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Biomedical Engineering
1. MODULE 1-TOPICS
BIOMETRICS
CHARACTERISTICS OF BIOMEDICAL INSTRUMENTS
PHYSIOLOGICAL SYSTEMS OF HUMAN BODY
BIOCHEMICAL SYSTEM
CARDIOVASCULAR SYSTEM- The Heart
RESPIRATORY SYSTEM
NERVOUS SYSTEM
THE KIDNEY
BIOELECTRIC POTENTIALS
BIO-POTENTIAL ELECTRODES
TRANSDUCERS- ECG, EEG, EMG
2. INTRODUCTION
Concept of biomedical engineering
Biometrics:- Science deals with the study of
measurements of physiological systems of the body
Physiology:- Study of the normal functionality of the
human body organ
Biomedical Instrumentation:- Provides the set of
equipments or tools required for the measurement
of physiological variables.
3. CHARACTERISTICS OF BIOMEDICAL
INSTRUMENTATION SYSTEM
Range:- Should have minimum to maximum range
Sensitivity:- Ability of instrument to measure small variations
accurately. Should not be too high or too low.
Linearity:- Output should be steady or linear with respect to input.
Hysteresis:- Should be minimum
Frequency Response
Accuracy:- True reading-Actual reading. Should be high
4. CHARACTERISTICS OF BIOMEDICAL
INSTRUMENTATION SYSTEM
Signal-to-Noise Ratio:- Noise content should be low.
S/N ratio should be very high.
Stability
Isolation
Simplicity
5. PHYSIOLOGICAL SYSTEMS OF
HUMAN BODY
BIOCHEMICAL SYSTEM
CARDIOVASCULAR SYSTEM
RESPIRATORY SYSTEM
NERVOUS SYSTEM
6. CARDIOVASCULAR SYSTEM
Closed complex hydraulic system with a four-
chambered pump connected to flexible tubular
structures(blood vessels).
Main functions:
Transportation
Blood purification
Structural details:
Two parts( right & left)
Each part has two chambers
• Atrium(Auricle)
• Ventricle
7. CARDIOVASCULAR SYSTEM
Heart wall has three layers:
Pericardium:-
• Moist
Myocardium:-
• Main muscle
• Short cylindrical fibers
• Automatic in action
Endocardium:-
• Smooth lining
9. CARDIOVASCULAR SYSTEM
It has four valves:-
Tricuspid valve or right atrio-ventricular valve
Bicuspid mitral valve or left atrio-ventricular valve
Pulmonary valve or semilunar valve
Aortic valve
o All these valves are unidirectional
o Provides synchronous operation
10. CARDIOVASCULAR SYSTEM
2 types of blood circulation
Pulmonary circulation
Right ventricle Pulmonary artery Lungs
Lungs Pulmonary veins Left atrium
Systemic circulation
Left atrium Left ventricle Aorta Arteries
(Exchange of gases)
Veins Superior/Inferior venacavae Right atrium
Right ventricle
13. RESPIRATORY SYSTEM
The respiratory system is the structure in the
human body which allows us to breathe. It brings
oxygen into our body and removes carbon dioxide
out of our body.
The respiratory system is made up of 5 main parts:
1. Nose
2. Mouth
3. Trachea (windpipe)
4. Lungs
5. Diaphragm
15. RESPIRATORY SYSTEM
Includes
Nostrils- opening of nasal cavity
Mouth- alternate vent
Pharynx- muscular tube
Larynx- vocal cords
Trachea- wind pipe through which air passes
Bronchus- tube like structure at the end of trachea
Lungs- main organ, bag like structure
Diaphragm- controls the inspiration and expiration by
relaxation and contraction
16. RESPIRATORY SYSTEM
o The lungs are made up of 3 main parts:
• Bronchus (right & left)
• Bronchioles
• Alveoli
17. TERMS RELATED TO RESPIRATORY SYSTEM
Tidal volume- volume of air inspired and expired during each
normal breathe
Inspiratory reserve volume- additional volume that can be
inspired after a normal inspiration
Expiratory reserve volume- additional volume that can be
expired after a normal expiration
Residual volume-amount of air remaining in the lungs after all
possible air has been forced out.
Vital capacity- sum of TV,IRV and ERV
18. KIDNEY
Main function- remove the residue from blood
plasma. It also maintains acid-base balance
It involves 2 processes
Removal of waste products from blood plasma
Regulation of the composition of blood plasma
Situated at the back of the abdominal cavity and
just below the diaphragm
24. NERVOUS SYSTEM
Controls and co-ordinates all the functions of
human body
Nervous system
Central Peripheral Autonomous
• Brain (all the nerves) (part of PNS)
• Spinal cord
o Brain-cerebrum, cerebellum, brain stem
26. NERVOUS SYSTEM
Spinal Cord
• Runs through vertebral column
• Nerve cells connected to it.
