Non-invasive Optical Blood Pressure Sensing and

International Journal of Engineering Trends and Technology (IJETT) – Volume 46 Number 5 April 2017
Non-invasive Optical Blood Pressure Sensing
and Measurement
Mr. Ketan Karambelkar #1, Ms. Sanika Balkawade #2,Ms. Jagruti Kapgate#3, Mrs. Kirti Adoni#4
#1,2,3
Student, B.E. Electronics & Telecommunication, Savitribai Phule Pune University
#4
Assistant Professor, Department of Electronics and Telecommunication
Progressive Education Society’s Modern College of Engineering, Shivajinagar, Pune-411 005, India.
Abstract: The paper presents design and
development of optical blood pressure sensingkit
based
on
Microcontroller
and
Bluetooth
transmission. Blood pressure is one of the important
vital signs that need to be monitored for personal
healthcare. The aim of this project is to construct an
optical system and to monitor blood pressure
continuously without use of any cuff or supervision.
It is a monitoring system that uses an IR light source
and a luminosity sensor to measure the blood
pressure. The optical pulsatile method of blood
pressure measurement is used to gather pulse data
obtained from various parts of body. Blood pressure
readings are calculated with the help of developed
algorithm and transmitted via Bluetooth module to
the computer. Numerical reading values of systolic
and diastolic blood pressure are recorded and
displayed on the computer.
.
Keywords —Blood pressure, optical, IR, PWTT,
Bluetooth, monitoring system
I.
INTRODUCTION
Blood pressure (BP) is one of the health parameters
that affect us or it can be said that it is a sign of
healthiness of a person. Measurement of blood
pressure is significant for detecting hypertension,
which is strongly related to cerebral strokes and
heart failure. BP if not monitored, may lead to blood
vessel damage, stroke, heart or kidney failure. Also,
a continuous blood pressure monitoring is required
for patients of diabetes and hypertension. Fig.1 gives
a range value of blood pressure, and their
classification.
In India, every government allopathic doctor serves
a population of over 11,000 people i.e. their
percentage is hardly 0.009%, with Bihar and
Maharashtra having the worst ratios.Yet in other
developed countries such as Norway this metric goes
up to 4.16%.This disparity between the number of
people and the available health workers limit the
effectiveness of the healthcare system.
Blood Pressure
Category
Systolic
(mm Hg)
Diastolic
(mm Hg)
Normal
less than 120
less than 80
120-139
80-89
140-159
90-99
Prehypertension
Hypertension
(Stage 1)
Hypertension
(Stage 2)
Hypertensive Crisis
160 or higher
Higher
than 180
100 or
higher
Higher
than 110
Figure 1 Classification of Blood Pressure readings
As the costs of medical treatments and amount of
money spent towards treatment increase, the quality
of treatments also increases, but the number of
people who can afford such healthcare services
decreases.
Most non-invasive BP measuring methods are based
on oscillometric method, which are widely accepted
and used worldwide but they restrict patients‟
mobility. They require uncomfortable cuffs and are
not suitable for home-care and continuous long term
monitoring applications. Continuous monitoring of
BP can be done hassle free by an accurate and
inexpensive device independent of patient's‟
movement and which does not require supervision of
a trained person or any physician.
.
These requirements can be satisfied using a
monitoring system that uses an IR light source and a
sensor to measure the blood pressure. The optical
pulsatile method of blood pressure measurement is
used to gather pulse data obtained from various parts
of body. This data collected can be used to track
one‟s health, prevent illness and can be sent to
doctors
for
analysis
using
an
App.
The main advantage of this system is its portability
and ease of use after learning some basic
instructions. Readings taken by this system are
designed to match readings taken by standard
instruments with some minimal amount of deviation.
By providing this data to both patients and doctors,
we hope to facilitate and augment the throughput of
doctors‟ efforts.
II. LITERATURE REVIEW
A. The report of University of Maryland states that,
health is multi-factorial and complex; influenced
by several things including our age, family
history,
employment
and
living
conditions.Today‟s hectic lifestyle, lack of
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International Journal of Engineering Trends and Technology (IJETT) – Volume 46 Number 5 April 2017
physical activity, obesity, stress, smoking, excess
consumption of salt and alcohol lead to
hypertension. High blood pressure is a silent
killer, because it produces no symptoms until
vital organs like heart, brain and kidneys are
damaged.[1]
B.
There are various methods to measure the
blood pressure. The standard instrument used to
measure
blood
pressure
is
called
a
sphygmomanometer. [2]
C.
The sphygmomanometer is not a seemly
device for household monitoring of the blood
pressure; as it requires someone‟s help to place
the cuff and pump the meter. It may not be
suitable for continuous monitoring as it restricts
patient mobility. Continuous measurement of BP
for home care requires an inexpensive method
that is independent from patient movement and
does not require continuous care by a
practitioner.
[3][3]
D. Abu Zneid, et al [4] designed a system using
Photoelectric Plethysmography (PPG) technique,
a simple non-invasive method to measure relative
changes in pulse blood volume in the tissues. It
uses the reflectance sensor that contained
infrared light source. The light source illuminates
a part of tissue like fingertip, toe, ear lobe and
photo detector receives the returning light. The
waveform obtained from this technique
represents the blood volume pulse which can be
used to measure blood pressure. Two stage
bandpass filters are used to remove DC
components from the signal detected by light
sensor and then amplified. The systolic and
diastolic readings of blood pressure were
displayed on the LCD.
E. Vinee Sinha, et al [5] developed a blood pressure
monitor
using
oscillometric,
impedance
plethysmography (IPG), Photoplethysmographic
(PPG) and Electrocardiographic (ECG) modules,
oscillometric module facilitate spot or periodic
measurement of blood pressure whereas other
modules yield various hemodynamic parameters
to obtain beat to beat pressure. Linear
multivariate equations have been used for this
purpose.
F. Pulse wave transit time [PWTT] parameter was
used to indicate change in blood pressure. PWTT
is measured by continuous monitoring of ECG
and pulse wave. The measurement device for
detecting pulse wave consists of infrared LED for
transmitted light illumination, pin diode as
detector, amplifier and filter. [6]
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III. BLOCK DIAGRAM
The block diagram of the proposed idea is as
shown in figure 2.
A. Microcontroller (ATmega328):
Figure 2. Block Diagram
Arduino Nano is a small, complete, breadboard
friendly board based on ATmega328, a highperformance Atmel 8-bit AVR RISC-based
microcontroller and it has 32KB ISP flash
memory
onboard
with
read-while-write
capabilities. For other storage, it has 1KB
EEPROM and 2KB SRAM.It has 23 GPIO lines,
32
working
registers,
three
flexible
timer/counters with compare modes, internal and
external interrupts, serial programmable USART,
a byte-oriented I2C interface, SPI serial port, 6channel 10-bit A/D converter, programmable
watchdog timer with internal oscillator, and five
software selectable power saving modes. The
board operates between 1.8-5.5 volts.
B. TIL32 (Infrared LED):
TIL32 is a low cost 3mm IR LED package. It
has wavelength of 940 nm. Maximum forward
voltage for TIL32 is 1.6V and maximum forward
current
is
20mA.
.
C. GY2561 (Luminosity Sensor):
The TSL2561 is a light-to-digital converter that
transforms light intensity to a digital signal
output capable of direct I2C interface. It
combines one broadband photodiode (visible plus
infrared) and one infrared-responding photodiode
on a single CMOS integrated circuit capable of
Figure 3. TIL32 IR LED
providing a near-photopic response over an
effective 20-bit dynamic range (16-bit
resolution). Two integrating ADCs convert the
photodiode currents to a digital output that
represents the irradiance measured on each
channel. This digital output can be input to a
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International Journal of Engineering Trends and Technology (IJETT) – Volume 46 Number 5 April 2017
microprocessor where illuminance (ambient light
level) in lux is derived using an empirical
formula to approximate the human eye response.
The TSL2561 device supports a traditional level
style interrupt that remains asserted until the
firmware clears it.
blood pressure.
F. Systolic and Diastolic M.A.P. values are derived
from optical M.A.P. and sent to PC or mobile via
Bluetooth Module.
Figure 4. TSL2561 Board
Figure 6. Relation between M.A.P. and BP readings
V. SOFTWARE SYSTEM DESIGN
Figure 5. TSL2561 Functional Diagram
D. HC-05 (Bluetooth Module):
HC-05 is a Bluetooth SPP (Serial Port Protocol)
module, designed for transparent wireless serial
connection setup. Bluetooth module is fully
qualified Bluetooth V2.0+EDR (Enhanced Data
Rate) 3Mbps Modulation with complete 2.4GHz
radio transceiver and baseband. It uses CSR
Bluecore 04-External single chip Bluetooth
system with CMOS technology and with
AFH(Adaptive Frequency Hopping Feature). It
has the footprint as small as 12.7mmx27mm.
IV. METHODOLOGY
The Arduino Nano excites IR LED for light
emission. The light reflected from blood is
sensed by the GY2561 sensor.
B. 5 consecutive readings taken from sensor are
stored in 5 variables and their mean is calculated.
C. The mean value is divided by some factor to
obtain optical M.A.P. (Mean Arterial Pressure)
value.
D. M.A.P. is defined as the average blood pressure
in a person‟s arteries during one cardiac cycle.
[7]
A.
E. M.A.P. is considered a better indicator of
perfusion to vital organs than systolic
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A. Arduino IDE
The Arduino Integrated Development
Environment (IDE) or Arduino Software
contains a text editor for writing code, a
message area, a text console, a toolbar with
buttons for common functions and a series of
menus. It connects to the Arduino and
Genuino hardware to upload programs and
communicate with them. Programs written
using Arduino software are called „sketches‟.
These sketches are saved with an extension
.ino. This editor allows writing, reviewing,
and compiling the desired code. Once the
code is compiled, it is uploaded to the board
using USB connector. In this project, Arduino
IDE is used extensively. A program that is
used to excite IR LED and get value from
light sensor is written and compiled in
Arduino IDE. The code to read and send data
via Bluetooth is also written in Arduino.
B. Processing IDE:
The Processing IDE or Environment includes
an intuitive text editor, a compiler, and a
display window. It enables the creation of
software within a carefully designed set of
constraints. In Processing, a computer
program is called a sketch. Sketches can draw
two- and three-dimensional graphics.
The purpose of using Processing in this
project is that it will receive the serial data
from the microcontroller via Bluetooth and it
will plot the data graphically on the
computer. In this way, understanding the
output i.e. blood pressure values will be
easier for people with zero technical skills
and it will enhance the usability of this
system.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 46 Number 5 April 2017
START
VI.
RESULTS
7
Initialize the system
Turn ON
IR LED
VII.
Figure 9. Output of Light sensor plotted on serial monitor
Wait for reception
of reflected light
Get the intensity of
light using TSL2561
Convert the optical value into
M.A.P. and then to SBP and DBP
Figure 10 Plot of Mean Arterial Pressure readings taken by
Sphygmomanometer Vs the System
Send the data serially via
Bluetooth to PC or Mobile
Go back
to step
1
80.66
Optical
Reading
4735
Optical
MAP
86.88
75
84
4765.33
87.43
114
88
96.66
5018
92.07
128
82
97.33
5246.66
96.26
SBP
DBP
MAP
94
74
102
Figure 11. Comparison of Readings Taken from Sphygmomanometer
and theSystem
Figure 7. Flowchart of the System
SBP: Systolic Blood Pressure
DBP: Diastolic Blood Pressure
MAP: Mean Arterial Pressure
Optical reading: Mean reading from sensor
Optical MAP: Optical reading/MAP factor
VIII. CONCLUSION
Figure 8. Circuit Diagram
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This proposed idea aims at reducing the hassle that a
patient faces in blood pressure measurement. The
main objective is to reduce the need of some doctor
or trained personnel in the process of blood pressure
measurement by means of a relatively inexpensive
yet user friendly device. It is easy to store data
which can be accessed by doctors for better analysis.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 46 Number 5 April 2017
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
University
of
Maryland
Health
Center.
http://umm.edu/health/medical/reports/articles/high-bloodpressure
Sphygmomanometer:
https://en.wikipedia.org/wiki/Sphygmomanometer
Photelectric
Plethysmography
(PPG)
https://en.wikipedia.org/wiki/Photoplethysmogram
Basem Abu Zneid, Mohammed Al-zidi, Tareq AlKharazi,“Non-invasive Blood Pressure Remote Monitoring
Instrument Based Microcontroller”, IEEE Region 10
Symposium, April 2014, Kuala Lumpur, Malaysia.
Vinee Sinha, R.K. Jain, G.D. Jindal, C.K. Pithwa, CD.
Kapse, BhagyashreeSarade, “Non-Invasive Blood Pressure
Monitor:
Beat
to
Beat”,
TECHNOLOGY
DEVELOPMENT ARTICLE, BARC Newsletter 62 , Issue
no. 328 , OCT 2012.
Gu-Yung Jeong, Kee-Ho Yu, Nam-Gyun Kim, “Continous
Blood Pressure Monitoring using Pulse Wave Transit
Time.”, ICCAS 2005, KINTEX, Gyeonggi-Do, Korea.
http://www.nursingcenter.com
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