LABORATORY MANUAL
PROGRAMME: B.Tech
SEMESTER /YEAR: V / III
SUBJECT CODE: BM0315
SUBJECT NAME: Biomedical Instrumentation Lab
Prepared By:
Name: S.P. Angeline Kirubha
Designation: A.P (Sr. Gr)
DEPARTMENT OF BIOMEDICAL ENGINEERING
SCHOOL OF BIOENGINEERING,
FACULTY OF ENGINEERING & TECHNOLOGY
SRM UNIVERSITY
(UNDER SECTION 3 of UGC ACT 1956)
KATTANKULATHUR-603203
Tamil Nadu, India
LIST OF EXPERIMENTS
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Sl. No
Experiment
Page .No
1
Blood Pressure Measurement
1
2
Real time monitoring of Echocardiography
6
3
Working of different types of Diathermy equipments – study
20
3.a
Shortwave Diathermy
22
3.b
Ultrasound Diathermy
26
3.c
Surgical Diathermy
28
4
ECG wave analysis using simulator
32
5
Real time patient monitoring system
35
6
Ultrasound blood flow measurement to identify arteries and
39
veins
7
Respiratory system analysis using Spirometer
41
8
Analysis of ECG abnormal wave pattern using Arrhythmia
47
Simulator
9
EEG wave analysis using simulator
52
10
Auditory system check up using Audiometer
56
11
Heart sound measurement using PCG
61
12
Biotelemetry
65
13
Pacemaker Module
68
14
ECG heart rate alarm system with HRV
73
15
EMG Biofeedback with NCV
78
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
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Ex. No 1 Blood Pressure Measurement
Aim: To Measure blood pressure using Sphygmomanometer, semi-automatic blood pressure
measuring instrument and automatic blood pressure measuring instrument.
Apparatus Required:
1.
Cuff
2.
Inflator
3.
Power supply
4.
Stethoscope
5.
Sphygmomanometer
6.
Semi-automatic bp measuring unit
7.
Automatic bp measuring unit
THEORY:
Blood Pressure
Blood pressure is a measurement of the force applied to the walls of the arteries as the
heart pumps blood through the body. The pressure is determined by the force and amount of
blood pumped, and the size and flexibility of the arteries. Blood pressure is continually changing
depending on activity, temperature, diet, emotional state, posture, physical state, and medication
use. The ventricles of heart have two states: systole (contraction) and diastole (relaxation).
During diastole blood fills the ventricles and during systole the blood is pushed out of the heart
into the arteries. The auricles contract anti-phase to the ventricles and chiefly serve to optimally
fill the ventricles with blood. The corresponding pressure related to these states are referred to as
systolic pressure and diastolic pressure .The range of systolic pressure can be from 90 mm of Hg
to 145mm of Hg with the average being 120 mm of Hg. The diastolic pressure typically varies
from 60mm of Hg to 90 mm of Hg and the average being 80 mmofHg.
PRINCIPLE
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bioengineering, SRM University
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The upper arm is wrapped with the cuff belt connected to a mercury pressure gauge and air is
pumped with a rubber ball to increase cuff pressure about 30 mmHg higher than the systolic
blood pressure to block the artery and stop blood flow downstream. Then, the cuff pressure is
slowly lowered. The artery opens at the instant when the cuff pressure decreases below the
systolic blood pressure and blood begins to flow on and off in synchrony with pulses causing the
opening and closing of the artery. The sound emitted by the pulses is named Korotkoff's and
continues until the cuff pressure decreases below the systolic blood pressure and the artery
ceases the opening and closing. The stethoscope placed closely to the artery downstream of the
cuff is used to hear Korotkoff's sound; the blood pressures are measured. Cuff pressure when
Korotkoff's sound begins to be heard is defined as the highest blood pressure and that when the
sound disappears is defined as the lowest pressure.
SPHYGMOMANOMETER
Mercury Sphygmomanometer
This includes a mercury manometer, an upper arm cuff, a hand inflation bulb with a pressure
control valve and requires the use of a stethoscope to listen to the Korotkoff sounds. Relies on
the ausculatory technique.
Advantages:
Regarded as the 'Gold Standard'. It is transportable and is understood by users. Can be used on
most patients.
Disadvantages:
It contains toxic mercury which can lead to maintenance problems, although it is safe in normal
useage. Can be prone to observer bias.
Semi-automated device
This includes an electronic monitor with a pressure sensor, a digital display, an upper arm cuff
and a hand bulb. The pressure is raised manually using the hand bulb. The device automatically
deflates the cuff and displays systolic and diastolic values. Pulse rate may also be displayed. Is
battery powered and uses the oscillometric technique.
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Advantages:
Is mercury-free, lightweight and compact. There is no observer bias and it is portable and easy to
use.
Disadvantages:
It was originally designed for home use and may not be suitable for all patients, particularly
those with arrhythmias. May be difficult to calibrate. Some cuffs cannot be washed or
decontaminated.
Automated device
This includes an electronic monitor with a pressure sensor, a digital display and an
upper arm cuff. An electrically driven pump raises the pressure in the cuff. Devices may have a
user-adjustable set inflation pressure or they will automatically inflate to the appropriate level,
about 30 mmHg above the predicted systolic reading. On operation of the start button the device
automatically inflates and deflates the cuff and displays the systolic and diastolic values. Pulse
rate may so be displayed. Devices may also have a memory facility that stores the last
measurement or up to 10 or more previous readings. It is battery powered and uses the
ocillometric technique.
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Block Diagram:
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bioengineering, SRM University
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Tabulation:
S.No Patient Sphygmomanometer
Semi Automated
Automated
Name
Systolic
Diastolic
(mmHg) (mmHg)
1
X
2
Y
3
Z
4
A
Systolic
Diastolic
(mmHg) (mmHg)
Pulse Systolic Diastolic Pulse
(bpm) (mmHg) (mmHg) (bpm)
Result:
Thus the blood pressure measurements are done using mercury sphygmomanometer, semi
automated and automated devices for human.
Ex. No 2 Real time monitoring of Echocardiography
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Aim: To acquire real time ECG of 12 lead ECG system and analyse the signals.
ECG is a transthoracic interpretation of the electrical activity of the heart over time captured and
externally recorded by skin electrodes. It is a noninvasive recording produced by an
electrocardiographic device.
OBJECTIVES:
Understand and be able to identify the different deflections seen in an electrocardiogram, a trace
of the heart’s electrical activity.
COMPONENTS REQUIRED:
S.NO
DESCRIPTION
1
ECG sensor with leads
(electrode patches)
RANGE
QUANTITY
10 lead
1 No
2
Computer interface
1 No
3
PC
1 No
4
Gel
some
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DIAGRAM:
Leads:
Graphic showing the relationship between positive electrodes, depolarization wavefronts (or
mean electrical vectors), and complexes displayed on the ECG.
In electrocardiography, the word lead (pronounced /lid/) refers to the signals transmitted and
received between two electrodes. The electrodes are attached to the patient's body, usually with
very sticky circles of thick tape-like material (the electrode is embedded in the center of this
circle).
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bioengineering, SRM University
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ECG leads record the electrical signals of the heart from a particular combination of recording
electrodes which are placed at specific points on the patient's body.
PLACEMENT OF ELECTRODE:
Ten electrodes are used for a 12-lead ECG. They are labeled and placed on the patient's body as
follows:
ELECTRODE
LABEL (in the ELECTRODE PLACEMENT
USA)
RA
On the right arm, avoiding bony prominences.
LA
In the same location that RA was placed, but on the left arm this time.
RL
On the right leg, avoiding bony prominences.
LL
In the same location that RL was placed, but on the left leg this time.
V1
In the fourth intercostal space (between ribs 4 & 5) to the right of the sternum
(breastbone).
V2
In the fourth intercostal space (between ribs 4 & 5) to the left of the sternum.
V3
Between leads V2 and V4.
V4
In the fifth intercostal space (between ribs 5 & 6) in the midclavicular line (the
imaginary line that extends down from the midpoint of the clavicle (collarbone).
Horizontally even with V4, but in the anterior axillary line. (The anterior
V5
axillary line is the imaginary line that runs down from the point midway
between the middle of the clavicle and the lateral end of the clavicle; the lateral
end of the collarbone is the end closer to the arm.)
V6
Horizontally even with V4 and V5 in the midaxillary line. (The midaxillary line
is the imaginary line that extends down from the middle of the patient's armpit.)
Unipolar vs. bipolar leads
There are two types of leads—unipolar and bipolar. Bipolar leads have one positive and one
negative pole. In a 12-lead ECG, the limb leads (I, II and III) are bipolar leads. Unipolar leads
have only one true pole (the positive pole). The negative pole is a "composite" pole made up of
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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signals from lots of other electrodes. In a 12-lead ECG, all leads besides the limb leads are
unipolar (aVR, aVL, aVF, V1, V2, V3, V4, V5, and V6).
Limb leads
In both the 5- and 12-lead configuration, leads I, II and III are called limb leads. The electrodes
that form these signals are located on the limbs—one on each arm and one on the left leg.The
limb leads form the points of what is known as Einthoven's triangle.
•
Lead I is the signal between the (negative) RA electrode (on the right arm) and the (positive)
LA electrode (on the left arm).
•
Lead II is the signal between the (negative) RA electrode (on the right arm) and the (positive)
LL electrode (on the left leg).
•
Lead III is the signal between the (negative) LA electrode (on the left arm) and the (positive)
LL electrode (on the left leg).
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Augmented limb leads
Leads aVR, aVL, and aVF are 'augmented limb leads'. They are derived from the same three
electrodes as leads I, II, and III. However, they view the heart from different angles (or vectors)
because the negative electrode for these leads is a modification of 'Wilson's central terminal',
•
Lead aVR or "augmented vector right" has the positive electrode (white) on the
right arm. The negative electrode is a combination of the left arm (black) electrode and the left
leg (red) electrode, which "augments" the signal strength of the positive electrode on the right
arm.
•
Lead aVL or "augmented vector left" has the positive (black) electrode on the left
arm. The negative electrode is a combination of the right arm (white) electrode and the left leg
(red) electrode, which "augments" the signal strength of the positive electrode on the left arm.
•
Lead aVF or "augmented vector foot" has the positive (red) electrode on the left
leg. The negative electrode is a combination of the right arm (white) electrode and the left arm
(black) electrode, which "augments" the signal of the positive electrode on the left leg.
The augmented limb leads aVR, aVL, and aVF are amplified in this way because the signal is
too small to be useful when the negative electrode is Wilson's central terminal. Together with
leads I, II, and III, augmented limb leads aVR, aVL, and aVF form the basis of the hexaxial
reference system, which is used to calculate the heart's electrical axis in the frontal plane.
aVR = -(I + II)/2
aVL = I - II/2
aVF = II - I/2
PRINCIPLE:
An electrocardiogram (ECG or sometimes EKG) is a reading of the electrical
activity of the heart The potentials originated in the individual fibers of heart muscle are added to
produce the ECG wave form , the ECG reflects the rhythmic electrical depolarization and
repolarization of the myocardium(heart muscle ) associated with the contractions of the atria and
ventricles.
There are electrical signals that can be detected from two different types of cardiac muscle, the
auto rhythmic fibers that make up the electrical conduction system of the heart and the cardiac
muscles that produce muscle contractions. The signals are detected by electrodes that measure
electrical potential between different points on the body. A typical ECG is taken using 10 wires
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bioengineering, SRM University
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and is referred to as a 12 lead ECG. Electrodes are place on each limb and are referred to as
augmented limb leads and 6 precordial leads are placed directly on the chest. The final lead is
the ground lead and is generally placed on the right leg, although it can be placed anywhere on
the body. The ground is used as a point of reference. In the ECGs that you will record in class,
we will use 3 leads. The leads will be placed on the inside of the forearms near the elbow joint
and the ground lead will be placed on the right wrist.
STANDARD ECG :
The electrical conduction system of the heart consists of the sinoatrial node (SA node), located
in the superior wall of the right atrium, which is the heart’s primary pacemaker. These fibers
automatically produce an electrical signal at a particular pace that is conveyed to
atrioventricular node (AV node), located in the medial wall of the right atrium. The signal
from the AV node travels to the atrioventricular bundle and the right and left bundle
branches, located in the interventricular septum. From the septum, the signal travels to the
Purkinje fibers, which project along the outer walls of the ventricles. Not only does the signal
travel through the autorhythmimc fibers that make up the electrical conduction system, but the
electrical signal travels through gap junctions to the cardiac muscles, where electrical impulses
lead to cardiac muscle contractions. The ECG is the electrical activity of the heart as it is
displayed on an oscilloscope. It has 5 different wave deflections: P. Q, R, S and T. In general,
ECGs are useful for detecting abnormal rhythms caused by damage to the autorhythmic fibers or
abnormal levels of electrolytes such as potassium, sodium or calcium. They are often not as
useful in detecting damage to cardiac muscle.
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bioengineering, SRM University
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Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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The P. Q, R, S and T deflections and intervals between indicate the following:
The P wave represents the electrical signal produced by the SA node in the right atrium and the
propagation of that impulse to the AV node and to the cardiac muscles of the atria.
The PR/PQ interval runs from the beginning of the P wave to the beginning of the QRS
complex. During this interval includes what is mentioned in the P wave as well as the contraction
produced by the atrial cardiac muscles. Atrial contraction occurs during the flat part of the
interval.
The QRS complex represents the depolarization of the ventricles. Reflected in this is the
movement of the electrical signal down the AV bundle, right and left bundle branches, Purkinje
fibers and the propagation of that signal to the cardiac muscles of the ventricles. Because of the
greater muscle mass of the ventricles, the signal is much larger than the P wave. Also during this
time you have repolarization of the atrial cardiac muscles, however the electrical signal is
masked by the large depolarization produced by the ventricular muscles.
The ST interval represents the contraction of the ventricles. It is measured from the junction of
where QRS ends and the T wave begins.
The T wave represents the repolarization of the ventricles. The absolute refractory period occurs
during the ST interval and extends to the apex of the T wave. The relative refractory period the
latter half of the T wave.
The QT interval runs from the beginning of the QRS complex to the end of the T wave. This
represents the time it takes for depolarization and repolarization of the ventricles. This interval
will vary with heart rate.
Typical times for segments of an
ECG
Segment
time (ms)
P/Q interval
120-200
QRS complex
60-100
ST interval
80-120
Q/T interval
300-440
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Bipolar Limb Leads
Unipolar Limb Leads:
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Unipolar Chest Leads
Right Leg Drive Circuit
ECG – Recording Setup
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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ECG Recorder
Experimental procedure:
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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1) Choose one member of your group to be the subject and apply the electrode patches as
described in the experimental setup.
2) Record the ECG of your subject at rest. The subject should be sitting, relaxed, and breathing
at a normal rate. You may want to record rate of breathing (optional) to compare how it changes
under the other conditions. Record the required interval times.
3) Record the ECG of your subject after three minutes of deep, slow breathing that is done in a
supine or sitting position. Try to get the breathing rate down to 5 breaths or less a minute. Record
the breathing rate. Record the required interval times.
4) Record the ECG of your subject after three minutes of mild exercise. You may choose
jogging in place or choose some other type of exercise for that length of time. Record the
breathing rate. Record the required interval times.
Analysis:
1) Choose three representative ECG traces and measure the intervals that are listed in the chart
above for the three different conditions. Your ECG Lab worksheet has a table for you to record
this information.
2) Calculate an average for the intervals.
3) Calculate heart rate and the average heart rate under the three different conditions.
Tabulation :
Parameters
(mv)
I
II
III
avR
avL
avF
V1
Max
In LEAD
R amp (µv)
R’ amp (µv)
P amp (µv)
P’ amp (µv)
T amp (µv)
T’ amp (µv)
Q amp (µv)
S amp (µv)
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
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ST elevation
(mm)
ST
Depression
(mm)
ST Slope
(mv/ sec)
QR Time
(m/ sec)
Interpretation Report:Parameters
Rate
Observatio
Normal
n
limits
Indications
Average Heart Rate(bpm)
Heart Variation
Median
PR Interval(ms)
P wave amp/
P duration(ms)
QRS Width(ms)
QRS&(deg)+
T axis
QTC(ms)
ST elev(mm)
ST depr(mm)
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Max T-wave
Rhythm
Conduction
Ischemia
Infarction
Hypertrophy
Other
Abnormality
RESULT:Thus the real time ECG is recorded and the signal is analysed for the subject
Ex. No 3 Working of different types of Diathermy equipments – study
AIM:
Heat energy is applied to the painful area which speeds up the cellular metabolism and increases
the blood flow
APPARATUS REQUIRED:
*Shortwave diathermy unit.
*Pad electrodes.
*Ultrasound diathermy unit.
*Surgical diathermy unit.
DESCRIPTION:
Diathermy involves heating deep muscular tissues. When heat is applied to the painful area,
cellular metabolism speeds up and blood flow increases. The increased metabolism and
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bioengineering, SRM University
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circulation accelerates tissue repair. The heat helps the tissues relax and stretch, thus alleviating
stiffness. Heat also reduces nerve fiber sensitivity, increasing the patient's pain threshold.
There are three methods of diathermy. In each, energy is delivered to the deep tissues, where it is
converted to heat. The three methods are:
•
Shortwave diathermy: The body part to be treated is placed between two capacitor plates.
Heat is generated as the high-frequency waves travel through the body tissues between the
plates. Shortwave diathermy is most often used to treat areas like the hip, which is covered with
a dense tissue mass. It is also used to treat pelvic infections and sinusitis. The treatment reduces
inflammation. Most machines function at 27.33 megahertz.
•
Ultrasound diathermy: In this method, high-frequency acoustic vibrations are used to
generate heat in deep tissue.
•
Surgical diathermy:The use of electrocautery for coagulation or cauterization, as for
sealing a blood vessel, resulting in local tissue destruction
Diathermy is also used in surgical procedures. Many doctors use electrically heated probes to
seal blood vessels to prevent excessive bleeding. This is particularly helpful in neurosurgery and
eye surgery. Doctors can also use diathermy to kill abnormal growths, such as tumors, warts, and
infected tissues.
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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A. SHORTWAVE DIATHERMY (SWD)
Aim:
To study the working of Shortwave Diathermy
Theory:
Short Wave diathermy current is a high frequency alternating current. The heat energy obtained
from the wave is used for giving relief to the patient. Its frequency is 27,120,000 cycles per
second and the wavelength is 11 metre.
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bioengineering, SRM University
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A shortwave diathermy unit is a device designed to generate radiofrequency radiation and
transfer it,via cables and electrodes, to the area to be treated. The units can be operated in either a
continuous wave or pulsed mode but both produce heat in deep tissue.
TWO FORMS OF SHORTWAVE DIATHERMY:
The units can be operated in either
¾
Continuous mode
¾
Pulsed mode
Two basic types of electrodes (applicators) are in use:
ƒ
Capacitor-type
ƒ
Inductor type.
In the first case tissue heating is basically due to the radiofrequency electric field, while for the
inductive electrodes (coils), heating occurs by a combination of electric field effects and currents
induced in the tissue by the magnetic field. The heating profile of the two mechanisms is
somewhat different.
These devices are capable of generating a sufficiently high level of radiation that there may be
cause for concern for the safety of the gonads and, in the case of pregnant patients, the foetus.
Improper use of the machine may result in burns and/or scalds and deep tissue or organ damage.
It must be noted that the level of radiation present in the vicinity of a diathermy unit may be
increased by the presence of nearby metallic objects or other units or by reflection from the wall.
Care must be taken to ensure that the shortwave radiation does not cause interference with other
equipment.
SWD is most commonly used for thermotherapy at a frequency of 27.12 MHz.
WORKING OF SHORT WAVE DIATHERMY:
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Shortwave diathermy heats the tissue by causing oscillations of electromagnetic energy of high
frequencies. The physiologic effects of temperature occur at the site of the application and in
distant tissue.
Circuit diagram of shortwave diathermy
The local effects occur due to the elevated local temperature which is associated with increased
local blood flow, capillary dilatation and capillary permeability. It results in higher level tissue
metabolism and more rapid transfer of nutritional ingredients to the end organs and tissues. It
promotes faster healing. Short wave heat increases connective tissue elasticity, reduces muscle
spasm, and sedates the nerve endings to change the pain threshold.
Distant changes from the heated target location include reflex vasodilatation and reduction of
muscle spasm, increase in body temperature, respiratory and pulse rates and decreased blood
pressure.
Diathermy increases white blood cell concentration in the area of chronic inflammation .
TREATMENT:
Before administering the treatment the operator should:
•
ensure that the thermal sensitivity of the patient is not impaired by analgesics,
•
ensure that the patient has removed all metallic objects (rings, watches, metal rimmed
glasses, etc.) from the treatment area,
•
Remove towelling or clothing from the treatment area,
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
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•
ensure that the skin is dry,
•
ensure that if the patient is wearing a hearing aid, it is removed, ask the patient to report
immediately any symptoms experienced during the treatment except 'a mild, comfortable
warmth,
•
ensure that the cables are correctly connected to both the machine and the applicator, not
rest the applicator or cables over metal surfaces, align the applicator accurately to ensure
an appropriate pattern of heating,
•
ensure that the testes are not directly irradiated and that care is taken to minimize indirect
irradiation,
•
ensure that the cables leading to the applicator are not placed in the vicinity of the
patient's non targetted tissue,
•
ensure that the chair or other patient support is not metallic and that other large metallic
objects are kept at least three metres from the electrodes and cables.
After activating the unit the operator should:
•
remain at least 1 m from the electrodes and 0.5 m from the cables during treatment,
•
ensure that the patient maintains the correct position and remains cooperative,
•
not leave the patient during the treatment, unless the patient has been supplied with an
emergency
•
cut-off switch and the patient is reliable,
•
not allow the patient to touch the unit,
•
ensure that no other person is in the vicinity of the unit or of the applicator during the
treatment, inaccordance with the administrative controls established by the user.
TREATMENT TIME:
Initial Stage
:5-10 minutes
Moderate Stage
:10-20 minutes
Severe State
:20-30 minutes
ADAVANTAGES:
1.
Relaxation of the muscles
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2.
Effective in bacterial infections
3.
Relief of pain
DISADVANTAGES:
1.
Burns
2.
Scalds (Boils)
3.
Overdose
4.
Shock
5.
Electric Sparking
6.
Faintness
Result:The working principle of shortwave Diathermy is studied
B. ULTRASOUND DIATHERMY
Aim:To study the working of Ultrasound Diathermy
Theory:Ultrasound is sound above the limits of human hearing. The therapeutic effects of ultrasound
result from the conversion of sound to heat energy. Ultrasound diathermy typically employs
frequencies between 0.8 and 1 MHz.
Ultrasound diathermy is considered a deep heating modality in that most absorption occurs far
beneath the skin. It is most commonly used to treat tendonitis and bursitis, musculoskeletal pain,
degenerative arthritis, and contractures. Maximal heating may be limited by deep tissue factors
and not by skin tolerance. Ultrasound may be applied directly by placing the applicator on the
skin, or indirectly by immersing the body part and applicator in a water-filled container.
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Because of the importance of appropriate technique and inherent dangers, ultrasound diathermy
should be applied by a trained attendant and the devices are not appropriate for unsupervised
home use.
It's an electromagnetic wave different from sound waves. The frequencies of waves employed for
medical purposes are between 5,00,000 and 3,000,000 cycles/sec.
GENERATION OF ULTRASONIC WAVES:
Ultrasonic waves are generated by vibration of a Crystal mounted on a special head.
Block diagram of ultrasonic diathermy unit
Ultrasound provides therapeutic benefit via thermal (continuous ultrasound) and nonthermal
(pulsed ultrasound) effects .
CIRCUIT DESCRIPTION:Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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The heart of the system is timed oscillator which produce the electrical oscillation of required
frequency. The oscillator output is given to the power amplifier which derives the piezoelectric
crystals to generate ultrasound waves. Power amplification is achieved by replacing the transistor
in a typical LC tuned colpitt oscillator by 4 power transistors placed in a bridge configuration.
The delivery of the ultrasounds power to a patient is to be done for a given time. This is
controlled by incorporating a timer to switch on the circuit. The timer can be mechanically spring
loaded type or an electronic one, allowing time settings from 0 to 30 minutes.
Procedure:
1.
The required time and frequency are set for treatment.
2. The ultrasound crystal will be kept on the portion of body which has to be treated.
Result:The study of Ultrasound Diathermy working principle is studied.
C. SURGICAL DIATHERMY
Aim:
To study the working of surgical diathermy
Theory:
Surgical diathermy apparatus comprising a power source, an active electrode for operation on a
patient, at least one circuit means for attachment to the patient, interconnection means
operatively interconnecting power source with active electrode and at least one circuit means,
each circuit means comprising a respective capacitive neutral plate for attachment to the patient,
a transformer interconnecting power source to capacitive neutral plate, and a
compensator comprising a
potential
amplifier transformer-coupled by transformer in series between
power source and capacitive neutral plate, said respective amplifier being operated to inject a
voltage through the transformer which is substantially equal to the potential drop across the
capacitive reactance of the capacitive neutral plate.
Block diagram of surgical diathermy
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PRINCIPLE:
Pertaining to the treatment of disease by manipulative and operative methods.
MONOPOLAR SURGICAL DIATHERMY:
Localized heating of tissue without muscle twitch or spasm can be effected by passing a large
alternating current of high frequency through parts of the body. This is surgical diathermy or
electrosurgery. If the power is sufficient, the temperature reached causes coagulation of the
blood or even disintegration of the tissue due to boiling.
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
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This technique is employed in a controlled manner during surgery to seal small blood vessels by
coagulation, and to cut through layers of tissue.
Cutting and coagulation is achieved by applying electric current to the tissues via small handheld probes (electrodes). The current flows out of the body (usually) through a very large
electrode placed on the skin at some remote site (e.g. on the thigh). At this electrode (the
indifferent electrode) the current density is very low, so little heating occurs. However, at the
hand-held electrode the density is very high due to its small contact area, and so great heat is
developed.
Surgical diathermy is a special electrical unit generating a high frequency current which
produces heat when passed through tissues.Depending upon the speed of the current and the
resulting heat, a diathermy unit can achieve the following results:
1. Cutting with high Speed or intensity.
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2. Coagulation (cooking compared to burning due to heated needle in electrocautery).
(a) If weak, epilation.
(b) If strong, coagulation producing destruction.
3. Desiccation ensues by passing medium current through a mono-terminal electrode at a slight
distance from the surface which produces sparking heat and results in drying up the tissues
•
Coagulation
o Produced by interrupted pulses of current (50-100 per second)
o Square wave-form
•
Cutting
o Produced by continuous current
o Sinus wave-form.
Diathermy currents may be generated by valve or transistor circuits and may include a range of
protection and monitoring systems. The frequencies used are typically in the range 0.5 to 3 MHz
and so it is difficult to achieve true earth-free operation due to the capacitance between the
patient and earth, and the capacitance of the leads of monitoring equipment. The system
described above is monopolar, whereas bipolar systems are available in which the heating
currents only flow between the two tips of special forceps. These are useful for fine work and
when the patient has a pacemaker which might malfunction in the presence of the very large
circulating high- frequency current.
BIPOLAR SURGICAL DIATHERMY
As an alternative to the conventional (monopolar) surgical diathermy, in which the electrical
current flows from a small active probe through the body to a large indifferent electrode, the path
of the current can be constrained to pass only through the tissue being treated. This is achieved
using a special forceps in which the two halves of the instrument are insulated from one another
and in effect one half becomes the source of the current and the other the destination, thus
replacing the active and indifferent electrodes mentioned above.
Bipolar diathermy has the advantage that electric currents do not pass through parts of the body
which are not being treated and also it is possible to be much more precise with the quantity of
tissue being coagulated. For instance, a small blood vessel gripped between the jaws of the
forceps will be coagulated, whereas tissue next to other parts of the forceps will not be heated at
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all. It is useful in microsurgery, but is often called for in other applications, particularly where
there may be interference with the action of a cardiac pacemaker by the stray diathermy currents
arising with monopolar systems.
Most modern diathermy machines can support the use of bipolar probes without modification.
Older types are generally unsuitable since the indifferent connection to the machine is at earth
potential, or is capacitively coupled to earth. An ideal bipolar diathermy current generator should
be fully isolated from earth so that there will be no tendency for diathermy currents to circulate
in the body to find other routes to earth. This is difficult to achieve at the frequencies used (1-3
MHz).
Result:The study of surgical diathermy is thus performed in a subject.
Ex. No 4 ECG wave analysis using simulator
Aim:
To stimulate ECG signal and to analyze the signals in Time and Frequency domain.
Apparatus Required:
ECG machine, conducting gel, leads
Theory:
The electrocardiogram is an instrument which records to electrical activity of heart.
Electrical signals from the heart, characteristically placed the normal mechanical functions and
monitoring of these signal has great clinical
significance. Electrographs are used in
authorization laboratories, coronary care units and for routine diagnostic applications in
cardiology.
The diagnostically useful frequency range is usually accepted as 0.05-150hz. The
interface of non-biological origin can be handled by using modern
differential amplifier
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which are capable of providing excellent rejection
capabilities CMMR of the order of 100-
200db with 5KΩ unbalance in the lead is a desirable feature of ECG machine. The instability of
the baseline originating from the chane of the contact impedance, demands the application of the
automatic baseline stabilizing circuit. A minimum of two paper feeds is necessary(20-50 per sec)
for ECG reading. The lead selector switch is used to drive the required lead configurations and it
to dc coupled amplifiers.
Einthoven Triangle:
It starts the vector sum of the projection of the frontal phase cardiac to vector to the 3 axis of
the Einthoven triangle will be zero.
Lead 1: Left arm and right arm
Lead 2: Left leg and right leg
Lead3: Left and right arm
Block diagram explanation:
The potentials are picked up by the patients electrode are taken to the lead selection switch. In
the lead selector, the electrodes are selected two by two
according to the lead program. By
capacitive coupling the lead is connected to differential pre amplifiers to avoid problem with
small dc voltage the way
originate from polarisation. The output of the power amplifier is fed
to the pen motor which deflect the writhing on the paper.
Bipolar Leads:
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ECG is recorded by using two electrodes such that the final trace corresponds to the difference
of electrical potentials existing between them, they are called standard leads and have been
universally accepted. They are also called as einthoven lead.
Unipolar Lead:
If the electrode is placed close to the heart , higher potentials can be obtained, that normally
available at limbs.
ECG is recorded between a single exploratory electrode and the central
a potential corresponding to the centre of the body. The
combination of several electrodes tied
terminal, which has
reference electrode is obtained by
together at one point, it is of 2 types
1 Limb lead
2 Pericordial leads
LEAD 1
WAVE
AMP(V)
TIME(s)
FREQUENCY
POWER
P
QRS
T
HEART RATE:
LEAD 2
WAVE
AMP(V)
TIME(s)
FREQUENCY
POWER
P
QRS
T
HEART RATE:
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
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LEAD 3
WAVE
AMP(V)
TIME(s)
FREQUENCY
POWER
P
QRS
T
HEART RATE:
Result:
The ECG physiograph was recorded and analyzed.
Ex. No 5 Real time patient monitoring system
AIM:- To display ECG, EEG and EMG signals along with pulse rate using patient monitor.
Apparatus Required: Display, leads and electrodes.
THEORY:
Patient monitoring systems are used for measuring automatically the value of the
patient’s important physiological parameters during a surgical operation. The patient is deprived
of several manual reaction mechanisms which normally restores abnormalities in his physical
conditions or alert other people. Harm done to the patient can be prevented.
BLOCK DIAGRAM EXPLANATION:
ECG: The biopotential generated by muscles of heart results in ECG. The voltage difference at
any two sites due to electrical activity of the heart is called “lead”. There are basically two leads;
i)
Unipolar leads
ii)
Bipolar leads
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UNIPOLAR LEAD:
There are two types, one is limb lead in which two of the limb leads are tied together and
recorded with respect to the third. The other one is pericardial lead which employs an exploring
electrode to record the potential of the heart action on the chest at six different positions.
BIPOLAR LEAD:
ECG is recorded by using two electrodes such that the final trace corresponding to the difference
of electrical potential existing between these two are called standard leads.
EEG:
The recorded representation of bio-electric potential generated by the neuron activity of
the brain is called EEG. Modern machines make the use of computerised EEG signal processing.
FREQUENCY ANALYSER:
It takes the low EEG wave mathematically , analyses them and breaks them into their
component frequencies. Hence EEG signal is converted into simplified waveform called
spectrum.
COMPRESSED ANALYSER:
The amplitude changes result in power of resulting frequency spectrum.
COMPRESSED SPECTRUM ARRAY:
In this format a series of computer smoothed spectral array are stretched vertically at
several intervals. The origin of plot shifts vertically with time which produces dimensional
graph.
DSA:
It displays power spectrum.
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SAMPLING RATE:
Signal with high band width requires sampling to be carried out at high rate. A high
sampling rate necessitates a large memory to store all the data. A sampling channel memory
display system has sampling rate of 256 samples and multiple channel displays work as 100
samples.
PULSE RATE:
The pulse rate can be felt by placing the finger tip over the radial artery in the wrist. The
pulse pressure and waveform are indicated for blood pressure and flow. The pulse gives a
measure of pulse wave velocity which can be recorded and compared with ECG signal.
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The method used for detection of pulse changes are:
a)
Electrical impedance change
b)
Strain gauge
c)
Optical changes
OBSERVATION TABLE:
CASE I:
ECG (bpm)
NIBP (mmHg)
SYS.
TEMP. ( F)
SPO2 %
TEMP. ( F)
SPO2 %
DIA.
CASE II:
ECG (bpm)
NIBP (mmHg)
SYS.
DIA.
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CASE III:
ECG (bpm)
NIBP (mmHg)
SYS.
TEMP. ( F)
SPO2 %
DIA.
RESULT:
Display of EEG, ECG, and EMG signals along with respective waveforms is
studied and verified using the patient monitoring system.
Ex. No 6. Ultrasound blood flow measurement to identify arteries and veins
AIM:
To measure the ultrasound blood flow inorder to identify arteries and veins.
APPARATUS REQUIRED:
• Power supply
• Transmitter
• Receiver
• Power supply
• Speaker
PRINCIPLE OF WORKING:
The principle of ultrasound blood flow measurement is the visualization and measurement of
blood flow velocity by the shift in frequency of a continuous ultrasonic wave.The sensor used
here is piezoelectric crystal.This sensor acts both as the transmitter and receiver.The ultrasonic
waves transmitted by the transmitter are reflected by the motion of blood and is received by the
receiver but here the received frequency is Doppler shifted.The Doppler frequency shift is a
measure of the size and direction of the flow velocity. It is based on the analysis of echo signals
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from the erythrocytes in the vascular structures. The relationship between blood velocity and
frequency is given by
V=(Δf.C)/(2fcosθ)
Where v=blood flow velocity
C=velocity of sound in blood
f=transmitted frequency
θ=angle of inclination of the incident wave to the direction of flow
PROCEDURE:
The sensor which is ultrasonic transducer is non-invasively placed on the subject’s wrist. This
sensor has the transmitter and receiver. The transmitted signal gets Doppler shifted. Because of
the Doppler effect, the frequency of these echo signals changes relative to the frequency to which
the probe transmits. The incident ultrasound is scattered by the blood cells and the scattered
wave is received by the receiver. This frequency shift is proportional to the velocity of the
scatterers. Alteration in frequency occurs first as the ultrasound arrives at the scatterer and
second as it leaves the scatterer. This Doppler shifted frequency wave can be viewed in the
Cathode Ray Oscilloscope by properly connecting the output of the speaker to the CRO probes.
To any one channel the probes are connected and the time period and offset are adjusted to get
the Doppler frequency shifted wave with appropriate amplitude. The output wave can thus be
traced out. Also when the output of the receiver is connected to the speaker we will be able to
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bioengineering, SRM University
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listen
to
the
sound
of
the
blood
flow
in
arteries
and
veins.
RESULT:
Thus arteries and veins are identified with ultrasound blood flow meter.
Ex. No 7 Respiratory system analysis using Spirometer
Aim :
To record the changes in pulmonary volume and capacities by using spirometer.
Apparatus required:
¾ Peak flow meter
¾ Mouth piece
¾ USB cable
¾ Computer.
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Theory :
Spirometry is the most common of the Pulmonary Function Tests (PFTs), measuring lung
function, specifically the measurement of the amount (volume) and/or speed (flow) of air that
can be inhaled and exhaled. Spirometry is an important tool used for generating
pneumotachographs which are helpful in assessing conditions such as asthma, pulmonary
fibrosis and cystic fibrosis.
The spirometry test is performed using a device called a spirometer,
which comes in several different varieties. Most spirometers display the following graphs, called
spirograms:
•
a volume-time curve, showing volume (liters) along the Y-axis and time (seconds) along
the X-axis
•
a flow-volume loop, which graphically depicts the rate of airflow on the Y-axis and the
total volume inspired or expired on the X-axis
•
Forced Vital Capacity (FVC): The basic forced volume vital capacity (FVC) test
varies slightly depending on the equipment used. Generally, the patient is asked to take
the deepest breath they can, and then exhale into the sensor as hard as possible, for as
long as possible. It is sometimes directly followed by a rapid inhalation (inspiration), in
particular when assessing possible upper airway obstruction. Sometimes, the test will be
preceded by a period of quiet breathing in and out from the sensor (tidal volume), or the
rapid breath in (forced inspiratory part) will come before the forced exhalation. During
the test, soft nose clips may be used to prevent air escaping through the nose. Filter
mouthpieces may be used to prevent the spread of microorganisms, particularly for
inspiratory maneuvers.
•
Turbine Transducer:
The transducer which is used in spirometry is turbine transducer. It converts the flow of air,
breathed by the patient, against a frictionless rotating vane into an electrical signal which is used
to produce relevant plots.
