Embedded Wearable Sensors Ecg

Clothing Embedded Wearable Devices for ECG

Monitoring: A Review

Magalhães, Joana

Msc in Medical Informatics

Faculty of Medicine, University of Porto

Porto, Portugal

[email protected]

Oliveira, Ana

Msc in Medical Informatics

Faculty of Medicine, University of Porto

Porto, Portugal

[email protected]

Abstract— Ageing of the world’s population have led to an

increasing need for chronic and geriatric care at home. Long

term continuous monitoring of electrocardiogram (ECG)

provides valuable information for prevention on the heart

attack and other high risk cardiovascular diseases. The

emergence of wireless technologies and advancements in

on-body sensor design can enable change in the

conventional health-care system, replacing it with wearable

health-care systems, centered on the individual. Wearable

monitoring systems can provide continuous physiological

data, as well as better information regarding the general health of individuals. Consequently, vital-sign monitoring

systems will reduce health-care costs by disease prevention

and enhance the quality of life of patients.

Keywords—vital signs; ECG; wearable sensors; telemedicine;

telemonitoring

I. INTRODUCTION

With the increasing of life expectancy and decreasing

fertility, ageing of population is now a profound and

pervasive concern [1], as well as the emergence of chronic

diseases because of the changes in lifestyle [2].

Since prevalence of chronic conditions among the elderly

is higher than in the younger population [1], there is an urgent need to monitor the health-status of individuals in

their daily routine to prevent fatal disorders [2]. Continuous

monitoring of vital signs such as heart rate, blood pressure,

cardiac activity and blood oxygenation is necessary in

determining the overall health of a patient and can help

identify a patient’s risk for stroke, heart attack, heart failure,

arterial aneurysm and renal failure [3].

Chronic diseases are becoming the world’s leading

causes of death, and this situation is inducing social

problems and escalating healthcare costs [1]. Each year,

number of deaths caused by cardiovascular diseases and

hypertension is estimated to be 16,7 million and 7,1 million, respectively [4].

Cardiovascular diseases (CVDs) have become one of the

leading underlying causes of death in both developing and

developed countries. Therefore, efficient long term

monitoring systems are motivated for personal in-home

healthcare [5].

Driven by these factors, the healthcare system is

undergoing a fundamental transformation, from the

conventional hospital-centered system to an individual-

centered system [6], which means that patients can receive

services such as prevention, diagnosis, therapy and

prognosis management at any time and in any place with the

help of advanced information and communication

technology [7].

Up to date, a number of studies funded and published by diverse organizations and governments indicate that

healthcare expenses are expected to rise considerably, as per

the rising population of elderly people. Consequently, it

becomes of paramount importance to research Wireless

Body Area Sensor Network (WBASN) technologies that

may help to keep patients in relatively good/stable condition

at home, which incurs a much lower cost to the healthcare

provider, contrary to building more hospitals [8].

One major benefit introduced by WBASNs is that the

lack of wires enables people to move freely in their

residence while they recover, which is otherwise cumbersome to achieve with existing health monitoring

technology [8].

The emerging developments and design of wearable

physiological measurement systems has been a growing

research interest in the last decade, due to the potential

applications in medicine [2].

Advances in wearable medical systems will enable the

accessibility and affordability of healthcare, so that

physiological conditions can be monitored not only at

sporadic snapshots but also continuously for extended

periods of time, making early disease detection and timely

response to health threats possible [6]. Wearable telemedicine, which can provide noninvasive

and continuous monitoring of multiple physiological

parameters, is expected to be the most important and

feasible method under the new generation medical care

system [9]. Intelligent wearable electronics and telemedicine

are very promising development areas, which will, not only

extend monitoring, increase patient’s comfort, and improve

the living standard of patients [9], but also provide more

realistic indication of the patient’s health status, and

information that is otherwise inaccessible in clinical settings

[4]. Wearable physiology sensing devices include those that

monitor heart rate, body temperature, respiration, blood

pressure, motion/acceleration, and blood glucose [10].

New emerging concepts as “wireless hospital”, “mobile healthcare” or “wearable telemonitoring” require the

development of bio-signal acquisition devices to be easily

integrated into the clinical routine [11].

This paper aims to review recent publications focused on

wearable solutions to measure ECG signals that can

improve patients’ life quality by continuous monitoring,

preventing fatal complications. Once, developments in

wearable sensor systems have led to a number of exciting

applications we chose to focus on these wearable

technologies that can be implemented into clothing.

