international journal of electronics and...

International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976

– 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 2, February (2014), pp. 83-92 © IAEME

83

MEASUREMENT OF HUMAN BLOOD CLOTTING TIME USING LabVIEW

Bharati. S R1, Parvathi. C S

2 and P. Bhaskar

2

1Department of Electroncs, Nutan Vidalaya Degree College, Gulbarga-585103, KA, INDIA

2Department of Instrumentation Technology, Gulbarga University, P.G. Centre, RAICHUR-584133,

KA INDIA

ABSTRACT

This paper focuses on development of a system where the human blood clotting time of is

determined by measuring the blood conductivity during coagulation. The minimum amount of blood

sample (1ml) is taken and conductivity cell is immersed into it. The signal produced by conductivity

cell will be in terms of millivolts which is further signal conditioned and acquired by the onchip

ADC of ATMEGA 328 microcontroller. This voltage is converted into corresponding conductivity

by curve fitting methodin microcntroller. The conductivity thus measured is transmitted to PC

through USB. Graphical user interface (GUI) is developed using LabVIEW software. Further

LabVIEW plots the graph of variation of conductivity with respect to time. From the graph, the

clotting time is determined when conductivity becomes almost constant and the same is displayed on

the front panel of the PC. The proposed device has advantages of portability, easy operation and real

time results for monitoring in the healthcare units. The results thus obtained from proposed device is

correlated against clinical test and found efficient and accurate.

Keywords: Blood Coagulation, ATMEGA328, Clotting Time, LabVIEW.

1. INTRODUCTION

The human blood is composed of cells distributed in an aqueous solution. Many charged or

polar molecules are present at both inside and outside the blood cells. Numerous inorganic ions are

distributed through the blood volume. Hence it is a good conductor. And we can measure the

conductivity by feeding small sinusoid amplitude [1].

Blood coagulation is one of the haemostatic processes of humans, which consists of a

complex, physiological cascade. When the blood vessel is damaged, the substances released from the

destroyed endothelium into blood induce formation of a platelet aggregation at first[2,3]. After

activation, platelets tend to adhere to the damaged vessel wall and finally, an aggregated platelet plug

INTERNATIONAL JOURNAL OF ELECTRONICS AND

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ISSN 0976 – 6464(Print)

ISSN 0976 – 6472(Online)

Volume 5, Issue 2, February (2014), pp. 83-92 © IAEME: www.iaeme.com/ijecet.asp

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84

is formed to prevent the loss of blood. During this process, plasma clotting also happens. When the

cells are placed in endothelium are exposed to blood, the plasma clotting, known as blood

coagulation, is activated. Blood coagulation process has more complex cascade, which consists of

enzymatic reactions in blood plasma [4]. As a result of complicated process, polymerized fibrin is

formed from fibrinogen to prevent the loss of blood cells.

It is important to monitor blood coagulation process because disorders in coagulation can

lead to higher risk of bleeding. Also, blood coagulation disorders have possibilities to bring

pathological complications in increasing thrombosis and embolism in the vascular system[5]. These

are life-threatening, which can induce fatal danger in various clinical circumstances, such as cardiac

surgery [6]. Therefore, it is essential to check the blood coagulation process regularly to allow the

detection of clotting problems.

Clinical laboratory examination of blood coagulation analysis allows observation of the

amount of vitamin K in the blood indirectly and diagnosis of liver disorder. The treatment of drugs

used in some hereditary and hemorrhagic diseases depends on the process of blood coagulation by

measuring the clotting time or prothrombin time [7]. The coagulation of blood is a complex process

during which solid clots are formed in the blood. The conversion of fibrinogen into fibrin and the

subsequent covalent cross-linking of fibrin play important roles in this process, and can be induced

by an imbalance between coagulant and anticoagulant factors. Although coagulating blood is vital to

the preservation of life, blood clots can impede blood flow in the vessels. Thrombus formation is

responsible for most heart attacks and strokes and complicates other pathological conditions such as

coronary thrombosis, peripheral deep venous thrombosis, and pulmonary embolus, and can

eventually cause death unless brought under control [8]. In addition, paralytic patients confined to

bed usually suffer from intravascular clots due to coagulation that tends to occur when the flowing

blood is obstructed for a few hours in any vessel of the body. Therefore, a clear understanding of

blood coagulation properties is crucial for clinical diagnosis, and techniques for detecting blood

coagulation need to be developed. A common method to assess the process of blood coagulation

involves adding blood to three or four test tubes and then tilting the tubes at 30-s intervals until the

blood can no longer flow. Clotting time is used as a screening test to measure all stages in the

intrinsic coagulation system and to monitor heparin therapy [9].

LabVIEW is visual programming software developed by National Instruments. LabVIEW is

an acronym for Laboratory Virtual Instrumentation Engineering Workbench. It is used in testing,

automation, instrument control, and monitoring and data acquisition. Programming is done by

connecting icons together to form a visual flow chart of processes. There is no code or syntax to

memorize or acronyms to learn. Programming is like drawing a flowchart [10].

