EC E25 MEDICAL ELECTRONICS

HANDLED BY
K.ALAMELU
AP/ECE
IV ECE A SEC
 EC E25 MEDICAL ELECTRONICS
• UNIT I
ELECTRO-PHYSIOLOGY AND BIO-POTENTIAL RECORDING
• UNIT II
BIO-CHEMICAL AND NON ELECTRICAL PARAMETER
MEASUREMENT
• UNIT III
ASSIST DEVICES
• UNIT IV
PHYSICAL MEDICINE AND BIOTELEMETRY
• UNIT V
RECENT TRENDS IN MEDICAL INSTRUMENTATION
 EC E25 MEDICAL ELECTRONICS

OBJECTIVE:
– To gain knowledge about the various electrical and non-
electrical physiological parameters and study the
methods of recording together with transmission
methods of these parameters.
– To study about the various assist devices used in the
hospitals and gain knowledge about equipment used for
physical medicine
– To understand the various recently developed diagnostic
and therapeutic techniques.
 UNIT I
ELECTRO-PHYSIOLOGY AND BIO-POTENTIAL RECORDING

Electrophysiology:
• It is a branch of physiology that related to flow
of ion current.
• It is a electrical activity of your heart.
• It is used to diagnose abnormal heart beat.
 UNIT I
ELECTRO-PHYSIOLOGY AND BIO-POTENTIAL RECORDING

The Origin of bio potentials:

• Biopotentials are electrical signals (voltages) that
are generated by physiological processes
occurring within the body.
• Biopotentials are produced by the
electrochemical activity of a type of cell, called an
excitable cell.
• Excitable cells are found in the nervous, muscular
and glandular systems in the body.
 The Origin of bio potentials:

• An electric potential that is measured

between points in living cells, tissues, and
organisms, and which accompanies all
biochemical processes.
• It describes the transfer of information
between and within cells.
 Basics
• Cell : Is the basic living unit of the cell
• Cell  nuclear membrane Nucleoplasm  nucleus
(cell core)
• Cytoplasam is separated from the surrounding fluid by
the cell membrane.
• Fluid  Water is the principle fluid (electrolyte,
proteins, lipids and carbohydrates).
• Electrolyte present in the cell are:
 Mg, K,P, bi carbonate (large quantities)  Ca, Cl, Na
(small quantities)
 Resting (Membrane) Potential(RMP)

• It is the electrical potential of a neuron.

• A resting (non-signaling) neuron has a voltage
across its membrane called the resting
membrane potential, or simply the resting
potential.
• The resting membrane potential of a cell is
defined as the electrical potential difference
across the plasma membrane when that cell is
in a non-excited state.
• Imagine taking two electrodes and placing one on the outside
and the other on the inside of the plasma membrane of a
living cell.
• If you did this, you would measure an electrical potential
difference, or voltage, between the electrodes. This electrical
potential difference is called the membrane potential.
• The resting membrane potential of a neuron is about
-70 mV (mV=millivolt) - this means that the inside of the
neuron is 70 mV less than the outside.(range: -30 mV- -90 mV)
• At rest, there are relatively more sodium ions outside the
neuron and more potassium ions inside that neuron.
 Resting (Membrane) Potential(RMP)

• RMP is a product of the distribution of

charged particles (ions).
• There are numerous numbers of ions in the
cells, positively charged ions called cations
(e.g., Na+, K+, Mg2+, Ca2+) and negatively
charged ions called anions (e.g., Cl- and
proteins that act as anions).
• Because there is a potential difference across
the cell membrane, the membrane is said to
be polarized.
• If the membrane potential becomes more
positive than it is at the resting potential, the
membrane is said to be depolarized.
• If the membrane potential becomes more
negative than it is at the resting potential, the
membrane is said to be hyperpolarized.
Resting (Membrane) Potential(RMP)
 Action potential