II. METHODS

A. Data source and search

Data source included the bibliographic databases Pubmed

and Google Scholar. The following mesh terms and

keywords were used: telemonitoring, telemedicine, vital

signs, vital parameters, electrocardiogram, biomedical

clothing, wearable sensors and wearable ECG monitoring. This search resulted in 156 articles, followed by

examination of references lists on selected papers, for

additional relevant studies not identified through the

preliminary search, 11 more reports were added through this

method.

B. Study inclusion and exclusion criteria

All studies that assemble the following inclusion criteria

were incorporated in the review: human studies; original

reports that developed a wearable health care system.

Studies were excluded if they focused on devices

technological details for creating new wearable devices, not

relevant for this review and if they report a wearable health

care system not embedded in clothing.

C. Study selection

Titles and abstracts were screened by relevance by two

reviewers until February 4, 2013 and, for the 77 studies

meeting the eligibility criteria full-text articles were

obtained, which led to 42 papers. Data were extracted until

February 10, 2013 for those studies that meet the inclusion

criteria.

D. Data extraction

All the eligible studies were critically appraised. For each

study, the reviewers extracted study characteristics, such as

the name of garments, the measurement parameters, sensors

type, advantages or disadvantages, connection method,

references, etc.

III. BACKGROUND

From the WHO’s statistics it has been well known that

cardiovascular diseases is the leading cause of death

worldwide [12]. An important aspect of the disease is that

the sooner it is detected, the better quality of life the patient

will have [13].

Nevertheless, under the existing medical care system,

cardiovascular diseases are diagnosed by visiting a doctor

when a subject feels any clear symptoms (e.g., heart palpitations, shortness of breath, and chest pain, etc.) or

having a periodic medical checkup [12]. Almost half of all

sudden cardiac deaths occur outside of the hospital, which

suggests that many people may not be familiar with early

warning signs [14].

Ambulatory electrocardiogram (ECG) monitoring is a

good candidate for the detection of heart diseases; however,

the difficulty comes from asymptomatic or intermittent

properties of many chronic heart problems. Therefore, long-

term monitoring is essential in detecting and treating the

disease [13].

Historically, long-term ECG monitoring has been a cumbersome task as the patient must wear electrodes and

carry recording apparatus for several days. This has resulted

in the development of systems such as the Holter monitor,

where just a handful of recording sites (typically in the

region of three to five) are used. Although widely utilized,

such systems can only practically facilitate the recording of

just a few channels of ECG information making anything

beyond arrhythmia detection difficult [15].

The first approach in detecting heart disease was the

clinical ECG monitoring system, but this system is not

appropriate for ambulatory monitoring because of the large size of the machine [13] . Therefore, several studies

attempted to continuously provide an ECG monitoring in

everyday life. A good example of this is the Holter monitor

system. The subject wears and records ECG data on 24-h

basis [13].

By moving routine monitoring out of the clinical setting

and into the patient’s home, health care expenditures on

hospital care and clinical services can be significantly

reduced. To gain patient acceptance at home, vital signs

monitors must be wearable [3].

A. What is an electrocardiogram (ECG)?

The ECG is a measure of the electrical activity of the

heart as projected onto the body’s surface. Variations in

frequency and morphology of the recorded signals can

provide an indication of the state of the heart. The ECG is

recorded by placing electrodes in contact with the skin and

attaching them to recording hardware capable of storage or real-time display. The greater the number of suitably placed

recording sites, and hence channels of sampled ECG

information, the more holistic is the picture of cardiac

activity [15].

The ECG has been extensively utilized as a non-invasive

tool for diagnosing the condition of the heart on the basis of

its morphology and heart rate [12], that provides a variety of

information on patient’s cardiac conditions, such as

arrhythmias and heart blocks. In general, even in the

patients with cardiovascular diseases, most of arrhythmias

are very difficult to be identified from a short-term

recording of the ECG during a routinely performed

examination in hospitals [16].

B. Monitoring Cardiac Activity using electrocardiogram

(ECG)

Monitoring heart activity using ECG is one of the most

important and commonly used medical investigations [17],

performed by placing at least three electrodes to the skin to

measure the electrical activity of heart [2].

