
 healthcare technology using wireless sensors has reached a high level of maturity and reliability and hence these devices are now being deployed in homes / nursing homes for use in managing people 's health . to take full advantage of the penetration of these pervasive systems in people 's well - being and reap their full benefits ,
a necessary condition for acceptance is the awareness of benefits to the user population in using the system .
since young adults are well acquainted with modern sensor devices , they willingly accept the introduction of new technologies in their care process .
in contrast , among the elderly , who are the main beneficiary population of these monitoring devices , there is still reluctance on their part to use them .
even though an increasing number of the elderly are aware of the advantages of a pervasive health monitoring system , they rarely understand how it works . with the increase in alzheimer 's disease ( ad ) among the elderly population , there is a crucial need for technological support in their care process .
since there is no cure yet to reverse the cognitive decline among these individuals , technology could contribute to safely perform their normal living activities .
unfortunately , people affected by ad have difficulties in understanding their health conditions , and the use of a device or systems that could help in their day - to - day activities . some of them have a different perception of objects and are prone to forget using them or be adamant in not using them . in our initial study
we found that even the simplest interactive devices such as wristband buttons or call buttons to alert a caregiver in an emergency situation are unlikely to be used by them . despite the technological maturity of healthcare devices and networking ,
little effort has been done to assess their usability and acceptability before deployments in homes and nursing homes .
health monitoring platforms developed so far have mainly focused on the functionalities using specific sets of sensors , vendor specific software , and protocols , for which usability issues have not been sufficiently addressed .
we addressed this gap by undertaking this exploratory study on how to increase the usability and acceptability of our wearable monitoring system to a small group of elderly affected by ad . in the study , we used the wireless accelerometer and electroencephalograph ( eeg ) logger integrated in our minimally invasive monitoring sensor ( mims ) system , with the aim of detecting possible falls and their preconditions .
however , the living environment should include a network infrastructure with wired alert systems to connect to central nurse care stations and/or wireless networks to hand - held devices carried by the nurses .
we defined ad hoc usability and acceptability parameters and evaluated them during a month long field test with long - term nursing home residents .
the results gave us some important insights , leading to ergonomics and aesthetics modifications to our system that significantly improved its usability and acceptance .
a number of systems engaged in health monitoring are surveyed here to compare our approach to those of others .
though every system studied here has been in deployment for a long period of time , it was disappointing to observe that none of them reported about user 's acceptability of the system .
survey of enabling technologies for wireless body area networks   discussed the network characteristics , such as the type of wireless connection ( bluetooth , ultrawideband , zigbee ) and path loss of the signal sent by body sensors according to their placement on the body and to the radio frequency used . performance evaluation and
a wearable monitoring system called satire   collects the motion and location information of a subject .
satire requires sensors inserted in the garment worn by the user without the need of user 's interaction .
the sensors collect and store data locally . periodically , the data is uploaded to a base station for further analysis and archive .
the paper presents the design which includes a layered architecture ( for both the base station and the sensors ) . real - world testing and adaptability study of this system are not known .
the mithril livenet system   is another distributed mobile system for real - time monitoring and analysis of the health status of an individual .
the mithril architecture offers many features to perform distributed sensing , classification in real - time , and context aware applications .
it makes use of a pda which should be worn by the patient at all times : body worn sensors send data through a network infrastructure for exchange of information and a machine learning infrastructure is used for classification of gathered data .
finally , the experience gained by the authors in developing fall monitoring systems presented in [ 5 , 6 ] definitely proved that a usability study is important to provide the required metrics to evaluate the performance of a health monitoring system in real - world applications , especially with the elderly population .
the equipment we used for the usability study was based on the mims system described in .
we developed mims with the aim of providing a flexible and scalable platform for building a comprehensive and customizable health monitoring system , which guarantees interoperability among different sensor systems .
mims can be easily integrated with any wireless communication system already in place and with any existing networked alert system .  
it consists of a wireless sensor node ( based , in our case , on the shimmer 2r platform ) able to sense human movements using an embedded accelerometer .
the microcontroller ( msp430 family ) can perform on - chip analysis and communicate with a base station using a bluetooth module or ieee 802.15.4 radio , as shown in figure 2 .
being battery powered , small , and lightweight , the device can be conveniently worn near the waist .
the device runs a simple yet very reliable algorithm for fall detection described in . in a nutshell , every time the acceleration reaches a given threshold , samples belonging to a fixed time window around the event are sent to the base station , which in turn analyzes the pattern of accelerations and decides whether the event was due to an activity of daily living ( i.e. , a false alarm ) or to a real fall . in the case of a real fall ,
system 2 consists of a wireless electrophysiology sensor ( based , in our case , on the enobio platform ) which is able to capture the brain activity of a person in real time .
