Download UNIT –2 - E

NEHRU ARTS AND SCIENCE COLLEGE, COIMBATORE
DEPARTMENT OF ELECTRONICS & COMMUNICATION SYSTEMS
MEDICAL ELECTRONICS
Part A
Unit 1
1. The bio signal frequencies from various sections of the human body are in the 0 to
few
kHz.
2. The EEG signals are originated from the Glia cells
3. The Range of frequency and voltage related to EEG are 0.5 Hz to 100 Hz and 10
micro volts to 100 micro volts.
4. The bundle of muscle fibers in a muscle supplied by a single motor nerve fiber is
called a motor unit
5. The bio electric generator of heart is situated at SA node.
6. The most abundant negative ions in our body are chlorides.
7. Among the following electrodes which have high Z? Micro electrodes
8. In the case of ERG what types of electrodes used to pickup signals?Retinal
electrodes
9 .Loud speakers is also in the EMG recorder
10. Pressure transducer for measuring blood pressure is from strain gauge or
capacitive
Transducer
Unit 2
1. The hydrogen ion concentration of the blood is most easily determined with a glass
electrodes
2. To obtain good contact between the electrode and the skin the gap is filled with an
electrode paste containing electrolytes
3. The active transducer in the measurement of pressure is piezoelectric transducer.
4. The amplifier which has no drift is chopper amplifier
5. To reduce common mode interference during recording of bio signals one can use
differential amplifier
6. Resistively generated interference arises through incorrect grounding
7. For biomedical application the mostly used amplifier is differential amplifier
8. EMG deals with the study of muscular activity
9. Mingographs are connected with ECG
10. The heart sounds are recorded by phonocardiography.
Unit 3
1. The heart dipole field is measured by lead system called orthogonal lead system
2. Arrhythmia can be diagnosed by ECG
3. The T wave is produced during repolarisation of the ventricles
4. Bicycle ergometer is related with ECG
5. For faithful reproduction of QRS complex of ECG signal, an amplifier band
width should be 0.05-100 Hz
6. Artifacts are time varying half cell potentials
7. The resting potential of the inside of the neuron is about -70mV
8. EEG waves include frequency content ranging from less than 1 Hz to 50 Hz.
9. Recording of the peripheral nerves action potentials is called Electro
neurography
10. The conduction velocity in a motor nerve is normally 50 m/s
Unit 4
1. During myocardial infarction one can use pacemaker
2. Inflammation of the kidneys is called rephritis
3. In the case of defibrillator a double square pulse type is used to restart the
heart rhythm after the open heart surgery.
4. The common source of energy for pacemaker is the mercury battery.
5. In the case of stable total AV block a pacemaker is chosen with constant
frequency.
6. After the chest operation the patient feels difficult to breathe. Then the patient
is connected to a Ventilator
7. Two low a blood pressure is known as hypotension
8. The normal pH of the blood is 7.4
9. The obstruction of blood flow is known as stasis
10. Blood flow can be measured using the electromagnetic principles because
blood has a high electrical conductivity.
Unit 5
1. To avoid electrode polarization and bio potential artifacts electromagnetic blood
flowmeters are using a.c magnetic fields
2. Blood plasma is obtained by centrifuging blood that has been prevented from
coagulating
3. Fluoroscopic observation of cardiac catheterization is made by X-ray imaging
4. In Biotelemetry FDM refers to frequency division multiplexing
5. The radiocapsules are biotelemetry transmitter
6. The term bionics means a science concerned with the application of data about the
functioning of biological systems to the solution of engineering problems.
7. Let-go current of men increases with the log frequency
8. Microshocks may occur due to flow of few mA current across the cardiac muscles
9. Let-go current are higher for men than women
10.Ground fault oriented electric shocks can be avoided by using isolated power
supplies.
PART - B
UNIT –I
1. Explain cell and its structure
Cell Structure
The cell is considered to be the smallest structure in biology that has
all the properties of living things and an understanding of cells and the
basics of cell structure and function is critical to making sense out of
biology. All cells at their essence have at least three things in common:
 Cell Membrane :
All cells have a phospholipid
based cell
membrane. The cell membrane is selectively permeable in that it
allows some materials to pass into or out of the cell but not others.
 Cytoplasm :
Cells are filled with a complex collection of of
substances in a water based solution. This substance is called
cytoplasm. Across all cells there are a number of common features to
all cell cytoplasm. For example all cells have ribosome . Also, in all
cells the first steps in cellular respiration take place in the cytoplasm.
 DNA :
All cells contain DNA. In the simplest cells, the DNA is in
one loop more loop like structures free in the cytoplasm. In some cells
such as those making up our body the DNA is isolated from the
cytoplasm in a special structure called a nucleus.
2. Write about the transport of ions through cell
The cell is bound by an outer membranethat, in accord with the fluid
mosaic model, is comprised of a phospholipid lipid bilayer with proteins—
molecules that also act as receptor sites—interspersed within the phospholipid
bilayerThere are three principal mechanisms of outer cellular membrane transport
(i.e., means by which molecules can pass through the boundary cellular
membrane). The transport mechanisms are passive, or gradient diffusion,
facilitated diffusion, and active transport.
Diffusion is a process in which the random motions of molecules or
other particles result in a net movement from a region of high concentration to a
region of lower concentration. Thus, if the concentration of the diffusing
substance is very high at the source, and is diffusing in a direction where little or
none is found, the diffusion rate will be maximized..
Facilitated diffusion is the diffusion of a substance not moving against
a concentration gradient but which require the assistance of other molecules.
These are not considered to be energetic reactions Transmembrane proteins
establish pores through which ions and some small hydrophilic molecules are able
to pass by diffusion.
Active transport is movement of molecules across a cell membrane or
membrane
of a cell organelle, from a region of low concentration to a region of high
concentration. Since these molecules are being moved against a concentration
gradient, cellular energy is required for active transport.
3. Explain the purpose of electrode paste
The dry oputer skin of the body is highly non-conductive and will not
establish a good electrical contact with an el;ectrode. The skin should therefore be
washed throughly and rubbed briskly to remove some of the outer cells. This area
should then be coated with an electrically conductive paste called electrode paste that
should be worked in by further rubbing. The electrode is hgen applied to the prepared
site and held in place with a rubber strap. Thus the electrode paste decreases the
impedance of the contact and it also reduces the artifacts resulting from movement of
the electrode or patient. Generally the conductivity of the skin is directly proportional
to moisture on the skin. Even after the application of electrode paste, the contact
impedance decreases with he increase of frequency of the signal. Among alcohol,
electrode paste, saline solution and multipoint electrode, multipoint electrode has less
contact impedance about 4kiloohms and alcohol has greater contact impedance.
4. Describe Half-cell potential
Half-cell potential corresponds to an equilibrium, in term of electrical
current, between metal (iron of steels) dissolution and the associated reduction
reaction, which leads to the formation of ions hydroxyls (OH- , from oxygen gas). It
should be noted that a current is exchanged between dissolution zones and those of
oxygen reduction. These zones can be numerous if metal has a large contact area with
its surrounding medium. In concrete, dissolution zones are very often fixed and rather
large An electric field (current line) connects these zones to those where oxygen is
reduced.