• An action potential is a rapid rise and

subsequent fall in voltage or membrane
potential across a cellular membrane with a
characteristic pattern.
• Sufficient current is required to initiate a
voltage response in a cell membrane; if the
current is insufficient to depolarize the
membrane to the threshold level, an action
potential will not fire.
• The maximum value of action potential is
generally 30 mV.
• When the depolarization reaches about -55
mV a neuron will fire an action potential. This
is the threshold.
• Neurons send messages electrochemically.
This means that chemicals produce electrical
signals.
 Propagation of Action Potential
• The important ions in the nervous system are
sodium and potassium (both have 1 positive
charge, +), calcium (has 2 positive charges, ++) and
chloride (has a negative charge, -).
• As sodium ions are more on the outside, and the
inside of the neuron is negative relative to the
outside, sodium ions rush into the neuron.
• When the potassium channel opens, potassium
rushes out of the cell, reversing the depolarization.
• A cell in the resting state is called polarized.
The process of changing from the resting state
to the action potential is called depolarization
and the process of returning back to the
resting state is called repolarization.
• During the process of repolarization, sodium
pump pushes three sodium ions quickly out of
the cell for every two potassium ions it puts
in.
• Following the generation of action potential, there is a
small gap within which the cell cannot respond to any
new stimulus and this period is called the absolute
refractory period which lasts for about 1ms.
• Beyond this point is the relative refractory period
when cells do respond but the stimulus needed is
much stronger and this may last for several
milliseconds.
• Measurement methods which are based on bio
potential are ECG, EEG, EMG, EOG, VCG and several
others.
 Bio Electrodes

• Bio electrodes function as an interface between biological structures and

electronic systems.
• Electrical activity within the biological structure is either sensed or stimulated.
• The electrical systems are either passively sensing(measuring ) or actively
stimulating(inducing) electrical potentials within the biological structure or
unit.
• Bioelectric potentials generated in our body are ionic potentials and it is
necessary to convert these ionic potentials into electronic potentials before
they can be measured by conventional methods.
• Devices that convert ionic potential into electronic potential are called
electrodes.
• A transducer that converts the body ionic current in the body into the
traditional electronic current flowing in the electrode is a Bio Electrode.
• Able to conduct small current across the interface between the
body and the electronic measuring circuit.
• Oxidation is dominant when the current flow is from electrode to
electrolyte, and reduction dominate when the current flow is in the
opposite.
• The net current that crosses the interface, passing from the
electrode to electrolyte consist of:
 Electrons moving in a direction opposite to that of current in the
electrode.
 Cations moving in the same direction.
 Anions moving in direction opposite to that of current in
electrolyte.
Bio potential electrodes
• Properties of Bio Electrodes:
• Good conductors.
• Low impedance.
• Should establish a good contact with the body and
not cause motion.
• Should not cause itching , swelling or discomfort to
the patient.
• Metal should not be toxic.
• Easy to clean.
Electrode - Skin Interface
 Electrode –Skin/Tissue Interface

• Interface between body and electronic measuring device.

• Conducts current across the interface.
• Ions carry current in the body.
• Electrodes are capable of changing ionic current into
electronic current.
• Termed as Electrode–Electrolyte or Electrode–Tissue
Interface.
Purpose of the Gel:
• Conducts electricity better than human body.
• More Flexible than the metal parts of the electrode.
 Electrode Types

• Surface Electrode
• Metal Plate
• Floating Electrodes
• Flexible Electrodes
 Microelectrodes
 Internal Electrode
 Needle Electrode
 Electrode Types
Surface:
• Primarily used in ECG, EEG and EMG
• With conductive path between metal and skin being
electrolyte paste or jelly.
• Subtypes are:
• Metal
• Suction
• Floating
• Flexible
 Electrode Types
• Surface -Metal
• Metal plate electrode used for application to
limbs.
• Metal-disk electrode applied with surgical
tape.
• Disposable foam pad electrodes, often used
with electrocardiograph monitoring
apparatus.
Electrode Types
 Electrode Types
• Surface -Suction
• A metallic suction electrode is often used as a
precordial electrode on clinical
electrocardiographs.
• No need for strap or adhesive and can be used
frequently.
• Higher source impedance since the contact
area is small.
Electrode Types
Electrode Types
 Electrode Types
• Surface -Floating
• The recess in this electrode is formed from an
open foam disk, saturated with electrolyte gel
and placed over the metal electrode.
• Minimize motion artifact.
Electrode Types
 Electrode Types
• Surface-Flexible
• Used for new born infants
• Compatible with X-ray
Electrode Types
 Electrode Types
• Microelectrodes:
• It Is an electrode of very small size, used in electrophysiology
for either recording of neural signals or electrical stimulation
of nervous tissue.
• MEAs are Circuit less chips
• Sufficiently small to be placed into cell.
• Sufficiently strong to penetrate cell membranes.
• Tip diameter: 0.05–10 microns.
• CMOS based MEA(Micro electrode Array) have high spatial
and temporal resolution at excellent signal quality.
• Useful to access the behavior of electrogenic cells.
Electrode Types
 Electrode Types
Internal Electrode:

• For detecting fetal electrocardiogram during

labour, by means of intracutaneous needles.
• No electrolyte–skin interface.
• No electrolytic gel is required.
Electrode Types
 Needle Electrodes

• It penetrates the skin to record the potentials.

