Biomedical Instrumentation

Course Name: Biomedical Instrumentation
Course Code: MC1652
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Books/References
 J. G. Webster , Medical Instrumentation: Application And
Design, 3rd edition ,Wiley Publishers
 D Reddy, Biomedical Signal Processing, Tata Mcgraw
Hill Publications.
 Sergio Cerutti Advanced Methods of Biomedical Signal
Processing, Oxford Publications.
 B. Jacobson, J.G. Webster, Medical and Clinical Engineering,
Prentice Hall, International.
 Cromwell, Biomedical Instrumentation and Measurements,
Prentice Hall, International.
 R.S. Khandupur, Handbook of Biomedical Instrumentation, -
Tata McGraw Hill

Introduction
Instrumentation : Instrumentation is the use
of measuring instruments to monitor and
control a process. It is the art and science of
measurement and control of process variables
within a production, laboratory, or
manufacturing area.

Introduction
Biomedical Instrumentation : Biomedical
Instrumentation is the field of creating such
instruments that help us to measure, record
and transmit data to or from the body
COMPONENT OF MAN INSTRUMENT SYSTEM

Basic Objectives of Instrumentation System
 Information Gathering
 Diagnosis
 Evaluation
 Monitoring
 Control

Classification of Bio Medical Instrumentation
System
 Clinical Instrumentation
Basically devoted to the area of
 Diagnosis
 Patient care
 Treatment of Patients ( Therapeutic use )

Classification of Bio Medical Instrumentation
System
 Research Instrumentation
 It is used primarily in the search for new knowledge
related to various systems that compose the human
organism.
 Some instruments can be used in both areas.

Classification of Instruments Used
CLASSIFICATION OF INSTRUMENTS
Engineering
Indicating
Recording
Monitoring
Data Logging
Analysis
Control
Medical
Diagnostic
Therapeutic
Supplementary

Engineering Classification of Biomedical
Instruments
 Measuring Instruments.
 Audiometer
 Blood cell counter
 Blood Pressure meter
 Blood PH meter
 Blood flow meter
 Digital BP meter
 GSR meter
 Stethoscope

Recording Instruments
 Electrocardiograph
 Electromyograph
 Electro encephalograph
 Expirograph
 Phonocardiograph
 Plethysmograph
 Thermograph
 Tomograph
 Ultra sonograph
 Radio graph ( x-ray)

Monitoring Instruments
 Bed – side monitor
 Bio – monitor
 Foetal monitor

Analysing Instruments
 Colorimeter
 Spectrometer
 Flame photo meter

Data Logging and Controlling
Instruments
 Data Logging
- Computer
 Controlling
- Defibrillator
- Dialysis instrument
- Heart lung machine

A) Medical Classification of BMI
 Diagnostic instruments
 Endoscope
 Stethoscope
 Microscope

B)Therapeutic Instruments
 Shortwave diathermy
 Ultrasound therapy
 Electro surgery
 Nuclear Medicine

B)Supplimentary Instruments
 Aid for blind
 Hearing aid
 Pace maker

Functional Classification of
Instruments
A] BLOOD INSTRUMENTS
1. Blood Pressure meter
2. Blood PH meter
3. Blood flow meter
4. Blood cell counter
5. Calorimeter
6. Spectra – Photometer
7. Flame photometer
8. Digital BP meter

Contd…
B] HEART INSTRUMENT
1. ECG
2. Pace Maker
3. Defibrillator
4. Heart Lung Machine
5. Bed side monitor
6. Plethysmograph
7. Electronic stethoscope
8. Phonocardiograph

Contd….
C] BRAIN INSTRUMENTS
1. EEG
2. Tomo-graph
D] MUSCLE INSTRUMENTS
1. EMG
2. Muscle Stimulator

Contd….
E) KIDNEY INSTRUMENTS
1. Dialysis Instrument
2. Lithotripsy
F] EAR INSTRUMENTS
1. Audiometer
2. Hearing aid

Contd….
G) EYE INSTRUMENTS
1.Occulometer
2.Aid for blind
H] LUNG INSTRUMENT
1. Spirometer

Contd….
I) BODY INSTRUMENTS
1. Ultra Sonography
2. Thermograph
3. Radiograph
4. Endoscope

Contd….
J) PHYSIOTHERAPY
INSTRUMENTS
1. Diathermy, Short wave
2. Vibrator ( Massage type )
3. U.V. Lymph
4. Microwave diathermy

Anatomy and Physiology
The science of structure of the body is
known as ANATOMY
Classification :
Gross ANATOMY
Topographical ANATOMY
Microscopic ANATOMY

Anatomy and Physiology
Physiology which relates to the normal
function of the organs of the body .
Example :
 Cell Physiology
 Pathaphysiology
- Circulatory Physiology
- Respiratory Physiology

Physiological Systems of the body
 Human body contains various systems
such as electrical ,mechanical, hydraulic,
pneumatic, chemical and thermal etc.
 Systems communicate internally with each
other and with external environment.
 With this, enable to perform useful tasks,
sustain life and reproduce itself.

Major Subsystems of the body
1. Cardiovascular System
 Cardio = “heart”
Vascular = “vessels”
It performs the essential service of transportation of oxygen, carbon dioxide
numerous chemical compounds and the blood cells.
 System made up of “heart” , “vessels and “blood”

Function of Cardiovascular System
 Delivering materials to cells
 Carrying wastes away
 In addition, blood contains cells that fight disease.

Heart
 Heart is divided into two parts right and Left-each part
has two chambers called atrium and ventricle.
 Heart has four valves:
-Tricuspid valve or Right Ventricle valve
- Bicuspid Mitral or Left Ventricle Valve
- Pulmonary Valve
- Aortic Valve
 Heart wall consist of three layers:
- Pericardium
- Myocardium
- Endocardium

4) Right Ventricle
The right ventricle
pumps oxygen-poor
blood to the lungs.
3) Right Atrium
The right atrium
receives blood from
the body that is low
in oxygen and high
in carbon dioxide.
The Heart
1
2
3
5
6
7
8
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1) Major vessel from
upper body to heart
2) Vessels from
lung to heart
5) The. aorta carries
blood from the left
ventricle to the body
6) Vessel from
heart to lungs
7) Vessels from
lung to heart
8) Left Atrium
Oxygen-rich blood is
carried from the lungs
to the left atrium.
9) Left Ventricle
The left ventricle
pumps oxygen-rich
blood from the heart.
Pathways of Blood
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Three types of blood vessels
 Arteries - move blood away from the heart
-Most arteries carry oxygen-rich blood
-The largest artery in the body is the Aaorta
have thick walls that are both strong and flexible.
Veins - move blood toward the heart
 Capillaries - tiny blood vessels that connect arteries and
veins
-Branching from the smallest arteries are capillaries, the
smallest blood vessels in your body.
-As blood flows through the capillaries, oxygen and
dissolved nutrients diffuse through the capillary walls and
into your body’s cells.
-Capillaries are involved in temperature regulation.

