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MEDICAL ELECTRONICS Mr. DEEPAK P. Associate Professor ECE Department

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1 MEDICAL ELECTRONICS Mr. DEEPAK P. Associate Professor ECE Department

2 Introduction to Human Physiological Systems and Transducers
SNGCE UNIT 1 Introduction to Human Physiological Systems and Transducers DEEPAK.P DEEPAK P

3 Objective At the end of this Unit You will learn
Physiological Systems of human body Bio medical Transducers and Electrodes DEEPAK.P

4 Introduction to Biomedical Engineering

5 Biomedical Engineering
Biomedical Engineering is the application of engineering principles and design concepts to medicine and biology The biomedical engineering provides electrical, electronic, electro-optical, and computer engineering support to clinical and biomedical applications. Biomedical Engineering improves the field of healthcare diagnosis, monitoring and therapy. DEEPAK.P

6 Medical Instruments DEEPAK.P

7 Biomedical Instruments
Classification of Biomedical Equipments Diagnostic equipment Therapeutic equipment Clinical equipment Laboratory equipment DEEPAK.P

8 Man- Instrument System

9 Components in Man – Instrument system
Control feedback Recording , data processing and transmission of data Signal conditioning equipment Display Transducer Stimulus DEEPAK.P

10 Man – Instrument system
Measurement in biomedical instrumentation can be divided in to two VIVO Measurement is made on or within the human body Eg . Device inserted in to the blood stream to measure PH of blood VITRO Measurement is performed outside of the body. Eg . Measurement of blood PH from blood samples. DEEPAK.P

11 Bioelectric Potentials

12 Sources of Bioelectric potentials
The systems in the human body generate their on monitoring signals when they carry out their functions. These signals provide useful information about their function. Bioelectric potentials are actually ionic voltages produced as a result of electro chemical activity of certain cell. Transducers are used to convert these ionic potentials in to electrical signals DEEPAK.P

13 Resting and Action potentials
Certain types of cells within the body , such as nerve and muscle cells are encased in a semi permeable membrane. This membrane permits some substances to pass through while others are kept out. Surrounding the cells of the body are the body fluids These fluids are conductive solutions containing charged atoms known as ions DEEPAK.P

14 Resting potentials The principle ions are sodium(Na+) Potassium(K+) and chloride(C-) The membrane of excitable cells permit entry of Potassium(K+) and chloride(C-) ions but blocks the entry of sodium(Na+) ions. So inside the cell is more negative than outside cell This membrane potentials is called Resting potentials This potential is measured from inside the cell with respect to body fluids. So resting potential of a cell is negative. DEEPAK.P

15 Resting potentials/Polarization
This resting potential ranging from -60mv to -100 mv. Cell in the resting state is called polarized cell. Ground V Cell Membrane -70 mV DEEPAK.P

16 Depolarization of cell
When a cell is exited, the membrane change its characteristic. The sodium ions are rushed in to the cell. At the same time potassium ions try move from inside. After a equilibrium state is reached, the sodium is moved back to outside DEEPAK.P

17 Depolarization of cell
Cell Membrane Na+ K+ DEEPAK.P

18 Action potentials Cell Membrane V Ground 20 mV DEEPAK.P

19 Re Polarization Cell comes from de polarized state in to polarized state is called Re polarization. Ground V Cell Membrane -70 mV DEEPAK.P

20 Resting and Action potentials

21 Propagation of Action potentials
When a cell is exited and generates an action potentials ionic currents to flow. This process excite neighboring cells or adjacent area of the same cell DEEPAK.P

22 Physiological Systems in Human body

23 Physiological systems of human body
In simple terms "Human Physiology" is the study of the body and its functions in each of the different systems in any living body. System Input Output DEEPAK.P

24 Physiological Systems in the Human body
Behavior Liquid wastes Solid wastes Body movements Expired air Appearance Speech Food intake Liquid intake Vision Smell Taste Hearing Inspired air Tactile sensation INPUTS OUTPUTS DEEPAK.P

25 Physiological systems of human body
There are 11systems in the body: The Skeletal System Bones & joints Muscular System Skeletal muscle Nervous System Brain, spinal cord & nerves Endocrine System Hormone-producing cells & glands Cardiovascular System Blood, heart & blood vessels Respiratory System Lungs & airways Digestive System Organs of the gastrointestinal tract Urinary System Kidneys, bladder and ureters Reproductive System Male & female reproductive organs The Integumentary System The skin & derived structures Lymphatic & Immune System Lymphatic vessels & fluid DEEPAK.P