• It reduces interface impedance.
• Single wire inside the needle which acts as the
unipolar electrode measuring potential at the
point of contact.
• Types are concentric, bipolar and monopolar.
 Applications of Bio Electrodes

• Cardiac Monitoring
• Infant Cardiopulmonary Monitoring
• Sleep Encephalography
• Diagnostic Muscle Activity
• Cardiac Electrogram
• Eye Movement
Basic Components of Biomedical Systems

Measurand:
• Here measurand is a subject i.e., human being
Sensor (Transducer):
• Usually it is used to convert bio signal in to
electrical signal.
• Eg: ECG signal is converted into electrical
waveform.
Basic Components of Biomedical Systems

Signal Conditioning and Processing Unit:

• The Electrical output coming from the transducer
is amplified and modified by using the block of
signal conditioning equipment or processing
equipment.
• This block process the signal from the transducer
to the measurement block or display.
• Signal processing equipment make the signal
suitable to operate the recording or display unit.
Basic Components of Biomedical Systems

Measurement or Display or Recording unit:

• This unit includes graphic pen recorder to
record the data.
• The output can be displayed by using CRT
display or Digital storage oscilloscope (DSO).
• In EMG system, speaker is also connected in
this block.
Basic Components of Biomedical Systems

Control Feedback:
• The part of the display unit is used to control
the operation of this system.
• The block which is used for this purpose is
known as control feedback. The output of the
control feedback block is connected with
effector block to control the input applied to
the subject.
Basic Components of Biomedical Systems

Effector (Stimulas):
• The response to external stimulus is necessary
in biomedical system.
• Eg: Visual(flash of light), Tactile(sensitive to
touch), Auditory (sense of hearing).
 BIO AMPLIFIER
• Why is Bio Amplifier Required?
• Generally, biological/bioelectric signals have low
amplitude and low frequency.
• Therefore, to increase the amplitude level of bio-
signals amplifiers are designed.
• The outputs from these amplifiers are used for further
analysis and they appear as ECG, EMG, or any
bioelectric waveforms.
• Such amplifiers are defined as Bio Amplifiers or
Biomedical Amplifiers.
Basic Requirements for Biological Amplifiers

• The biological amplifier should have a high input

impedance value. The range of value lies between 2 MΩ
and 10 MΩ depending on the applications. Higher
impedance value reduces distortion of the signal.
• Every bio-amplifier should consist of isolation and
protection circuits, to prevent the patients from electrical
shocks.
• Since the output of a bioelectric signal is in millivolts or
microvolt range, the voltage gain value of the amplifier
should be higher than 100dB.
• Throughout the entire bandwidth range, a constant gain
should be maintained.
Basic Requirements for Biological Amplifiers

• A bio-amplifier should have a small output

impedance.
• A good bio-amplifier should be free from drift
and noise.
• Common Mode Rejection Ratio (CMRR) value of
amplifier should be greater than 80dB to reduce
the interference from common mode signal.
• The gain of the bio-amplifier should be calibrated
for each measurement.
 Types of Bio Amplifiers

• Differential Amplifier
• Operational Amplifier
• Instrumentation Amplifier
• Chopper Amplifier
• Isolation Amplifier
 Differential Amplifier

• Differential Amplifier is a device which is used

to amplify the difference between the
voltages applied at its inputs. Such circuits can
be of two types viz.,
• Differential amplifiers built using transistors,
either Bipolar Junction Transistors (BJTs)
or Field Effect Transistors (FETs)
• Differential amplifiers built using Op-Amps.
Differential Amplifier
 Differential Amplifier
• V1 and V2 represent the voltages applied at its
inverting and non-inverting input terminals (can be
taken in any order) and Ad refers to its differential
gain.
• As per this equation, the output of the Op Amp must
be zero when the voltages applied at its terminals are
equal to each other.

• However practically it will not be so as the gain will

not be same for both of the inputs.
Operational Amplifier

• The term Op Amp is used to

denote an amplifier which can
be configured to perform various
operations like amplification,
subtraction, differentiation,
addition, integration etc.
• An example is the very popular
IC 741.
 Ideal Op-Amp Characteristics

• Infinite voltage gain (So that maximum output is

obtained)
• Infinite input resistance (Due to this almost any source
can drive it)
• Zero output resistance (So that there is no change in
output due to change in load current)
• Infinite bandwidth
• Zero noise
• Zero power supply rejection ratio (PSSR = 0)
• Infinite common mode rejec on ra o (CMMR = ∞)
Instrumentation Amplifier
• In biomedical applications, high gain and the high input
impedance are attained with an instrumentation amplifier.
• Usually, a 3-amplifier setup forms the instrumentation
amplifier circuit.
• The output from the transducer is given as input to the
instrumentation amplifier.
• Before the signal goes to the next stage, a special amplifier is
required with high CMRR, high input impedance and to avoid
loading effects.
• Such a special amplifier is an instrumentation amplifier, which
does all the required process.
 Isolation Amplifier