Function of the blood
 Carries oxygen from lungs to all body cells and removes carbon dioxide from the
cells
Carries waste products of cell activity to the kidneys to be removed from the body
Transports nutrients from the digestive system to body cells
Red blood cell
White blood cell

Conduction System of the heart
 Cardiac conduction system: The electrical conduction system
controls the heart rate
 This system creates the electrical impulses and sends them
throughout the heart. These impulses make the heart
contract and pump blood.

2. Respiratory System
 The Primary function of respiratory system is to supplies the blood
with oxygen so that the blood can deliver oxygen to all parts of the
body.
 It also removes carbon dioxide waste that cells produce.

Amazing Facts About the Respiratory System
Did you know that...
 Your right lung has three lobes and your left lung
only has two?
 The right lung is a little larger than the left lung?
 A person sleeping almost always breathes twelve
or fifteen times a minute?

More Amazing Facts About the Respiratory System
Did You Know That...
 The exhaling rate is faster in kids than in adults?
 The trachea is made out of cartilage shaped rings?
 The fastest recorded “ sneeze speed” is 165 km per
hour?
 It is healthier to breathe through your nose than
your mouth, because your nose hairs and mucus
clean the air.

3. Nervous System
 Control center for all body activities.
 Responds and adapts to changes that occur both
inside and outside the body
(Ex: pain, temperature, pregnancy)

your nervous system
is divided into the central
nervous system
(CNS)
and the
peripheral nervous
system (PNS)
which is the brain and
spinal cord
which connects everything
to the brain and spinal
cord

Central Nervous System
 Brain : a mass of 100 billion neurons located inside the
skull.
- Cerebrum : largest part of human brain
- Cerebellum : at base of brain
- Brain Stem : connects brain to spinal cord
 Spinal Cord : Column of nerves from brain to tailbone –
protected by vertebrae of spine
-Responsible for:
- Conducting impulses between the brain and the rest of
the body
*Impulses may travel as fast at 268 miles/hr.
 Neurons

Credit:MarkLythgoe&ChloeHutton,WellcomeImages
different regions have different
functions
Cerebral cortex
Functions include:
planning; reasoning;
language; recognising
sounds and images;
memory.
Corpus
callosum
connects the brain’s
right and left
hemispheres
Cerebellum
important for
coordination,
precision and timing
of movement
Brain stem
regulates heart
rate, breathing,
sleep cycles
and emotions

Peripheral Nervous System
Nerves : visible bundles of
axons and dendrites that
entend from the brain and
spinal cord to all other parts
of the body
- Motory Nerves
- Sensory Nerves

the cells of the nervous system are called neurones
cell body
axon
myelin sheath
dendrites nerve endings
nucleus
structure of a neurone

there are different typesof neurone
sensory neuronemotor neurone relay neurone
direction of
electrical
signal
sends signals to your muscles
to tell them to move
sends signals from
your sense organs
connects neurones to
other neurones
dendrites
cell body
axon
myelin
sheath
nerve
endings

neurones communicate with each other using a
mixture of electrical & chemical signals
cell body
axon
myelin sheath
dendrites nerve endings
nucleus an electrical
signal is
transmitted
along the axon
But what happens when the signal
reaches the end of the axon?

What do you think can change
neurons and their connections?
• Accidents
• Drugs
• Alcohol
• Disease

Accidents
• Physical injury of your neurons

Drugs and alcohol bind important receptors on neurons

Alcohol damages dendrites - can
repair after abstinence
Alcohol blocks
receptors and slows
down transmission

•Parkinson's Disease
•ALS - Lou Gehrig’s Disease
•Huntington’s Disease
•Multiple Sclerosis
•Alzheimer's
•Cerebral Palsy
•Epilepsy
•? SIDS

Facts-Did you know
There are around 47 miles of nerves in
your body.
One nerve cell may be connected to 1000
more.
Your nerve impulses can travel up to 390
feet per second.
Thousands of nerve cells die each day

What if
neurons die
here?
or hereor here
or here
or here

Transducers
• Transducer
– a device that converts primary form of energy into other different
energy form only for measurement purposes.
• Primary Energy Forms: mechanical, thermal, electromagnetic, optical,
chemical, etc.
• Sensor
– It is a wide term which covers almost everything from human eye
to trigger of a pistol.
– Senses the change in parameter(specific).

CLASSIFICATION OF TRANSDUCERS
 Active & Passive Transducers
 Analog & Digital Transducers
 Primary & secondary Transducers
 On the basis of principle used

Active vs Passive Transducers:
Passive Transducers:
 Add energy to the measurement environment as part of the
measurement process.
 Requires external power supply.
Strain gauge, potentiometer & etc.
Active Transducers :
 Do not add energy as part of the measurement process but may remove
energy in their operation.
 Does not require external power supply
Thermocouple, photo-voltaic cell & etc.

ANALOG & DIGITAL TRANSDUCERS
ANALOG TRANSDUCER - The
transducers which convert the input
quantity into an analog output which is a
continuous function of time.
DIGITAL TRANSDUCERS - The
transducers which convert the input
quantity into digital form means in the form
of pulses.

PRIMARY vs SECONDARY
TRANSDUCERS
 PRIMARY TRANSDUCERS - Some transducers contain
the mechanical as well as electrical device. The mechanical
device converts the physical quantity to be measured into a
mechanical signal. Such mechanical device are called as
the primary transducers.
 SECONDARY TRANSDUCERS - The electrical device
then convert this mechanical signal into a corresponding
electrical signal. Such electrical device are known as
secondary transducers

CLASSIFICATION ON THE BASIS OF
PRINCIPLE USED
 Capacitive
 Inductive
 Resistive
 Electromagnetic
 Piezoelectric
 Photoconductive
 Photovoltaic

Selecting a Transducer
 What is the physical quantity to be measured?
 Which transducer principle can best be used to measure this quantity?
 What accuracy is required for this measurement?
 Fundamental transducer parameters
 Physical conditions
 Environmental conditions
 Compatibility of the associated equipment
 Reducing the total measurement error :
 Using in-place system calibration with corrections performed in the
data reduction
 Artificially controlling the environment to minimize possible errors

Transducers for Physiological Variable
Measurements
• A variable is any quantity whose value changes
with time. A variable associated with the
physiological processes of the body is known as
a physiological variable.
• Physiological variables occur in many forms: as
ionic potential, mechanical movements,
hydraulic pressure ,flows and body temperature
etc.
• Different transducers are used for different
physiological variables.