These current lines are normal on equipotential surfaces (for a given
value of the potential), which can be intersected by the concrete surface. In other
words, the potential value can be measured by using a reference electrode placed on
the concrete surface The half-cell potential is a parameter used for assessing the
reinforcement condition.
5. Write about Needle Electrodes?
Any terminal by which an electric current passes in or out of a
conducting substance; for example, the anode or a cathode in an electrolytic cell. The
anode is the positive electrode and the cathode is the negative electrode. The terminals
that emit and collect the flow of electrons in thermionic valves (electron tubes) are
also called electrodes: for example, cathodes, plates (anodes), and grids.
Needle electrodes are used to record the peripheral
nerves action
potentials. The needle electrode resembles a medicine dropper or hypodermic needle.
Ashort length of the fine insulated metal wire is bent at its one end and the bent
portion is inserted through the iumen of the needle and is advanced into the muscle.
The needle is with drawn and the bent wire is resting inside the muscle. When the
reference electrode is placed on the skin, then the needle electrode is called
monopolar. When we insert two insulated wires into the lumen of the needle, then the
two wires constitute bipolar electrode such that one wire is active electrode and the
other wire is reference electrode.
UNIT II
1. Give an introduction about bio potential recorders
The bio potential recorder is playing an important role in the biomedical
instrumentation. If the recorder is not faithful or the fidelity is poor, then there is
improper diagnosis. Thus the recorders are very useful to interpret the nature of
the biological source during its working condition. During 1887, Waller recorded
the first electrocardiogram using capillary electrometer, immersion type electrodes
and
moving
light
sensitive
paper.
Then
Einthoven,
the
father
of
electrocardiography, introduced the string galvanometer during 1903. These are
further improved by introducing servomotors, ink jet recorders to extend the
frequency response and signal recovery circuits
2. What are the characteristics of recording system?
 Sensitivity of the recording system is the magnitude of input voltage
required to produce a standard deflection in the recorded trace. The
sensitivity is composed of gain of the amplification system and
sensitivity of writer in the recorder. There are provisions to change the
sensitivity.
 A recorder is said to be linear if the pen deflection is proportional o
amplitude of the input signal.
 The range over which the system is linear is called the dynamic range.
Beyond the dynamic range, the nonlinear distortion occurs.

Non linearity can occur separately in the amplifier and writer.
 Frequency response of the recorder is the frequency characteristics of
the system such that the variation of the sensitivity for different
frequency components of the biosignal. The interval between the turn
over frequencies is the bandwidth of the system.
 A low noise is maintained by special circuits and use of quality
electronic components
3. Explain about writer and pen damping effects
Sensitivity of the writer with respect to different frequencies
The writer is usually a pen motor and is electromagnetic system of
moving coil or moving iron type. The moving coils type has he pen attached to the
coil, carrying current and so behaves like a magnet whose strength is proportional
to the current. The coil rotates in the field of permanent magnet and the angle of
rotation is proportional to the current in case of moving iron type of write. The
sensitivity of the writer is dependent on frequency because of inertia, mechanical
resonance and friction.
Many writers are constructed so that the pen arm moves in an arc. This
introduces both amplitude and timing errors which increase in nonlinear manner
with the deflection and cause some distortion of he wave shape.
4. Explain the origin of electrocardiography
Electrocardiography (ECG or EKG) is the recording of the electrical
activity of the heart over time via skin electrodes. It is a noninvasive recording
produced by an electrocardiographic device. The etymology of the word is derived
from electro, because it is related to electrical activity, cardio, Greek for heart,
graph, a Greek root meaning "to write". The electrocardiography deals with he
study of electrical activity of the heart muscles. The potential originated in the
individual fibers of heart muscle are added to produce the ECG waveform. The
electro cardiogram is the recorded ECG waveform. It reflects the rhythmic
electrical depolarization and repolarization of the myocardium associated with the
contractions of the atria and ventricles. Any form of arrhythmia can be easily
diagnosed using electrocardiogram
ECG WAVEFORM
5. Explain about vectorcardiography
In case of electrocardiography only the
voltage generated by he electrical
activity of the heart is recorded. But in vectorcardiography, the cardiac vector is
displayed along with its magnitude and spatial orientation. Even though the cardiac
vector ia a three dimensional, its projection on orthogonal planes converts into two
dimensional vector. By means of orthogonal lead system, the spatial relations of he
cardiac dipole vector are usually displayed on cathode-ray oscilloscope.
Thisaccomplished by resolving the signal into three images, corresponding to frontal,
sagittal and transverse planes. The vector cardiogram appears as loops in each plane.
The iso-electric line in the standard lead system is represented by the endpoint of the
vectors in the vector cardiogram . With the modern computer facilities, the
vectorcardiography may be clinically used in an extensive manner, even though it is
not used clinically now.
UNIT – 3
1. Explain the origin of EEG
Electroencephalography deals with the study of electrical activities of
the brain. Initially it was thought that brain waves represent a summation of the
action potentials of the neurons in the brain. It is believed that the electrical
patterns obtained on the surface of the skull are the result of graded potentials on
the dendrites of neurons in the cerebral cortex and other parts of the brain.
Electrical charges are transferred between one nerve fiber and the other through a
dendrite te of a post synaptic neuron during the release of acetylcholine.
Action potentials of the brain
Progressive transient disturbance of the resting potential along a nerve fiber
is used to transmit information from one end to the other. This action potential is
caused by very rapid change of membrane permeability to sodium ions followed
by a recovery period.
Evoked potentials
Evoked potentials are the potentials developed in the brain as the response
to external stimuli like light sound etc. The external stimuli are detected by the
sense organs which cause changes in the electrical activity of the brain. Good
recording techniques are to be used for evoked potential studies
2. Explain with block diagram EMG recording unit
The surface electrodes or needle electrodes pick up potentials produced by
certain muscle fibers. The surface electrodes are from Ag-AgCl are in disc shape. The
surface of the skin is cleared and electrode paste is applied. The electrodes are kept in
place by means of elastic bands. There are two types of conventional electrodes:
bipolar and unipolar type electrodes. In case of bipolar electrode, the potential
difference between two surface electrodes resting on the skin is measured. In case of
unipolar electrode, the reference electrode is placed on the skin and needle electrode
which acts as active electrode is inserted into the muscle The needle is inserted into
the muscle. Further to record the action potentials from a nerve fiber, microelectrodes
are used
The amplitude of EMG signals depends upon the type and placement of
electrodes used and the degree of muscle exertions. That is, the surface electrode
picks up many overlapping spikes and produces an average voltage from various
muscles and motor units. The needle electrode picks up the voltage from the single
muscle fiber.
Thus EMG is useful for studying neuro muscular function, neuron
muscular condition, reflex response and extent of nerve lesion and diagnosing
muscular disease.
3. Explain with block diagram ERG recording unit
The recording and interpreting the electrical activity of eye is called
electroretinography. All sense organs are connected to the brain but the eye has a
special relation ship as the retina is an extension of cerebral cortex. Potentials
within the eye may be recorded relatively easily because of its exposed position.
The corona is about 20 mv positive relative to the fundus of the eye. The fundus is
back to the interior of the eyeball. If the illumination of the retina is changed, the
potential changes slightly in a complex manner. The recording of these changes is
called electroretinogram.
Electrode placement :
A bipolar recording technique is used. The exploring electrode is
placed on a saline filled contact lens. The contact lens is tightly attached to an eye.