four digital electrodes are attached to the enobio communication module and placed in the enobio headband .
data from such electrodes / channels are wirelessly transferred to a base station using the ieee 802.15.4 low power radio standard .
two wired ear clip electrodes ( potential ground and potential ground feedback ) act as references for sensed signals .
enobio ( see figure 3 ) is worn like a hat and can record not only brain activity but also heart activity through an electrocardiogram ( ecg ) and eye movements through an electrooculogram ( eog ) .
the enobio software is a java application that allows ( i ) wireless communication between the enobio and pc ; ( ii ) data recording ; ( iii ) data display ; ( iv ) forwarding of data to other clients .
data is coded as simple ascii file of tab delimited columns and can also be exported to the very common scientific format edf ( european data format ) .
we used system 2 to analyze eeg potentials during the different stages of sleep , with the aim of studying brain signal patterns preceding a fall .
system 3 is composed of ambient sensors such as pressure pads , which are placed in the care environment to monitor lying on a bed or sitting on a chair , and volumetric motion detectors , which cover an area of 10.7  9.1 meters and are used to detect motion and activities such as entering / leaving a room .
door sensors are placed on the top of doors , windows , and drawers to detect when they are opened or closed ; the toilet mat sensor detects both presence on or near the toilet to monitor bathroom activity and potential safety issues such as falls near to the toilet ; emergency buttons can be placed where accidents are likely to happen ; they are 7.6 centimeters in diameter ; when pressed , they send an alert to the caregiver or to an emergency response service .
the main panel acts as a base station and collects data from sensors exploiting the radio channel and a proprietary protocol ( general electric ) ; the base station has battery backup and is equipped by a gsm transceiver and an interface to the landline .
system 4 is a camera - based monitoring system using the internet to continuously stream the video recording human activity ( visual motion detection ) over a selective region and over a specified observation period ( e.g. , at nighttime ) .
two types of cameras have been used : a fixed wireless camera ( adcv510 ) and a pan / tilt camera ( adc - v610pt ) .
they both have the live resolution options 640  480 , 320  240 , and 176  144 , whereas the recording resolution options are 640  480 and 320  240 ; the recording compression is based on mpeg-4 .
the video motion detection can be configured with three different windows having adjustable sensitivity and thresholds .
the streaming of video to the internet relies on a wireless wi - fi router and standard encryption ( wep , wpa , or wpa2 ) ; cameras can also be connected using a standard ethernet connection .
they are designed to work with the alarm.com hosted video service which provides a surveillance solution .
high - quality live and recorded videos are available to customers through web browsers or via mobile apps .
users can set and recall  preset  views or manually pan and tilt the camera remotely . in the case of resource constraints for sensing , processing , storing , and communicating , some computational operations are delegated to the virtual hub , which is a base station running on a smart phone environment .
the virtual hub receives data from the subsystems and is connected to the local healthcare information system through a friendly graphical user interface .
system 1 and system 2 are examples of active monitoring sensor system ( amss ) .
as they are based on wearable devices , they offer advantages in terms of continuous monitoring , cost , and efficiency .
system 3 and system 4 , instead , were not considered in this study as they are environmental systems , whose major concerns are intrusion and privacy rather than usability . according to the human engineering principles
, the design of a system must follow the users ' needs , fear , mental models , self - learning ability , social behavior , lifestyle , and fashion tastes .
in fact , an accurate knowledge of end users can be achieved only by observing them closely . in the case of monitoring people with ad / dementia living in a home or a nursing home , providing suitable care to them
some of their regular daily activities are walking in a corridor , watching television , and , with the help of caregivers , having breakfast , lunch , dinner , and medication ; some subjects have a small nap in the afternoon .
they are prone to disorientation and wandering at any time of the day or night , and statistics show that they are more prone to falls compared to general elderly population . to compensate psychomotor deficiencies ,
variant medical equipment is used such as canes , crutches , and wheelchairs . however , not all the subjects are able to understand ( or remember ) that they need to use them during their walking activity to prevent fall . in this context , we define usability as the level at which a device can assist a user without interfering with his / her normal activities of daily living
. acceptability is defined as the constraints which guide the designer to realize factors that satisfy one 's need and therefore people 's willingness to use .
the following are the evaluation criteria we developed to measure usability and acceptability : willingness to use ( wtu),easiness to learn ( etl),time to accept ( tta),willingness to keep ( wtk),number of errors ( noe ) due to incorrect interactions , level of satisfaction ( los),interference with activities of daily living ( iwa ) .
willingness to use ( wtu ) , easiness to learn ( etl ) , time to accept ( tta ) , willingness to keep ( wtk ) , number of errors ( noe ) due to incorrect interactions , level of satisfaction ( los ) , interference with activities of daily living ( iwa ) . 