Conventional monitoring of cardiac activity is performed

in a clinical setting in real-time during a visit to the facility,

by recording electrocardiography (ECG) signals [2]. It

usually uses a direct-wired connection between the subject and the instrument; the subject is therefore confined to the

monitoring instrument, and it is usually only used for

collecting data, while the data processing and diagnosis are

done offline [5].

The commonly used ECG monitoring systems capture

signals from body surface using exactly located wet

electrodes on patient’s body, where conductive gels are used

for an improvement of the measurement. Their application

is constraining, time consuming and could cause allergic

reactions [17].

Currently, heart monitoring is usually done by Holter monitors, which continuously measure the

electrocardiogram (ECG) from the chest [3]. A Holter

monitor is a small, battery-operated device that worn with a

patient to record the ECG signal over a 24-hour period,

which provides a variety of information useful for the

frequency analysis of the signal and the identification of

cardiac arrhythmia [12]. Although wearable for the short-

term, Holter monitors use adhesives and wet electrodes, that

cause skin irritations, making them impractical for long-

term wear [3].

Up to now, a Holter monitor or an event recorder has

been broadly utilized for a long-term monitoring of ECG over a 24-hour period during daily activities [16] or for

patients who are having heart problems or discomfort over a

24–48 hours period [14].

To improve the existing Holter monitor use model,

several groups have worked on wearable monitors to

improve patient acceptance. These monitors often adhere

directly to the chest to avoid long wires. However, these

monitors either protrude far from the chest, which can limit

patient acceptance, have bulky base-stations, or do not save

all of the raw data which makes them ineffective for

analyses such as morphological variability. They all rely on transmitting data to a base station, which also limits their

effectiveness when a cell phone or computer is not nearby,

for example, during periods of exercise [14].

For remote monitoring of ECG it is extremely important

to maintain the clinical integrity of the signals. Continuous

monitoring of ECG is widely used in many clinical setting,

including intensive care units (ICUs), post-operative

monitoring, emergency care and in ambulatory settings such

as Holter monitoring [18].

C. Limitations of monitoring systems

Health monitoring already takes place in various

settings: at home for prevention and in hospital for

continuous assessment. It has become a pressing need for

patients, to provide better quality of care, and also for

society, to lead to more effective and lower cost health care

provision. Unfortunately, ambulatory monitoring must

overcome many constraints [19].

The common problem of ECG measurement is the

influence of motion artifacts (caused by breathing, muscle

activity and slow changes of impedance properties caused

by body-sensor coupling) that could be reduced with better electrode fixation or new algorithms for the suppression of

motion artifacts [17].

Conventional clinical healthcare is primarily based on

wired technology. Although signal quality is high, wires

significantly limit the wearer’s mobility [20].

Although Holter devices produce manageable datasets,

they have several shortcomings:

Requires that a device be clipped into a belt or be

worn in a pocket;

The monitor attaches to electrodes on the patient’s

chest via long wires;

These wires can be a significant noise source and can

be inadvertently detached if pulled;

Even though new Holter monitors can take data for

up to 1 week, patients can have arrhythmias that

occur once every ten days to one month that are not

recorded by the Holter;

To capture these occasional episodes, patients can be

fitted with event monitors, which can be worn for a

month or longer. However, event monitors typically

only save ECG data around the irregular cardiac

episode, which limits the degree of analysis that can be performed.

Continuous long-term data allow the clinician to detect

overall heart health trends and possibly see initial markers

before the cardiac irregularity occurs [14].

In the same way, systems with multiple sensors typically

feature many wires between the electrodes and the

monitoring devices. These wires may limit a patient’s

activity and reduce the level of comfort [9].

On the contrary, patch sensors that can adhere to human

skin provides wearers with more freedom of movement, and

hence is a very good candidate platform for long term

healthcare [20]. Therefore, there has been an increasing interest in

healthcare monitoring devices with wearable technology [9].

To enhance mobility and ubiquitousness of these

applications, various parties have developed wearable

sensors and systems that monitor different bio-signals,

aiming at providing easy-to-use and affordwiable solutions

for serving the chronic and elderly populations [1].

D. Limitations of commonly-used electrodes

Commonly-used electrodes for clinical applications are

gel-type Ag/AgCl wet electrodes. Even though these

electrodes have been reliable, compact and low-cost, its

continuous usage of causes skin irritations, since these

electrodes employs conductive adhesives in order to

maintain the resistive electrical contact with the skin. Also

the signal quality decreases significantly the gel dries, due

to the loss of proper contact with the skin [2]. Since Ag/AgCl wet electrodes may irritate skin in long term

monitoring, some proposed sensors use dry fabric electrodes

instead [20].