During eye movement there is no slip of contact lens by using negative pressure
attachment techniques. Specially made contact lenses are used to record the action
potentials of eye during flash of light incident on the eye.
Recording Techniques:
When light falls on retina he absorption of photons by photo pigments localized in
the outer segment of the retinas photoreceptor is taking place, This causes the
breakdown of photo pigments which results in liberation of ions. This in turn results
in the development of action potential that is transmitted down the optic nerve. This
action potential is picked up.
4. Explain with block diagram EOG recording unit
A record of corneal-retinal potentials associated with eye
movements is called electrooculogram. This is more simpler to record than the
electroretinogram.
The electrodes are to be placed. One pair of disc like skin
electrodes on either side of eye for recording of horizontal movement of the eyes
and another pair of electrodes on the forehead and cheeks for recording of vertical
movement of eyes. The output from these two pairs are given separately to the
preamplifiers and then are recorded. During recording, the eye rhythmically
rotated as the vision shifts between two fixed points
Some disease which affect the steady potential of the eye can be
studied using EOG:
 The effects of certain drugs on the eye movemebnt system can b e
determned.
 The state of the semicircular canals is analysed by EOG
 Diagnosis of the neurological disorders may be possible
 The level of anesthesiacan be indicated by characteristic eye movements
5. What are the special applications of phonocardiogram
 Fetal phonocardiogram :
A stethoscope microphone with a large chest piece is over
that part of the maternal abdomen where auscultation reveals
fetal
heart sounds. Simultaneously with fetal sound tracing maternal ECG is
recorded for comparison
 Esophageal phonocardiogram :
In general, sounds and murmurs have lower frequencies than
when recorded by conventional techniques. The heart sounds are with
shorter duration.
 Tracheal phonocardiogram :
Tracheal phonocardiogram have been recorded in patients by
means of a tracheal canella. The technique of connecting the outer end of
the cannula with a microphone by means of short piece of rubber tube. The
heart sounds are with shorter duration and have W
UNIT – 4
1. Give an introduction about pacemakers
Pacemaker is an electrical pulse generator for starting and or
maintaining the normal heartbeat. The output of he pacemaker is applied either
externally to the chest or internally to he heart muscle. In the case of cardiac stand
still, the use of pacemaker is temporary – just long enough to start a normal
rhythm, In cases requiring long term pacing, the pacemaker is surgically
implanted in the body and its electrodes are in direct contact with the heart. In
cardiac diseases, where the ventricular rate is too own, it can be increased to
normal rate by using pacemaker. The various arrhythmias that result in heart both
and Adams stokes attacks represent a serious pathological condition. During that
time, the patient becomes invalid because of the constant risk of sudden losing
consciousness. By fixing artificial electronic pacemakers, he above defects in he
heart can be eliminated. With conventional drug therapy, the failure within a year
is 50%. Pacemaker’s therapy lowers to 15% and leads to a considerable
improvement in the patient mental and physical well-being
2. What are the methods of stimulation
There are two types of simulation or pacing : External stimulation and
internal stimulation.
External stimulation:
It is employed to restart the normal rhythm of the heart in case
of cardiac stand still. Stand still can occur during open-heart surgery or whenever
here is a sudden physical shock or accident. Attaché paddle shaped electrodes are
applied on he surface of the chest and the current in the range of 20 – 150 Ma are
employed.
Internal stimulation
It is employed in cases during long term pacing because of permanent
damage that prevents normal self-triggering of the heart. In some cases during
restarting of the heart after open-heart surgery, spoon like electrodes are used. The
e current range of 2-25 Ma is employed. The bipolar and unipolar electrodes are
used. In the bipolar electrode there are stimulating electrode and contact electrode
which serves as a return path for the current to the pacemakers. In the unipolar
electrode, there is only stimulating electrode and the return path for current to the
pacemaker is made through body fluids
3. What are the differences between external and internal pacemakers?
External Pacemakers :
 The pacemaker is placed outside the body. It may be in the form of
wrist watch or in the pocket, from that one wire will go into the heart
through the vein
 The electrodes are called end cardiac electrodes and are applied to the
heart by means of electrode c catheter with electrode tip situated in the
apex of right ventricle.
 It does need necessitate he open chest surgery
 The battery can be easily replaced
 During
placement, swelling and pain don’t arise due to minimal
foreign body reaction
 They are used for temporary heart irregularities.
Internal pacemakers :
 The pacemaker is miniaturized and is surgically implanted beneath the
skin near the chest or abdomen with it output leads are connected direcly
to the heart muscle
 The electrodes are called myocardial electrodes and are in contact with the
outer wall of myocardium
 It requires an open chest minor surgery to place the circuit
 The battery can be replaced only after minor surgery
 During placement, swelling and pain arise due to foreign body reaction
 They are used for permanent damages
4. What are the different types of artificial heart valves
Today cardiac surgery has advanced tremendously to enable repair
of all congenital heart defects, replacement of damaged valves and bypassing
coronary block. About 1 in 1000 babies is born with deformed heart. The
imperfect functioning of heart is due to various defects like holes in the heart,
atrial septal defects and ventricular septal defects. In several cases like pulmonary
stenos is, the valves of the major vessels are narrow. When the major vessels of
the heart are wrongly connected then there is mixing of pure and impure blood.
This accounts for he blue co lour if the body
There are two types of valves
i)
Prosthetic Valves :
These are made from high grade plastics and metal. They need life long
coagulating agent blood thinning agent. The average durability of these
valves is about 8 to 10 years
ii)
Tissue valves
These may be either homograph of hetero graft. Homograph valves
are taken from human being. Heterograft valves aren taken fro animals. Here
blood thinning agent is not necessary.
5. Give an introduction about Defibrillators
A defibrillator is an electronic device that creates a sustained
myocardial depolarization of a patients heart in order to stop ventricular
fibrillation or atrial fibrillation. Ventricular fibrillation is a serious cardiac
emergency resulting fro asynchronous contraction of heart muscle
Defibrillation is the definitive treatment for the life-threatening
cardiac arrhythmias, ventricular fibrillation and pulseless ventricular
tachycardia
Defibrillation consists of delivering a therapeutic dose of
electrical energy to the affected heart with a device called a defibrillator. This
depolarizes a critical mass of the heart muscle, terminates the arrhythmia, and
allows normal sinus rhythm
to be reestablished by the body's natural
pacemaker in the sinoatrial node of the heart.
Defibrillators can be external, transvenous, or implanted, depending on the
type of device used or needed. Some external units, known as automated external
defibrillators (AEDs), automate the diagnosis of treatable rhythms, meaning that lay
responders or bystanders are able to use them successfully with little, or in some cases
no training at all.
UNIT –5
1.What is meant by biotelemetry system?
Biotelemetry is an important technique for biomedical research and
clinical medicine. Perhaps cardiovascular research and treatment have benefited the
most from biotelemetry. Heart rate, blood flow, and blood pressure can be measured
in ambulatory subjects and transmitted to a remote receiver-recorder. Telemetry also
has been used to obtain data about local oxygen pressure on the surface of organs (and
for studies of capillary exchange (that is, oxygen supply and discharge). Biomedical
research with telemetry includes measuring cardiovascular performance during the
weightlessness of space flight and portable monitoring of radioactive indicators as
they are dispersed through the body by the blood vessels.