LabVIEW is growing in popularity. LabVIEW is completely graphical in its programming

and visualization of the data and controls [11]. The program that we create is called VI the Virtual

Instrument. Within this VI there are two screens. The front panel is the GUI (Graphical User

Interface) where the human interacts and monitors the program while it is running. The front panel

contains the voltage readings and the measurements etc. The block diagram contains the

programming working behind the front panel. Just like wires, switches and circuits would work

behind an instrument panel. The block diagram is icons wired visually together to create a flowchart

of the program. Icons represent the functions of what is being controlled and wires contain the data

that connects the icons together [12]. The present work utilizes LabVIEW 12.0 version.

Literature survey on measurement of human blood clotting time reveals that many

researchers re have done measurement using different techniques. George S Sutton has done

measurement using Lee & White method [13]. Hyunjung Lim et al have done measurement using

Light Transmission method where co-agulation of blood is measured by intensity of the light

transmitted [14]. Robert A Schneider et al have done measurement by observing viscosity of blood



85

during Coagulation [15]. Chih-Chung Huang et al, have studied the coagulation by Ultrasound

Elastography Method [16].

The measurement methods as mentioned above authors are found to be time consuming and

complex. This motivated us to design an instrument to measure human blood clotting time by

measuring electrical conductivity which is found to be fast and easy compared with conventional

analysis techniques. This work is valuable for the development of clinical equipment for routine

coagulation tests.

2. HARDWARE DETAILS

In this manuscript, we present a new blood coagulation monitoring method using LabVIEW.

Fig. 1 shows the block diagram of the microcontroller based human blood conductivity measurement

system.

Fig 1. Block diagram of human blood clotting time measurement system

It consists of

• Conductivity cell

• Signal conditioning circuit

• Microcontroller

• PC

The complete schematic diagram of Atmel microcontroller based human blood conductivity

measurement system is shown in figure 2.

Microcontroller

AD

C

Ser

ial

Port

Sine wave

Generator

(1Khz) R

R

R C

Instrumentati

on

Technology

Amplifier Rectifier

and filter

Pers

onal

Com

pute

r

LabV

iew

Monitor

Keyboard



86

Fig 2. Schematic diagram of human blood clotting time measurement system

i. Conductivity Cell The conductivity cell consists of a pair of electrodes that are firmly located in a constant

geometry. The cell used in the present study consists of two platinum electrodes of 1 cm2 cross

sectional area that are separated by a distance of 1 cm. the cell constant of the cell used in the present

study is 1.01. [Elico manual]

ii. Signal Conditioning Circuit

The proposed signal conditioning circuit is designed for this particular application which

utilizes AC conductivity measurement. This circuit consists of a stable sine wave oscillator

constructed by using an operational-amplifier {WEIN-BRIDGE OSCILLATOR}. This oscillator is

designed to generate a sine wave frequency equal to 1 KHz at amplitude equal to nearly 10 VPP. The

generated AC sine wave is used as an excitation source for the impedance bridge containing a sample

in one of the bridge arm. The AC excitation source is capacitively coupled or coupled through the

capacitor to the bridge. The differential voltage is amplified using differential amplifier designed by

using an operational amplifier. The differential gain can be varied from 1 to 10. The amplified

differential output is further amplified by another with maximum gain of 10, thus amplified AC

voltage is rectified and filtered to get the average DC voltage, corresponding to the conductivity of

the blood sample. This analog output is converted to 10 bit digital data by using an ADC which is

inbuilt in the microcontroller which is being used.

iii. Microcontroller In present system ATMEG 328 microcontroller is used. This microcontroller is a high-

performance Atmel 8-bit AVR RISC-based microcontroller combines 32KB ISP flash memory with

read-while-write capabilities, 1KB EEPROM, 2KB SRAM, 23 general purpose I/O lines, 32 general

purpose working registers, three flexible timer/counters with compare modes, internal and external

interrupts, serial programmable USART, a byte-oriented 2-wire serial interface, SPI serial port, 6-

channel 10-bit A/D converter (8-channels in TQFP and QFN/MLF packages), programmable



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watchdog timer with internal oscillator, and five software selectable power saving modes. The device

operates between 1.8-5.5 volts.

3. SOFTWARE DETAILS

The program to acquire the data and to process is written in embedded C languagefor

microcontroller.. The detailed flow chart is shown in figure 3. The conductivity measurement of the

blood can be impacted by various criterions. One among them would be the curve fitting method.

Finally the data is processed using the relation y= mX+C to get the result of the conductivity where

y is voltage acquired by the ADC, X is conductivity of blood , m is slope and C is intercept. The

equivalent conductivity is calculated for each voltage variation.