26 Physiology of Cardiovascular system

27 Physiology Physiology can be classified in to Cell Physiology
Study of cells Patho Physiology Pathological Functions Circulatory Physiology Study of blood circulation Respiratory Physiology Study of breathing organs DEEPAK.P

28 Cardio Vascular system
Cardio vascular system can be viewed as closed hydraulic system with 4 chamber pump. Cardio Vascular system is mainly used for transportation of oxygen, Carbon dioxide, numerous chemical compounds and the blood cells. Pump-----Heart Flexible tubes---Blood vessels DEEPAK.P

29 Cardio Vascular system
In some part of the system diameter of the arteries are changed to control pressure. Pump(heart) is a isolated two stage synchronized chamber The first stage is to collect blood from the system and pump it in to 2nd stage. The second stage then pump these blood to the system DEEPAK.P

30 Heart & Valves Bicuspid/ Left Atrio-ventricular valve
Right Atrio-ventricular valve DEEPAK.P

31 Heart Layers Heart wall consists of three layers Pericardium
Outer most layer, keeps outer surface moist, prevents friction Myocardium Middle layer, Main muscle of heart, made up of short cylindrical fibres Endocardium Inner layer of heart, Provides smooth lining for blood flow DEEPAK.P

32 Heart Valves Heart has 4 valves
Tricuspid/Right Atrio-Ventricular valve Between Right A and V, Prevents blood flow from right V to A Bicuspid/ left Atrio-Ventricular valve Between left A and V, Prevents blood flow from left V to A Pulmonary valve At right ventricle, It has 3 cusps Aortic Valve Between left ventricle and aorta, It has 3 cusps DEEPAK.P

33 Cardio Vascular systems

34 Cardio Vascular System
One of the two stage pump(Right side) collect fluid from the system and pump it through oxygenation system(Lungs). Other side pump receives blood from oxygenation system(Lungs) and pump blood to main hydraulic system. Blood act as communication and supply network for all parts of the body DEEPAK.P

35 Cardio Vascular system
Fluid contains fuel suppliers and waste particles are transported to destination. Fluid contain mechanism for rejecting foreign elements and mechanism for repairing small system puncture. Sensors are provided to detect the changes in the need of suppliers, the build of waste material and out-of- tolerance pressure in the system known as chemoreceptors, Pco2 sensors and baroreceptors respectively. DEEPAK.P

36 Cardio Vascular Circulation
The blood is carried out to the various parts of the body through blood vessels. There are three types of blood vessels Arteries--- Thick, Carries oxygenated blood Veins--- Thin, De-oxygenated blood Capillaries---Smallest, Last level of blood vessels, km of capillaries DEEPAK.P

37 Cardio Vascular Circulation
Heart pumps blood through the pulmonary circulation to the lungs and through the systemic circulation to the other parts of the body. Pulmonary circulation Systemic circulation In pulmonary circulation, venous blood(de-oxygenated) flows from right ventricle through pulmonary artery to lungs . The arterial( oxygenated) blood flows to left atrium through pulmonary veins. In systemic circulation blood flows from left auricle to left ventricle and it is pumped to aorta and its branches DEEPAK.P

38 Cardio Vascular Circulation

39 Respiratory system DEEPAK.P

40 Respiratory systems It is the Pneumatic system.
A system that work with air pressure. An air pump(diaphragm) which alternatively create negative and positive pressures in a sealed chamber(Thoracic cavity). Thoracic cavity sucked air in to and forced out to two elastic bags(Lungs). The lungs are connected to the external environment through a pass way (nasal cavities, pharynx, larynx, trachea, bronchi and bronchioles) DEEPAK.P

41 Respiratory systems DEEPAK.P

42 Respiratory systems At one point , this passage is common with the tube that carries liquid and solids to stomach. A special valving arrangement interrupts the respiratory system whenever solid or liquid passes through the common region. The passage divides to carry air in to each bag. In each bag , it is sub divided many times to carry air in to and out of each of many tiny air spaces (pulmonary alveoli). DEEPAK.P

43 Respiratory systems In case of nasal blockage , air input can be taken from mouth. Oxygen is taken from the air and transferred in to blood. Cabondioxide is transferred from blood to air. The system has a number of fixed volumes and capacities. DEEPAK.P