• Isolation amplifiers are known as Pre-amplifier

isolation circuits.
• An isolation amplifier increases the input
impedance of a patient monitoring system.
• It also helps to isolate the patient from the
device.
• Using the isolation amplifier prevents accidental
internal cardiac shock.
• It provides up to 1012 Ω insulation between the
patient and the power line in the hospital.
Isolation Amplifier
 Isolation Amplifier
• The electrical signals are obtained with electrodes.
• The signals received goes to the amplifier block,
where signals amplification occurs.
• After amplification, the signal enters the
modulation block.
• When either it goes to the isolation barrier, optical
cable or transformer can be used.
• If in case of optical cable, modulator output travels
to LED.
 Isolation Amplifier
• The LED converts electrical signals into light energy.
• If the transformer acts an isolation barrier, modulator
output connects the primary winding of the
transformer.
• Energy from primary transfers to the secondary
winding based on the mutual induction principle.
• At the next stage, secondary output enters the
demodulation block.
• Finally, the amplified demodulated signal is
obtained.
ECG Isolation Amplifier
• During ECG measurement, signals generated from all leads are
sent to the low pass filter.
• This filter is named as Electro surgery filters because it
decreases the interference between electro surgery and radio
frequency.
• Next block is the high voltage and overvoltage protection that
can withstand large voltage during defibrillation.
• Proceeding further, it goes to Lead Selector Switch block,
which selects the required configuration.
• Lead selection output goes to the DC amplifier.
• We have a transformer, whose primary winding is
connected to the oscillator and secondary to rectifier
and filter.
• ECG signal is modulated with the Synchronous
modulator.
• The second transformer delivers the output from the
synchronous modulator to the synchronous
demodulator.
• The output from the demodulator is fed as input to
the power amplifier.
Electro surgery

• Electro surgery is a term

used to describe multiple
modalities that use
electricity to cause
thermal destruction of
tissue through
dehydration, coagulation,
or vaporization.
Chopper Amplifier for Biomedical Instrumentation

• When recording bio potentials noise and drift are the two
problems encountered.
• Noise is due to the recording device and by the patient when
they move.
• Drift is a shift in baseline created due to various thermal effects.
• A DC amplifier has a shift or sudden peak in the output when the
input is zero.
• Therefore, a chopper amplifier solves the problems of drift in
DC amplifiers.
• The name Chop means to sample the data.
• The amplifier circuit samples the analog signal.
• So it is known as chopper amplifier.
Chopper amplifier
 Recording Systems
• ECG (Electro-Cardio-Gram ) (record the electrical activity of
the Heart)

• EEG (Electro-Encephalo-Gram) (record the electrical activity of

the Brain)

• EMG (Electro-Myo-Graphy) ( record the electrical activity of

the muscles).

• PCG (Phono-Cardio-Gram) (Graphically record the Heart

Sound )
 ECG (Electrocardiogram)
• An electrocardiogram
records the electrical
signals in your heart.
• It's a common and
painless test used to
quickly detect heart
problems and monitor
your heart's health.
 Why it's done

• An electrocardiogram is a painless, noninvasive way to help

diagnose many common heart problems in people of all ages.
 Your doctor may use an electrocardiogram to determine or
detect:
• Abnormal heart rhythm (arrhythmias)
• If blocked or narrowed arteries in your heart (coronary artery
disease) are causing chest pain or a heart attack.
• Whether you have had a previous heart attack.
• How well certain heart disease treatments, such as a
pacemaker, are working.
 When u need ECG??