The result thus obtained is transmitted to PC through USB where the LabVIEW is used for

determining clotting time. A GUI has been designed in LabVIEW for the user sake i.e. for the

display of the result such as clotting time. Figure 4 shows the designed GUI where the information

about results can be viewed. A GUI program is a graphical based approach to execute the program in

a more user friendly way. It contains components with proper labels for easy understanding to a less

experienced user. These components help the user to easily understand how to execute or what to do

to execute the program. When an user responds to a GUI’s components by pressing a pushbutton or

clicking a check box or radio button or by entering some text using text box, the program reads the

necessary information for that particular event, hence GUI programs are also known as event driven

programs.

Fig:3 Detailed flowchart for measurement of conductivity using microcontroller



88

Fig 4 and Fig 5 show the block diagram of the VI designed to plot the graph of variation of

conductivity with respect to time and display of clotting time on the front panel.

Fig 4. VI Block diagram for measurement of conductivity

Fig 5. VI Block diagram for measurement of clotting time.



89

The LabVIEW program is written to acquire the data, to process, to measure and to display

the clotting time on the front panel. The data analysis file is to be kept in the required format and

placed in the a subdirectory. This file path is to be given to the path reference to read. All the

variables such as convert data array, conductivity versus time, array length, clotting time, min and

max values etc are to be initialized for default values or zero. Infinite while loop is executed with

time delay so that other applications need time from cpu to work in multitasking mode and also to

enable the polling of other functions. As the program has to be fit in the same screen stacked

sequence is used which will also make debugging and any modifications simpler. When the program

is running, inside the while loop the various inputs are continuously polled for the relevant input. The

buttons which are polled are Read Data File and Plot buttons. The file path is to be entered to read

the data file.

During polling, pressing the read button, the raw data is read and converted to the tab

separated string format for further processing. The data are further separated and put into two

dimensional array as conductivity in one column and time in another column. Then string formatted

array is converted to floating decimal number array which is required for plotting.

By pressing the plot button, the 2D array is transposed and graph is plotted as conductivity vs

time in the front panel. It will also find the total size of the array which is required for differentiation.

Differential equation is applied for clot conductivity values versus time to find where the clot

conductivity values remain constant. After finding the duration of the clotting time in seconds, which

in turn is expressed in terms of minute and displayed on the front panel. Again the polling will

continue for the next data set from different file to be input. This process will continue till we

terminate the program. Fig 6 shows the front panel of GUI where we can see the display of clotting

time. The detailed flowchart for measurement of conductivity and display of clotting time is shown

in fig 7.

Fig 6. Front panel of LabView showing clotting time



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4. RESULTS AND DISCUSSION

Fig 8 shows the graphical representation of variation of actual conductivity with respect to

time. It is clear from the plot that the conductivity decreases as time elapses due to disappearance of

conductive ions. Once the blood is clotted, conductivity reduces to great deal and becomes almost

constant.

Fig 7. Flow chart

Initialization of constants and variables

Input path for data file

Start

Is button

pressed?

Read data and display

Convert data into 2 dimensional array

Is button

pressed?

Convert string array to floating array

Plot graph time Vs conductivity

Fine array size

Find out constant dx/df

Conductivity

Find total duration

Convert to minute and display

Next set of data

No

Yes

No

Yes



91

Fig 8. Variation of conductivity with respect to time

The designed Instrument is subjected to measure the clotting time of 20 individuals. Fig 9

shows the clotting time of each individual measured by the instrument developed and also compared

with the clinical measurements and found that there is 96% of accuracy. The normal range of time

for the blood clotting is 5 to 15 min.

Fig9. Results of testing Sample

5. CONCLUSION

This work demonstrates the development of a system that allows precise detection of the

coagulation time of whole blood by measuring conductivity during coagulation using LabVIEW. The

method is shown to be useful for determination of the blood disorders like lack of hemoglobin,

hemophilia, and hematocrit etc., Clotting time is used as a screening test to measure all stages in the

intrinsic coagulation system and to monitor heparin therapy during major surgeries. In this work,

analysis of the conductance change of blood sample during coagulation was conducted successfully

and results showed that the clotting time measurement using LabVIEW is a sensitive and promising

technique for monitoring blood coagulation process. This method found to be fast and easy

measurement compared with other conventional analysis techniques. This work is found valuable for

the development of clinical equipment for routine coagulation tests.



92

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[16] Chih-Chung Huang, Yi-Hsun Lin, Ting-Yu Liu, Po-Yang Lee, Shyh-Hau Wang, Study of

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[17] Chandrika V, Parvathi C.S. and P. Bhaskar, “Design and Development of Pulmonary

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Network in Matlab”, International Journal of Electronics and Communication Engineering

&Technology (IJECET), Volume 4, Issue 2, 2013, pp. 357 - 372, ISSN Print: 0976- 6464,

ISSN Online: 0976 –6472.

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