biomedical engineering mod-1
DESCRIPTION
module 1, bio medical engineering, MG University KeralaTRANSCRIPT
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
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.
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
CHARACTERISTICS OF BIOMEDICAL INSTRUMENTATION SYSTEM
Signal-to-Noise Ratio:- Noise content should be low. S/N ratio should be very high.
Stability Isolation Simplicity
BIOCHEMICAL SYSTEM
CARDIOVASCULAR SYSTEM
RESPIRATORY SYSTEM
NERVOUS SYSTEM
PHYSIOLOGICAL SYSTEMS OF HUMAN BODY
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
CARDIOVASCULAR SYSTEM
Heart wall has three layers: Pericardium:-
• Moist Myocardium:-
• Main muscle• Short cylindrical fibers• Automatic in action
Endocardium:- • Smooth lining
CARDIOVASCULAR SYSTEM- THE HEART
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 unidirectionalo Provides synchronous operation
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
CARDIOVASCULAR SYSTEM - CIRCULATORY SYTEM
RESPIRATORY SYSTEM
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
RESPIRATORY SYSTEM
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
RESPIRATORY SYSTEM
o The lungs are made up of 3 main parts:
• Bronchus (right & left)
• Bronchioles
• Alveoli
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
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
KIDNEY
KIDNEY
Filtration system Main organs involved kidney(two bean-
shaped organs), ureter, bladder, urethra. Small individual units- nephrons Main parts- glomerulus and tubule Three main operations
• Filtration- glomerulus• Secretion• Reabsorption tubule
STRUCTURE OF NEPHRON
NERVOUS SYSTEM
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
NERVOUS SYSTEM
cerebrum• Frontal• Temporal• Occipital• Parietal
o cerebellum:- muscular activities
Brain stem:- thalamus, hypothalamus, medulla oblangata
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…
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
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.
RESTING POTENTIAL
ACTION POTENTIAL
ACTION POTENTIAL
BIOELECTRIC POTENTIAL
EQUIVALENT CIRCUIT OF BIOPOTENTIAL ELECTRODE
INTERFACE
EQUIVALENT CIRCUIT OF BIOPOTENTIAL ELECTRODE
INTERFACE
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.
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
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
TRANSDUCERS FOR BIO MEDICAL APPLICATIONSPHYSICAL VARIABLE TYPE OF TRANSDUCER
Force (or Pressure) PiezoelectricUnbonded strain gauge
Displacement Variable resistance, ind, capVariable inductanceVariable capacitanceLVDTMercury strain gauge
Surface strain Strain gauge
Velocity Magnetic induction
Temperature Thermocouple, Thermistor
Light Photovoltaic, Photoresistive
Magnetic field Hall effect
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.
ECG TRANSDUCER(RECORDING SET UP)
BLOCK DIAGRAM OF AN ECG MACHINE
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.
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
ECG WAVEFORM
ECG WAVEFORM
Electrocardiography Electrocardiogram-waveform Electrocardiograph- instrument Waveform Details:-
P wave
R wave(QRS complex)
T wave
S-T interval
U wave
PHYSIOLOGICAL NATURE OF ECG WAVEFORM
Wave Origin Amplitue in mv
Duration sec
P wave contraction of right and left atrium(depolarization of atrial musculature)
0.25 0.12 to 0.22 (P-R interval)
R wave(QRS complex)
Repolarization of the atria & the depolarzn. of the ventricles which occur almost simultaneously
1.60 0.07 to0.1
T wave ventricular repolarization(relaxation of myocardium)
0.1 to 0.5 0.05 to 0.15(S-T interval)
S-T interval
Ventricular contraction < 0.1 0.2
U wave Slow repolarisation of intraventricular system.
< 0.1 0.1(T-U interval)
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.
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
SCHEMATIC DIAGRAM OF AN EEG MACHINE
EEG TRANSDUCER(RECORDING SET UP)
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
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.
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
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.
BLOCK DIAGRAM FOR EMG RECORDING SET UP
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
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.
ELECTROMYOGRAM-EMG
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.
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?
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.
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.