A remote patient monitoring system for congestive heart failure.

Abstract

Congestive heart failure (CHF) is a leading cause of death in the United States affecting approximately 670,000 individuals. Due to the prevalence of CHF related issues, it is prudent to seek out methodologies that would facilitate the prevention, monitoring, and treatment of heart disease on a daily basis. This paper describes WANDA (Weight and Activity with Blood Pressure Monitoring System); a study that leverages sensor technologies and wireless communications to monitor the health related measurements of patients with CHF. The WANDA system is a three-tier architecture consisting of sensors, web servers, and back-end databases. The system was developed in conjunction with the UCLA School of Nursing and the UCLA Wireless Health Institute to enable early detection of key clinical symptoms indicative of CHF-related decompensation. This study shows that CHF patients monitored by WANDA are less likely to have readings fall outside a healthy range. In addition, WANDA provides a useful feedback system for regulating readings of CHF patients.

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ORIGINAL PAPER
A Remote Patient Monitoring System for Congestive
Heart Failure
Myung-kyung Suh & Chien-An Chen & Jonathan Woodbridge & Michael Kai Tu &
Jung In Kim & Ani Nahapetian & Lorraine S. Evangelista & Majid Sarrafzadeh
Received: 17 January 2011 /Accepted: 3 May 2011
# Springer Science+Business Media, LLC 2011
Abstract Congestive heart failure (CHF) is a leading cause
of death in the United States affecting approximately
670,000 individuals. Due to the prevalence of CHF related
issues, it is prudent to seek out methodologies that would
facilitate the prevention, monitoring, and treatment of heart
disease on a daily basis. This paper describes WANDA
(Weight and Activity with Blood Pressure Monitoring
System); a study that leverages sensor technologies and
wireless communications to monitor the health related
measurements of patients with CHF. The WANDA system
is a three-tier architecture consisting of sensors, web
servers, and back-end databases. The system was developed
in conjunction with the UCLA School of Nursing and the
UCLA Wireless Health Institute to enable early detection of
key clinical symptoms indicative of CHF-related decom-
pensation. This study shows that CHF patients monitored
by WANDA are less likely to have readings fall outside a
healthy range. In addition, WANDA provides a useful
feedback system for regulating readings of CHF patients.
Keywords Health monitoring.Telemedicine.Wireless
health.Congestive heart failure patients monitoring.Real-
time feedback.Data integrity.Database backup
Introduction
Congestive Heart Failure (CHF, [1]) occurs when the heart
is unable to adequately supply enough blood for a healthy
physiological state. CHF typically occurs when cardiac
M.-k. Suh (*):J. Woodbridge:A. Nahapetian:M. Sarrafzadeh
Computer Science Department, University of California,
Los Angeles,
Los Angeles, CA, USA
e-mail: dmksuh@cs.ucla.edu
J. Woodbridge
e-mail: jwoodbri@cs.ucla.edu
A. Nahapetian
e-mail: ani@cs.ucla.edu
M. Sarrafzadeh
e-mail: majid@cs.ucla.edu
A. Nahapetian:M. Sarrafzadeh
Wireless Health Institute, University of California, Los Angeles,
Los Angeles, CA, USA
C.-A. Chen
Electrical Engineering Department, University of California,
Los Angeles,
Los Angeles, CA, USA
e-mail: chienanc@ee.ucla.edu
M. K. Tu
Biomedical Engineering IDP, University of California,
Los Angeles,
Los Angeles, CA, USA
e-mail: emtu@ucla.edu
L. S. Evangelista
School of Nursing, University of California, Los Angeles,
Los Angeles, CA, USA
e-mail: levangel@ucla.edu
J. I. Kim
Department of Biostatistics, University of North Carolina,
Chapel Hill, NC, USA
e-mail: jikim@email.unc.edu
J Med Syst
DOI 10.1007/s10916-011-9733-y

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tissue becomes ischemic from coronary vessel blockage.
Ischemia reduces the mechanical functionality of the heart
and disrupts normal electrophysiological processes.
Recentstatistical literatureissuedbythe Center for Disease
Control and Prevention [2] indicates that approximately
670,000 individuals are diagnosed with CHF every year. In
2006, it was reported that CHF was the cause of 282,754
deaths. CHF is the leading cause of death in the United
States; greater than the deaths caused by cancer or strokes.