• Chest pain
• Dizziness (your surroundings are spinning or moving),
lightheadedness or confusion (include standing up too
quickly, heat exposure, dehydration, extreme physical
exertion or medication side effects)
• Heart palpitations (Palpitations make you feel like
your heart is beating too hard or too fast, skipping a
beat)
• Rapid pulse
• Shortness of breath
• Weakness, fatigue or a decline in ability to exercise
Cross section heart
 Cross section heart
 Heart is divided into 4  Blood vessels:
chambers: • Arteries (carry
• Right atrium oxygenated blood away
• Right ventricle from the heart i.e., carry
• Left atrium pure blood from heart to
• Left ventricle other organs)
 3 layers: • Veins (impure blood
• Peri cardium (outer) returns to the heart)
• Endo cardium(inner)
• Myo cardium (middle)
 Types of Circulation
• Pulmonary circulation moves blood between
the heart and the lungs. It transports
deoxygenated blood to the lungs to absorb
oxygen and release carbon dioxide. The
oxygenated blood then flows back to the heart.
• Systemic circulation moves blood between the
heart and the rest of the body. It sends
oxygenated blood out to cells and returns
deoxygenated blood to the heart.
 SA node
• SA node: The SA node (SA stands for sinoatrial) is
one of the major elements in the cardiac conduction
system, the system that controls the heart rate.
• The SA node is the heart's natural pacemaker.
• The SA node consists of a cluster of cells that are
situated in the upper part of the wall of the right
atrium (the right upper chamber of the heart). The
electrical impulses are generated there.
• The SA node is also called the sinus node.
 AV node
• The electrical signal generated by the SA node
moves from cell to cell down through the heart
until it reaches the atrioventricular node (AV
node), a cluster of cells situated in the center of
the heart between the atria and ventricles.
• The AV node serves as a gate that slows the
electrical current before the signal is permitted
to pass down through to the ventricles.
• It delays the spread of excitation of about 0.12s
ECG graph
 Parts of the ECG

P waves
• P waves represent atrial depolarisation.
• In healthy individuals, there should be a P
wave preceding each QRS complex.
PR interval
• The PR interval begins at the start of the P
wave and ends at the beginning of the Q wave.
• It represents the time taken for electrical activity
to move between the atria and ventricles.
 Parts of the ECG
QRS complex
• The QRS complex represents depolarisation of the ventricles.
• It appears as three closely related waves on the ECG (the Q, R
and S wave).
ST segment
• The ST segment starts at the end of the S wave and ends at
the beginning of the T wave.
• The ST segment is an isoelectric line that represents the
time between depolarisation and repolarisation of
the ventricles (i.e. ventricular contraction).
 Parts of the ECG
T wave
• The T wave represents ventricular repolarisation.
• It appears as a small wave after the QRS complex.
RR interval
• The RR interval begins at the peak of one R
wave and ends at the peak of the next R wave.
• It represents the time between two QRS complexes.
 Parts of the ECG
• QT interval
• The QT interval begins at the start of the QRS
complex and finishes at the end of the T wave.
• It represents the time taken for
the ventricles to depolarise and
then repolarise.
 How to read ECG paper

• The paper which ECGs are recorded on

is standardized across most hospitals:
• Each small square represents 0.04 seconds
• Each large square on the paper represents 0.2
seconds
• 5 large squares = 1 second
• 300 large squares = 1 minute
How to read ECG paper
ECG LEAD SYSTEM
 TYPES OF LEAD SYSTEM
• The electrical signals from the heart are measured with surface
electrodes.
• The resulting electrode potential in the heart conducts to the
body surface.
• Standardized electrode positions are used to record the ECG.
• The three types of electrode systems are:

 Bipolar lead system (Standard lead system)

 Unipolar lead system (Augumented unipolar limb lead system)
 Chest lead system.
 Bipolar Limb leads – Standard
Lead I, Lead II and Lead III

• This lead system is also known

as Einthoven lead system.
• Two electrodes record the ECG
signal.
• As shown in figure from four
body locations of our body
namely :
• Right Arm(RA),
• Left Arm(LA),
• Right Leg(RL)
• and Left Leg(LL) potentials are
recorded.
 Bipolar Limb leads – Standard
Lead I, Lead II and Lead III

• Final output is the difference between the

electrical potential generated between these
two electrodes.
• Right leg is the ground reference electrode.
Lead I
• Voltage drop occurs from
left arm to right arm.
• Generated voltage is VI
Lead II
• Voltage drop occurs from
left leg to right arm.
• Generated voltage is VII.
Lead III
• Voltage drop occurs from
left leg to left arm.
• Generated voltage is VIII.
 Einthoven Triangle

• Einthoven triangle is the closed path formed

between right arm, left arm, left leg and right
arm.

• We can tell, by Kirchhoff’s law, the amplitude of

R wave along the lead III is equal to the
summation of amplitude of R wave along lead I
and lead II.
• LEAD III= LEAD I + LEAD II
Einthoven Triangle
Einthoven Triangle
 Augmented Unipolar Leads

• A person named Wilson introduced augmented unipolar limb lead system.

