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Transcript of Testing of a long-term fall detection system incorporated into a custom vest for the elderly....
Testing of a long-term fall detection system incorporated into a custom vest for the elderly.
1. Department of Electronic and Computer Engineering, University of Limerick, Limerick, Ireland
2. Department of Electronic Engineering, National University of Ireland, Galway, Ireland.
3. NCBES, National University of Ireland, Galway, Ireland.4. University of Pittsburgh, Pittsburgh, U.S.A.
Alan K Bourke1,3 ,Pepijn WJ van de Ven1,
Amy E. Chaya4, Gearóid Ó Laighin2,3, John Nelson1
Falls and the long-lieFalls and the long-lieFalls in the elderly are a major international health concernOne in every three community dwelling elderly experience
at least one fall every year. (Nevitt et al.,1989,JAMA)A serious consequence of a fall is the so-called ‘long-lie’
(Lord et al., 2001) which is defined as remaining on the ground, following a fall, for longer than one hour (Wild et al., 1981,BMJ)Approx 50% of those elderly who lie on the floor for an hour or more
die within 6 months. (Wild et al.,1981,BMJ)The solution to the problem of the long-lie:
Automatic detection of falls followed by transmission of an alert to the emergency services or care-giver
Current Autonomous long-term Fall-detection systems
Previously the end of a fall is characterized by an impact shock and/or the person being in a horizontal orientation
A number of long-term autonomous long-term fall-detection systems currently exist
Doughty et al., 2000 Jnl. of Telemedicine and Telecare(Tunstall group)
Noury et al., 2004, EMBCIncorporated into a vest
Karantonis et al., 2006, IEEE Trans. Info. Technol. Biomed.Worn at the waist Fall sensor by Noury et al.
Fall sensor
Tunstall group fall detector
Karantonis et al. fall and activity monitor
The Fall-sensorA fall-sensor was
developed which consists of:μController Bluetooth moduleTri-axial Accelerometer
(MMA7261)BatteryμSD card
The Vest Developed using feedback from elderly
subjects using questionnaire on donning, wearing the vest for an hour, then doffing the vest
The fall sensor can be located at the CHEST or LEFT UNDER-ARM, attached using Velcro
Zips closed at the front for ease of donning and doffing
100% polyester which is easy to clean, durable and stretchable
Additional elastic incorporated to support the sensor
Features of the Vest The vest is made fully
adjustable at the sides to fit subjects from 2XS to 3XL
Minimum amount of Fabric is located around the shoulders to allow for freedom of movement
Elastic was only present on one location where the sensor was to be located
Fall sensor
ObjectivesObjectives1. Test the light-weight sensor to implement the
fall detection algorithm2. Gain user feedback on the design of the
suitability of the vest to be worn by the elderly3. Evaluate the threshold based algorithm to
automatically distinguish between fall events and ADL.
StudiesStudies Two separate studies were completed:
1. A simulated fall-event and ADL study - used to establish the thresholds that would indicate that a fall had occurred. This was carried out using 10 young healthy subjects performing falls and normal activities
2. A long term Activities of Daily Living (ADL) study - to determine the accuracy of the algorithm in a long term trial. This was carried out using 10 elderly (>65 years) volunteers in a nursing home over the course of 4 weeks.
Study 1 - Falls and ADL with Study 1 - Falls and ADL with Young healthy subjectsYoung healthy subjects
This was carried out using 10 young healthy subjects performing falls and normal ADL while wearing the vest and attached fall sensor
A total of 8 different fall types were performed
Falls in all four direction, performed with both legs straight and knee flexion
A total of 5 different ADL were performed which included
sitting, lying, standing and walking activities
Fall Detection Algorithm Study 1 Fall Detection Algorithm Study 1 resultsresultsThe shaded algorithm was tested
against the recorded data
Following this subject posture is continually monitored forfall-alert: Lying for >75% of
10minutesfall-recovery: Lying for < 75% of
10minutes
Sensitivity Specificity Accuracy
Chest 91.3% 99.6% 94.4%
LU arm 97.1% 98.6% 97.7%
Study 2 - Long-term ADL trial with Elderly Study 2 - Long-term ADL trial with Elderly subjectssubjects
A total of 10 elderly subjects wearing the vest and fall-sensor over the course of 4 weeks.