Block diagram:
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Procedure :
¾ Sit on the edge of your chair if possible, or sit up as far as you can in bed.
¾ Hold the incentive spirometer in an upright position.
¾ Place the mouthpiece in your mouth and seal your lips tightly around your lips.
¾ After each set of 10 deep breaths, practice coughing to be sure your lungs are clear. If
you have an incision, support your incision when coughing by placing a pillow firmly
against it.
¾ Load the patient’s details ie. Name, age, sex, height, weight, patient ID, etc.
¾ Click onto the FVC (Forced Vital Capacity) graph on the window; the forced expiration
followed by forced inspiration will be recorded here.
¾ Click onto the SVC (Slow Vital Capacity) graph on the window; the SVC, being the
maximum volume of air that can be exhaled slowly after a slow maximum inhalation will
be recorded here.
¾ Click onto the MVV (Minute Ventilatory Volume) graph on the window; the measure of
the maximum amount of air that can be inhaled and exhaled in one minute will be
recorded here.
¾ Save the recorded values and analyse them using respective software.
SPIROMETRY GRAPHS:
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FIG 1. FVC GRAPH
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FIG 2. SVC GRAPH
FIG 3. MVV GRAPH
SIPROMETRY RESULTS:
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FVC RESULT
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SVC RESULTS
MVV RESULTS
Result :
Thus the changes in pulmonary volume and capacities are recorded using spirometer and
analysed for a subject.
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Ex. No 8 Analysis of ECG abnormal wave pattern using Arrhythmia Simulator
Aim:To record the changes in amplitude for a subject having arrhythmia.
Theory
The (ECG-A-S) is significantly and exclusively brought into existence to serve and poor and
needy who reside in remote places, where proper medical facilities are not persistent. The (ECGA-S) system brings about the measuring certain of the patient’s normal and abnormal ECG
parameters like Brachycardia, Tachycardia, Atrial fibrillation, Ventricular fibrillation. The main
purpose of using a solar energy is to truly fulfill the purpose of the (ECG-A-S). The remote
locations which could not even provide sufficient medical facilities cannot afford to bring about
a regular power supply either. Thus the use of solar potential will surely bring in the demand for
the same.
It consists of an efficient solar panel which receives the incident solar energy and converts into
electrical potential. The energy thus produced can be either saved for direct usage or can be used
for charging a battery, which in turn can be used to power the biomedical equipment (the simple
ECG Arrhythmia).
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ECG ARRHYTHMIA SIMULATOR:
ECG Arrhythmia simulator is used for gathering physiological data (ECG) of organism
under normal condition and processing the signals over time to find various heart blocks. ECG
Arrhythmia simulator is an important technique for biomedical research and clinical medicine.
Various grades of heart block can be measured in ambulatory subjects and proper diagnosis can
be physician. Biomedical research in ECG Arrhythmia simulator is currently with producing
patient monitoring equipment for the detection of ECG arrhythmias. To make comparative
evaluations of the widely differing specification, it is necessary to be able to simulate such
arrhythmias while retaining control of both number and frequency of abnormal beats and the
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degree of deviation from normality. This enables not only the counting circuits of such
monitoring equipment, but also the threshold levels below which an ECG complex is considered
abnormal, to be tested.
The similar described is designed for this purpose and utilizes pulse-shaping techniques
together with appropriate logic control circuitry and powered using solar energy via battery
which is a major advantage in using in rural areas. The most common symptom of arrhythmia is
an abnormal awareness of heartbeat, termed palpitations. These may be infrequent, frequent, or
continuous. Some of these arrhythmias are harmless but many of them predispose to adverse
outcomes. These abnormalities in the functioning of the heart invariably manifest themselves in
ECG waveform. Arrhythmia could be classified by rate (Normal, Tachycardia, Bradycardia), or
mechanism (Automaticity, Fibrillation). It is also appropriate to classify by site of origin like
Atrial, junctional arrhythmias, Atrio-ventricular, ventricular, heart blocks.
Power supply is connected to the simulator. A simulator is a device which is an imitation
of the real time record of ECG. All the abnormality and normal ECG waveforms are stored in it.
DIFFERENT ECG WAVEFORMS
NORMAL ECG WAVEFORM
BRACHYCARDIA
TACHYCARDIA
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ATRIAL FIBRILLATION
VENTRICULAR FIBRILLATION
Each heart beat originates as an electrical impulse from a small area of tissue in the right
atrium of the heart called the sinus node. The impulse initially causes both of the atria to
contract, then activates the atrioventricular (or AV) node which is normally the only electrical
connection between the atria and the ventricles , which can be called as main pumping chambers.
The impulse then spreads through both ventricles via the Bundle of His and the Purkinje fibres
causing a synchronised contraction of the heart muscle, and thus, the pulse. In adults the normal
resting heart rate ranges from 60 to 80 beats per minute. The resting heart rate in children is
much faster
Bradycardia (Brad)
A slow rhythm, beats less than 60 beats/min, is called bradycardia. This may be caused
due to a pause in the normal activity of the sinus node or by blocking of the electrical impulse on
its way from the atria to the ventricles. There is a long RR interval in bradycardia
Tachycardia (Tach)
Any resting heart rate faster than 100 beats/minute is called as tachycardia. Increased
heart rate is a normal response to physical exercise or emotional stress. Inverted QRS waveform
is obtained with short RR intervals in tachycardia.
Atrial Fibrillation (A-fib)
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Atrial fibrillation affects the upper chambers of the heart, known as the atria. Atrial
fibrillation may be due to serious underlying medical conditions. It is not typically a medical
emergency. P wave and T wave is fibrillated or lost in fibrillation.
Ventricular Fibrillation (V-fib)
Ventricular fibrillation occurs in the ventricles (lower chambers) of the heart; it is always
a medical emergency. If left untreated, ventricular fibrillation can lead to death within minutes.
When a heart goes into V-fib, effective pumping of the blood stops. Vfib is considered a form of
cardiac arrest. No amplitude and frequency could be seen in Vfib as it is an irregular waveform.
There is no FFT obtained.
Thus the different abnormal ECG waveforms are monitored using ECG-A-S in remote areas
using the mobile unit (ECG-A-S). It is also possible to connect an alarm to the ECG-A-S or
setting up threshold limits over the parameters. Thus when the patient’s ECG parameters exceed
or cross over the preset limits, then the sensors alarms and alert the attention towards the patient,
and this entire set up is possible to be connected to a solar panel so that it can work even in the
absence of electricity or even during night.
Result:The abnormal changes in amplitude for a subject having arrhythmia is verified and recorded.
Ex. No 9 EEG wave analysis using simulator
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AIM:
To measure and record the amplitude and time taken for the different alpha , theta, beta and
gamma EEG waves.
APPARATUS REQUIRED:
1. EEG stimulator
2. Connecting probes
3. Biokit physiograph
4. PC
THEORY:
Electroencephalography (EEG) is the recording of electrical activity along the scalp produced by
the firing of neurons within the brain. In conventional scalp EEG, the recording is obtained by
placing electrodes on the scalp with a conductive gel or paste. Electrode locations and names are
specified by the International 10–20 system for most clinical and research applications. Each
electrode is connected to one input of a differential amplifier (one amplifier per pair of
electrodes); a common system reference electrode is connected to the other input of each
differential amplifier. These amplifiers amplify the voltage between the active electrode and the
reference.
A typical adult human EEG signal is about 10µV to 100 µV in amplitude when
measured from the scalp and is about 10–20 mV when measured from subdural electrodes.
EEG WAVE PATTERNS:
DELTA WAVE:
Delta is the frequency range up to 4 Hz. It tends to be the highest in amplitude and the slowest
waves. It is seen normally in adults in slow wave sleep. It is also seen normally in babies.
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THETA WAVE:
Theta is the frequency range from 4 Hz to 7 Hz. Theta is seen normally in young children. It may
be seen in drowsiness or arousal in older children and adults; it can also be seen in meditation.
ALPHA WAVES:
Alpha is the frequency range from 8 Hz to 12 Hz. Hans Berger named the first rhythmic EEG
activity he saw, the "alpha wave. It emerges with closing of the eyes and with relaxation, and
attenuates with eye opening or mental exertion. The posterior basic rhythm is actually slower
than 8 Hz in young children.
BETA WAVES:
Beta is the frequency range from 12 Hz to about 30 Hz Beta activity is closely linked to motor
behaviour and is generally attenuated during active movements. It is the dominant rhythm in
patients
who
are
alert
or
anxious
or
who
have
their
eyes
open.
Since an EEG voltage signal represents a difference between the voltages at two electrodes, the
display of the EEG for the reading encephalographer may be set up in one of several ways. The
representation of the EEG channels is referred to as a montage.
BIPOLAR MONTAGE:
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Each channel (i.e., waveform) represents the difference between two adjacent electrodes. The
entire montage consists of a series of these channels. For example, the channel "Fp1-F3"
represents the difference in voltage between the Fp1 electrode and the F3 electrode. The next
channel in the montage, "F3-C3," represents the voltage difference between F3 and C3, and so
on through the entire array of electrodes.
REFERENTIAL MONTAGE:
Each channel represents the difference between a certain electrode and a designated reference
electrode. There is no standard position for this reference; it is, however, at a different position
than the "recording" electrodes. Midline positions are often used because they do not amplify the
signal in one hemisphere vs. the other. Another popular reference is "linked ears," which is a
physical or mathematical average of electrodes attached to both earlobes or mastoids.
AVERAGE REFERNTIAL MONTAGE:
The outputs of all of the amplifiers are summed and averaged, and this averaged signal is used as
the common reference for each channel.
LAPLACIAN MONTAGE:
Each channel represents the difference between an electrode and a weighted average of the
surrounding electrode.