• Decision without thinking
Peripheral Nervous System
• Sensory nerves-brings sensory info into the CNS
• Motor nerves-control the motor functions of muscles
Autonomous Nervous System
• Part of PNS
• Involved in emotional responses and controls smooth
muscles in various parts of the body
• controls heart rate, respiration rate, salivation,
perspiration…
27. BIOELECTRIC POTENTIAL
Bioelectric potential?
Resting Potential?
Polarized state of a cell?
Action Potential?
Depolarized state of a cell?
Depolarization & Repolarization?
Terms related to ionic potential of a cell?
• Net height of the action potential
• Absolute refractory period
• Relative refractive period
28. BIOELECTRIC POTENTIAL
Bioelectric potential
Certain systems of the body generate their on monitoring
signals which convey useful information about the functions
they represent.
These signals are bioelectric potentials associated with
nerve conduction, brain activity, heartbeat, muscle activity and
so on.
So, bioelectric potentials are actually ionic voltages produced
as a result of the electrochemical activity of certain special
types of cells.
Through the use of transducers capable of converting
ionic potentials into electric voltages, these natural monitoring
signals can be measured and results displayed in a
meaningful way to aid the physician in his diagnosis and
treatment of various diseases.
35. CLASSIFICATION OF ELECTRODES
Micro electrodes- to measure potential within a cell
or near the cell.
Metal Microelectrodes- are formed by electrolytically
etching the tip of a fine tungsten or stainless steel wire
to the desired size.
Micropipette Electrodes- here, a glass micropipette with
the tip drawn out to the desired size (usually 1 micron)
contains an electrolyte compatible with the cellular
fluids.
36. CLASSIFICATION OF ELECTRODES
Skin surface or body surface electrodes- mainly for
ECG, EEG and EMG
Immersion electrodes
Floating type electrodes-with conductive path between
metal and skin being electrolyte paste or jelly
Various Spray-on-electrodes and disposable electrodes
are available
Ear clip electrode for EEG
Scalp surface electrode for EEG
37. CLASSIFICATION OF ELECTRODES
Needle electrodes:-
Used to penetrate the skin to record the EEG potentials
or EMG potentials of a group of muscles.
They reduce interface impedance
A single wire inside the needle serves as a unipolar
electrode which measures the potential at the point of
contact with respect to some reference.
Some of the needle electrodes are
• Concentric needle electrodes
• Bipolar needle electrodes
• Monopolar needle electrodes
38. TRANSDUCERS FOR BIO MEDICAL
APPLICATIONS
PHYSICAL VARIABLE TYPE OF TRANSDUCER
Force (or Pressure) Piezoelectric
Unbonded strain gauge
Displacement Variable resistance, ind, cap
Variable inductance
Variable capacitance
LVDT
Mercury strain gauge
Surface strain Strain gauge
Velocity Magnetic induction
Temperature Thermocouple, Thermistor
Light Photovoltaic, Photoresistive
Magnetic field Hall effect
39. TRANSDUCERS FOR BIO MEDICAL
APPLICATIONS
In medical applications, the basic
physiological variables are first
transformed into one of the physical
variables listed before. Examples
would be measurement of blood
pressure using strain gauges and
blood flow by magnetic induction.
42. ECG TRANSDUCER(RECORDING SET UP)
Defibrillation and protection circuit:-
Patient is connected to this circuit through different
connecting cables.
Contains buffer amplifier and over voltage protection
circuit.
Over voltage occur when ECG is used in conjunction
with the radiofrequency diathermy units.
Over voltage protection circuit includes resistors and
neon lamps so as to avoid the entrance of excess of
voltage.
Lead Selector Switch:-
Used to feed the input voltage from the appropriate
electrode to the preamplifier.
43. ECG TRANSDUCER(RECORDING SET UP)
Calibrator:-
Push button closed, standardization of 1mV is
introduced to pre amplifier.
BioAmplifier:-
Consists of a pre amplifier, power amplifier
Auxiliary Amplifier(CM Reduction Amplifier):-
To reduce interference
Isolated Power supply:-
To power the bio amplifier
Output unit:-
Cathode Ray Oscilloscope or a paper chart recorder
45. ECG WAVEFORM
Electrocardiography
Electrocardiogram-waveform
Electrocardiograph- instrument
Waveform Details:-
P wave
R wave(QRS complex)
T wave
S-T interval
U wave
46. PHYSIOLOGICAL NATURE OF ECG WAVEFORM
Wave Origin Amplitue in Duration
mv sec
P wave contraction of right and left 0.25 0.12 to 0.22
atrium(depolarization of atrial (P-R interval)
musculature)
R Repolarization of the atria & 1.60 0.07 to0.1
wave(QRS the depolarzn. of the ventricles
complex) which occur almost
simultaneously
T wave ventricular 0.1 to 0.5 0.05 to 0.15
repolarization(relaxation of (S-T interval)
myocardium)
S-T interval Ventricular contraction < 0.1 0.2
U wave Slow repolarisation of < 0.1 0.1(T-U
intraventricular system. interval)
47. ANALYSIS OF ECG SIGNALS
Normal ECG curve
First degree AV block, due to prolonged conduction
time.