Telemetry has been applied widely to animal research, for example,
to record electroencephalograms, heart rates, heart muscle contractions, and
respiration even from sleeping mammals and birds. Telemetry and video recording
have been combined in research of the relationships between neural and cardiac
activity and behavior. The use of telemetry methods for sending signals from a living
organism over some distance to a receiver. Usually, biotelemetry is used for gathering
data about the physiology, behavior, or location of the organism. Generally, the
signals are carried by radio, light, or sound waves. Consequently, biotelemetry
implies the absence of wires between the subject and receiver.
2.What are the considerations in designing a biotelemetry system
 The telemetering system should be selected to transmit he bioelectric signals
with maximum fidelity and simplicity
 There would not be any constraint for living system due to these telemetry
systems and there would not be any reaction
 The size and weight of the telemetry system should be small. In he case of
long term units or implant units, the weight and size limit is in the order of 1%
of th subject
 It should have more stability and reliability
 The power consumption should be very small to extend the source life time in
case of implanted units
 The miniaturized radio telemetry system should be used to reduce noises
3.Explain about surgical diathermy
Diathermy is the treatment process by which cutting
coagulation etc of tissues are obtained. It is found hat when high frequency
current in the range 1-3mhz is applied, heating of tissues takes place. The
evoking steam bubbles in the tissues at the surgical tip continuously
rupture the tissue and by that way the cutting action is obtained. Similarly
during the passage of the high frequency current through the tissue, the
tissue is heated locally. So that the tissue is melted instantaneously and
sealing of capillary and other blood vessels is taking place. Thus the
coagulation of the tissue takes place. The us of high frequency current is to
avoid he intense muscle activity and the electrocution hazard, which
occurs if low frequencies are used.
4.Explain about Microwave diathermy
Here the frequency used is 2,450mhz corresponding to the
wavelength of 12.25 cm Heating of the tissues is produces due o
absorption of microwave energy. Better therapeutic results are obtained by
using microwave diathermy than short wave diathermy. Here there is no
pad shaped electrode. Instead the microwaves are transmitted into the
portion of the body to be treated directly from the director of the unit.
Normally magnetrons are used to produce microwaves
A delay of about 3 or 4 minute is required for the warming of the
magnetron. Arrangement is made such that a lamp lights up after 4
minutes indicating the magnetron is ready to deliver its output to the
director. Proper cooling of the magnetron is provided.
5.What are the various electrosurgery techniques? Explain
Fulguration :
By passing sparks from a needle or ball electrode of small diameter to the tissue,
the developed heat dries out the superficial tissue without affecting the deep
seated tissues. This is called fulguration in which the electrode is held near the
tissue without touching it and due to the passage of the electric arc, the destruction
of the superficial tissue takes place
Desiccation :
The needle point electrodes are struck into the tissue and kept steady while
passing electric current. This creates a high local increase in heat and drying of
tissues takes place
Electrotonmy :
When the electrode is kept above the skin electrical arc is sent. The developed
heat produces a wedge shaped narrow cutting of the tissue on the surface
Coagulation:
When the electrode is kept near the skin high frequency current is sent through
the tissue in the form of burst and heating it locally so that it coagulates from
inside
Blending:
When the electrode is kept above the skin the separated tissues or nerves can be
welded or combined together by an electric arc
PART-C
UNIT -1
1. Explain in detail the chemical electrodes
Hydrogen Electrode
The standard hydrogen electrode (abbreviated SHE), also called normal
hydrogen electrode (NHE), is a redox electrode which forms the basis of the
thermodynamic scale of oxidation-reduction potentials. Its absolute electrode
potential is estimated to be 4.44 ± 0.02 V at 25 °C, but to form a basis for comparison
with all other electrode reactions, hydrogen's standard electrode potential (E0) is
declared to be zero at all temperatures.
Potentials of any other electrodes are
compared with that of the standard hydrogen electrode at the same temperature.
Hydrogen electrode is based on the redox half cell
2H+(aq) + 2e- → H2(g)
This redox reaction occurs at platinized platinum electrode. The electrode is dipped in
an acidic solution and pure hydrogen gas is bubbled through it. The concentration of
both the reduced form and oxidised form is maintained at unity. That implies that the
pressure of hydrogen gas is 1 bar and the concentration of hydrogen in the solution is
1 molar
Reference electrode:
The silver/silver chloride or Ag/AgCl reference electrode is many
electrochemists' reference electrode of choice. It is easily and cheaply prepared. It is
stable, and quite robust. It is sometimes referred to as "SSCE" (Silver/Silver Chloride
Electrode) l
The body of the electrode is made from 4 mm glass tube. Vycor porous glass is
available in 4 mm diameter rod and serves as the ironically conducting electrical pathway
between the inside of the reference electrode and the bulk of your cell. It has low electrical
resistance (under 10 kohl for the common filling solutions) and a modest leak rate. The
electrical resistance of the reference electrode 'frit' is an important factor in determining the
stability . The leak rate may be important because of possible contamination of your solution
by the reference electrode filling solution and vice versa.
The Vycor frit (about 1/8" long) is attached to the glass tube by 'heat shrink' Teflon tubing.
The heat-shrink tubing should be cut flush with the end of the Vycor frit to prevent trapping
any air bubbles.. The cap is conveniently made out of scrap Teflon or plastic cap or protector
made to fit 5/32" OD tubing. It should be snug, but easily removable for replenishing the
filling solution. Saturated solutions of KCl or NaCl have the advantage that the
concentration is reproducible even if the temperature changes (if solid salt is present)
and are immune to the effects of water evaporation. However, the solid salts harden
into an impenetrable block which may lead to a high impedance electrode. A "nearly
saturated" solution (3.5M KCl or 3M NaCl) can change concentration due to
evaporation.
Glass pH electrode
Most often used pH electrodes are glass electrodes. Typical model is
made of glass tube ended with small glass bubble. Inside of the electrode is usually
filled with buffered solution of chlorides in which silver wire covered with silver
chloride is
immersed. pH of internal solution varies - for example it can be 1.0 (0.1M HCl) or7.0
(different buffers used by different producers). Active part of the electrode is the glass
bubble. While tube has strong and thick walls, bubble is made to be as thin as
possible. Surface of the glass is protonated by both internal and external solution till
equilibrium is achieved. Both sides of the glass are charged by the adsorbed protons,
this charge is responsible for potential difference. This potential in turn is described
by the Nernst equation and is directly proportional to the pH difference between
solutions on both sides of the glass
The majority of pH electrodes available commercially are combination
electrodes that have both glass H+ ion sensitive electrode and additional reference
electrode conveniently placed in one housing. For some specific applications separate
pH electrodes and reference electrodes are still used - they allow higher precision
needed sometimes for research purposes.
2. Explain
in detail about Resting and Action Membrane Potentials
Resting Potential
There is normally a charge difference across the plasma membrane of a
neuron. The outside of the membrane has a positive charge. The inside has a negative
charge. Resting potential results from differences between sodium and potassium
positively charged ions and negatively charged ions in the cytoplasm. Sodium ions are
more concentrated outside the membrane, while potassium ions are more concentrated
inside the membrane. This imbalance is maintained by the active transport of ions
across the membrane known as the sodium potassium pump. This difference or
potential is measured in mill volts. The resting potential is usually about -70mv.