44 Respiratory systems Tidal volume
The volume inspired and expired during each normal breath 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. DEEPAK.P

45 Respiratory systems Residual volume
Amount of air remaining in the lungs after all possible air has been forced out. Vital capacity Tidal volume+ Inspiratory reserve volume+ Expiratory reserve volume DEEPAK.P

46 Respiratory systems DEEPAK.P

47 Blood purification in the human body
The overall functioning of our body heavily depends on the proper functioning of our blood. We take toxins into our body daily and these toxins disrupts the functions of our internal organs. Regular detoxification of our blood is important Detoxifying the blood and body helps to remove harmful toxins from our body and improve the functioning of our vital organs such as the kidney and liver DEEPAK.P

48 Blood purification in the human body
When our body has too much toxins, our vital organs start to get damage and under-perform and we start to develop symptoms of allergies, low immunity, headaches, fatigue and several other health related problems. The lungs help remove carbon dioxide, the kidneys remove water-soluble waste and the liver removes fat soluble wastes and many other impurities from the blood. DEEPAK.P

49 Blood purification by lungs
The un oxygenated (unpurified) blood comes into right atrium of heart by superior and inferior vena-cava which then passes to right ventricle, then to lungs by pulmonary artery. In lungs this blood gets oxygenated (purified) which then goes into left chamber of heart from which blood is passed to aorta and then circulated to whole body DEEPAK.P

50 Blood purification by lungs

51 Blood purification by lungs

52 Muscular System DEEPAK.P

53 Muscular System The muscular system is the biological system of humans that produces movement. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular system is controlled through the nervous system. Muscles provide strength, balance, Posture, movement and heat for the body to keep warm. DEEPAK.P

54 Muscular System More than 50% of body weight is muscle.
Muscle is made up of proteins and water DEEPAK.P

55 Muscular System There are three distinct types of muscles: skeletal muscles, cardiac or heart muscles, and smooth muscles. DEEPAK.P

56 Muscular System Smooth muscle or "involuntary muscle" consists of spindle shaped muscle cells found within the walls of stomach, intestines, bronchi, uterus, ureters, bladder, and blood vessels. Smooth muscle cells contain only one nucleus. Cardiac muscle is also an "involuntary muscle" but it is striated in structure and appearance. Like smooth muscle, cardiac muscle cells contain only one nucleus. DEEPAK.P

57 Muscular System Cardiac muscle is found only within the heart.
Skeletal muscle or "voluntary muscle" is anchored by tendons to the bone and is used to effect skeletal movement such as locomotion. Skeletal muscle cells are multinucleated with the nuclei peripherally located. Skeletal muscle is called 'striated' because of the longitudinally striped appearance under light microscopy. DEEPAK.P

58 Muscular System Muscle is composed of muscle cells (sometimes known as "muscle fibers"). Within the cells are myofibrils; myofibrils contain sarcomeres which are composed of actin and myosin. Individual muscle cells are lined with endomysium. Muscle cells are bound together by perimysium into bundles called fascicles. DEEPAK.P

59 Muscular System These bundles are then grouped together to form muscle, and is lined by epimysium. DEEPAK.P

60 Muscular System DEEPAK.P

61 Muscular System DEEPAK.P

62 Nervous systems DEEPAK.P

63 Nervous systems The task of controlling various functions of body and coordinating them in to a integrated living organism(human body) is the function of Nervous system It is the most complex system in the human body It is the communication network in the human body. It composed of Brain, Sensors, high speed communication links ,spinal cord. DEEPAK.P

64 Nervous systems It provides regulation of body functions and sensory perception. Functions of Nervous systems Control of the body Integration Communication DEEPAK.P

65 Nervous systems Its center is a self adapting processor(Brain).
Self adapting means --- If a certain section is damaged, other sections can adapt take over the function of damaged sections This processor has memory, computational power, decision making capability. DEEPAK.P

66 Nervous systems With the use of this processor , human can take decisions, solve complex problems, create art, poetry and music, feel emotions and integrate input information from all parts of the body and produce output signals of meaningful information. Central computer has millions of communication lines( afferent and efferent nerves) that bring sensory information and transfer control information from brain. DEEPAK.P

67 Nervous systems DEEPAK.P

68 Nervous systems This lines are not single lines but complicated networks. Information signal are normally coded by means of electro chemical pulses that travel along the nerves. The output control signals are channeled to specific motor devices(motor units of muscles) DEEPAK.P

69 Nervous systems In addition to brain , a large number of simple decision making g devices(Spinal reflexes) are present to control directly certain motor devices from certain sensory inputs. DEEPAK.P

70 Divisions of Nervous systems
The human nervous system can be divided into three main parts: Central nervous system (CNS) *is composed of brain and spinal cord...* Peripheral nervous system (PNS) *is composed of all body nerves that lie outside of your central nervous system...* Autonomic nervous system (ANS) *Controls the involuntary actions of your body organs...* DEEPAK.P

71 Central Nervous systems
Central Nervous System (CNS) Structures of the CNS: [1]  Brain [2]  Spinal cord The CNS coordinates and interprets information to determine the best response  DEEPAK.P

72 Anatomy of the Central Nervous systems
Spinal cord Cerebellum Brain stem Cerebrum DEEPAK.P

73 Peripheral Nervous systems
The primary role of the PNS is to connect the CNS to the organs, limbs and skin. The nerves that make up the peripheral nervous system are actually the axons or bundles of axons from neuron cells. The peripheral nervous system is divided into two parts: The somatic nervous system The autonomic nervous system DEEPAK.P

74 Somatic Nervous systems
The somatic system is the part of the peripheral nervous system responsible for carrying sensory and motor information to and from the central nervous system. This system contains two major types of neurons: Sensory neurons (or afferent neurons) that carry information from the nerves to the central nervous system. Motor neurons (or efferent neurons) that carry information from the brain and spinal cord to muscle fibers throughout the body. DEEPAK.P

75 Autonomic Nervous systems
The autonomic system is the part of the peripheral nervous system responsible for regulating involuntary (reflex/Un intentional)body functions, such as blood flow, heartbeat, digestion and breathing. This system is further divided into two branches: The sympathetic system regulates the flight-or-fight responses. DEEPAK.P

76 Autonomic Nervous systems
The "fight or flight response" is our body's primitive, automatic, inborn response that prepares the body to "fight" or "flee" from perceived attack, harm or threat to our survival. Parasympathetic system helps maintain normal body functions and conserves physical resources DEEPAK.P

77 Anatomy of the Nervous systems
Basic unit of nervous system is the neuron. Neurons are the basic building blocks of the nervous system. Neuron is a single cell with a cell body. It is sometimes called soma DEEPAK.P

78 Anatomy of the Nervous systems
Neuron cells are the information-processing units of the brain responsible for receiving and transmitting information. One or more I/P fibers branches are called dendrites Long transmitting fiber is called axon Each part of the neuron plays a role in the communication of information throughout the body. DEEPAK.P

79 Anatomy of the Nervous systems

80 Anatomy of the Nervous systems
Neurons Composed of: a.     Cell Body Part that contains the nucleus b.      Dendrite(s) Carries a nerve impulse towards the cell body c.       Axon(s) Carries a nerve impulse away from the cell body (and towards the dendrite of the next neuron) Axons are also called nerve fibers. DEEPAK.P

81 Types of Neurons The three basic types of idealized neurons include;
Bipolar, (Pseudo) Uni polar Multi polar neurons, Typically these neurons are found in different places around the body: DEEPAK.P

82 Types of Neurons DEEPAK.P

83 Types of Neurons Bipolar – Specialized sensory neurons for the transmission of special senses. As such, they are part of the sensory pathways for smell, sight, taste and hearing functions. The most common example are the bipolar neurons found in the retina DEEPAK.P

84 Types of Neurons (Pseudo) Unipolar
Many types of primary sensory neurons are Unipolar. Multi polar – Multi polar neurons constitute the majority of neurons in the brain and include motor neurons and interneuron's. DEEPAK.P

85 Sources of Biomedical Signals

86 Sources of Biomedical Signals

87 Bio- Potential Electrodes

88 Measurement of Bioelectric potentials
To measure bioelectric potentials , a transducer is required. Electrical signals produced by various body activities are used in monitoring / diagnosis In order to measure and record potentials and, hence, currents in the body, it is necessary to provide some interface between the body and the electronic measuring apparatus. . DEEPAK.P

89 Bio Potential Electrodes
Bio-potential electrodes carry out this interface function. A transducer consists of two electrodes, which measure ionic potential difference between two points. The designation of the Bio potential waveform ends with “Gram”. The name of the instrument bio potential normally ends with “Graph” DEEPAK.P

90 Bio Potential Electrodes
Propagation of action potential through different body tissues produces final waveform recorded by electrodes Electrical activity is explained by differences in ion concentrations within the body (sodium, Na+; cloride, Cl–; potassium, K+) A potential difference (voltage) occurs between 2 points with different ionic concentrations DEEPAK.P

91 Electrodes Theory DEEPAK.P

92 Equivalent circuit for bio-potential electrode
Metal Electrode Body Electrolytes Vha=Electrode potential developed across interface C=Charges at the Interface at the skin metal interface DEEPAK.P

93 Polarizable and Non-Polarizable Electrodes
No charge crosses the electrode-electrolyte interface when a current is applied. (e.g Platinum electrode) Non-Polarizable Electrode Current passes freely across the electrode-electrolyte interface. (e.g. Ag/AgCl Electrode)

94 Equivalent circuit for bio-potential with two electrode

95 Bio Potential Electrodes
Bio-potential electrodes transduce ionic conduction to electronic conduction so that bio-potential signals can be obtained They generally consist of metal contacts packaged so that they can be easily attached to the skin or other body tissues DEEPAK.P

96 Classification of Electrodes

97 Bio Potential Electrodes
Micro Electrodes--- Bio electric potential near or within a single cell Metal Type—Tip must be tungsten or stainless steel Micro pipette---It is a glass micropipet with size of 1 micron, It is filled with electrolyte Skin surface electrode —Measure ECG,EEG,EMG Needle electrode ---Penetrate the skin to record EEG DEEPAK.P

98 Microelectrodes Used to measure bio-potential signals at the cellular level Due to small dimensions (mm), impedance levels are high So amplifier needs very high input impedance

99 Microelectrodes



102 Surface electrodes These are placed in contact with the skin of the subject Early stages immersion electrodes were used. A bucket of saline water is used An improvement of immersion electrode is the plate electrode. Another old type electrode is suction type

103 Immersion electrodes

104 Surface electrodes

Historically, one of the most frequently used forms of bio-potential sensing electrodes is the metal-plate electrode. In its simplest form, it consists of a metallic conductor in contact with the skin. An electrolyte soaked pad or gel is used to establish and maintain the contact.


107 Floating electrodes Conductive paste reduces effect of electrode slippage and resulting motion artifact

108 Needle electrodes Unipolar electrode---Single wire inside a needle
Bipolar electrode---Two wires inside a needle Mostly used for contacting with internal body tissues (a) Insulated needle electrode . (b) Coaxial needle electrode . (c) Bipolar coaxial electrode . (d) Fine -wire electrode connected to hypodermic needle, before being inserted . (e) Coiled fine -wire electrode in place

109 Needle electrodes

110 Implantable electrodes



113 Transducers DEEPAK.P

114 Transducers A transducer is necessary to convert one variable in to another form Used to measure physiological variables Variable is a quantity that vary with time. The term active and passive has different meaning when they are applied to Transducers DEEPAK.P

115 Transducers Transducer can be classified in to two Active Transducer
Known principles is used to convert variables in to electrical signal Passive Transducer It involves control of an excitation voltage or modulation of a carrier signal DEEPAK.P

116 Principles used in Active Transducers
It can convert electrical signal in to physical variables and also in reverse direction. Magnetic Induction Piezoelectric effect Thermoelectric effect Photoelectric effect DEEPAK.P

117 Passive Transducers Utilize the principles of controlling a DC excitation or an AC carrier signal. It consists of a passive circuit element which changes it value as a function of physical variables to be measured. It cannot convert electrical signal in to physical variables DEEPAK.P

118 Principles used in Passive Transducers
Using Resistive element Ordinary Potentiometer Linear Rotary Strain gage Un bonded Bonded Semiconductor strain gage Using Inductive element Variable reluctance Transducer LVDT Using Capacitive element DEEPAK.P

119 Transducers for Biomedical field
Force transducer Photoelectric displacement transducer Pressure Transducers Flow transducers Transducers with digital O/P DEEPAK.P

120 Transducers for Biomedical field
Resistive transducers - Muscle force and Stress (Strain guge), Spirometry (Potentiont) , humidity, (Gamstrers), Respiration (Thermistor) Inductive Transducers - