfe P, Tanaka N, Kim K, Yamakoshi KI. Validation of normalized pulse volume in the outer ear as a simple measure of sympathetic activity using warm and cold pressor tests: towards applications in ambulatory monitoring. Physiol Meas 2013; 34:359-75. [PMID: 23442846 DOI: 10.1088/0967-3334/34/3/359] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Normalized pulse volume (NPV) derived from the ear has the potential to be a practical index for monitoring daily life stress. However, ear NPV has not yet been validated. Therefore, we compared NPV derived from an index finger using transmission photoplethysmography as a reference, with NPV derived from a middle finger and four sites of the ear using reflection photoplethysmography during baseline and while performing cold and warm water immersion in ten young and six middle-aged subjects. The results showed that logarithmically-transformed NPV (lnNPV) during cold water immersion as compared with baseline values was significantly lower, only at the index finger, the middle finger and the bottom of the ear-canal. Furthermore, lnNPV reactivities (ΔlnNPV; the difference between baseline and test values) from an index finger were significantly related to ΔlnNPV from the middle finger and the bottom of the ear-canal (young: r = 0.90 and 0.62, middle-aged: r = 0.80 and 0.58, respectively). In conclusion, these findings show that reflection and transmission photoplethysmography are comparable methods to derive NPV in accordance with our theoretical prediction. NPV derived from the bottom of the ear-canal is a valid approach, which could be useful for evaluating daily life stress.
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Affiliation(s)
- Jihyoung Lee
- Graduate School of Nature Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa-shi, Ishikawa 920-1192, Japan
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24
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Venema B, Blanik N, Blazek V, Gehring H, Opp A, Leonhardt S. Advances in Reflective Oxygen Saturation Monitoring With a Novel In-Ear Sensor System: Results of a Human Hypoxia Study. IEEE Trans Biomed Eng 2012; 59:2003-10. [DOI: 10.1109/tbme.2012.2196276] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Bonato P. Wearable sensors and systems. From enabling technology to clinical applications. ACTA ACUST UNITED AC 2011; 29:25-36. [PMID: 20659855 DOI: 10.1109/memb.2010.936554] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
It is now more than 50 years since the time when clinical monitoring of individuals in the home and community settings was first envisioned. Until recently, technologies to enable such vision were lacking. However, wearable sensors and systems developed over the past decade have provided the tools to finally implement and deploy technology with the capabilities required by researchers in the field of patients' home monitoring. As discussed, potential applications of these technologies include the early diagnosis of diseases such as congestive heart failure, the prevention of chronic conditions such as diabetes, improved clinical management of neurodegenerative conditions such as Parkinson's disease, and the ability to promptly respond to emergency situations such as seizures in patients with epilepsy and cardiac arrest in subjects undergoing cardiovascular monitoring. Current research efforts are now focused on the development of more complex systems for home monitoring of individuals with a variety of preclinical and clinical conditions. Recent research on the clinical assessment of wearable technology promises to deliver methodologies that are expected to lead to clinical adoption within the next five to ten years. In particular, combining home robots and wearable technology is likely to be a key step toward achieving the goal of effectively monitoring patients in the home. These efforts to merge home robots and wearable technology are expected to enable a new generation of complex systems with the ability to monitor subjects' status, facilitate the administration of interventions, and provide an invaluable tool to respond to emergency situations.
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Affiliation(s)
- Paolo Bonato
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, 125 Nashua Street, Boston, MA 02144, USA.
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26
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Bonato P. Advances in wearable technology and its medical applications. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2010:2021-4. [PMID: 21097220 DOI: 10.1109/iembs.2010.5628037] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The concept of monitoring individuals in the home and community settings was introduced more than 50 years ago, when Holter monitoring was proposed (in the late 1940s) and later adopted (in the 1960s) as a clinical tool. However, technologies to fully enable such vision were lacking and only sporadic and rather obtrusive monitoring techniques were available for several decades. Over the past decade, we have witnessed a great deal of progress in the field of wearable sensors and systems. Advances in this field have finally provided the tools to implement and deploy technology with the capabilities required by researchers in the field of patients' home monitoring. These technologies provide the tools to achieve early diagnosis of diseases such as congestive heart failure, prevention of chronic conditions such as diabetes, improved clinical management of neurodegenerative conditions such as Parkinson's disease, and the ability to promptly respond to emergency situations such as seizures in patients with epilepsy and cardiac arrest in subjects undergoing cardiovascular monitoring. Current research efforts are focused on the development of systems enabling clinical applications. The current focus on developing and deploying wearable systems targeting specific clinical applications has the potential of leading to clinical adoption within the next five to ten years.
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Affiliation(s)
- Paolo Bonato
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, Boston, MA 02114, USA.
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