Action Potential
When a neuron receives signals, an abrupt, temporary reversal in the polarity is
generated (an action potential). The inside becomes more positive. Any membrane
that can produce action potentials is said to show membrane excitability. Voltage
change causes voltage-gated channels in the membrane to open. As a result of ion
flow through these channels, the inside of a neuron briefly becomes more positive
than outside.
Two properties of the neuron membrane permit a resting potential:

The lipid bilayer bars the free passage of potassium ions and sodium ions.

Ions can flow from one side to the
other through channels in transport
proteins.
There are more potassium ions inside and more sodium ions outside the
resting neuron membrane. Potassium ions have a tendency to leak out by facilitated
diffusion through channel proteins. Most of the sodium channels are "gated" and
remain closed most of the time, keeping the concentration outside high. However,
small amounts of sodium do leak in and must be pumped out (and potassium pumped
in) by the sodium-potassium pump. When a stimulus reaches a certain minimum, a
threshold-gated channels open and sodium rushes in. In an accelerating way, more
and more gates open (At threshold, the opening of more gates no longer depends on
the stimulus but is self-propagating
All action potentials are the same size. If stimulation is below threshold
level, no action potential occurs. If it is above threshold level, the cell is always
depolarized to the same level.
Polarization, depolarization,hyperpolarization: Polarization literally means having
poles. Because a cell is negative inside (as a result of being dominated by the
electrochemical equilibrium potential
of potassium) it is said to be polarized.
Increasing that polarization (i.e. making is more negative inside) is a hyper
polarization and decreasing it (i.e. making it less negative inside) is a depolarization.
Repolarization :
When depolarization in one region is ended, the sodium gates close and
potassium gates open. The sodium-potassium membrane pumps also become
operational to fully restore the resting potential. Movement of potassium out of the
cell repolarizes the cell.
The action potential is self-propagating and moves away from the stimulation site to
adjacent regions of the membrane undiminished. A brief (refractory) period follows at
each depolarization site. Sodium gates shut and potassium gates open. During this
period the membrane is insensitive to stimulation.
3. Explain about nerve tissues and organs
Nervous tissue is the main component of the nervous system-the brain,
spinal cord, and nerves-which regulates and controls body functions. It is composed
of neurons which transmit impulses, and the neuroglia which assist propagation of
the nerve impulse as well as provide nutrients to the neuron. Every time you get
pinched, part of your nerve tissue is damaged. All nervous tissue of a living organism
makes up its nervous system which includes the brain, spinal cord, and nerves
throughout the organism. Nervous tissue is made of nerve cells that come in many
varieties, all of which are distinctly characteristic by the axon or long stem like part of
the cell that sends action potential signals to the next cell.
All living cells have the ability to react to stimuli. Nervous tissue is
specialized to react to stimuli and to conduct impulses to various organs in the body
which bring about a response to the stimulus. Nerve tissue (as in the brain, spinal cord
and peripheral nerves that branch throughout the body) are all made up of specialized
nerve cells called neurons. Neurons are easily stimulated and transmit impulses very
rapidly. A nerve is made up of many nerve cell fibers (neurons) bound together by
connective tissue. A sheath of dense connective tissue, the epineurium surrounds the
nerve. This sheath penetrates the nerve to form the perineurium which surrounds
bundles of nerve fibers. Blood vessels of various sizes can be seen in the epineurium..
The cell body is enclosed by a cell (plasma) membrane and has a central
nucleus. Granules called Nissl bodies are found in the cytoplasm of the cell body.
Within the cell body, extremely fine neurofibrils extend from the dendrites into the
axon. The axon is surrounded by the myelin sheath, which forms a whitish, noncellular, fatty layer around the axon. Outside the myelin sheath is a cellular layer
called the neurilemma or sheath of Schwann cells. The myelin sheath together with
the neurilemma is also known as the medullary sheath. This medullary sheath is
interrupted at intervals by the nodes of Ranvier.
structure of a nerve cell. The nerve impulse enters the nerve cell by the dendrites
and is then carried away from the cell body by the axon
Tissues
:
Cells group together in the body to form tissues - a collection of similar cells
that group together to perform a specialized function. There are 4 primary tissue
types in the human body: epithelial tissue, connective tissue, muscle tissue and nerve
tissue.
1. Epithelial Tissue - The cells of epithelial tissue pack tightly together and form
continuous sheets that serve as linings in different parts of the body. Epithelial
tissue serve as membranes lining organs and helping to keep the body's organs
separate, in place and protected. Some examples of epithelial tissue are the
outer layer of the skin, the inside of the mouth and stomach, and the tissue
surrounding the body's organs.
2. Connective Tissue - There are many types of connective tissue in the body.
Generally speaking, connective tissue adds support and structure to the body.
Most types of connective tissue contain fibrous strands of the protein collagen
that add strength to connective tissue. Some examples of connective tissue
include the inner layers of skin, tendons, ligaments, cartilage, bone and fat
tissue. In addition to these more recognizable forms of connective tissue,
blood is also considered a form of connective tissue.
3. Muscle Tissue - Muscle tissue is a specialized tissue that can contract. Muscle
tissue contains the specialized proteins actin and myosin that slide past one
another and allow movement. Examples of muscle tissue are contained in the
muscles throughout your body.
4. Nerve Tissue - Nerve tissue contains two types of cells: neurons and glial
cells. Nerve tissue has the ability to generate and conduct electrical signals in
the body. These electrical messages are managed by nerve tissue in the brain
and transmitted down the spinal cord to the body.
Organs
:
Organs are the next level of organization in the body. An organ is a structure
that contains at least two different types of tissue functioning together for a common
purpose. There are many different organs in the body: the liver, kidneys, heart, even
your skin is an organ. In fact, the skin is the largest organ in the human body and
provides us with an excellent example for explanation purposes. The skin is
composed of three layers: the epidermis, dermis and subcutaneous layer. The
epidermis is the outermost layer of skin. It consists of epithelial tissue in which the
cells are tightly packed together providing a barrier between the inside of the body
and the outside world. Below the epidermis lies a layer of connective tissue called the
dermis. In addition to providing support for the skin, the dermis has many other
purposes. The dermis contains blood vessels that nourish skin cells. It contains nerve
tissue that provides feeling in the skin. And it contains muscle tissue that is
responsible for giving you 'goosebumps' when you get cold or frightened. The
subcutaneous layer is beneath the dermis and consists mainly of a type of connective
tissue called adipose tissue. Adipose tissue is more commonly known as fat and it
helps cushion the skin and provide protection from cold temperatures.
UNIT –2
1. Explain in detail the ECG Lead configurations
In electrocardiography, the word, "lead" (rhymes with 'speed') refers
to the signal that goes between two electrodes These electrodes are attached to the
patient's body, usually with very sticky circles of thick tape-like material 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 electrodes
Ten electrodes are used for a 12-lead ECG. They are labeled and placed on the
patient's body as follows
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 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) aVR electrode (on the right arm)
and the (positive) aVL electrode (on the left arm).

Lead II is the signal between the (negative) aVR electrode (on the right arm)
and the (positive) aVF electrode (on the left leg).