Bio-Electric Potential
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Electrical Activity Measurement
• Electrodes:
– Electrodes convert ionic potential into electrical signals.
– Used for EEG, ECG, EMG, ERG and EOG etc.
– Different types of Electrodes are:
1) Surface Electrodes(no. Of muscles)
These electrodes are used to obtain bioelectric potentials from the surface of the
body.
2) Needle electrodes(specific to a muscle)
These electrodes are inserted into body to obtain localized measurement of potentials
from a specific muscle.
3) Microelectrodes(cellular level record)
Electrodes have tips sufficiently small to penetrate a single cell in order to obtain
readings from within cell.

Electrical Activity Measurement(cont.)
• Working of Electrodes:
• When metal electrodes come in contact with electrolyte then ion-electron exchange
takes place as a result of electro-chemical reaction.
One cation M+
out of the electrolyte
becomes one neutral
atom M
taking off one free
electron
from the metal
One atom M out
of the metal
is oxidized to form
one cation M+ and
giving off one free
electron e- to the
metal.

Half-cell potential
Oxidation and reduction processes take place when metal comes in contact
with Electrolyte .
Net current flow is zero but there exists a potential difference depends upon
the position of equilibrium and concentration of ions. That p.d. is known as
half-cell potential.
Over-potential
If there is a current between the electrode and electrolyte then half-cell
potential altered due to polarization is known as over-potential.
Electrical Activity
Measurement(cont.)

Electrical Activity
Measurement(cont.)
Types of Electrodes:
 Perfectly Polarizable Electrodes
- only displacement current, electrode behave like a capacitor
example: noble metals like platinum Pt
 Perfectly Non-Polarizable electrode
- current passes freely across interface,
- no overpotential
examples:
- silver/silver chloride (Ag/AgCl),
- mercury/mercurous chloride

ECG
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EEG
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Electrode Placement
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Block Diagram of ECG
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Effects of Artefacts on ECG Recording
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 Power Line Interference
Shifting of the baseline
Muscle tremors

Types of ECG Recorder
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 Single-channel Recorders
 Three –channel Recorders
 Vector electrocardiographs( vector-cardiography)
 Electrocardiograph systems for stress testing
 Electrocardiographs for computer processing
 Continuous ECG recording (Holter Recording )

Phonocardiograph (PCG)
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• A Phonocardiogram is a recording of the heart sounds and
murmurs.
• Eliminates subjective interpretation of the heart sounds
• Enables evaluation of the heart sounds and murmurs with
respect to the electric and mechanical events in the cardiac
cycle.
• Evaluation of the result is based on the basis of changes in the
wave shape and various timing parameters.

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• S1 – onset of the ventricular contraction
• S2 – closure of the semilunar valves
• S3 – ventricular gallop
• S4 – atrial gallop
• Other – opening snap, ejection sound
• Murmurs
Heart Sounds

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• The phonocardiograph transducer is a contact or air-
coupled acoustical microphone held against the
patient's chest (shown in fig).
• Various types of microphones are used, but most are
the piezoelectric crystal or dynamic type of
construction.
Microphones for Phonocardiography

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• The crystal microphone generally costs less and is more
rugged than the dynamic type.
• Also, the crystal microphone produces a larger output signal
for a given level of stimulus
• The dynamic microphone uses a moving coil coupled to
the acoustical diaphragm.
• The dynamic microphone is used when it is desirable to
have a signal frequency response similar to that of the
medical stethoscope.
• An air-coupled microphone with a 2-s time constant is
often used in apex phonocardiography.
Microphones for Phonocardiography

EEG
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 Electrical Activity of the brain
EEG electrodes are smaller than ECG
It is an Effective method for diagnosing
many neurological, disorder such as
epilepsy, tumour etc.

EEG Electrode Placement
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Brain Wave Classification
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EEG rhythms correlate with patterns of behavior (level of attentiveness,
sleeping, waking, seizures, coma).
Rhythms occur in distinct frequency ranges:
Gamma: 20-60 Hz (“cognitive” frequency band)
Beta: 14-20 Hz (activated cortex)
Alpha: 8-13 Hz (quiet waking)
Theta: 4-7 Hz (sleep stages)
Delta: less than 4 Hz (sleep stages, especially “deep sleep”)
Higher frequencies: active processing, relatively de-synchronized activity
(alert wakefulness, dream sleep).
Lower frequencies: strongly synchronized activity (nondreaming sleep,
coma).

Brain Wave Classification
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The period of High Frequency EEG that occurs during sleep is called
Paradoxical sleep or REM (Rapid Eye Movement).

Effects of Artefacts on EEG
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 Biological Artefacts
 Eye Induced Artefacts
 Cardiac Artefacts
 Muscle Artefacts
 Respiration Artefacts
Physiological Artefacts
 60 Hz Interference
 EEG Electrodes
 Environmental Artefacts
Non Physiological Artefacts

Block Diagram of EEG
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Evoked Potential
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If an external stimulus is applied to the sensory area of
brain, it responds by producing a electrical potential
known as Evoked Potential.
 Classification:
Visual Evoked Potential
Auditory Evoked Potential
SomatoSensory Evoked Potential

Blood Pressure
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Blood pressure is indicates your heart health
It is determined by the contractions of the heart
Your pressure varies depending on the condition of your
heart and blood vessels
Pressure is measured in millimeters of mercury (mm Hg)

Blood Pressure
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Blood Pressure Risks
12/3/2013
• High blood pressure (hypertension) increases the risk of:
 Chest pain (angina).
 Heart attack.
 Heart failure.
 Kidney failure.
 Stroke.
 Blocked arteries in the legs or arms (peripheral arterial disease.
 Eye damage .
 Aneurysms (permanent cardiac or arterial dilatation).

BMTS 353 88
Cont. Blood Pressure Risks
12/3/2013
• Low blood pressure (hypotension) increases the risk of:
 Reduces the blood flow to the brain and other vital organs.
 Dizziness or fainting.
 Lack of concentration.
 Blurred vision.
 Fatigue.
 Cold and clammy skin.
 Rapid shallow breathing.