CHF also has a significant fiscal impact. The CDC
reports that CHF costs Americans 29 billion dollars per
year in medical expenses. Bundkirchen [3] reports that the
average hospital visit in Europe due to CHF costs 10,000
Euros. In addition, 24% of patients must be readmitted to
the hospital within 12 weeks of discharge.
Due to the prevalence and economic burden of CHF, it’s
necessary to seek out methodologies that would facilitate
the prevention, monitoring, and treatment of heart disease.
Experts and researchers in cardiac medicine suggest
monitoring and tracking patients’ symptoms on an everyday
basis in order to prevent emergencies. However, patients
often lack the motivation to exercise and/or monitor their
own health related measurements. Hence, a remote health
monitoring system with medical oversight should serve
useful for observing patients with CHF. In addition, remote
health monitoring systems are extremely cost effective due
to the availability of inexpensive monitoring devices and
infrastructure.
This paper presents WANDA (Weight and Activity with
Blood Pressure Monitoring System [4, 5]); a remote health
monitoring system for patients with CHF. WANDA has
four objectives: 1) Improve a physician’s ability to monitor
daily progress of a patient. 2) Provide a pervasive
monitoring solution that easily integrates into the lifestyles
of patients. 3) Improve a physician’s ability to make
decisions making through automated data analysis of
patient data. 4) Provide a modular and customizable mobile
monitoring platform to meet the specific needs of patients.
WANDA monitors the following four health related
measurements: weight, blood pressure, physical activity,
and the Heart Failure Somatic Awareness Scale (HFSAS).
WANDA flags notable trends in monitored data alerting
physicians of potential health risks. Notable trends are
defined as abnormal changes in measured values and are
displayed in Table 2.
Critical health related measurements for congestive heart
failure
Weight
In a study of 5,881 subjects (3,177 women and 2,704 men)
by Kenchaiah [6], the risk of CHF was increased by 5% for
men and a 7% for women when the BMI (Body Mass
Index) was increased by only 1%. WANDA can monitor
the BMI of patients who are at risk of CHF and aid in
weight management and preventative care. WANDA is not
only useful to physicians, but can function as a tool for
patients to become self-aware of their own weight.
Blood pressure and heart rate
A study by Vasan [7] of 6,859 patients establishes that
increased blood pressure is correlated with an increased risk
of cardiovascular disease. CHF is often caused by systolic
dysfunction where the heart muscle cannot adequately
pump or eject the blood out of the heart, or by a diastolic
dysfunction where the atrium does not fill up. As this
pumping procedure stops, blood may back up in other areas
of the body, producing congestion in the lungs, liver,
gastrointestinal tract, arms, or legs.
Heart rate is an additional factor that predicts the risk for
CHF in an elderly person. Heart rate may help identify
patients at high risk for overt CHF who are candidates for
aggressive blood pressure control [8, 9]. The WANDA
platform can be used for continuous daily monitoring of a
patient’s systolic and diastolic blood pressure and heart rate.
Physical activity
He’s study [10] suggests several risk factors for CHF
including low physical activity, which accounts for 9.2% of
risk. The results of Hambrecht’s work [11] suggests that
long-term aerobic exercise training in patients with CHF
restores function of the skeletal muscle microvasculature of
the lower limb. WANDA monitors calorie expenditure and
metabolic equivalents.
Heart failure somatic awareness scale (HFSAS)
The Heart Failure Somatic Awareness Scale (HFSAS) in
Table 1 is a 12-item Likert-type scale for the purpose of
measuring awareness and perceived severity of CHF specific
signs and symptoms. The 12 items of the HFSAS reflect the
most common signs and symptoms of CHF. A 4-point
Likert-type scale is used to address the degree of these
symptoms and ascertain how much the patient is bothered by
the specific symptom (0: Not at all, 1: A little, 2: A great
deal, 3: Extremely). Scores range from 0 to 36, with higher
score showing higher perceived somatic awareness and
symptom distress [12], The HFSAS is useful in studies
designed to improve symptom recognition and self-
management. Fostering awareness of the early CHF symp-
toms of decompensation averts repeated hospital admission
for symptom management. The HFSAS questions are asked
daily by WANDA’s mobile smartphone application.
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The aforementioned health related measurements can be
monitored through weight scales, blood pressure monitors,
activity monitors, and questionnaires. WANDA allows for
customization for the specific monitoring needs of a
physician. For example, if a physician has recommended
an increase in physical exercise, the WANDA activity
sensing function can be used to help patients maintain
acceptable levels of physical activity.