Dry electrodes are highly desirable for long-term

monitoring applications [21]; however most of them when

placed on skin, they have a higher impedance than gel-type

ones [2].

Unlike the wet electrodes used for clinical monitoring,

dry electrodes avoid the “drying out” phenomenon

associated with the adhesives and gel membranes used with

wet electrodes. Dry electrodes are generally biocompatible

with the skin because they do not use adhesive or gel membranes. Because dry electrodes are well suited for long-

term monitoring, they are used almost exclusively in

electronic–textile-based health monitoring clothing that is

available to date [21].

More flexible dry electrodes have been developed by

using conductive rubber or elastic materials instead of hard

substrates, which uses human sweat to maintain the contact

with the skin, instead of conductive gel. These electrodes

can be integrated into clothing. As well as being flexible,

the conductive rubber is approved for short-term implants;

thus, it is expected to cause the least skin irritations. However, these electrodes still require contact with the skin

and long-term usage of rubber-based dry electrodes still

causes skin irritation [2].

Dry electrodes do, however, suffer from noise

interference because they typically have higher skin-

electrode contact impedances than wet electrodes. Noise, in

this case, is typically generated from motion artifacts and

power line interference [21].

IV. WEARABLE PATIENT-MONITORING SYSTEMS

Since chronic diseases require “long-term, continuous”

healthcare, convenience of usage becomes of primary

interest in realizing a wearable healthcare system [15, 20]. The goal is to continuously monitor a persons’ health during

normal daily life [20]. Long-term heart activity recording in

patient’s home allows to determine and predict the

development of patient’s cardiovascular system health and

to diagnose chronic heart diseases [17].

To cope with the shortcomings inherent in the

conventional devices, the need for a personalized wearable

heart activity monitoring devices has recently increased

owing to the advances in sensor technology, micro-

fabrication, embedded microcontroller, and radio interfaces

on a single ship, as well as in communication technology. These devices can provide with physicians the useful data to

timely detect and efficiently manage the abnormal

conditions of the heart. In result, they can recommend

treatment that would prevent further deterioration and make

confident professional decisions based on objective

information-all in a reasonably short time [12].

In most prototypes of wearable systems,

microelectronics and electrical sensors are integrated in

body-worn devices, e.g., gloves [22], wrist-worn devices

[23], finger rings[24], earlobe devices [25] and patches [26]. An alternative approach is the development of intelligent

biomedical clothing with embedded sensing capability [6].

Body-worn medical systems can typically gather data

from sensors located only in a specific and usually relatively

small body area and cannot fulfill, alone, all the needs for

sensing, actuating, displaying, and interacting with the user.

Intelligent biomedical clothing refers usually to clothes

with sensors that are close to or in contact with the skin. The

sensors are either embedded in the fabric of the garment, or

it is the fabric itself that is used as a sensor or a sensor suite

[6].

Developments in “smart textiles” have supported the acquisition of the ECG through fabric-based electrodes.

Such fabric-based systems have been established through

the use of metal-based conductive threads that can be

knitted into the garment to be worn by the user. With this

technology, it is possible to acquire the ECG using a

specially developed garment (usually in the form of a shirt

or vest). This offers a number of advantages: Primarily, the

number of recording sites can be increased, to a number

comparable to that used in resting ECGs. This allows much

more information to be acquired. In addition, given that the

electrodes are already placed in the correct location in the garment, the need for clinical personnel to place the

electrodes is avoided [15].

Smart fabrics are conceived as innovative and high

knowledge content garments, integrating sensing, actuation,

electronic, and power functions. Their main goal is to

develop a wearable and washable garment for monitoring

vital signs data; they are usually aimed at cardiac asthma

and sleep apnea patients [2].

Due to their multifunctional interactivity [4], enabled by

wearable devices, e-textiles are considered relevant

promoters of a higher quality of life and progress in

biomedicine, as well as in several health-focused disciplines, such as biomonitoring rehabilitation,

telemedicine, teleassistance, ergonomics and sport medicine

[27].

Intelligent biomedical clothes are based on conductive

and piezoresistive fabric developed to work as textile

sensors, i.e. working as transducers of vital signs to

electrical signals to be sent to a unit of microprocessors

[27].