Blood Pressure Measurement
 Blood pressure measurement techniques are generally put into two broad
classes:
1) DIRECT TECHNIQUES
Direct techniques of blood pressure measurement, which are also known as
invasive techniques, involve a catheter to be inserted into the vascular system.
eg. Percutaneos insertion, Catheterization etc
2) INDIRECT TECHNIQUES
The indirect techniques are non-invasive, with improved patient comfort and
safety, but at the expense of accuracy. eg. Sphygmomanometer, Rheographic
Method, Oscillometric Method, Ultrasonic Doppler Method etc

Blood Pressure (Sphygmomanometer/ Auscultatoy
Method)
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Auscultatory Method (cont.)
-) The observations differ from observer to another
-) A mechanical error might be introduced into the system e.g. mercury
leakage, air leakage, obstruction in the cuff etc.
-) The observations do not always correspond with intra-arterial pressure
-) Auscultatory tecnique cannot be used in noisy environment
+) Auscultatory technique is simple and does not require much
equipment
ADVANTAGES
DISADVANTAGES
-) The technique does not give accurate results for infants and
hypotensive patients

March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 15
How to measure?
 Non-invasive blood pressure
 Auscultation
 Oscillometry
Mercury sphygmomanometer
+ stethoscope
Mechanical manometer
+ stethoscope

The auscultation method

Systolic BP
Diastolic BP

The oscillometric method

The oscillometric method
 It is based on the
change of the
magnitude of
oscillation
 MAP – Mean Arterial
Pressure

Oscillometric Method
http://colin-europe.com/docpdfdemos/oscillo0104.wmv
The intra-arterial pulsation is
transmitted via cuff to transducer (e.g.
piezo-electric)
The arterial pressure oscillations
(which can be detected throughout the
measurement i.e. when P > SP and
P < DP) are superimposed on the cuff
pressure
SP and DP are estimated from the amplitudes of the oscillation by using a (proprietary)
empirical algorithm.
cuff
cuff
The cuff pressure is deflated either
linearly or stepwise

Oscillometric Method (cont.)
DISADVANTAGE
-) Many devices use fixed
algorithms leading to
large variance in blood
pressures
+) In the recent years,
oscillometric methods have
become popular for their
simplicity of use and
reliability.
ADVANTAGES
+) MP can be measured
reliably even in the case of
hypotension

Ultrasonic Method
A transcutaneous (through the skin)
Doppler sensor is applied here.
The motion of blood-vessel walls in
various states of occlusion is
measured.
The frequency difference between
transmitted (8 MHz) and received
signal is 40-500 Hz and it is
proportional to velocities of the wall motion and the blood.
The vessel opens and closes with each
heartbeat when
DP < P < SPcuff

Ultrasonic Method (cont.)
+) Can be also used in noisy environment
ADVANTAGES & DISADVANTAGES
+) Can be used with infants and hypotensive individuals
-) Subject’s movements change the path from sensor to vessel
As the cuff pressure is increased, the time between opening and closing
decreases until they coincide Systolic pressure
Again as the cuff pressure is decreased, the time between opening and closing
increases until they coincide Diastolic pressure

Direct Methods
in
Blood Pressure Measurements

General Facts
Direct measurement = Invasive measurement
Used only when essential to determine the blood pressure continuously and
accurately in dynamic circumstances
A vessel is punctured and a catheter (a flexible tube) is guided in
The most common sites are brachial and radial arteries but
also other sites can be used e.g. femoral artery
A division is made into extravascular and intravascular
sensor systems
This method is precise but it is
also a complex procedure
involving many risks….

Extravascular Sensor
The sensor is located behind the
catheter and the vascular pressure is
transmitted via this liquid-filled
catheter.
The ’normal’ measuring system
The actual pressure sensor can be e.g.
strain gage
variable inductance
variable capacitance
optoelectronic
piezoelectric, etc…

Extravascular Sensor (cont.)
The hydraylic link is the major source of errors. The system’s natural frequency
may be damped and degraded due (e.g.):
too narrow catheter
too long tubing
various narrow connections
air bubbles in the catheter
The catheter-sensor system must be flushed
with saline-heparine solution every few
minutes in order to prevent blood from
clotting at the tip.
.

Extravascular Sensor (cont.)
Normally the interesting frequency range is 0 – 100 Hz.
If only MP is measured the bandwidth is 20 Hz (harmonics > 10 are ignored)

Intravascular Sensor
The sensor is located in the tip of the catheter. This way the hydraulic connection is
replaced with an electrical or optical connection
+) The frequency response is not limited
by the hydraulic properties of the system.
No time delay.
-) Breaks easily
-) More expensive
+) Electrical safety and isolation when
using fiber optics
The dispacement of the diaphragm is
measured

Blood Pressure
Blood pressure is an important signal in determining the functional integrity of the
cardiovascular system. Scientists and physicians have been interested in blood
pressure measurement for a long time.

Transducers for Blood Pressure
Measurement
Strain Gauges
Resistance is related to length and area of cross-section of the
resistor and resistivity of the material as
By taking logarithms and differentiating both sides, the equation
becomes
Dimension
al
piezoresistanc
e
Strain gage component can be related by poisson’s ratio as

Measurement(cont.)
Gage Factor of a strain gage
G is a measure of
sensitivity
Think of this as a
Transfer Function!
Input is strain
 Output is dR
Put mercury strain gauge around an arm or chest to measure force of muscle
contraction or respiration, respectively
 Used in prosthesis or neonatal apnea detection, respectively
Strain Gauges

Measurement(cont.)
Strain Gauges

Measurement(cont.)
An inductor is basically a coil of
wire over a “core” (usually ferrous)
It responds to electric or magnetic
fields
A transformer is made of at least
two coils wound over the core: one
is primary and another is secondary
Primary Secondary Displacement Sensor
Inductors and tranformers work only for ac signals
Inductive Pressure Sensors ( LVDT)

Measurement(cont.)
Capacitive Pressure Sensors
When there is difference in P1 & P2
then diaphragm moves toward low
pressure side and accordingly
capacitance varies. So, capacitance
becomes function of pressure and
that pressure can be measured by
using bridge ckt.
It can be used for blood pressure
measurent.

Measurement(cont.)
Capacitive Pressure Sensors
Pressure
An example of a capacitive sensor is a pressure sensor.
In parts a, the thin sensor diaphragm remains parallel to the
fixed electrode and in part b, the diaphragm deflects under
applied pressure resulting in capacitance change

Measurement(cont.)
The other pressure sensing approach, characterized by a
diaphragm in front of the fibre optic link, is based on the
light intensity modulation of the reflected light caused by
the pressure-induced position of the diaphragm.
Fibre-optic pressure sensor

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Blood Flow
• Blood flow helps to understand basic physiological
processes and e.g. the dissolution of a medicine into the
body.
• Blood flow and changes in blood volume, are usually
correlated with concentration of nutrients and other
substance in the blood.
• Also, Blood Flow measurement reflects the
concentration of O2.