The 10 elderly were divided into 2 teams Each team wearing the system for 2 week each for 8 hours a day from
Monday to Sunday. The trials took place in the nursing home “Benincasa” in the city of
Ancona, Italy and were coordinated by COOSS Marche Onlus
Team 1 Team 2
Week 1 CAALYX Fall system (Chest) rest
Week 2 rest CAALYX Fall system (Chest)
Week 3 CAALYX Fall sensor (Left under-arm) rest
Week 4 rest CAALYX Fall system (Left under-arm)
MethodMethodSubjects donned the system in the morning and then
proceeded to carry out their normal daily routine which included:Sitting transitionsLying transitionsWalkingTravelling by bus and carDiningTaking the stairsUsing the elevator
MethodMethodMessages from the fall-sensor
were relayed to the care-centre using Bluetooth to the Nokia N95 (which was attached to the subject in a pocket on the vest)
Messages were relayed further via the 3G network and the internet.
Messages includedFall-eventFall-alertFall-recovery
Fall-message transmission algorithmFall-message transmission algorithmFall-messages associated with falls are sent by the fall-sensor to the
mobile-phone and further propagated to the care-centreAcknowledgement of receipt of the fall-messages are sent from the
mobile phone to the fall-sensor and from the care-centre to the mobile-phone.
An acknowledgement of receipt of the fall-message from the mobile-phone to the care-centre is also sent back to the fall-sensor
No indication that this procedure is in progress is relayed to the elderly subject thus achieving automatic independent fall detection.
MethodMethodThe following messages thus appeared at the care-taker
terminal:Fall-eventFall-alertFall-recovery
The relevant steps were then taken by the care-staff to ensure the elderly subjects safety.
These messages were also logged by the fall-sensor along with the raw accelerometer data to the μSD card
Care-taker site
Results – Fall AlgorithmResults – Fall Algorithm In total 833 hours of monitoring was recorded over the course of 4
weeks onto the SD cardsFall-events
115 true fall-events were recorded and transmitted by the fall-sensor 144 true fall-events were registered at the care-taker site
Fall-alerts 42 fall-alerts were recorded and transmitted by the fall-sensor 9 fall-alerts were registered at the care taker site
Fall-recoveries 73 fall-recoveries were recorded and transmitted by the fall-sensor 52 fall-recoveries were registered at the care taker site
The discrepancy between the fall-messages received and those registered is due Bluetooth transmission errors with the short battery life of the N95 when
Bluetooth is activated on the phone The higher number of fall-events is due to the resending of these when
no acknowledgements were received.
Results – Fall AlgorithmResults – Fall AlgorithmDuring the trials a number of falls did occur and were
recorded onto the SD cards.Here is one of those falls
Results – Fall AlgorithmResults – Fall Algorithm
Results – The vestResults – The vestThe vests were worn for the full length of
the trial by all 10 elderly subjectsHowever feedback from the elderly subject
and the nursing staff indicated that the vests were not appreciated.
The elderly subjects felt the vest was uncomfortable and they disliked wearing it for eight hours each day.
The nursing staff felt that they too bulky and too intrusive if to be worn under clothes, along with the fall-sensor.
Results – The vestResults – The vestA number of improvements were
suggested:The vest should be made larger but
shorter so that the subjects have no difficulty in wearing and move about especially when using the toilet.
During the summer vest would not be appropriate for the high temperatures.
The vest should be made from more elastic material
Discussion\ConclusionDiscussion\ConclusionThrough incorporating the fall sensor into a vest that can
be worn by the elderly, it is considered that greater compliance with wearing and using a fall detection system can be achieved.
During the long term trials, 42 fall-alerts were recorded by the fall-sensor however only 9 were received at the care taker siteThus indicating that further development of the fall-
detection algorithm and the transmission protocol and method is required.
Discussion\ConclusionDiscussion\Conclusion
Also following feedback from the elderly subject’s it is clear that the vest were sufficient for a short term clinical trial.
However further development of the vest is required to make it more comfortable, breathable and easier to don and doff.
Further development of the system will include:more accurate fall-detection and fall-message transmission
algorithm,more comfortable method of attachment, lighter and smaller
sensor as well as, mobility monitoring and energy expenditure
measurement.