A. Designing systems for health monitoring

The design of wearable physiological measurement

systems has been a growing research interest in the last

decade, due to the potential applications in medicine [2].

Designing a telemetry system for health monitoring is a

very troublesome task. There are many key issues to be

addressed, including: designing reliable sensors, ensuring

the reliable transmission of vital signs data and providing

privacy and security for individuals. Mobility is both a key

benefit of such systems and a constraint on their design. To

achieve this benefit, wireless physiological sensors must be

small, low-weight, low-power, reliable, secure, with a

conformal design and, of course, wireless [2, 5].

Current sensors technology for vital-sign monitoring is promising to alter the traditional chronic monitoring routine.

However, designing non-invasive body-worn sensors is very

challenging, often requiring a broad understanding of the

nature of the disease and its effect on physiological

parameters. Although there are sensors available off-the-

shelf for cardiac and blood-pressure monitoring, there is still

a need for improvement to achieve continuous and truly

non-invasive monitoring of these parameters [2].

A wireless data communication technology allows data

to be transmitted from the body to a storage device, such as

a cell phone, wristwatch, or remote computer server [10].

Wireless body area sensor networks (WBASNs) have great potential in personal health monitoring, as

demonstrated by Jovanov et al. in usage of intelligent

sensors in heart rate variability studies, ECG monitoring,

and physical rehabilitation. Each of the sensors acquires

signal performs low-level, real-time signal preprocessing,

and wirelessly communicates with the same personal server,

which is in turn connects to a mobile gateway for further

signal processing and storage [4]. To enhance usability,

convenience and comfort for users, sensor configurations in

the form of clothing WBASNs have become one of the most

promising technologies for enabling health monitoring at home, facilitating the collection of vital signs in people with

a health condition [4].

V. WEARABLE ECG MONITORING SYSTEMS

Table I in appendix shows all wearable ECG monitoring

systems here presented. The majority of these systems were

designed for multi-parameters monitoring and not only ECG

monitoring.

A. LifeShirt

LifeShirt (Vivometrics Inc, USA) [28] is an example of

a multi-parameter monitoring system, which includes a

garment, analysis software and a data recorder. Respiration,

ECG, activity and posture are monitored with the

plethysmographic sensors, accelerometer and a single-

channel ECG sensors attached to the garment [2]. Data are

recorded to a small belt-worn personal digital assistant

(PDA) where they are stored or sent to a monitoring center

via cellular network. This is a noninvasive, continuous ambulatory monitoring system that can collect data during a

person’s daily routine. However, it is unsuitable for lengthy

continuous monitoring due to the cumbersome recorder and

peripheral attachment to be carried around. Additional

devices for recording other parameters can also be added

[4].

B. VTAMN

Another example is VTAMN [29], which objective is to

obtain a biocloth, or second skin, both comfortable and

washable. The T-shirt incorporates four smooth, dry ECG

electrodes, a shock/fall sensor, a respiration rate sensor, and

two temperature sensors. The electronic bus is also part of

the textile. The motherboard, the transmission module, and

the power supply are mounted on a belt and connected to the

VTAMN T-shirt through a micro-connector [6].

C. Smart Shirt

The Smart Shirt [30], originally developed and patented

by researchers at Georgia Institute of Technology, collects

analog signals through conductive fiber sensors and

transfers them through a conductive fiber grid knitted in the

T-shirt [4]. Several versions of the wearable motherboard – smart shirt – have been produced, and with each succeeding

version, the garment has been continually enhanced from all

perspectives: functionality, capabilities, comfort, ease of

use, and aesthetics. The developed interconnection

technology has been used to create a flexible and wearable

framework to plug in sensors for monitoring a variety of

vital signs including heart rate, respiration rate, ECG, body

temperature, and pulse oximetry (SpO2). The Smart Shirt

can be used in a variety of applications such as: battlefield,

public safety, health monitoring, sports and fitness, among

others [30].

D. WEALTHY

The WEALTHY [32]

(http://www.smartex.it/index.php/it/ricerche/progetti/progett

i-europei/whealty) is another textile-based garment

developed to monitor ECG, respiration, activity and

temperature measurements. It is made up of a sensorized cotton or lycra shirt that integrates carbon-loaded elastomer

strain sensors and fabric bio-electrodes [9]. ECG monitoring

is performed with knitted yarn-based sensors integrated into

the wearable garment. When the patient is in a resting state,

good quality signals are obtained; however, during physical

activity, the movement of the arm causes significant noise.