Bundle block, due to the improper conduction of the
stimulus to the ventricle.
48. ANALYSIS OF ECG SIGNALS
Myocardial infarction, due to obstruction of the
tissue’s blood supply
Coronary insufficiency, ST segment depressed &
negative T wave is present.
Ventricular fibrillation
51. EEG TRANSDUCER(RECORDING SET UP)
Electro encephalography - study of electrical
activities of the brain.
Electrodes attached to different parts of the skull of
a patient.
8 channel EEG recorder:-
Patient cable consists of 21 electrodes
Electrodes connected to selector in groups of 8-
Montage of electrodes
Right ear electrode reference electrode right brain
electrodes
Left ear electrode reference electrode left brain
electrodes
52. EEG TRANSDUCER(RECORDING SET UP)
Interference problem is reduced by differential
amplifier(preamplifiers)
Filter bank:- consists of appropriate filters to select
different types of brain waves.
Output can be given to 8-channel pen recorder,
display unit, computer storage memory for further
processing.
Evoked Potential:- Measure of the “disturbance” in
the EEG pattern that results from external stimuli.
Time delay between stimulus and response can be
measured in signal processing unit.
53. EEG FREQUENCY BANDS
Below 31/2 Hz -Delta waves
From 31/2 Hz to about 8 Hz - Theta waves
From 8 Hz to about 13 Hz - Alpha waves
Above 13 Hz - Beta waves
54. BRAIN WAVES
Alpha waves-normally
persons Awake and alert
,occipital region.
Beta waves- recorded
from parietal and
temporal regions.
Theta waves- recorded
from parietal and
temporal regions of
Children, adults-
emotional stress
Delta waves-deep sleep,
premature babies, every
serious organic brain
diseases.
56. BLOCK DIAGRAM FOR EMG RECORDING SET UP
Electro myography :- study and interpreting of muscle
action potential.
potentials measured by placing surface electrodes on
the skin.
Individual cell potential measured by means of needle
electrode
EMG appears like random noise waveform.
Contraction of muscle fibers produce action potentials
57. BLOCK DIAGRAM FOR EMG RECORDING SET UP
Amplitude of EMG signals depends
• Type & placement
• Degree of muscular exertions
Normal frequency of EMG signals is 60 Hz
EMG signal amplitude ranges from 0.1 to 0.5 mV.
Amplifier with high CMRR and input impedance
Output can be given to oscilloscope, tape recorder or AF
amplifier.
59. UNIVERSITY QUESTIONS- 4 MARKS
Explain resting potential and how it is produced?
Explain the respiratory system and bring out its
analogy with pneumatic system?
Describe man-measurement system with diagram
and explain each.
Define biometrics and the characteristics of
instruments used in BMI
Explain bioelectric potentials, resting and action
potential with waveform.
Differentiate Tidal Volume, Inspiratory Reserve
Volume, Expiratory Reserve Volume, Residual
Volume, Vital Capacity.
60. UNIVERSITY QUESTIONS-4 MARKS
Define the important lung capacities and explain
them.
How blood gets purified?
Briefly explain pulmonary and systemic blood
circulation?
What are the functions of kidney
Explain different electrodes used in BMI
Explain in brief about the transducers used for
ECG, EEG and EMG.
Explain the cardiovascular system and bring out its
analogy with hydraulic system?
61. UNIVERSITY QUESTIONS- 12 MARKS
(i) What are bioelectric potential? Discuss the
frequency and voltage range of ECG, EEG and
EMG signals- 8 marks.
(ii) How does the blood circulate throughout the
body?- 4 marks
o What is meant by central nervous system? With
diagrams, explain the different parts of it and their
activities.- 12 marks
o Draw the structure of a living cell of a human body
and explain its constituents. Discuss the different
methods of transport of ions through the cell
membrane.
62. UNIVERSITY QUESTIONS- 12 MARKS
With neat diagrams explain the anatomy and the
function of the heart.
Describe in detail about the function of kidney with
relevant diagram.
With diagram explain in detail about the respiratory
system and lung capacities.
Explain the recording and analyzing of ECG with
typical waveform.
Explain the recording and analyzing of EEG with
typical waveform.
Describe in detail about EMG recorder with typical
waveform.