WANDA
This paper presents the components of WANDA, which
leverage sensor technologies and wireless communications
to monitor the health status of CHF patients. WANDA was
developed in conjunction with the University of California,
Los Angeles Wireless Health Institute (WHI) and School of
Nursing. WANDA is built upon a three-tier architecture.
The first tier is composed of sensors for monitoring
patients’ health related measurements. These readings are
wirelessly transmitted to the second tier. The second tier
consists of web servers that store sensed data and maintain
its integrity. The third tier is a back-end database server that
performs backup and recovery jobs.
This study shows WANDA to be an effective platform
for reducing the number of notable trends in CHF risk
factors. This study has enabled patients to reduce 5.6% of
weight and blood pressure values that are out of the
acceptable range (Table 2). For weight data, the paired t-test
results show that the WANDA study is effective for CHF
patients.
Related works
Chaudhry [13, 14] utilized a telephone-based interactive
voice response system (Pharos Tel-Assurance system
[15]) for CHF patients. This system collected daily
information about symptoms and weight reviewed by the
patients’ clinicians. Patients in this study were required to
make daily calls to the system. During each call, patients
were asked a series of questions about their general health
and CHF symptoms. Responses were entered into the
system using the telephone keypad. Information from the
telemonitoring system was downloaded daily and
reviewed by nurses on every non-holiday weekday. The
study suggests that telemonitoring did not improve patient
outcomes.
Soran’s [16, 17] used an electronic scale and an
individualized symptom response system (the Alere
DayLink monitor [18]) for CHF patients. System com-
ponents were linked via a standard phone line to
recording databases. If criterion values were met for
weight or symptom alerts, the nurses immediately
contacted the patient to check on the status of the patient.
After nurse-patient interactions, the primary physician
was notified by a fax report to adjust medications and
schedule an appointment. Soran’s work showed that
enhanced patient education and follow up was as
successful as a home monitoring device for elderly
patients receiving care from a community-based primary
care practitioner.
Desai’s work [19] attempted to explain the reason why
there was no benefit seen with telemonitoring intervention
in Chaudhry’s study. First, the signals of weight and
symptoms do not provide adequate warnings for CHF.
Results from trials of CHF patients monitoring [20]
suggest that only monitoring weight is inadequate, since
the target dry weight changes on the basis of caloric
intake. Second, the telemonitoring system was underutil-
ized, with only 55% of patients making three calls week
by week. Third, the intervention may not have been
structured for timely and appropriate corrective action.
With regard to timing, the requirement that coordinators
review data may have caused a serious break in patient
care. The team member receiving the data should have
been able to contact the patient directly to discuss a
treatment plan, without having to triangulate the discus-
sion with a physician. Similar to Chaudhry’s work,
Soran’s study also only monitored weight and symptom
responses, and was limited by the need to wait on a
physician’s decision.
ValuesRange
Systolic
Diastolic
Heart rate
Weight
> 90
> 50
< 90 and >40
< +2 (lb./day)
Table 2 Acceptable range of
each measured value
Table 1 WANDA B.’s daily SMS questions
Questionnaire items
I could feel my heart beat faster
I could not breathe when I laid down
I felt pain in my chest
I had an upset stomach
I had a cough
I was tired
I could not catch my breath
My feet were swollen
I woke up at night because I could not breathe
My shoes were tighter than usual
I gained 3 or more pounds in the past week
I could not do my usual daily activities because I was short of breath
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In order to design an effective remote health monitoring
system for CHF, it is important to make an automated real-
time system for checking important values such as weight,
blood pressure, heart rate, daily activity, and symptom
responses. A system must send a reminder to patients to
reduce gaps in the dataset. In addition, the system should be
in real-time to ensure the timely delivery of data to
physicians. These results were used to tailor and develop
the WANDA system, which addresses all of these
requirements.
System architecture
WANDA is built using a three-tier architecture as shown in
Fig. 1. The first tier is a sensor tier that takes patients’
health related measurements and transmits data to the web
server tier. The second tier consists of web servers that
receive data from the first tier and maintains data integrity.
The third tier is a back-end database server that performs
data backup and recovery jobs. Additionally, data in the
third tier is used for data analysis such as linear regression,
missing data imputation, signal search, early adaptive
alarm, and clinical data security projects.
Sensor tier
The first tier is comprised of wireless sensors and mobile
devices. Sensors in this layer monitor patients and transfer
data to web-servers. The first iteration of WANDA is
designed for elderly CHF patients who are not accustomed
to smart phones or computers. Thus, WANDA only uses
devices that look and function as standard weight scales
and blood pressure monitors with a standard phone line
connection. The second version of WANDA uses a
smartphone to collect and transfer data. This mobile version
also allows patients to view their own health data through a
smartphone interface. The second version’s graphical user
interface provides detailed instructions with images to make
the device easy to use for patients.