Lead III is the signal between the (negative) aVL electrode (on the left arm)
and the (positive) aVF electrode (on the left leg).
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 because the negative electrode for these leads is a
modification of 'Wilson's central terminal', which is derived by adding leads I, II,
and III together and plugging them into the negative terminal of the ECG machine.
This zeroes out the negative electrode and allows the positive electrode to become the
"exploring electrode" or a unipolar lead. This is possible because Einthoven's Law
states that I + (-II) + III = 0. The equation can also be written I + III = II. It is written
this way (instead of I - II + III = 0) because Einthoven reversed the polarity of lead II
in Einthoven's triangle, possibly because he liked to view upright QRS complexes.
Wilson's central terminal paved the way for the development of the augmented limb
leads aVR, aVL, aVF and the precordial leads V1, V2, V3, V4, V5, and V6.

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.
In modern digital equipment, the augmented leads are derived from the limb leads by
simple calculation:
aVR = -(I + II)/2
aVL = I - II/2
aVF = II - I/2
Precordial leads
The electrodes for the precordial leads (V1, V2, V3, V4, V5, and V6,) are placed
directly on the chest. Because of their close proximity to the heart, they do not require
augmentation. Wilson's central terminal is used for the negative electrode, and these
leads are considered to be unipolar (recall that Wilson's central terminal is the
average of the four limb leads.).The precordial leads view the heart's electrical activity
in the so-called horizontal plane. The heart's electrical axis in the horizontal plane is
referred to as the Z axis.
Leads V1, V2, and V3 are referred to as the right precordial leads and V4, V5, and
V6 are referred to as the left precordial leads.
The QRS complex should be negative in lead V1 and positive in lead V6. The QRS
complex should show a gradual transition from negative to positive between leads V2
and V4. The equiphasic lead is referred to as the transition lead. When the transition
occurs earlier than lead V3, it is referred to as an early transition. When it occurs
later than lead V3, it is referred to as a late transition. There should also be a gradual
increase in the amplitude of the R wave between leads V1 and V4. This is known as R
wave progression. Poor R wave progression is a nonspecific finding. It can be caused
by conduction abnormalities, myocardial infarction, cardiomyopathy, and other
pathological conditions.
Ground
An additional electrode (usually green) is present in modern four-lead and
twelve-lead ECGs. This is the ground lead and is placed on the right leg by
convention, although in theory it can be placed anywhere on the body. With a threelead ECG, when one dipole is viewed, the remaining lead becomes the ground lead by
default.
2. Explain in dertail the ECG waveform analysis
A typical ECG tracing of a normal heartbeat (or cardiac cycle) consists of a
P wave, a QRS complex and a T wave.] A small U wave is normally visible in 50 to
75% of ECGs. The baseline voltage of the electrocardiogram is known as the
isoelectric line. Typically the isoelectric line is measured as the portion of the tracing
following the T wave and preceding the next P wave. The four deflections were
originally named ABCDE but renamed PQRST after correction for artifacts
introduced by early amplifiers.
P wave
During normal atrial depolarization, the main electrical vector is directed
from the SA node towards the AV node, and spreads from the right atrium to the left
atrium. This turns into the P wave on the ECG, which is upright in II, III, and aVF
(since the general electrical activity is going toward the positive electrode in those
leads), and inverted in aVR (since it is going away from the positive electrode for that
lead). A P wave must be upright in leads II and aVF and inverted in lead aVR to
designate a cardiac rhythm as Sinus Rhythm.

The relationship between P waves and QRS complexes helps distinguish
various cardiac arrhythmias.

The shape and duration of the P waves may indicate atrial enlargement.

Absence of the P wave may indicate atrial fibrillation
QRS complex
The QRS complex is a structure on the ECG that corresponds to the
depolarization of the ventricles. Because the ventricles contain more muscle mass
than the atria, the QRS complex is larger than the P wave. In addition, because the
His/Purkinje system coordinates the depolarization of the ventricles, the QRS
complex tends to look "spiked" rather than rounded due to the increase in conduction
velocity. A normal QRS complex is 0.08 to 0.12 sec (80 to 120 ms) in duration
represented by three small squares or less, but any abnormality of conduction takes
longer, and causes widened QRS complexes.
Not every QRS complex contains a Q wave, an R wave, and an S wave. By
convention, any combination of these waves can be referred to as a QRS complex.
However, correct interpretation of difficult ECGs requires exact labeling of the
various waves. Some authors use lowercase and capital letters, depending on the
relative size of each wave. For example, an Rs complex would be positively deflected,
while a rS complex would be negatively deflected. If both complexes were labeled
RS, it would be impossible to appreciate this distinction without viewing the actual
ECG.

The duration, amplitude, and morphology of the QRS complex is useful in
diagnosing cardiac arrhythmias
conduction abnormalities, ventricular
hypertrophy myocardial infarction electrolyte derangements, and other disease
states.

Q waves can be normal (physiological) or pathological. Pathological Q waves
refer to Q waves that have a height of 25% or more than that of the partner R
wave and/or have a width of greater than 0.04 seconds. Normal Q waves,
when present, represent depolarization of the interventricular septum. For this
reason, they are referred to as septal Q waves, and can be appreciated in the
lateral leads I, aVL, V5 and V6.

Q waves greater than 1/4 the height of the R wave, greater than 0.04 sec (40
ms) in duration, or in the right precordial leads are considered to be abnormal,
and may represent myocardial infarction

"Buried" inside the QRS wave is the atrial repolarization wave, which
resembles an inverse P wave. It is far smaller in magnitude than the QRS and
is therefore obscured by it.
ST segment
The ST segment connects the QRS complex and the T wave and has a duration of
0.08 to 0.12 sec (80 to 120 ms). It starts at the J point (junction between the QRS
complex and ST segment) and ends at the beginning of the T wave. However, since it
is usually difficult to determine exactly where the ST segment ends and the T wave
begins, the relationship between the RT segment and T wave should be examined
together. The typical ST segment duration is usually around 0.08 sec (80 ms). It
should be essentially level with the PR and TP segment.
QT interval
The QT interval is measured from the beginning of the QRS complex to the end of the
T wave. Normal values for the QT interval are between 0.30 and 0.44 secondsThe QT
interval as well as the corrected QT interval are important in the diagnosis of long QT
syndrome and short QT syndrome
Long QT intervals may also be induced by
antiarrythmic agents that block potassium channels in the cardiac myocyTE The QT
interval varies based on the heart rate, and various correction factors have been
developed to correct the QT interval for the heart rate. The QT interval represents on
an ECG the total time needed for the ventricles to depolarize and repolarize.
The most commonly used method for correcting the QT interval for rate is the one
formulated by Bazett and published in 1920Bazett's formula is, where QTc is the
QT interval corrected for rate, and RR is the interval from the onset of one QRS
complex to the onset of the next QRS complex, measured in seconds. However, this
formula tends to be inaccurate, and over-corrects at high heart rates and undercorrects at low heart rates.
2. Explain wih block diagrm ECG Recording unit
The important parts of ECG recorder are
1. Patient cable and Defibrillator protection circuit :
Fibrillation circuit. It consists of buffer amplifiers and over voltage
protection circuit. The leads are connected with the buffer amplifier such that one
buffer amplifier for each patient lead. This reduces means the input impedanc is in
creased and the effects arising from the variations in the electrode impedance.