Therefore, hydrogel is required to maintain the ohmic

connection with the skin. The system employs piezoresistive

sensors for respiration and activity sensing. The main goal

of textile-based systems was to develop a wearable and

washable garment for monitoring vital signs data [2]; an

“intelligent” system for the alert functions, able to create an “intelligent environment” by delivering the appropriate

information for the target professional is the complementary

function to be implemented. The system is targeting the

monitoring of patients suffering from heart diseases during

and after their rehabilitation [33].

E. MagIC

MagIC (Maglietta Interattiva Computerizzata) [34] is a a

textile based wearable system, designed for unobtrusively

recording cardiorespiratory and motion signals during daily

life and in a clinical environment on patients with different

cardiovascular conditions [35]; it detects ECG and

respiratory activity, and a portable electronic board for

motion detection, signal preprocessing and wireless data

transmission to a remote monitoring station [34]. The

MagIC system has been tested in freely moving subjects at

work, at home, while driving and cycling and in

microgravity condition during a parabolic flight.

Preliminary data derived from recordings performed on

patients in bed and during physical exercise showed 1) good

signal quality over most of the monitoring periods, 2) a correct identification of arrhythmic events, and 3) a correct

estimation of the average beat-by-beat heart rate. These

positive results support further developments of the MagIC

system, aimed at tuning this approach for a routine use in

clinical practice and in daily life [34].

F. Healthwear service

The Healthwear service is based on the Wealthy

prototype system. A new design has been made to increase

comfort in wearing of the system during daily patient

activities. The cloth is connected to a patient portable

electronic unit (PPU) that acquires and elaborates the

signals from the sensors. The PPU transmits the signal to a

central processing site through the use of GPRS wireless

technology. This service is applied to three distinct clinical

contexts: ehabilitation of cardiac patients, following an

acute event; early discharge program in chronic respiration

patients; promotion of physical activity in ambulatory stable cardio-respiratory patients. HealthWear solution is applied

to three distinct clinical contexts, respectively located in

Italy, Greece and Spain: Rehabilitation of cardiac patients,

following an acute event; Early discharge program in

chronic respiration patients; Promotion of physical activity

in ambulatory stable cardio-respiratory patients. HealthWear

facilitates distant monitoring of the health status of

individuals requiring medical care that is, otherwise,

available only in hospitals. This is achieved by wearable

medical sensors, a portable data acquisition and

transmission device connected to the sensors, wireless

telecommunications and monitoring software installed at a central processing site. The technical solution presented in

this paper enables remote health monitoring addressing the

needs different kind of patients. Typical use-cases include

early discharge from hospital of patients with chronic

diseases or after an acute episode, health status monitoring

and prompt response as well as the rehabilitation of

individuals who underwent heart surgery. Use-cases for two

categories of chronic patients has been designed: subjects

with Chronic Obstructive Pulmonary Disease (COPD) and

patients recovering from cardiac ischemic episodes. This

new approach may contribute to the implementation of innovative models for the delivery of care [36].

G. Smart Vest

The Smart Vest consists of a comfortable to wear vest

with sensors integrated for monitoring physiological

parameters, wearable data acquisition and processing

hardware and remote monitoring station. The wearable data acquisition system is designed using microcontroller and

interfaced with wireless communication and global

positioning system (GPS) modules. The physiological

signals monitored are ECG, PPG, body temperature, blood

pressure, galvanic skin response (GSR) and heart rate. The

acquired physiological signals are sampled at 250 samples/s,

digitized at 12-bit resolution and transmitted wireless to a

remote physiological monitoring station along with the geo-

location of the wearer [37].

H. A wearable mobihealth care system supporting real-time diagnosis and alarm

Zheng et al. [9] developed a wearable mobihealth care

system, which provides long-term continuous monitoring of

vital signs for high-risk cardiovascular patients. They used a

portable patient unit (PPU) and a wearable shirt (WS) to

monitor ECG, respiration (acquired with respiratory inductive plethysmography), and activity. Owing to

integrating fabric sensors and electrodes endowed with

electro-physical properties into the WS, long-term

continuous monitoring can be realized without making

patients feel uncomfortable and restricting their mobility.

The PPU analyzes physiological signals in real time and

determines whether the patient is in danger or needs external

help. The PPU will alert the patient and an emergency call

will be automatically established with a medical service

center (MSC) when life-threatening arrhythmias or falls are

detected. The WS mainly woven with cotton and lycra materials is comfortable like a common article of T-shirt.