The first version’s sensor tier uses Bluetooth-based
weight scales, blood pressure monitors, WHI [21] Personal
Activity Monitors (PAMs), cell phones, and an SMS
message server system in order to monitor CHF patients
(Fig. 2). As previously mentioned, patients using this
system are generally unfamiliar with computers or smart-
phones, thus WANDA interfaces with the second tier
through a phone line system in real-time. PAMs (Personal
Activity Monitors) are delivered to the users via mail and
are used to record patient movements. Data collected by the
PAMs are uploaded to the databases every 2 weeks.
The second version of WANDA (Fig. 3) utilizes a
different collection of health monitoring devices from the
first version in order to implement a mobile version of
WANDA. The second version not only has all the functions
of the original system, but also gives developers greater
customizability compared to the first system. In the sensor
tier, we use Bluetooth-based weight scales, blood pressure
monitors, Android-based activity monitors, fall detection
monitors, and symptom questionnaire applications. In terms
of the Bluetooth device-smartphone interface, all of the
devices act as masters that initiate Bluetooth communica-
tion with an Android phone. The Bluetooth protocol has a
range of approximately 10 m and provides secure data
transmissions. The communication between the phone and
the medical server is through Wi-Fi or 3G networks. Data
Fig. 1 WANDA system
architecture
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measured from a sensing device is uploaded to the Android
phone within 5 s. The Android phone transfers data to a
networked server as well as stores data on a local SD card.
Survey system
The survey system unit (NIDA) is used at the beginning of
the WANDA study in order to gather basic user informa-
tion. This system is also used periodically to track the
user’s health status.
NIDA (Fig. 4) is a touch-screen-based survey system
that is operated on desktops, laptops and tablet PCs. NIDA
uses an open XML-based format for questions and results,
and supports text-to-voice functionality. For various users it
provides several language options, such as English and
Spanish. Therefore, depending on users’ preferences, users
can choose a language and choose to communicate by
either text or voice. NIDA stores and retrieves data from the
remote site using a 3G wireless network. If there is no 3G-
network connection, NIDA stores data in a local database
and waits until the device is in a 3G-network area to upload
data to the web database. Since it is computer-based,
questionnaires are more standardized and easily completed,
as McHorney [22] emphasizes and implements. Addition-
ally, since users don’t need to be with interviewers, NIDA
improves efficiency and reduces costs. Using lightweight
tablet PCs, patients are more likely to answer frankly and
freely than in the presence of interviewers.
Weight scale
The Ideal Life system [23] is a part of the first tier of the
first version of WANDA. It includes the Body Manager™
body weight scale and the BP Manager™ blood pressure
monitor device. The Body Manager™ system collects
weight data and sends it to the Ideal Life Pod™. Since
the system supports Bluetooth, the components can
communicate in a range up to 300–400 ft.
The mobile version of WANDA uses a Tanita BC-
590BT body composition scale, which measures body
weight, body fat, body water, bone mass, muscle mass,
metabolic age, and visceral rating. With the additional body
data provided by the scale, health providers may be able to
make an even more thorough analysis of patients’ symp-
toms. For example, since one of the most effective means
of monitoring HF patients is monitoring one’s fluid status,
the weight scale features that relate to measuring the fluids
in the body may help doctors diagnose patients more
precisely.
Blood pressure monitor
The Ideal Life [23] BP Manager™ blood pressure monitor
device measures diastolic blood pressure, systolic blood
pressure and heart rate in the first version of WANDA. The
BP Manager™ system collects blood pressure and heart
rate data and sends it to the Ideal Life Pod™ via a
Bluetooth connection.
The blood pressure monitor used in the mobile version
is a UA-767PBT Bluetooth blood pressure monitor from
AND [24]. This blood pressure monitors measures
systolic and diastolic blood pressure, mean-arterial-
pressure, and heart rate values. This version of blood
pressure monitor does not natively support Bluetooth
connection to the smartphone. In order to solve this lack
of compatibility, we connected the blood pressure monitor
with a RN-270M Bluetooth adapter from Roving Net-
works via a 3.5 mm DB9 cable [25] (Fig. 5). A UA-767PC
Fig. 2 Devices used in WANDA
Fig. 3 Devices used in Mobile
WANDA
J Med Syst