Further over voltage protection circuit is necessary to avoid any damage to the
bioamplifiers in the recorder. The over voltage protection circuits consists of a
network of resistors and neon lamps which fire when a pulse from a
defibrillator is present
2. Lead selector switch:
After the defibrillator protection circuit, there is lead selector, which
is used to feed the input voltage from the appropriate electrode to the preamplifier.
.3. Calibrator:
A push button allows the insertion of standardization voltage of 1mv to the
preamplifier. This enables the technician to observe the output on display unit
and adjust the scale so that a known own deflection corresponds to a I mv
input signal. From the leads selector switch the ECG signal goes to bioamplifier.
3. Bio-Amplifier :
The bio-amplifier consists of preamplifier and power amplifier.
The sensitivity or the gain of the amplifier can be varied. Followed by the
preamplifier there is power amplifier, which is used to drive the recorder. Power
amplifiers are required with high power gain.
To avoid the cross over distortion in a push pull amplifier, an ideal no
inverting amplifier is inserted on the input. The offset control is provided by
resistance and is used to position the output stylus pen.
4. Auxiliary amplifier :
Since the electrode impedance are not equal, a differential amplifier
doesn’t completely reject the common mode signals. The common mode signals
can be reduced to a minimum level by adding an auxiliary namplifier between the
driven right leg lead and the ECG unit.
5. Isolated power supply :
The isolated power supply is used to give power to the bioamplifier and by
means that, the electrical safety for the patient is increased.
6. Output Unit :
The output unit is cathode ray oscilloscope or a paper chart
recorder. In the case of paper chart recorder, the power or pen amplifier supplies
required power to drive pen motor. A position control on the pen amplifier is used
to position the pen at the center ion recording paper.
Power switch :
The power switch of the recorder has three positions. ON,OFF and
RUN
UNIT - III
1. Explain in detail the placement of electrodes inn EEG
In EEG electrodes are placed in standard locations on the skull in an
arrangement called 10-20 system, a placement scheme devised by the international
federation of societies of EEG
i)
Draw a line on the skull from the nasion, the root of the nose, to the inion,
ossification center on the occipital lope
ii)
Draw a similar luine from the left preauricular point to the right
preauricular point
iii)
Mark the intersection of these two lines which is the mid point of the
distance between nasion and anion.
iv)
Mark points atb10,20,20,20,20, and 10%of the total nasion-inion distance
v)
Mark points at 10,20,20,20,20 and 10/% of the total distance between the
preauricular points
Before placing the electrodes, the scalp s cleaned, tightly
abraded and electrode paste is applied between electrode and skin. Both bipolar and
un bipolar electrod systems are used to facilitate location of foci, that is cortical areas
from which abnormal waves spread. The phase relationship of the waves indicates the
position of the focus and in sometimes it enables the velocity at which the waves
spread to be calculated. Aian bipolar technique the difference in potential between
two adjacent electrodes is measured. In the monopolar technique the potential of each
electrode is measured with respect to he reference electrode attached to the ear lobe
2. Explain in the the recording set up of EEG unit
The patient cable contains of 21 electrodes and is connected to the eight channel
selector. The electrodes are attached to the channel selector in groups og eight
called montage of electrodes. The right ear electrode acts as referenc electrode for
the righ brain electrodes and the left ear electrode acts as reference electrode for
the left brain electrodes. The 50hz interference is
reduced by employing
differential amplifiers and preamplifiers with more than 80db CMRR and ny use
of 50 hz notch filters. The effect of notch filter in signal distortion is not so much
because
important EEG signals have frequencies below 30hz.
. The 50hz interference is
reduced by employing differential amplifiers and
preamplifiers with more than 80db CMRR and ny use of 50 hz notch filters. The
effect of notch filter in signal distortion is not so much because
important
EEG signals have frequencies below 30hz. Because the source of brain wave has
high internal impedance, th input impedance of the preamplifier should be more to
prevent reducion of signal amplitude.
Further by cascading the gain of the amplifier is increased. Ahe output
vbvoltage fro the preamplifier may either be applied directly to the eight channel
display through filter bank or it may be stored in data on a tape recorder or in
computer memory for further processing.
3. Explain in detail Phonocardiography
The graphic record of heart sounds is calle phonogram.
Because the sound is from the heart it is called phonocardiogram. The
instrument used to measure the heart sounds is called phonocardiogram.
This instrument uses a phonocather, a device similar to a convential catheter,
with a microphone at the tip.
The basic aim of phonocardiogram
is to pick up different
heart sounds, filter out the heart sounds and to display them or record them.
Heart bsounds sare acustoic events of heart can be divided into two categories
heart sounds amd murmurs. Heart sounds have a transient character and are of
short dration. Heart murmurs have a noisy characteristic and last fo longer
time
Heart sounds :
Heart sound are clasified into four types
i)
Valve closure sounds
ii)
Ventricullar filling sounds
iii)
Valve openiong sounds
iv)
Extra cardiac sounds
Valve closure sounds:
These sounds occur at he beginning of the systolem and the beginning of
the diastole. The first heart sound is due to clousre of mitral and trcuspid
valves. The second heart sound is due to clousre of arotivc pulmonary valves
Ventricullar filling sounds:
These sounds occur either at the period of rapid filling of the
ventricles or during terminal phas of ventricular filling. These sounds are
normally inaudiable
Valve openiong sounds:
These sounds occur at the time of opening of
the artiventricvular valves and semilunaar valved
Extra cardiac sounds:
These sounds occur in mid or late systole or early systole and are
believed to causeby thickened pericardium
Heart sounds and murmurs are characterised by hre physical ,properties they
are
1. Frequency
2. Amplitude
3. Quality
UNIT –4
1.
Explain in detail about square wave and double square wave
defibrillators
Square wave defibrillators :
Here the capacitor is discharged through the subject on a
series silicon controlled rectifier. When sufficient energy has been
delivered to the subject a shunt SCR short circuits the capacitor and
terminates the pulse. The output can be controlled by varying he voltage
on the capacitor or duration of discharge. Here the defibrillation is
obtained at less peak current and so there is no side effect. Digital circuits
can also produce a square pulse used for defibrillation
Double Square wave defibrillators:
Double square pulse defibillator is used normally after the open
heart surgery. Conventional d.c and a,.c defibrillators are producing
myocardial injury with a diminished ventricular function for a period of
approximately 30 minbutes. I f he chest is open only lower energy electric
shock should be given. When the first pulse is delivered some of he
fibrillating cells will be excitable and will be depolarised. In order to
obtain oal defibrillation the second pulse operates on this later gyoup of
cells. Using double square pulse defibrillator, efficie and quick recovery of
heart norml manner without any sid effect.