• In this system, ECG is recorded between single exploratory electrode and
central terminal.
• Central terminal relates to the center of the body. Two equal and large
resistors are used.
• Pair of limb electrodes is connected to the resistors.
• The center joint connection of this resistive network forms the central
terminal.
• The remaining portion of the limb electrode forms the exploratory
electrode.
• In this lead system, a very small increase in ECG voltage can be found.
• Three types of connections are used.
 • Two resistors are
Lead Avr
connected to left arm
and left leg.
• The middle point of the
resistor connection is
connected with negative
terminal.
• Right arm is connected
with the positive
terminal of the amplifier.
• Here also right leg acts
as a reference terminal.
 • Two resistors are
Lead aVF connected to right arm
and left arm.
• The middle point of the
resistor connection is
connected with negative
terminal.
• Left leg is connected with
the positive terminal of
the amplifier.
• Here also right leg acts as
a reference terminal.
 • Two resistors are connected
Lead aVL to right arm and left leg.
• The middle point of the
resistor connection is
connected with negative
terminal.
• Left arm is connected with
the positive terminal of the
amplifier.
• Right leg acts as a reference
terminal.
Chest Leads
Electrodes placed in chest
• V1 – Fourth intercostal space of right sternal margin,
V2 – Fourth intercostal space at left sternal margin,
V3 – Midpoint between V2 and V4,
V4 – Fifth intercostal space at mid – clavicular line,
V5 – Same as V4 position but on anterior auxiliary
line,
V6 – Same as V4 position but on mid auxiliary line.
ECG Recording Setup (Block Diagram and Waveform)
• Depolarization
• When electrical activity occurs, heart muscle fibers are
contracted and produces a movement. This condition is
referred as Depolarization.
• When blood is pumped around the body, it results in
contraction.
• When chambers are contracted, it is called systolic.
• Repolarisation
• The relaxation of heart muscles are called electrical
repolarisation. Relaxed heart chambers are called diastolic.
 Defibrillator Protection Circuit
• The one end of the electrode leads are connected along RA,
LA, chest and LL of the patient.
• The other end of electrode passes through defibrillator
protection circuit.
• The protection circuit has buffer amplifier and over-load
voltage protection circuit.
Lead Selection Logic
• This block helps to select the type of electrode lead system.
• We can choose either bipolar or augmented electrode system.
 Calibration Circuit:
• Calibration is a process that helps to eliminate errors in
the system.
• Here, any changes in the lead selection circuit results in
artefacts in the ECG output.
• Therefore, the calibration unit helps the technician to
correct the error in ECG output.
Pre Amplifier:
• An instrumentation amplifier and a differential amplifier
with high gain and high CMRR is used as pre amplifier.
• Power Amplifier
• The output unit is driven with power amplifier. After the signal is
amplified using pre-amplifier it goes to the power amplifier.
• The output unit is attached with a pen motor. A high electrical
power is required to initiate recording with pen recorder.
• Hence, a high power gain amplifiers are used as power
amplifier.
• Feedback Network
• Feedback network is used to provide damping to the pen motor.
 Output Display Unit
• Either a CRO or a pen chart recorder acts as
the output device.
• The paper Speed=25mm/s in US
manufacturing system
• The paper Speed=50 mm/s in European
manufacturing system
Amplitude and Duration
Analysis of ECG waveform
 PCG (Phono Cardiogram)

• The graphical record of heart sound is known

as Phono Cardiogram.
• Here Cardio means the Heart.
• The device which is used to measure heart
sound is known as phonocardiograph.
• Auscultation: The technique of listening
sound produced by organs and vessels of the
body is known as auscultation.
• In PCG, different types of heart sounds are
measured.
• These heart sounds are due to the vibrations set up
in the blood inside the heart by the sudden closure
of valves.
• In abnormal heart additional sounds are heard
between the normal heart sound.
• These additional sounds are known as murmurs.
• Murmers is generally caused by improper opening of
the valves or by regurgitation (A backward flowing).
CLASSIFICATION OF HEART SOUND
• It is divided into four types:

• Valve closure sound

• Ventricular filling sound
• Valve opening sound
• Extra cardiac sound
 1. Valve closure sound
• This sound occurs at the beginning of systole and at the beginning of
diastole.

2. Ventricular filling sound

• This sound is occurred at the time of filling of the ventricles,.

3. Valve opening sound

• This sound occurs at the time of opening of atrio- ventricular valves and
semi lunar valves.

4. Extra cardiac sound

• This sound occur in mid systole or late systole or early diastole
• Systole: The contraction of the heart muscle.
The systolic pressure is 120mm of Hg.

• Diastole: The relaxation of the heart muscle.