The position of the electrodes and sensors is fixed and the

elasticity of the WS allows a good fitting to the body. The

WS consists of electrodes, sensors, and a small-size printed

circuit board. With advanced gpsOne technology, the patient

can be located and rescued immediately whether he/she is

in-doors or outdoors in case of emergency. The fabric

sensors and electrodes endowed with electro-physical

properties enable the realization of wearable shirt capable of

continuously recording a full 12-Lead ECG, respiration, and

activity. The physiological signals measured by the WS are

transferred to the PPU via short-range wireless communication. The PPU provides real-time visualization,

memorizing, analysis, diagnosis, and three degrees of alarm.

In case of emergency, an emergency call will be

automatically initiated and an immediate act of rescue will

be taken according to the location information of the patient

acquired through gpsOne. Moreover, the PPU also has three

manually activated buttons for summoning helps. The MSC

is composed of a medical data server (MDS) and many

monitoring terminals (MTs), where the doctors and medical

assistants will provide around-the-clock medical helps. The

physiological data received from the PPU will be processed by specialized software running on the MT and more

detailed diagnosis information would be provided [9].

I. Vital Jacket

Cunha et al. developed the Vital Jacket

(www.vitaljacket.com) that is a wearable vital signs

monitoring system that joins textile with microelectronics. It was designed and developed to be a usable practical

approach for different clinical scenarios, in hospitals, home

or on the move, that need continuous or frequent high

quality vital signs monitoring from its wearer. The first

http://www.vitaljacket.com/

prototypes were focused on the wearable platform on

cardiology and high performance sports, scaling it down

into a simple and comfortable t-shirt. Depending on the

specific needs of the user, the wearable system can be setup

to acquire different vital signs (ECG, temperature,

respiration, movement/fall, posture, oxygen saturation, etc.) and psycho-social variables (panic button, medication

delivery, activity habits, location, etc.) through wearable or

bed-side sensors. Furthermore, this garment is washable,

easy to wear by using disposable electrodes and large

number of these wearable monitors can be connected to its

IT infrastructure. All vital variables are transmitted through

wireless channels, stored and processed to generate alarms,

trends and result charts that are presented to health

professionals or caregivers through web-based IT

infrastructure. Vital Jacket Cardio has 1, 3 or 5 ECG leads

and a 3 axis accelerometer. All this information can be

relayed in real time, not only to a PDA or a PC, but also to a cardiology information system through wireless Local area

network (LAN), General pocket radio service (GPRS) or

Universal Mobile Telecommunications System (UMTS)

[38].

J. My Heart

The MyHeart wearable monitoring system focuses on

integration of unobtrusive sensors into everyday garments

and miniaturized on-body electronic modules for data

processing and storage with dedicated software for data

analysis like ECG preprocessing and motion artifact

detection, computation of heart rate (HR) and heart rate

variability (HRV) [6, 39]. MyHeart (www.hitech-

projects.com/euprojects/myheart/) is a public research

project funded by the European Commission in the 6th

framework programme dealing with the prevention and

early diagnosis of cardiovascular diseases. The project is a

major research initiative by Philips and more than 30 other industrial and academic partners. The idea behind MyHeart

is to apply continuous or periodic monitoring of vital signs,

in order to gain knowledge about a person’s health status.

To achieve this, MyHeart integrates functional clothes with

on-body sensors textile and non-textile and electronics into

intelligent biomedical clothes. These are capable of

acquiring, processing and evaluating physiological data

[27]. Shortly after completion of the EUR 33 millions

project, Philips launched another project entitled HeartCycle

(http://www.heartcycle.eu/)in March 2008 that represents a

further step in the direction of developing wearable systems for clinical applications [6] .

K. Planar-fashionable circuit board-based shirt

Yoo et al. [13] developed a wearable ECG acquisition

system with compact planar-fashionable circuit board-based

shirt, which removes cumbersome wires from conventional

Holter monitor system for convenience. Dry electrodes screen-printed directly on fabric enables long-term

monitoring without skin irritation. The ECG monitoring

shirt exploits a monitoring chip with a group of electrodes

around the body, and both the electrodes and the

interconnection are implemented using P-FCB to enhance

wearability and to lower production cost.

VI. CONCLUSIONS

The world’s ageing population has led to an urgent need

for long-term and patient-centered healthcare solutions.

