Biomedical Engineering Mod-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

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


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


Heart wall has three layers: Pericardium:-

• Moist Myocardium:-

• Main muscle• Short cylindrical fibers• Automatic in action

Endocardium:- • Smooth lining

CARDIOVASCULAR SYSTEM- THE HEART


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


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 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

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.


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


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


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.


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)


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


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


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


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.

Biomedical Engineering Mod-1

Technology

Transcript of Biomedical Engineering Mod-1