The diastolic pressure is 80 mm of Hg.
PCG RECORDING SYSTEM
 PCG RECORDING SYSTEM
• Microphone is used to convert heart sound
into the electrical signals.
• Certain positions are recommended to pick up
the heart sound by using microphone.
• The electrical signal picked up by the
microphone is amplified by the amplifier
block.
• The amplified output is given to filter block.
PCG RECORDING SYSTEM
• Here high pass filter is used.
• Its cut of frequency is 1 kHz.
• Here ECG electrode system
and ECG amplifiers are used
for reference for PCG.
• So ECG and PCG outputs are
connected to FM tape
recorder and output display
unit.
 PCG RECORDING SYSTEM
• TYPES OF MICROPHONES USED IN PCG

• 1. Air coupled microphone- Movement of chest is

transferred through the air cushion. It provides low
mechanical impedance to the chest.

• 2. Contact microphone – it is directly coupled to the chest

wall and provides high impedance, high sensitivity, and low
noise. Its light weight is also one of the advantageous factor.
• The first heart sound is developed during the opening of
aortic valve and during the closing of mitral valve
PCG RECORDING SYSTEM
 PCG RECORDING SYSTEM
• Frequency of first heart sound consists of 30 to 45 Hz.
• Second heart sound is usually higher in pitch than the first.
• Its frequency range is 50Hz to 70 Hz.
• Third heart sound is extremely weak vibrate sound is extremely weak vibration.
• Its frequency is below 600 Hz.

• Aortic stenos are murmur occurred when the blood is ejected from the left
ventricle through aortic valve due to resistance to ejection, the pressure in the left
ventricle increased.
• So turbulent blood flow occur.
• This turbulent blood impinging the aortic valve.
• So intense vibration is produced. It produces loud murmur.
• Mitral regurgitation murmur- In this murmur, blood
flows in backward direction through the mitral valve
during systole.
• Aortic regurgitation murmur – During diastole,
sound is heard. In diastole blood flows in
the backward direction from aorta to left ventricles
when valves are damaged, then this sound is heard.
• Mitral stenosis murmur – This murmur is produced
when blood is passed from left atrium to left
ventricle. This sound is very weak.
 ElectroEncephaloGram (EEG)
• Electroencephalography (EEG) is an
electrophysiological monitoring method to
record electrical activity of the brain.
• It is typically noninvasive, with the electrodes
placed along the scalp, although invasive
electrodes are sometimes used, as in
electrocorticography.
 Why is an EEG performed?
• An EEG is used to detect • Head Injury
problems in the electrical • Encephalitis (Inflammation Of
activity of the brain that may The Brain)
be associated with certain
• Brain Tumor
brain disorders.
• Encephalopathy
• The measurements given by
an EEG are used to confirm or (Disease that Causes Brain
rule out various conditions, Dysfunction)
including: • Memory Problems
• Sleep Disorders
• Stroke.
• Seizure Disorders (Such
As Epilepsy)
 Anatomy of the brain
• Cerebrum: is the largest part of the brain and is
composed of right and left hemispheres.
• It performs higher functions like interpreting
touch, vision and hearing, as well as speech,
reasoning, emotions, learning, and fine control
of movement.
• Cerebellum: is located under the cerebrum. Its
function is to coordinate muscle movements,
maintain posture, and balance.
• Brainstem: acts as a relay center connecting
the cerebrum and cerebellum to the spinal
cord.
• It performs many automatic functions such
as breathing, heart rate, body temperature,
wake and sleep cycles, digestion, sneezing,
coughing, vomiting, and swallowing.
Lobes of the brain
• The cerebral hemispheres have distinct
fissures, which divide the brain into lobes.
Each hemisphere has 4 lobes:
• frontal,
• temporal,
• parietal, and
• occipital
 Frontal lobe:
• Personality, behavior, emotions
• Judgment, planning, problem solving
• Speech: speaking and writing (Broca’s area)
• Body movement (motor strip)
• Intelligence, concentration, self awareness
 Parietal lobe:
• Interprets language, words
• Sense of touch, pain, temperature (sensory
strip)
• Interprets signals from vision, hearing, motor,
sensory and memory
• Spatial and visual perception
 Occipital lobe:
• Interprets vision (color, light, movement)
Temporal lobe:
• Understanding language (Wernicke’s area)
• Memory
• Hearing
• Sequencing and organization.
 Evoked Potential
• These are the Potentials developed in the
brain as the response to external stimuli like
Light, Sound, etc.,
• The external stimuli are detected by sense
organs that cause some changes in the
electrical activity of the Brain.
 10-20 ELECTRODE SYSTEMS
• International Federation of EEG society has
suggested 10 – 20 electrode placement system
for EEG recording.
• Silver / silver chloride electrodes are used as
surface electrodes in this setup.
• On the scalp, distances between two
electrodes are given as 10% and 20% of the
distance between specified points.
 10-20 ELECTRODE SYSTEMS
• Nasion and Inion are the two reference points
near the ear lobes of the human.
• Over the head, the distance between nasion
and inion are divided into 5 points.
• The nasion – inion distance via the vertex is
measured and three electrodes are placed as
1 in frontal, 1 in central and 1 in parietal.
• They are placed at a distance of 10%, 20%, 20%,
20%, 20% and 10% of this length.
• Now, similarly nasion – inion distance is
measured along the temporal lobes and five
electrode are placed as 2 in frontal, 2 in
temporal and 1 in occipital lobes respectively.
• They are also placed at a distance of 10%, 20%,
20%, 20%, 20% and 10% of this length on either
side.
• Lastly, on the peripheries of the circle
remaining six electrodes are fixed as 2 in
frontal, 2 in central and 2 in parietal.
• So, in the setup totally 19 electrode are placed
on the brain scalp and one electrode which
acts as reference is placed at the ear lobe.
• This is popularly known as 10 – 20 EEG
system.
 EEG RECORDING SETUP
• Here 21-electrode system is used.
• Electrodes are connected to 8-channel
selector.
• Output from 8-channel connector goes to the
differential amplifier bank.
• Differential amplifier is made of preamplifiers
that are used to reduce noise.
 EEG RECORDING SETUP
• 50 Hz noise is created due to A.C interference
that can be reduced using differential
amplifier.
• The output obtained from differential
amplifier is connected with signal processing
unit.
• After further processing, the display unit
displays the data.
 EEG RECORDING SETUP
• This system helps to record the potentials
generated from the sensory parts of the brain.
• To achieve this, output unit is connected with
audio stimulus, visual stimulus and touch
stimulus.
• It can also measure the time delay between
stimulus and response from brain.
 EEG RECORDING SETUP
• In addition, we have a filter bank consisting of
low pass filters, high pass filters and band pass
filters.
• They help to remove noise from the brain waves.
• For the output recording, we can use either pen
recorder or CRO.
• Three modes namely Unipolar, Average mode and
bipolar recording are used to measure EEG.
 Applications of EEG