Blood Flow
• A measure of the velocity of blood in a major vessel. In a
vessel of known diameter , this can be calibrated as flow and
is most successful accomplished in arterial vessels. Used to
estimate heart output and circulation. Requires exposure of
the vessel. Flow transducer surrounds vessel. Methods of
measurement include
• Electro-magnetic
• Ultrasonic principles
• Fibre-optic laser Doppler flowmetry
• Thermal Convection
• Blood Flow Determination by Radiographic Method

Blood Flow Measurement
• Based on Faraday’s law of induction that a conductor that moves through a
uniform magnetic field, or a stationary conductor placed in a varying
magnetic field generates emf on the conductor:
• When blood flows in the vessel with velocity u and passes through the
magnetic field B, the induced emf e measured at the electrodes is.
 
L
de
0
LBu
For uniform B and uniform velocity profile
u, the induced emf is e=BLu. Flow can be
obtained by multiplying the blood velocity u
with the vessel cross section A.
Electromagnetic Flow meters

Blood Flow Measurement(cont.)
Electromagnetic Flow meter Probes
• Comes in 1 mm increments for
1 ~ 24 mm diameter blood vessels
• Individual probes cost $500 each
•Only used with arteries, not veins,
as collapsed veins during diastole
lose contact with the electrodes
• Needless to say, this is an
INVASIVE measurement!!!
• A major advantage is that it can
measure instantaneous blood
flow, not just average flow.

Ultrasonic Flow meters
 Based on the principle of measuring the time it takes for an
acoustic wave launched from a transducer to bounce off red blood
cells and reflect back to the receiver.
 All UT transducers, whether used for flowmeter or other
applications, invariably consists of a piezoelectric material, which
generates an acoustic (mechanical) wave when excited by an
electrical force (the converse is also true)
 UT transducers are typically used with a gel that fills the air gaps
between the transducer and the object examined

Ultrasonic Flow meters
The Doppler blood-flow measurement
Doppler blood flow detectors
operate by means of continuous
sinusoidal excitation. The
frequency difference calibrated
for flow velocity can be
displayed or transformed by a
loudspeaker into an audio
output.

122
Cont. Blood Flow
Normal blood flow velocity 0,5 m/s 1 m/s (Systolic, large vessel)

123
Blood Pressure

124
Ultrasonic Doppler Method
Blood Pressure
• The blood cells in the fluid
reflects the ultrasound signal
with a shift in the ultrasonic
frequency due to its movement.
• In the recent years ultrasound contrast agents have been used in
order to increase the echoes.
c
v
ff cd 2
f = 2 – 10 MHzc
c = 1500 - 1600 m/s (1540 m/s)
f = 1,3 – 13 kHzd

125
Laser Doppler Flowmetry
Blood Pressure
• The principle of measurement is the
same as with ultrasound Doppler.
• The laser parameter may have e.g.
the following properties:
5 mW
He-Ne-laser
632,8 nm wavelength
• The method is used for capillary
(microvascular) blood flow
measurements.

(1) Bios current => Thermister heating
(2) T2 Thermister is cooled by thermal convection.
Invasive, probe positioning is difficult.
The stronger F gets, The sharper the temperatur
is decreased.
(cf.) respiratory monitoring by thermister
Temp. of inspiration is 25˚C.
Temp. of expiration is 36.5˚C.
Thermal convection flowmeter

Radiographic Method
 Blood is not normally visible on an X-ray image because it has about the same
radio density as the surrounding tissue.
 By the injection of a medium into the blood vessel, the circulation pattern can
be made locally visible.
 On a sequential record of the X- ray image, the progress of the contrast
medium can be followed,obstructions can be detected and the blood flow in the
blood vessels can be estimated known as CINE or ANGIOGRAPHY.

128
Plethysmography Method
(Strain Gage)
Blood Pressure
Plethysmography means the methods
for recording volume changes of an
organ or a body part.
• Strain gage is made of silicone rubber tubes, which are filled with
conductive liquid (e.g. mercury) whose impedance changes with
volume.
• Venous occlusion cuff is inflated to 40 – 50 mmHg. In this way
there will be the arterial inflow into the limb but no venous outflow.

129
(Electric-Impedance)
Blood Pressure
• Different tissues in a body have a different resistivity. Blood is one
of the best conductors in a body.
• A constant current is applied
via skin electrodes.
• The change in the impedance
is measured.
• The accuracy is often poor.

130
(Photoelectric)
Blood Pressure
• A beam of IR-light is directed to
the part of the tissue which is to
be measured for blood flow (e.g.
a finger or ear lobe).
• The blood flow modulates the attenuated / reflected light which is
recorded.
• The light that is transmitted / reflected is collected with a photo
detector.
Poor measure for changes in volume
Very sensitive to motion artefacts
Method is simple
Heart rate is clearly seen

Pulse sensors
Heart rate measurement is one of the very important parameters of the human
cardiovascular system. The heart rate of a healthy adult at rest is around 72 beats
per minute (bpm).
Basically, the device consists of an infrared transmitter LED and an infrared
sensor photo-transistor. The transmitter-sensor pair is clipped on one of the
fingers of the subject. The LED emits infrared light to the finger of the subject. The
photo-transistor detects this light beam and measures the change of blood volume
through the finger artery. This signal, which is in the form of pulses is then
amplified and filtered suitably and is fed to a low-cost microcontroller for analysis
and display

Pulse Sensor(cont.)
The microcontroller counts the number of pulses over a fixed time interval
and thus obtains the heart rate of the subject. Several such readings are
obtained over a known period of time and the results are averaged to give a
more accurate reading of the heart rate. The calculated heart rate is displayed
on an LCD in beats-per-minute in the following format:
Rate = nnn bpm

133
Blood Pressure

134
Indicator Dilution Methods
(Dye Dilution)
Blood Pressure
• A bolus of indicator, a colored dye (indocyanine green),
is rapidly injected in to the vessel.
• The concentration is measured in the downstream
• The blood is drawn through a colorimetric cuvette and
the concentration is measured using the principle of
absorption photometry.

135
Indicator Dilution Methods
(Thermal Dilution)
Blood Pressure
• A bolus of chilled saline solution is injected into the
blood circulation system (right atrium).
• This causes decrease in the artery temperature.
• Catheter-tip probes are used to measure the change in
tempreture.