When analog (paper) EEGs are used, the technologist switches between montages during the
recording in order to highlight or better characterize certain features of the EEG. With digital
EEG, all signals are typically digitized and stored in a particular (usually referential) montage;
since any montage can be constructed mathematically from any other, the EEG can be viewed by
the electroencephalographer in any display montage that is desired.
TABULAR COLUMN:
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AMPLITUDE(V)
WAVES
TIME(S)
FREQUENCY(Hz)
POWER
ALPHA
BETA
THETA
DELTA
PROCEDURE:
1. From the EEG stimulator input is given to the biokit physiograph.
2. The physiograph kit is connected to the PC using RS232.
3. For the respective alpha, beta , theta and delta waves the amplitude and time are noted.
4. The FFT is performed for the respective waves and the values are noted.
Result:
Thus the EEG waves are studied and the amplitude and time for each waveforms are noted for a
subject.
Ex. No 10 Auditory system check up using Audiometer
AIM:
To plot audiogram of the subject using air conduction pure tone audiometer
EQUIPMENTS REQUIRED:
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a)
b)
c)
d)
e)
f)
g)
Sine wave generator 0 to 10KHz
White noise generator
L‐R selector
Audio Amplifier – 2 Nos.
Level Indicator Log
Battery
Charger
THEORY:
The human ear has three main sections, which consist of the outer ear, the middle ear, and the inner
ear. Sound waves enter the outer ear and travel through the ear canal to the middle ear. The ear canal
channels the waves to the eardrum, a thin, sensitive membrane stretched tightly over the entrance to
the middle ear. The waves cause the eardrum to vibrate. It passes these vibrations on to the hammer,
one of three tiny bones in the ear.
The hammer vibrating causes the anvil, the small bone touching the hammer, to vibrate. The anvil
passes these vibrations to the stirrup, another small bone which touches the anvil. From the stirrup, the
vibrations pass into the inner ear. The stirrup touches a liquid filled sack and the vibrations travel into
the cochlea, which is shaped like a shell. Inside the cochlea, there are hundreds of special cells attached
to nerve fibers, which can transmit information to the brain. The brain processes the information from
the ear and this distinguishes between different types of sounds.
Air and bone conduction:
Air conduction, by definition, is the transmission of sound through the external and middle ear to the
internal ear. Bone conduction, on the other hand, refers to the transmission of sound to the internal ear
mediated by mechanical vibration of the cranial bones and soft tissues. The most important diagnostic
differential from the standpoint of the functional hearing tests is the relationship between air and bone
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conduction acuity. Clinical observation has shown that hard‐of‐hearing patients with middle ear disease
have normal hearing by bone conduction, whereas patients with inner ear involvement have decreased
or diminished bone–conduction.It has been concluded from clinical observations that approximately
60dB loss is the maximal air conduction impairment to be anticipated with middle ear defect. Therefore,
if the air conduction loss in a patient with apparently typical middle ear pathology exceeds 60 dB, it is
likely that inner ear impairment is superimposed on the middle ear lesion.
BLOCK DIAGRAM:
BLOCK DIAGRAM DESCRIPTION:
Sine wave generator
Sine wave generator is used to generate a signal representing the periodic value of a given mathematical
function, especially sine waveform, the range here is 0‐ 10 KHz and the output ranges from 2V Pk to Pk.
White noise generator
A white noise generator produces a sound that is random in character which sounds like a rushing
waterfall or wind blowing through trees. White noise is a random signal with a flat power spectral
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density. In other words, the signal contains equal power within a fixed bandwidth at any center
frequency.
Audio amplifier
Audio amplifier is an electronic amplifier that amplifies low power audio signals to a required level. The
audio amplifier used in this application has a frequency range of 0‐10KHz.
Level Indicator
The level indicator displays the level of sound in decibels it has LEDs which indicates the sound level
given to the subject.
L‐R selector
The L‐R selector is used to select the ear in which the subject wishes to determine the threshold of
hearing.
PROCEDURE:
1) To plot audiogram of the subject using air conduction pure tone audiometer
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
Connect the modules as per the block diagram.
Switch ON the battery.
Adjust masking level to a suitable level so that it does not cause discomfort to the subject
Put L, R switch in L position.
Keeping x1, x10 switch and set frequency in steps of 100Hz.
Adjust output dB level till the subject hears the sound.
Note the frequency and output dB level from DSO and level indicator respectively.
Repeat the above mentioned procedure for different set of frequencies.
Put L, R switch in R position
Repeat the above mentioned procedure for the right ear.
Plot the graph of frequency versus output dB level for L, R.
TYPICAL AUDIOGRAM
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bioengineering, SRM University
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-10
0
Sound Level in dB
+10
+20
+30
+40
+50
+60
+70
+80
200
500
1K
2K
3K
4K
5K
6K
7K
8K
9K
10K
11K
Frequency in Hz
Left Ear Response
Right Ear Response
L + R Ear Response
TABULAR COLUMN
Frequency
Decible(dB)
Left
Right
Left & Right
GRAPH
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bioengineering, SRM University
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-20
-15
(dB)
-10
200
-5
400
600
--------------Æ Frequency
800
1000
RESULT:
The graph of frequency verses output dB level gives audiogram of the subject.
Ex. No 11 Heart sound measurement using PCG
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bioengineering, SRM University
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AIM
The basic aim of phonocardiograph is to pick up the different heart sounds, filter out the heart
sounds and to display or record them.
APPARATUS REQUIRED
•
Power supply
•
Digital storage oscilloscope
•
Head phone
•
Phonocardiograph
THEORY
A Phonocardiogram or PCG is a plot of high fidelity recording of the sounds and murmurs made
by the heart with the help of the machine called phonocardiograph, or "Recording of the sounds
made by the heart during a cardiac cycle". The sounds are thought to result from vibrations
created by closure of the heart valves. There are at least two: the first when the atrioventricular
valves close at the beginning of systole and the second when the aortic valve closes at the end of
systole. It allows the detection of sub audible sounds and murmurs, and makes a permanent
record of these events. In contrast, the ordinary stethoscope cannot detect such sounds or
murmurs, and provides no record of their occurrence. The ability to quantitate the sounds made
by the heart provides information not readily available from more sophisticated tests, and
provides vital information about the effects of certain cardiac drugs upon the heart. It is also an
effective method for tracking the progress of the patient's disease.
Heart sounds are classified into four groups on the basis of their mechanism of origin, they are
1. Valve closure sound
2. Ventricular filling sound
3. Valve opening sounds and
4. Extra cardiac sounds
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bioengineering, SRM University
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HEART SOUNDS
First heart sound
Second heart sound
BLOCK DIAGRAM
AMPLIFIER
TRANSDUCER
AMPLIFIER
PCG DISPLAY
BUFFER
OUT LEVEL
5 FILTERS
AMPLIFIER
AMPLIFIER
AUDIO (DSO)
MICROPHONE
Valve closure sound
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These sounds occur at the beginning of systole (first heart sound) and the beginning of
diastole (second heart sound). The first heart sound is due to the closure of mitral and
tricuspid valves associated with myocardial contraction. And the second heart sounds is due
to the closure of the aortic and pulmonary valves. The first heart sounds are low frequency
vibrations occur approximately 0.05s after the onset of the QRS complex of the ECG, the
first heart sounds last for (0.1 to 0.12s) and the frequency ranges 30-50Hz.The second heart
sound is due to the vibrations set up by the closure of semilunar valves. These sounds start
approximately ( 0.03 to 0.05)s after the end of T wave of the ECG, this lasts for (0.08 to
0.14)s and have a frequency up to 250Hz.
Ventricular filling sounds
These sounds occur either at the period of rapid filling of the ventricles (third heart sound) or
during the terminal phase of ventricular filling. These sounds are inaudible. Third heart
sound starts at (0.12 to 0.18) s after the onset of the second heart sound.it last approximately
(0.04 to 0.08) s. The frequency is about 10 to 100 Hz.
Valve opening sounds
These sounds occur at the time of opening of the atria ventricular valves and semi lunar
valves. The fourth heart sound starts approximately (0.12 to 0.18) s after the onset of the P
wave. The sound last for (0.03 to 0.06)s. And the frequency is 10 to 50 Hz.
Extra cardiac sounds
These sounds occur in late systole or early diastole and are believed to be caused by
thickened pericardium which limits ventricular distensibility. Murmurs are sounds related to
non-laminar flow of blood in the heart and the great vessels. They are distinguished from the
basic heart sounds such that they have noisy character having long duration and with high
frequency components up to 1000 Hz.
OBSERVATION TABLE:
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bioengineering, SRM University
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Period:
Peak-peak value:
SL.NO:
HEART SOUNDS
AMPLITUDE
1.First heart sound
.
2.Second heart sound
PROCEDURE
1. Switch on the main power supply.
2. Connect the transducer and microphone.
3. The heart beat is sensed by keeping the sensor on the chest position.
4. Press the acquire button in DSO, when a proper signal is formed.
5. Press the stop button to freeze the signal.
6. Finally measure the peak to peak voltage and time period by using the measure button.
RESULT:
Thus by using a Phonocardiograph, different heart sounds have been identified, displayed and
recorded.
Ex. No 12 Biotelemetry
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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AIM:
To understand the transmission and reception of biological signal using a telemetry system
EQUIPMENTS REQUIRED:
ECG Amplifier
Low Pass Filter – 2 Nos.
FM Modulator
FM Transmitter
FM Receiver
FM Demodulator
Charger
Battery – 2 Nos.