results of a nielsen 's research   have shown that a usability study can be suitably performed with up to 5 subjects , because the behavior of users does not change significantly as their number increases .
this matches the obvious fact that performing small tests does not require huge investments for devices , and it makes the test feasible when , as in our case , it is done on a very critical population such as the elderly affected by ad . of course
, this does not hold for statistical studies , but here we are interested in only qualitative results , as the goal is to gain insights for improving the design of wearable devices based on feedback received by users to increase the usability and adaptability .
based on these observations , we tried to get the maximum benefit - cost ratio by delivering the usability and acceptability test to four subjects affected by ad with advanced age .
all of them were at staggering stages of dementia progression and associated abnormal behaviors , thus limiting the usability study .
in particular , ad subjects were at levels 5/6 of reisberg stage and they resulted below a score of 12 out of 30 ( severe cognitive impairment ) of the mmse ( folstein test ) .
it should be mentioned here that , for 24  7 monitoring of ad individuals , a number of trials had to be conducted before a full data collection is accomplished , with the result that some of these tests could not be completed in consecutive days .
some contributing factors to the difficulty in monitoring were age , disease , and associated behavior .

 table 2 summarizes the results of the study using systems 1 and 2 of the mims platform .
experiences and reactions of the subjects in adapting to the wearable devices and to the monitoring sessions are reported in terms of the usability and acceptability criteria described above , together with observed reactions from the subjects . in the overall , the study showed that with a few modifications to the way devices are placed , colored , or integrated with clothing , and after some convincing story about the importance of wearing the devices , ad individuals eventually wore and benefited from the monitoring technologies . since the shimmer sensor has to be placed on the waist , system 1 achieved higher usability and acceptance than system 2 . from the study , we found that integrating the sensor with clothing , so that it could be considered as an everyday accessory , made it better accepted . in doing so , the device must be prevented from choking the individual , and the difference in dress code between women and men must be considered . since the device is sensitive to movements , careful wearing practices
must be observed while placing / removing the device , and touching , meddling , or breaking the device should be prevented during specific activities such as lying on a bed ( during the afternoon nap ) or sitting on a chair .
therefore , we adopted the following two solutions.the device was integrated onto a belt buckle ( see figure 4(a ) ) .
a leather style gave the buckle a retro aesthetic that made it suitable for both men and women.the device was attached to a velcro stripe belt .
two small stripes were crossed to hold the device firm and properly placed on the waist ( figure 4(b ) ) . for women ,
a leather style gave the buckle a retro aesthetic that made it suitable for both men and women .
two small stripes were crossed to hold the device firm and properly placed on the waist ( figure 4(b ) ) . for women ,
a significant effort was necessary to improve the usability of system 2 , as the enobio sensor must be worn like a hat during night sleep .
the main problem arose from the presence of a bulky battery pack and transmitter on the user 's nape , and this initially made it almost impossible to carry out sleep tests . during the study ,
we repeatedly modified the device in order to improve its acceptability ( measured by wtu ) and to make it as least intrusive as possible in order to avoid the user feeling embarrassed while wearing it ( measured by wtk ) . to improve the ergonomics of the enobio sensor , we moved the battery / transmitter from the back of head / neck to the top of the head on a belt . for acceptability , we observed that the elderly enjoy wearing caps in the night to keep them warm ; so we worked on the aesthetic side by embedding the sensor in a bonnet style cap with a light texture to prevent sweating ( see figure 5 ) .
however , it happened that some users took the hat off before getting into a deep sleep .
this problem was partially solved by asking them to wear the hat without the sensing device during daytime . in this way ,
they got acquainted with wearing the hat and no longer noticed the sensing device was embedded in the hat during the sleep time .
an important factor to be considered here is the color of the device 's enclosure .
warm colors such as orange red , pink , yellow , brown , and their shades are favorable for identifying objects .
cool colors such as blue , green , purple , and their shades are useful to give an impression of coolness , discretion , and serenity .
the study gave us evidence that when a device comes in one 's favorite colors , it is easier to make it acceptable , as it happened with subject 1 to whom we provided the enobio with a pink cap .
the usability study showed that the design and development of a monitoring device must consider its target users ' preferences before it can be broadly deployed .
nontechnical factors depending on both the users and the environment must be considered for quick adaptability and reap the benefit to improved care .
the wireless sensor devices developed within our fall monitoring project were tested to assess their usability among ad elderly in a long - term care home .
this rare opportunity gave us many insights leading to positive changes in our system in terms of ergonomics and aesthetics , as well as some modifications to our system architecture .
though the sample size was small due to the complexity in conducting the tests and the difficulty to manage ad subjects for test during day and night , we were able to achieve a qualitative usability assessment .
for example , the enobio eeg wearable sensor was formerly tested with healthy subjects informed of the sleep study . even though they reported a slight discomfort , they were always conscious of wearing the hat and often restricted their movements while being in the bed . during the study ,
some of them thought that the hat was to keep them warm . while someone did not move at all in the bed , assuming a supine position for the entire night
their sleep was interrupted by the testing , as the hat had to be put back to the correct position several times .
the study suggests that ergonomic and aesthetic modifications are necessary to improve the level of usability and acceptability , especially in an elderly user population .
analysis of the users ' dress code was fundamental to figure out a comfortable and easily wearable solution .
typically , the elderly are attached to a specific aesthetic dress code , characteristic of their likes / dislikes .
they prefer simple , loose , and comfortable dress and therefore the focus should be on a retro style .
unfortunately , such loose dresses make it difficult to put wearable devices close to the body in order to monitor accurately . at the same time
, care must be taken such that these devices should not cause itching , rashes , or skin diseases if worn too tight . from a manufacturing point of view , the devices worn by a patient must be robust and waterproof to avoid accidental damages ( e.g. , the sensor can fall to a sink full of water , or it can be thrown away or tampered ) . the device should also provide a switch or a special combination of buttons in order to be activated and deactivated by the nurse before placing it . a battery indicator
is another element that would help nurses to identify if the device needs to be charged .
the caregivers interface is fundamental to understand how to assign each sensing node to a person , to check the history and general status . in particular , the sensing devices should periodically send a message to signal that they are working correctly and , in this case , they will also provide an update to a localization system . from the technical point of view
, it was found that the deployment of a monitoring system should consider existing communication network infrastructure and the range of sensors in a pretesting phase .
feedback from such testing would enable modifications to system 's functions in order to improve its performance and adaptability .
for example , in designing the shimmer - based prototype we initially set the sensors to work within a 100-meter range from the base station , without considering that our subjects were used to walk back and forth along the corridors even far from their bedrooms .
after the study , we realized the need of extending the coverage of the sensors for continuous monitoring .
a possible solution would have been to adopt a multihop routing protocol , with each node running a message forwarding program besides the monitoring one .
however , this would have drastically reduced the nodes ' battery lifetime and , in the end , the system 's usability .
we identified the right solution by distinguishing nodes into two types : sensing nodes , worn by the individuals , and forwarding nodes , connected to power outlets at fixed locations in the nursing home .
sensing nodes send data to the base station through the forwarding nodes , by selecting the closest node at one - hop distance .
forwarding nodes run a routing algorithm that guarantees no packet loss , which is a critical requirement because the system can not tolerate undelivered alarms . as final remarks ,
even though a cost analysis is beyond the scope of this paper , we would like to stress on the fact that , as argued by analysts addressing the problem of why technology innovation tends to increase the cost of healthcare rather than making things simpler and cheaper , the best way technology can save costs is if it is used to better organize the healthcare system . in this sense ,
systems like the mims platform offer an automatic and seamless monitoring system , enabling continuous data collection otherwise very difficult or even impossible to obtain .
the bare technological cost of the mims equipment used for our experiments , which glues together known and mature technologies , is in the order of 200  usd and 2,000  usd for systems 1 and 2 , respectively .
however , we must be aware that the market cost of such systems is driven by healthcare stakeholders other than the research laboratories , whose role is only to propose proof - of - concept , innovative healthcare systems . in commercial use ,
the entire set of the ambient monitoring systems shown in figure 1 are being deployed by healthcare companies in homes and nursing homes of some north american provinces , for an approximate cost of 100  usd for a month .
so , when deployed in large numbers , there are considerable savings in healthcare cost with manageable equipment cost .
 healthcare technologies are slowly entering into our daily lives , replacing old devices and techniques with newer intelligent ones . 
 although they are meant to help people , the reaction and willingness to use such new devices by the people can be unexpected , especially among the elderly . 
 we conducted a usability study of a fall monitoring system in a long - term nursing home . 
 the subjects were the elderly with advanced alzheimer 's disease . 
 the study presented here highlights some of the challenges faced in the use of wearable devices and the lessons learned . 
 the results gave us useful insights , leading to ergonomics and aesthetics modifications to our wearable systems that significantly improved their usability and acceptance . 
 new evaluating metrics were designed for the performance evaluation of usability and acceptability . 
1. Introduction
2. Related Work
3. Materials and Methods
4. Results and Discussion
5. Conclusions