Cardiac Output
Whenthe heartcontracts

CardiacOutput
Cardiac Output is the volume of blood pumped
each minute, and is expressed by the following
equation:
• CO = SV xHR
• Where:
• CO is cardiac output expressed in L/min
(normal ~5 L/min)
• SV is stroke volume per beat
• HR is the number of beats per minute

140
Cardiac Output Measurement
(Fick Technique)
Blood Pressure

141
Cardiac Output Measurement
(Fick Technique)
Blood Pressurehttps://www.youtube.com/watch?v=nAgmCoqAoPo

Echocardiogram
• An echocardiogram is a test in which ultrasound is
used to examine the heart.
• Displaying a cross-sectional "slice" of the beating
heart, including the chambers, valves and the
major blood vessels that exit from the left and
right ventricle
• M-mode
• two- dimensional (2-D) Echo
• Doppler Examination
• 3-D echo

What information does
Echocardiography and Doppler
provide?
• Size of the chambers of the heart
• Pumping function of the heart
• Valve Function
• Volume status
• Other Uses: fluid in the pericardium,
congenital heart diseases, blood clots or
tumors within the heart

Electromyography(EMG)
• Electromyogram (EMG) is a technique for
evaluating and recording the activation signal of
muscles.
• EMG is performed by an electromyograph,
which records an electromyogram.
• Electromyograph detects the electrical potential
generated by muscle cells when these cells
contract and relax.

INTRODUCTION Contd.
EMG Apparatus Muscle Structure/EMG

ELECTRICAL
CHARACTERITICS
• The electrical source is the muscle membrane
potential of about -70mV.
• Measured EMG potentials range between
< 50 μV up to 20 to 30 mV, depending on the
muscle under observation.
• Typical repetition rate of muscle unit firing is
about 7-20 Hz.
• Damage to motor units can be expected at
ranges between 450 and 780 mV

ELECTRODE TYPES
Intramuscular -
Needle Electrodes
Extramuscular - Surface
Electrodes

EMG PROCEDURE
• Clean the site of application
of electrode;
• Insert needle/place surface
electrodes at muscle belly;
• Record muscle activity at rest;
• Record muscle activity upon
voluntary contraction of the
muscle.

EMG Contd.
• Muscle Signals are
Analog in nature.
• EMG signals are also
collected over a
specific period of
time.
Analog Signal

EMG Contd.
EMG processing:
Amplification
& Filtering
Signal pick up
Conversion of Analog
signals to Digital signals
Computer

APPLICATION OF EMG
• EMG can be used for diagnosis of
Neurogenic or Myogenic Diseases.
• You tube link of EMG

155
Patient Care, Monitoring and Safety Measures
Blood Pressure
 The Patient Monitoring System (PMS) is a very critical monitoring systems,
it is used for monitoring physiological signals including Electrocardiograph
(ECG), Respiration , Invasive and Non-Invasive Blood Pressure, Oxygen
Saturation in Human Blood (SpO2), Body Temperature and other Gases etc.
 In PMS, the multiple sensor and electrodes is used for receiving
physiological signals like as ECG Electrodes, SpO2Finger Sensor, Blood
Pressure Cuff and Temperature Probe to measure the physiological signals.

156
Patient Care, Monitoring and Safety Measures
Blood Pressure
 During treatment, it is highly important to continuously monitor the vital
physiological signs of the patient. Therefore , patient monitoring systems has
always been occupying a very important position in the field of medical devices.
 The continuous improvement of technologies not only helps us transmit the vital
physiological signs to the medical personnel but also simplifies the measurement
and as a result raises the monitoring efficiency of patients.

157
Classes of Patient Monitoring System
Blood Pressure
In the past, the dominant products manufactured by
medical device manufacturers are mainly those for
single parameter measurement. Nowadays however,
a multi-parameter patient monitor is commonly
used.
1.Single-Parameters Monitoring Systems
2.Multi-Parameter Patient Monitoring Systems

158
Single Parameter Monitoring System
Blood Pressure
The single parameter monitoring system
is available for measuring blood pressure
of a human body, ECG
(Electrocardiograph) monitor, SpO2
(Oxygen Saturation in Blood) monitor etc..

159
Multi- Parameter Monitoring System
Blood Pressure
 A multi-parameter Patient Monitoring System (PMS) is used for multiple
critical physiological signs of the patient to transmit the vital information
like Electro cardiograph , Respiration Rate, Blood pressure etc. Therefore,
multi parameter PMS has always been occupying a very significant
position in the field of medical devices.
 Most diseases of the heart and of the circulatory system , referred to as
cardiovascular diseases, strike with out warning and prompt treatment is
required .
 Such treatment is best provided in a specialized area of hospital referred
to as “intensive care unit.”(ICU).
 These specialized hospital units provide constant observation of the
subject, constant monitoring of the subject’s physiological condition
and provide immediate emergency treatment whenever it is required.

160
Three Important Intensive Care Units
Blood Pressure
 Coronary intensive care: units used for treatment of
diseases of the heart such as the heart attacks
 Stroke intensive care: Units used for treatment of
diseases of the circulatory system such as stroke.
 Pulmonary intensive care units: Pulmonary
intensive care unit s are used for treatment
of respiratory diseases.

161
PHYSIOLOGICAL FUNCTIONS TO BE MONITOR DURING
INTENSIVE CARE UNIT
Blood Pressure
 Cardiac monitoring
 Hemodynamic monitoring,
 Respiratory monitoring
 Neurological monitoring
 Blood glucose monitoring
 Childbirth monitoring
 Body temperature

ECG MONITORING
• The principal physiological signal monitored in an intensive
care unit is often the electrocardiogram. The electrocardiogram
is usually monitored in the lead-II configuration with two active
electrodes.
• These two electrodes are placed approximately 12inches apart
along the maximum potential axis of the subject’s heart.
• A third electrode (ground) should be located elsewhere on the
chest. This electrocardiogram monitoring configuration is
referred to as three-lead chest cluster.
• The electrodes used for ECG monitoring during intensive care
must be suited for long term monitoring applications.
• The set of leads used for monitoring purpose is called ‘rhythm’
• strip and its purpose is just to note the heart beat and not for
analyzing it.

Blood Pressure Monitoring
• The second physiological parameter often of prime importance
in intensive care monitoring is blood pressure.
• Korotkoff system-Riva-Rocci Method
• Blood pressure can be monitored using the automatic cuff pump
and Korotkoff microphone blood- pressure measurement
system this system is occasionally used in intensive care units. ,
• It also possesses the disadvantage of it does not provide a
continuous record of the subject’s blood pressure.
• Thus, if for some reason the subjects blood pressure were to
suddenly drop, this system may take some minutes or so to
detect this pressure drop.
•

Blood Pressure Monitoring……
• PLETHYSMOGRAPH
• Blood pressure monitoring with plethysmograph
offers the least discomfort to the subject; however, it
provides only a relative indication of the well being
of the circulatory system rather than providing
absolute values for diastolic and systolic pressure.
• Digital blood pressure monitors are now-a-days often
used in many intensive care units. Any intensive care
unit may employ one or more of these techniques
and indeed all three may be available if required.