Electrodes
THEORY:
Telemetry is a system of sending data, usually measurements, over a distance. Telemetric data
may be physical, environmental or biological. Telemetry is typically used to gather data from
distant, inaccessible locations, or when data collection would be difficult or dangerous for a
variety of reasons. In telemetry, specialized instruments carry out measurements of physical
quantities, and store or transmit the resulting signal, often after some initial signal processing or
conversion. Biotelemetry is the electrical measuring, transmitting, and recording of qualities,
properties, and actions of organisms and substances, usually by means of radio transmissions
from a remote site. There are single channel and multi channel telemetry systems. For a single
channel system, a miniature battery operated radio transmitter is connected to the electrodes of
the subject. This transmitter broadcasts the biopotential over a limited range to a remotely
located receiver, which detects the radio signals and recovers the signal for further processing. In
this situation there is a negligible connection or stray capacitance between the electrode circuit
and rest of the system. The receiving system can even be located in a room separate from the
subject.
BLOCK DIAGRAM:
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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BLOCK DIAGRAM DESCRIPTION:
ECG Amplifier
ECG has amplitude of only about 1 mV, so to detect it an amplifier is required. The ECG
amplifier used here has a Gain of 1000 and CMRR of more than 80dB.
Low Pass Filter
A low-pass filter allows low-frequency signals but attenuates (reduces the amplitude of) signals
with frequencies higher than the cutoff frequency. When the ECG is amplified, the noise is
amplified too, and often swamps the ECG signal. The noise is usually of a higher frequency than
the ECG. So the noise can be reduced by low-pass filtering.
FM Modulator
Modulation is used to embed a message (voice, image, data, etc.) on to a carrier wave for
transmission. A bandlimited range of frequencies that comprise the message (baseband) is
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translated to a higher range of frequencies. The bandlimited message is preserved, i.e. every
frequency in that message is scaled by a constant value. Here the incoming ECG signal is
modulated at around 110MHz. The modulated ECG signal is given to the FM Transmitter.
FM Transmitter
FM Transmitter sends a signal (typically 4-20mA) from a process location to a central location
for control and monitoring. Here FM transmitter transmits the modulated ECG signal.
FM Receiver
A receiver receives its input through an antenna. It receives the modulated signal from the
transmitter. The receiver then passes on the information to the FM Demodulator where the ECG
signal is demodulated to obtain the original ECG signal.
FM Demodulator
Demodulation, in radio is the technique of separating a transmitted audio frequency signal from
its modulated radio carrier wave. Here the modulated ECG signal is demodulated at a frequency
of around 100Hz and the original ECG signal is recovered.
PROCEDURE:
Connect the modules as per the block diagram.
Switch ON the battery.
Connect the ring electrodes to the subject.
View the transmitted signal on the DSO.
The various outputs from each of the modules can be viewed on the DSO by connecting the
output banana pin to the desired module.
RESULT:
Thus we understand the transmission and reception of biological signal using a telemetry system.
Ex. No 13 Pacemaker Module
AIM:
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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To understand the working of an external pacemaker and the various modules included in it.
EQUIPMENTS REQUIRED:
a) Oscillator
b) Refra Generator –2 Nos.
c) Pulse width control
d) Amplitude Control
e) Paced output
f) Synch Generator
g) QRS Detector
h) QRS Filter
i) ECG Amp Pacemaker
j) Patient Simulator
k) Electrodes
l) Charger
m) Battery
THEORY:
A pacemaker is an electronic device equipped with a battery, electronic circuits and memory that
generates electronic signals (pacing pulses), which are carried along insulated wires (leads) to the
heart to make the muscle beat at a normal rhythm. Bradycardia, a heartbeat that slows to an
unhealthy rate, is the most frequent reason for a pacemaker. There are three basic types of
temporary or permanent pacemakers, and each may work on demand, constantly or according to
the heart's activity. Pacemakers are also of internal and external type. Internal pacemakers are
mostly used for permanent heart damages are surgically implanted beneath the skin near the
chest or abdomen with its output leads connected directly to the heart muscle. The external
pacemakers are mostly used for temporary heart irregularities and are placed outside the body in
the form of a wrist watch or in the pocket, from which one wire will go into the heart through the
vein. Pacemakers may also be of single-, dual-, or triple chambered.
Demand Pacemakers
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When the heart's rate is too slow or it misses a beat, demand pacemakers, which monitor the
heart's activity, will send an electrical pulse to set the heart back to a more normal rhythm.
Fixed-rate Pacemakers
Fixed-rate pacemakers discharge steadily, regardless of the heart's natural electrical activity.
Rate-responsive Pacemakers
Rate-responsive pacemakers have sensors that adjust automatically to changes in your physical
activity. They are designed to raise or lower the heart rate to meet the body's needs.
Here we consider demand pacers having circuitry that analyze the ECG (as detected by the
pacer's electrodes). If a QRS is detected, the internal clock is reset thereby delaying the time until
when the next pulse is due (i.e. the escape cycle length). The escape interval (the time between
the last intrinsic beat and the paced beat) is equivalent to the rate at which the pacemaker is set to
activate. Once the pacemaker begins pacing, it will not stop until the intrinsic heart rate climbs
above the paced rate.
BLOCK DIAGRAM:
BLOCK DESCRIPTION:
Oscillator
An oscillator produces a repetitive electronic signal, often a sine wave or a square wave. The
oscillator synchronises with the synch generator. If an R wave is detected the oscillator circuit is
reset. In the absence of R wave, the oscillator circuit starts and delivers pulses at a paced rate till
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the heart rate climbs above the paced rate. The output voltage is 5V and a 10msec pulse. the
oscillator has rate control knob on the top panel.
Refractory Generator
The refractory generator is a non-retrigerrable monostable multivibrator which generates a
250ms delay following an output pulse or a sensed R-wave during which the amplifier in the
sensing circuit will not respond to outside signals. The input is a pulse of 0-5V (Min 1msec) and
output is pulse of 0-5V (250msec).
Pulse Width Control
The pulse width circuit is a basic RC network which determines the duration of the pulse
delivered to the heart. The pulse width control has a range of 0.1- 2.1 msec and output of 5V.
Amplitude Control
The output of the pulse width control is given to the amplitude control which controls the
amplitude of the delivered pulses.
Paced output
The paced output delivers the pulse to the heart, the duration and amplitude being controlled by
the pulse width control and amplitude control. The output also goes to the ECG amplifier as a
feedback signal.
ECG Amp. Pacemaker
The input to the ECG amplifier is from the Paced output which gives ECG signal as the feedback
and it is amplified here.
QRS Filter
The Demand type pacemaker works on the presence or absence of R wave hence a QRS filter is
used to selectively filter the QRS wave. The QRS Filter used here is a Bandpass Filter having
limits from 22Hz to 45Hz with a gain of 10.
QRS Detector
With the presence of an R wave, the QRS detector will generate a pulse. The input voltage is 1V
Pk –Pk and output voltage is 5V. It has a frequency range of 15-30Hz.
Synch Generator
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The Synch Generator synchronises with the QRS Detector and in presence of an R wave it resets
the oscillator circuit. In the absence of R wave it allows the oscillator to deliver pulses at its
preset rate.
Patient Simulator
The Patient Simulator simulates the abnormal heart condition- Bradycardia, Tachycardia and AV
Block.
Front Panel
a) It has 3 buttons to simulate any of the three conditions mentioned above.
b) A control knob to limit the rate of simulating heart conditions.
c) Control the threshold of the simulating conditions.
Top Panel
The top panel of the Simulator has the sketch of the heart. Red and Yellow LEDs arranged in
various regions of the heart. The flashing of the Red LEDs indicates the simulated abnormal
heart condition. Once the Green LED flashes it signifies the pacemaker has taken over. Output
pin connectivity to the DSO to view the paced output.
Back Panel
Feedback to the paced output through banana pins.
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bioengineering, SRM University
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PROCEDURE:
1. Connect the modules as per the block diagram.
2. Select one of the abnormal conditions in the Pacemaker Simulator and keep holding the
button for simulating the condition.
3. The Paced output leads detect this abnormality and the output is given as a feedback to
the ECG Amplifier.
4. As a normal QRS wave is not detected, the Oscillator is now triggered and the Pacemaker
takes over and Green LEDs flash.
5. Once the abnormal condition is removed the Paced output leads detect this change, the
oscillator is reset and the Pacemaker stops functioning.
RESULT:
Biomedical Instrumentation Lab Manual Biomedical Engineering Department, School of
bioengineering, SRM University
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Hence the working of a Pacemaker along with its various modules is studied.
Ex.No 14 ECG Heart rate alarm system with HRV
AIM:
To understand the various modules of an ECG heart rate alarm system with heart rate variability.
EQUIPMENTS REQUIRED:
a) ECG Amplifier
b) QRS Filter
c) QRS Detector
d) Refra Generator
e) Synch Generator
f) F to V Converter
g) High Alarm
h) Low Alarm
i) DVM
j) HRV
k) Audio Buzzer
l) Battery
m) Charger
n) Electrodes
THEORY:
Heart rate is the number of heartbeats per unit time - typically expressed as beats per minute
(bpm) .The measurement of heart rate is used to assist in the diagnosis and tracking of medical
conditions. The R wave to R wave interval (RR interval) is the inverse of the heart rate.
Normally, heart rate varies depending on the person's age and activity. The term "arrhythmia”
refers to abnormally fast or slow heart rates and to irregular heart rhythms. Arrhythmias are
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usually diagnosed with an electrocardiogram (ECG). A heart rate that's faster than normal is
called tachycardia. Tachycardia may reduce the heart's pumping ability and may require
treatment. Sometimes tachycardia is due to an abnormality of the heart's electrical circuits, while
other times it may be due to abnormally high adrenaline levels as seen, for example, after
surgery. A heart rate that's slower than normal is called bradycardia. Bradycardia may be
associated with certain congenital heart defects or may develop by itself before birth or after
heart surgery. In some more serious cases if the heart rate is very slow, an artificial pacemaker
may be needed. Heart rate variability (HRV) is a physiological phenomenon where the time
interval between heart beat varies. HRV analysis is based on measuring variability in heart rate;
specifically, variability in intervals between R waves - “RR intervals”. These RR intervals are
then analyzed by spectral or some other form of mathematical analysis (e.g., chaos, wavelet
theories).
BLOCK DIAGRAM:
BLOCK DIAGRAM DESCRIPTION:
ECG Amplifier
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bioengineering, SRM University
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ECG has amplitude of only about 1 mV, so to detect it an amplifier is needed. The ECG
amplifier used here has a Gain of 1000 and CMRR of more than 80dB.
QRS Filter
Heart rate is the number of heartbeats per unit time - typically expressed as beats per minute
(bpm). The R wave to R wave interval (RR interval) is the inverse of the heart rate. Hence a QRS
filter is used to selectively filter the QRS wave. The QRS filter used here is a Bandpass Filter
having
limits from 22Hz to 45Hz with a gain of 10.
QRS Detector
With the presence of an R wave, the QRS detector will generate a pulse. The input voltage is 1V
Pk –Pk and output voltage is 5V. It has a frequency range of 15-30Hz.
Refractory Generator
The refractory generator is a non-retrigerrable monostable mutivibrator which generates a
250msec delay following an output pulse or a sensed R-wave during which the amplifier in the
sensing circuit will not respond to outside signals. The input is a pulse of 0-5V (min 1msec) and
output is pulse of 0-5V (250msec).
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Synch Generator
The synch generator generates a synchronous pulse with the incoming wave. The input is a pulse
of 0-5V (< 200msec) and output is pulse of 0-5V (100msec).
HRV Module
It is the analysis of variations in the instantaneous heart rate time series using the beat to beat RR
intervals is known as heart rate variability analysis. These RR intervals are then analyzed by
spectral or some other form of mathematical analysis (e.g., chaos, wavelet theories). Such
mathematical analysis generates multiple parameters; typically 20-30. HRV analysis has been
shown to provide an assessment of cardio vascular diseases.
F-V Converter
The output of synch generator is frequency hence it is converted into voltage for detection of an
increase or decrease of the heart rate. The input pulse width is of 100msec and output voltage is
1V/100 pulse per minute.
High Alarm & Low Alarm
The modules high alarm and low alarm are calibrated at a certain rate. These are analog
comparators which compare the incoming signal to the fixed rate. The high alarm and low alarm
modules are calibrated using DVM at a fixed rate of 90 pulses/min and 60 pulses/min
respectively. In case of the value being more than/less than the fixed rate the high alarm/low
alarm triggers the audio buzzer. The input and output for High Alarm is 0-2.5V DC and 0-5V
Pulse (100msec) respectively. The input and output for Low Alarm is 0-2.5V DC and 0-5V Pulse
(100msec) respectively
DVM
The output of the High Alarm and Low Alarm is given to the DVM which gives the numerical
display of the voltage.
Audio Buzzer
The audio buzzer generates an audio beep when the heart rate increases or decreases beyond the
specified limits. The frequency of buzzer is 1 kHz and minimum input voltage is 5V.
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bioengineering, SRM University
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PROCEDURE:
1. Connect the modules as per the block diagram.
2. Connect the electrodes to the subject.
3. Switch ON the battery.
4. Observe the heart rate on the DVM.
5. If the heart rate deviates from the normal range the audio buzzer generates an audio beep.
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bioengineering, SRM University
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RESULT:
Thus we understand the various modules of an ECG heart rate alarm system with heart rate
variability.
Ex. No 15 EMG Biofeedback with NCV
AIM:
To understand the EMG system and also calculate the Nerve Conduction Velocity
I) a) EMG BIOFEEDBACK:
EQUIPMENTS REQUIRED:
a) EMG Amplifier
b) High Pass Filter
c) General Amplifier
d) Audio Amplifier
e) Level Indicator Linear
f) Electrodes
g) Battery
h) Charger
THEORY
Electromyography (EMG) is a test of a muscle’s electrical activity. It is used to test how a
muscle responds to signals from the nerves responsible for muscle movement, called motor
nerves. An EMG may also include a test of how fast the motor nerve conducts impulses. This is
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called a nerve conduction study (NCS) or nerve conduction velocity (NCV) test. Nerve
Conduction Velocity (NCV) measures the speed of conduction of impulses through a nerve. The
impulses being measured are artificially supplied by a stimulating electrode placed on the skin
over the nerve. Electrical activity in the nerve being stimulated is measured by recording
electrodes placed on the skin at various distances from the stimulating electrode. The distance
between the stimulating and recording electrodes and the time taken for an electrical impulse to
travel between the electrodes are used to calculate the nerve conduction velocity. Nerve
conduction tests have two parts – testing motor and sensory nerve testing. Nerve conduction
velocity studies are performed to evaluate and document a variety of sensory and motor
neuropathological conditions in patients with a suspected diagnosis of nerve dysfunction. Nerve
dysfunction can be manifested in decreased signal amplitude, slowed conduction velocity or
increased latency. Proximal and distal nerve segments may be tested separately to help identify
and localize the cause of the patient’s condition. Additional tests are sometimes used to evaluate
the results of treatment. Although the stimulation of nerves is similar with all NCV studies, the
characteristics of motor, sensory, and mixed NCS are different.
• Motor NCV studies are performed by applying electrical stimulation at various points
along the course of a motor nerve while recording the electrical response from
appropriate muscle. Response parameters include amplitude, latency, configuration, and
motor conduction velocity.
•
Sensory NCV studies are performed by applying electrical stimulation near a nerve and
recording the response from a distant site along the nerve. Response parameters include
amplitude, latency, configuration, and sensory conduction velocity.
BLOCK DIAGRAM:
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bioengineering, SRM University
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BLOCK DIAGRAM DESCRIPTION:
EMG Amplifier
The amplitude of the EMG signal depends upon the type and placement of electrodes used and
the degree of muscular exertion. Generally EMG signals range from 0.1 to 0.5mV which is a
weak signal hence it has to be amplified. This amplification is done by the EMG amplifier. Here
the gain of the EMG amplifier is 1000 and the output is1 V pk to pk per mV of input.
High Pass Filter
A high-pass filter, allows high frequencies well but attenuates frequencies lower than the filter's
cutoff frequency. The actual amount of attenuation for each frequency is a design parameter of
the filter. It is sometimes called a low-cut filter. Here the HPF has a cut off frequency of 70Hz
and a Minimum input voltage 1V Pk to Pk
Audio Amplifier
Audio amplifier amplifies low power audio signals to a required level. Audio amplifier used in
this application has a frequency range of 0-10KHz.
Level Indicator Linear
The level indicator displays the level of contraction of the muscle.
PROCEDURE:
1. Connect the modules as per the block diagram.
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bioengineering, SRM University
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2. Switch ‘ON’ the battery
3. Connect the subject to EMG amplifier through Ring electrodes.
4. Observe the output in the level indicator.
I) b) EMG NERVE CONDUCTION VELOCITY
EQUIPMENTS REQUIRED:
a) Monostable multivibrator.
b) Amplitude control
c) High voltage generator
d) EMG amplifier
e) High pass filter
f) Charger
g) Battery
BLOCK DIAGRAM:
BLOCK DIAGRAM DESCRIPTION:
Monostable multivibrator
A monostable multivibrator is an electronic circuit used to implement a variety of simple twostate systems such as oscillators, timers and flip-flops. In the monostable multivibrator one of the
states is stable, but if the other is not then the circuit will flip into the unstable state for a
determined period, but will eventually return to the stable state. Such a circuit is useful for
creating a timing period of fixed duration in response to some external event. This circuit is also
known as a one shot multivibrator.
Amplitude control
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The amplitude control controls the amplitude of the triggering pulse from the monostable
mutivibrator.
High voltage generator
For the calculation of nerve conduction velocity an external high volt stimulus is required which
is provided by the high voltage generator that produces an output voltage of 100V.
EMG Amplifier
The amplitude of the EMG signal depends upon the type and placement of electrodes used and
the degree of muscular exertion. Generally EMG signals range from 0.1 to 0.5mV which is a
week signal hence it has to be amplified. This amplification is done by the EMG amplifier. Here
the gain of the EMG amplifier is 1000 and the output is1 V peak to peak per mV of input.
High Pass Filter
A high-pass filter, or HPF, allows high frequencies well but attenuates frequencies lower than the
filter's cutoff frequency. The actual amount of attenuation for each frequency is a design
parameter of the filter. It is sometimes called a low-cut filter or bass-cut filter. Here the HPF has
a cut off Frequency 70Hz and a Minimum input voltage 1V Pk to Pk.
PROCEDURE:
1.
2.
3.
4.
Connect the modules as per the block diagram.
Connect the ring electrodes to the subject.
Give the stimulus using the electrode of the high voltage generator to the subject’s elbow
The settings for the DSO are
Trigger: External
Edge: Rising Edge
Mode: Normal Mode
5. Press trigger switch and observe the waveform on the DSO.
6. Calculate nerve conduction velocity by measuring distance between stimulator electrodes
and amplifier electrode and measuring time from oscilloscope reading.
Nerve conduction velocity = distance /time.
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RESULT:
Hence the working of EMG Biofeedback System and calculation of Nerve Conduction Velocity
is understood and performed.
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bioengineering, SRM University
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