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
PHYSIOLOGICAL SYSTEMS OF HUMAN BODY BIOCHEMICAL SYSTEM CARDIOVASCULAR SYSTEM RESPIRATORY SYSTEM NERVOUS SYSTEM
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 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 valveo 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
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 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 SYSTEMo 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
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 cordo Brain-cerebrum, cerebellum, brain stem
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.
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 MEDICALAPPLICATIONSPHYSICAL 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
TRANSDUCERS FOR BIO MEDICALAPPLICATIONS 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) 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 Electrocardiography Electrocardiogram-waveform Electrocardiograph- instrument Waveform Details:- P wave R wave(QRS complex) T wave S-T interval U wave
PHYSIOLOGICAL NATURE OF ECG WAVEFORMWave Origin Amplitue in Duration mv secP 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 to0.1wave(QRS the depolarzn. of the ventriclescomplex) which occur almost simultaneouslyT 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 0.2U wave Slow repolarisation of < 0.1 0.1(T-U intraventricular system. 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
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 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.
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 markso What is meant by central nervous system? With diagrams, explain the different parts of it and their activities.- 12 markso 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.