RESPIRATION MONITORING
• It is often desirable to monitor the subject’s
respiratory activity during intensive care ;
• this may be accomplished with
thermistor pneumograph placed in the subject’s
nostril.
• BODY TEMPERATURE
•
• It is often also desirable to monitor body temperature
in intensive care subjects via a rectal or armpit
thermistor probe

CENTRAL NURSE’S STATION….
• Multi connector cable connects the output form the four
subject- monitoring sites located beside each intensive care bed
to the central nurse’s station.
• Each subject’s ECG is continuously displayed via a four channel
CRT display. And also these signals are being recorded
continuously on a memory loop tape recorder.
• This tape recorder contains the previous one-minute ECG
history for each subject by recording the ECG on a
tape loop“one minute” in length

Present Parameters in Patient
Monitoring System
• ECG 3/5/10 leads
• Respiration
• Invasive Blood Pressure (IBP)
• Non Invasive Blood Pressure(NIBP)
• Pulse Oxy Meter (SpO2)

Non invasive
Blood pressure
ECG
MONITOR
PULSE
OXYMETER

Hemodynamic monitoring
• Cardiac output and flow rate ;
• The heart is the driver of the circulatory system, pumping blood
through rhythmic contraction and relaxation.
• The rate of blood flow out of the heart meaning literally "blood
flow, motion and equilibrium under the action of external
forces", is the study of blood flow or the circulation. It explains
the physical laws that govern the flow of blood in the blood
vessels.

Respiratory monitoring
• Measurement of airway pressure (Paw), flow (F) and volume (Vol)
during mechanical ventilation assists in the differential diagnosis of
respiratory failure. Airway occlusion technique makes possible to
carefully characterize the mechanics of the lung, chest wall, and the
total respiratory monitoring system
• Pulse oximetry ;which involves measurement of the saturated
percentage of oxygen in the blood, referred to as SpO2, and
measured by an infrared finger cuff,
• Capnography ;, which involves CO2 measurements, referred to as
(EtCO2) or end-tidal carbon dioxide concentration. The respiratory
rate monitored as such is called AWRR or (airway respiratory rate).

Neurological monitoring - EEG
• Intracranial pressure. Also, there are special
patient monitors which incorporate the
monitoring of brain waves
• Blood glucose meter ; is an electronic device
for measuring the blood glucose level
• Childbirth; also known as labour, delivery,
birth,

Body temperature monitoring
• Body temperature" redirects here. For
information regarding normal human
body temperature,

Components of Medical monitor
• Sensor
• Translating component
• Display device
• Communication links
• Alarm

Hospitals may have ICUs that cater to a specific
medical specialty below using all medical monitor
Neonatal intensive care unit (NICU)
Pediatric intensive care unit (PICU)
Psychiatric intensive care unit (PICU)
Coronary care unit (CCU):
Medical intensive care unit (MICU)
Neurological intensive care unit (Neuro ICU)
Trauma intensive care unit (Trauma ICU).
Post-anesthesia care unit (PACU):
Surgical Intensive Care Unit (SICU):
Mobile Intensive Care Unit (MICU)

Use of computers for patient
monitoring
real-time monitoring
Wherever you are – in the hospital, at home, or on the
road – you have access to the patient information you
need to make informed clinical decisions viaWeb and
iPad access. IntelliVue Information Center iX offers
virtually anywhere, anytime access to key patient
monitoring information.

Use of computers for patient monitoring
Automatic
control
Patient equipment Computer DBMS
Reports
Mouse and
keyboard
Display
Transducers
Clinician

ICU
Bed Bed BedBed
Nurse station
Telemetry
WEB
connection

FUTURE TRENDS IN PATIENT
MONITORINGSY STEM
• Blood Gas Analyzer
• Drug Dosage calculator
• Drug Management System
• Wearable PMS
• Telemetry / Telemedicine

189
Patient Safety
Blood Pressure
 The main objective of any healthcare system should be the safe progress
of the patients through all parts of the system.
 Harm from their care as well as from the environment in which it is
carried out, must be avoided and risk minimized in care delivery
processes.
 Electrical shocks, burns and fire hazards caused by medical equipment
are one of the highest risks that may harm the patient.
 Electric shock: When the human body comes in contact with the live
wire and an uninsulated electric power, the power flows naturally and
easily through the body and we experience it as an E-shock.

Electrical safety
Medical procedures usually expose the patient to more hazards than
the typical home or workplace, because :-
1. In medical environments the skin and mucous membranes are
frequently penetrated or altered.
2. There are many sources of potentially hazardous substances and
energy forms that could injure either the patient or the medical
staff.
These sources of hazards include:-
 fire, air, earth, water, chemicals, drugs, microorganisms
 Waste products
 Sound and electricity
 Natural and unnatural disasters surroundings, gravity, mechanical
stress
 People responsible for acts of omission and operation

Physiological effects of electricity
 For a physiological effect to occur, the
body must become part of an electric
circuit. Current must enter the body at
one point and leave at some other point
 The magnitude of the current is equal to
the applied voltage divided by the sum
of the series impedances of the body
tissues and the two interfaces at the
entry points
Three phenomena can occur when electric
current flows through biological tissue:
(1) Electric stimulation of excitable tissue
(nerve and muscle)
(2) Resistive heating of tissue
(3) Electrochemical burns and tissue
damage for direct current and very
high voltages
psychophysical and physiological effects
of electrical current in humans:-
70 kg
AWGNo.8copperwires

psychophysical and physiological effects of electrical current in humans:-
Threshold of perception = the minimal current that an individual can detect.
This threshold varies considerably among individuals and with the measurement
conditions (wet or dry skin)
Thresholds for dc current range from 2 to 10 mA, and slight warming of the skin is
perceived (realized)

Let-go current:-
Is defined as the maximal current at which the subject can withdraw
voluntarily.
Involuntary contractions of muscles or reflex withdrawals is occur
The minimal threshold for the let-go current is 6 mA
Respiratory paralysis, pain, and fatigue:-
 respiratory arrest has been observed at 18 to 22mA
 Strong involuntary contractions of the muscles and stimulation of the
nerves can be painful and cause fatigue if there is long exposure.
psychophysical and physiological effects of electrical curren
in humans:-

Ventricular fibrillation
Ventricular fibrillation:-
Is a rapid and disorganized cardiac rhythm.
If the magnitude of the current is sufficient to excite only part of the heart
muscle and disrupted the heart rate
The heart rate can rise to 300 beats/min
The fibrillation does not stop when the current that triggered it is
removed.
Ventricular fibrillation is the major cause of death due to electric shock.
The threshold for ventricular fibrillation for an average-sized human
varies from about 75 to 400 mA
Normal rhythmic activity returns only if a brief high-current pulse from a
defibrillator is applied to depolarize all the cells of the heart muscle the
cells relax together, a normal rhythm usually returns

Body weight and fibrillation, duration of the current
Several studies using animals of various
sizes have shown that the fibrillation
threshold increases with body weight
Fibrillating current increases from 50 mA
rms for 6 kg dogs to 130 mA rms for 24
kg dogs.