2, Explain the working of heartlung machine
During open heart surgery for installation of valla prosthesis or
correction of a congenital mal information, the heart cannot maintain th
circulation. It is then necessary o provide extra-corporeal circulation with a
special machine call heart lung machine. The Heart lung machine replaces
the functions of heart and lungs there by providing the rest of the body
with a continuous supply of oxygenated blood while the heart is stopped
In the lungs the blood is oxygenated to about 95 to 98% saturation
and that it is going to hr left atrium of heart which acts as a receiver
chamber From there the blood flows into the left ventricle through the
mistrals valve
i)
In an intact heart venous or unoxygenated blood is returned to the
right side of the heart
ii)
From the right side of the heart, the blood is pumped into lungs
through pulmonary artery
iii)
In the lungs the blood is oxygenated to about 95 to 98% saturation
and that it is going to hr left atrium of heart which acts as a receiver
chamber
iv)
From there the blood flows into the left ventricle through the
mistrals valve
v)
The ventricle ejects the blood into the aorta with peak pressures
ranging from 100 to 150 mm Hg
vi)
The heart pumps about 5 liters of blood per lire. At any time the
veins contain 75 o 80 % of blood volume and arteries contain 20 to
25 percents of blood volume
3. Explain with diagram Verntricular synchronous pacemaker and
Ventricular inhibited pacemaker
Verntricular synchronous pacemaker
Patients with only short periods of AV block or bundle block can
be supplied with a ventricular synchronous pacemaker. This type of
pacemaker does not compete with the normal heart activity. A single
transverse electrode placed in the right ventricle both senses the R wave and
delivers the stimulation, thus no separate sensing electrode is required. A Rwave from an arterial generated ventricular contraction triggers the ventricular
synchronized pacemaker, which provides an impulse falling in the lowest part
of normal QRS complex. This ensures that the pacemaker does not interfere
with the sinus rhythm. If a trial generated ventricular contractions are absent,
the pacemaker provides impulse at a basic frequency 0f 70impulse/minute.
Thus it provides impulses only when the atrial generated ventricular
contractions are absent, thus conveying energy
Using he sensing electrode, the heart rate is detected and is given to
the timing circuit in the pacemaker. If the detected heart rate is below a certain
minimum level, the fixed rate pacemaker is turned on to pace he heart. The
lead used to detect R wave is now used to stimulate the heart. If a natural
contraction occurs, the asynchronous pacemaker timing circuit is reset so that
it will time its next pulse to detect heart beat. Otherwise the asynchronous
pacemaker produces pulses at its preset rate
Ventricular inhibited pacemaker
The R wave inhibited pacemaker also allows the heart to pace at its
normal rhyhm when it is able to do so. If the R wave is missing for a preset period of
time, the pacer will supply the stimulus. Therefore if the heart rate falls below a
predetermined value, the pacemaker will turn on and provide the heart a stimulus.
The sensing electrode picks up the R wave The refractory circuit provides a
period of time following a output pulse or sensed R wave during which the amplifier
in the sensing circuit will no respond to outside signals. The sensing circuit detects the
R wave and resets the oscillator. The reversion circuit allows the amplifier to detect R
wave in low level signal to noise ratio. In the absence of R wave it allows the
oscillator in the timing circuit to deliver pulses at the preset rate. The pulse width rate
determines duration of the pulse delivered to the heart. Then the output of the pulse
width circuit fed into the rate limiting circuit, which limits the pacing rate to a
maximum of 120 pulses. The output circuit provides a proper pulse to stimulate the
heart Thus the timing circuit, pulse width circuit, rate limiting circuit and output
circuit are used to produce the desired pacemaker pulses to pace the heart. The energy
compensation circuit produces an increase in he pulse duration as the battery voltage
decreases to maintain constant stimulation energy to the heart
UNIT –5
1. Explain short-wave diathermy and ultrasonic diathermy with
diagran
The heating of the tissues is carried out at a high frequency of 27.12mhz and a wave
length of 11 meters. When we use currents having high frequencies the motor or
sensory nerves are not stimulated and there is no contraction of muscles. The RF
energy creates the tissues and promotes the healing of injured tissues and
inflammations. There are sev real provisions to regulate the intensity of current passed
through the patient circuits. The pads are placed so that the portion of body to be
treated is sandwiched between them
When RF current is applied to the pads the dielectric loss of capacitor produces heat
in the intervening tissues. This technique is called condenser or capacitor method.
There is also an inductive method in which a flexible cable is coiled around the arm
or knee or any other portion of the patient body where plate electrodes are
inconvenient to use
Utrasonic diathermy
Ultrasonic therapy is used where short wave treatment is failed and in
cases where localization of heat effect is desires. The ultrasonic diatheraphic units are
helpful to cure he diseases of peripheral nervous systems like neuritis, skeletal and
muscular systems. The heating effect is produced because of absorption of ultrasonic
energy by tissues. The effect of ultrasonic on the tissues is high speed vibration of
micro massage. Micro massage is use in the treatment of soft tissue lesions. I t is
better than manual massage because of depth of massage and can be obtained without
any pain to the paient
The transducer is made of bariumtitanite The ultrasonic waves can be applied in
continuous or pulsed mode. The treatment timer is an electrically operated contact
which can be set from 1 to 15 minutes
3. Explain wih block diagram Multiple channel telemetry system
For most biomedical instruments it is desirable to have simultaneous
recording of several signals for correlation study. Each signal require a
telemetry channel.
There are two types
i)
Frequency division multiplex
ii)
Time division multiplex
Frequency division multiplex System :
Each signal is frequency modulated on a sub carrier frequency. Then these
modulated sub carrier frequencies are combined to modulate the main R.F.carrier.
A t the receiver side the modulated sub carriers will be separated by proper band
pass filters after the first discrimination The individual signals are recovered from
these modulated sub carriers by the second set of discriminator The frequency of
sub carriers has to be carefully selected to avoid interferences. The low p[ass
filters are used to extract signals without any noise.
Time division multiplex system:
Since most biomedical signals have low frequency bandwidth requirements
we can use time division multiplex system by the timesharing scheme. The
transmission channel is connected to each signal channel input for a short time to
sample and transmit the signal. Then the transmitter is switched to the next signal
channel in a definite sequence. When all the channels have been scanned once a
cycle is com placed the next will start. The operation is repeated again. Th the
receiver end the process is reversed. The sequenciality is arranged, signal pulse
are distributed to individual channels by a synchronized switching circuit.
4. What are the problems in biotelemetry? Give its uses
Problems in biotelemetry:
 For long term monitoring implant telemetry is more useful one. The
whole electronic circuit is fully packed as a capsule and then implanted
 For implant telemetry, the size and weight limitations are much more
serous and the reliability requirements is more critical
 Body reaction size, weight, surface condition and shape of the implant
system will have effects on the body reaction. Mean while medical
grade silastic, Teflon, glass and some metals which are used as
enclosures cause little foreign body reaction on tissue
 The coating materials of electronic circuits to protect them from body
fluid are silicon ruby, epoxy, plastics, paraffin, glass and metal
 Power supply : Two special power supplies are used for long term
implant telemetry units along with the mercury and lithium cells
i)
Environmental Power supply : Radio induction has been
applied to transmit mill watt of power to the implanted
telemetry units for months
ii)
Microwatt Power supply circuits using piezoelectric
crystals laced on any blood vessel or aortas
Uses of Biotelemetry :
 Biotelemetry helps us record biosignals over long periods and while the
patient is engaged in his normal activities
 The medical attendant or computer can easily diagnosis the nature of
disease by seeing the telemetries signals without attending the patient room
 Patient is in his room without any mechanical or physical disturbance during
recording by mean of biotelemetry
 For future reference the biotelemetry is essential one
 For recording animals, particularly for research ths biotelemetry is greatly
used For monitoring the persons