For people with heart diseases, it is important that the medical disorders can be early detected, to avoid

emergencies that often occur.

Thus, using the telecommunication infrastructure,

signals can be directly delivered to the clinics, where

doctors can remotely analyze real-time physiological status

of the subject, and make correct diagnosis timely.

Advances in wearable health systems, from a smart

textile, signal processing, and wireless communications

perspective, have resulted in the recent deployment of such

systems in real clinical and healthcare settings.

A new concept in healthcare is emerging, aimed at

fulfilling the need to continuously monitor the patient’s vital signs through a ground-breaking woven sensing interface to

be worn without any discomfort for the user. Wearable

wireless sensors for the monitoring of physiological signals

attract more and more attentions. Moreover, conventional

ECG systems do not satisfy the requirements for long term

measurements in home healthcare applications.

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TABLE I. WEARABLE ECG MONITORING SYSTEMS

Name Selected

measurement

parameters

Sensors Advantages/Disadvantages Transmission

method

References

LifeShirt ECG,

Respiration,

Activity,

Posture

Single channel

ECG,

Phethysmographic

sensors,

Accelerometer,

Additional devices for

recording other parameters

can also be added.

Unsuitable for lengthy

continuous monitoring due to

the cumbersome recorder and

peripheral attachment to be

carried around.

Cellular network [28]

Smart Shirt ECG,

Heart rate,

Respiration,

SpO2,

Temperature

Sensors Comfortable, no skin

irritation, lightweight,

breathable, easy to wear and

take off…

Wireless [30]

VTAMN ECG,

Respiration,

Falls,

Temperature

Dry ECG

electrodes,

Respiration rate

sensor,

Shock/fall sensor,

Temperatures

sensors

The mother board, the

transmission module and

power supply are kept on a

belt and connected to the

VTAM T-shirt through a

micro connector.

GSM/GPRS [29]

WEALTHY ECG,

Respiration,

Activity,

Temperature

Fabric bio-

electrodes,

Piezoresis-

tive sensors

An “intelligent” system for

the alert functions, able to

create

an “intelligent environment”

by delivering the appropriate

information for the target

professional is the

complemen-

tary function to be

implemented. The system is

targeting

the monitoring of patients

suffering from heart diseases

during and after their

rehabilitation.

GPRS [32]

MagIC ECG,

Respitation,

Activity

Textile electrodes,

Textile-based

transducer,

Accelerometer

Good signal quality over most

of the monitoring periods.

A correct identification of

arrhythmic events.

A correct estimation of the

average beat-by-beat heart

rate.

Wireless [34]

Healthwear

service

ECG,

Respiration,

Activity,

Temperature

Fabric bio-

electrodes

Increased comfort in wearing

of the system during daily

patient activities.

GPRS wireless [36]

Smart Vest ECG,

PPG,

Body temperature,

Blood pressure,

Galvanic skin

response,

Heart rate

Silicon rubber with

pure silver filling

Red light 630nm

Derived by

analyzing ECG and

PPG waveform

Thermistor

(PT100) resolution

0.39/◦C

Ag–AgCl electrode

Derived from ECG

waveform

Comfortable to wear vest.

The wearable data acquisition

system is designed using

microcontroller and

interfaced with wireless

communication and global

positioning system (GPS)

modules.

Wireless [37]

Wearable

mobihealth

care

ECG,

Respiration,

Activity

Fabric electrodes,

Respiratory

inductive

plethysmography,

Accelerometer

Long-term continuous

monitoring can be realized

without making patients feel

uncomfortable and restricting

their mobility.

Wireless [9]

Vital Jacket ECG,

Temperature,

Respiration,

movement/fall,

posture, oxygen

saturation, etc

Electrodes,

Accelerometer

Is washable, easy to wear by

using disposable electrodes

and large number of these

wearable monitors can be

connected to its IT

infrastructure.

Wireless LAN,

GPRS or UMTS

mobile data

networks

[38]

My Heart ECG,

Heart Rate

Textile electrodes Prevention and early

diagnosis of cardiovascular

diseases.

Bluetooth [39]

A wearable

ECG

acquisition

system with

compact

planar-

fashionable

circuit

board-based

shirt

ECG Dry electrodes Low power comsuption;

Dry electrodes;

Interconnection in the

monitoring shirt at low cost.

Wireless [13]

Documents

Embedded Wearable Sensors Ecg