196
Types of Shocks
Blood Pressure
Gross Shock/Macro Shock: The current flows through the
body of the subject ,e.g. as from arm to arm.
Micro current Shock: The current passes directly through the
heart wall. This is the case when cardiac catheters may be
present in the heart chambers.

Point of entry (macroshock and microshock)
Macroshock:-
When current is applied at two points on
the surface of the body, only a small
fraction of the total current flows through
the heart (macroshock).
The magnitude of current needed to
fibrillate the heart is far greater when the
current is applied on the surface of the
body than it would be if the current were
applied directly to the heart
Microshock:-
All the current applied through an
intracardiac catheter flows through the
heart
small currents called microshocks can
induce Ventricle fibrillation
Current of about 20 µA can cause
microshock .
The widely accepted safety limit to prevent
microshocks is 10 mA.

Distribution of electric power
Electric power is needed in health-care
facilities for :-
1. The operation of medical
instruments
2. Lighting, maintenance appliances
3. Patient conveniences (such as
television, hair curlers, and electric
toothbrushes)
4. Clocks, nurse call buttons, and an
endless list of other electric devices
• So the first step on providing
electrical safety is to control the
availability of electric power and the
grounds in the patients’ environment
Safe distribution of power in health-care
facilities:-
High voltage (4800 V)
enters the building—
usually via underground
cables

Patients’ electrical environment
 A shock hazard exists between the two
conductors supplying either a 240 V or
a 120 V appliance.
 Because the neutral wire on a 120 V
circuit is connected to ground, a
connection between the hot conductor
and any grounded object poses a shock
hazard.
 Microshocks can occur if sufficient
potentials exist between exposed
conductive surfaces in the patients’
environment
THE maximal potentials permitted
between any two exposed conductive
surfaces in the vicinity of the patient are
specified by the 2006 NEC, Article 517-
15:
1. General-care areas, 500 mV under
normal operation
2. Critical-care areas, 40 mV under
normal operation
Things must be done:-
1. All exposed conductive surfaces in
the vicinity of the patient must be
grounded at a single patient
grounding point.
2. Periodic testing for continuity
between the patient ground and all
grounded surfaces is required
3. Each patient-bed location in general-
care areas must have at least four
single or two duplex receptacles ,the
receptacle must be grounded
4. At least two branch circuits with
separate automatic overcurrent
devices must supply the location of
each patient bed.
5. For critical-care areas at least six
single or three duplex receptacles are
required for each location of a patient
bed

Isolated-power systems
Any ground faults can posses hazard .
A ground fault :-
Is a short circuit between the hot
conductor and ground that injects large
currents into the grounding system.
 Isolation of both conductors from
ground is commonly achieved with an
isolation transformer
isolation transformer + line isolation monitor
Measures the total possible resistive and
capacitive leakage current (total hazard current)
that would flow through a low impedance if it
were connected between either isolated
conductor and ground.
When the total hazard current exceeds 3.7 to 5.0
mA for normal line voltage, a red light and an
audible alarm are activated
Checking the lines by the LIM can interfere
with (ECG,EEG ,ect.) ,or it can trigger
synchronized defibrillators

Microshock hazards
Leakage currents:-
Small currents (usually on µA) that flow between any adjacent insulated
conductors that are at different potentials
The leakage current in line operated equipment flows through:
1. The stray capacitance between the two conductors.
2. Resistive leakage current flows through insulation, dust, and moisture.
If the ground wire is broken, then the chassis potential rises above ground,
and a patient who touches the chassis and has a grounded electric
connection to the heart may receive a micro shock

Electrical-safety codes and standards
A code
is a document that contains only mandatory requirements.
A standard
also contains only mandatory requirements, but compliance
tends to be voluntary, and more detailed notes and explanations
are given.
Standards are designed for voluntary use and do not impose any
regulations.
However, laws and regulations may refer to certain standards
and make compliance with them compulsory.
A manual or guide
is a document that is informative and tutorial but does not
contain requirements

Limits on Leakage Current
Limits on Leakage Current for Electric
Appliances
one fault is applied to the equipment to see
what happens

Basic approaches to protection against shock
There are two fundamental methods of
protecting patients against shock:-
1. The patient should be completely
isolated and insulated from all
grounded objects.
2. All sources of electric current and all
conductive surfaces within reach of
the patient can be maintained at the
same potential, which is not
necessarily ground potential
 In practical neither of these approaches
can be fully achieved so we used :-
 Grounding system
 Isolated power-distribution system
 Ground-fault circuit interrupters
(GFCI)
 Reliable grounding for equipment
 Reduction of leakage current
 Double-insulated equipment
 Operation at low voltages
 Electrical isolation
 Isolated heart connections
For the power distribution
 For the equipment

Protection: power distribution
The patient equipment grounding point
is connected individually to all :-
receptacle grounds
Metal beds
Metal door and window frames
Water pipes
Any other conductive surface.
These connections should not exceed
resistance of 0.15 Ω
The difference in potential between
receptacle grounds and conductive
surfaces should not exceed 40 mV

Chassis leakage current
Chassis leakage current:-
Leakage current emanating from the chassis should not exceed :-
500 mA for appliances with single fault not intended to contact
patients .
300 mA for appliances that are intended for use in the patient care
vicinity.
These are limits on rms current for sinusoids from dc to 1 kHz,
and they should be obtained with a current-measuring device of
1000 Ω or less
Chassis leakage-current test

Leakage current in patient leads
Limits on leakage current in patient leads should be 50 µA.
Isolated patient leads must have leakage current that is less than 10 µA.
leakage current between any pair of leads or between any single lead and all
the other patient leads should be measured.
Test for leakage current from patient leads to ground

Test for leakage current between patient leads
Test for leakage current between patient leads
leakage current between any pair of leads or
between any single lead and all the other patient
leads should be measured

ELECTRICAL SYSTEM IN THE
HEART

WHEN DO WE NEED A PACEMAKER
???
• Bradycardia – a condition in which the heart
beats too slowly – less than 60 beats per
minute
• Tachycardia – a condition in which the heart
beats too fast – more than 80 beats per
minute
• Atrial fibrillation – the upper chambers of
the heart beat rapidly

WHAT IS A PACEMAKER
The basic parts :
• Power source
• Pulse generator
• Electrodes

Biomedical Instrumentation

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