• Epilepsy diagnosis. (வ ப் )
• Anesthetic level.
• Brain injury.
• Monitoring during surgery.
 Analysis of EEG waveform
1. Frequency range : > Active, busy thinking, • Usually associated
40 Hz active processing , with
• Name : Gamma waves active concentration, Deep meditation
arousal, and cognition. /relaxation, REM sleep
• Usually associated
with: 3. Frequency range: 7– 5.Frequency range: <
13 Hz 4 Hz
Higher mental activity,
including perception, • Name : Alpha waves • Name: Delta waves
problem solving, and • Usually associated • Usually associated
consciousness with with
2. Frequency range: Calm relaxed yet alert Deep dreamless sleep,
13–39 Hz state. loss of body awareness
• Name : Beta waves 4. Frequency range: 4–
• Usually associated 7 Hz
with • Name: Theta waves
 EMG (Electro Myograph)
EMG (ELECTRO MYOGRAPH):
• It is an instrument used for recording the
electrical activity of the muscles to determine
whether the muscle is contracting or not.

• Study of neuromuscular function is also

possible by using EMG.
 ELECTRODES USED FOR EMG
• Two types of electrodes:

• Surface electrodes- Usually this electrode is used

for EMG. But by using this electrode, it is not
possible to take the deeper potential.

• Needle electrodes – These are inserted into

tissue or closer to tissue to measure the electrical
activity of muscle.
 EMG RECORDING SYSTEM
• EMG potentials are taken from the tissue by using
electrodes.
• These EMG potentials are given to differential
amplifier.
• This is the high gain amplifier.
• Its frequency range is given as 10 Hz to 10 KHz.
• Bandwidth of EMG is large.
• CMRR (Common mode Rejection Ratio) of this
differential amplifier is 80 to 100 db.
• Input Impedance of this amplifier is 10 MΩ.
• Here there is no lead selector switch.
• Because only two electrodes are available. The
output of the differential amplifier is given to
loudspeaker system, tape recorder and CRO.
• Before giving the output of differential amplifier
to loudspeaker, it is given to power amplifier.
• Power amplifier amplifies the signal that is
received by loudspeaker.
• The amplified signal from the output of the
differential amplifier is displayed by using
CRO.
• Here storage oscilloscope is used.
• Output cab be displayed and the same can be
stored in the CRO.
• The signal from the differential amplifier is
recorded by using tape recorder.
• It is used for the future purpose.
 Applications of EMG:
• EMG is used in the field of:

• Electrophysiological testing.
• Clinical neurophysiology.
• Neurology.
• Psychiatry.
THANK YOU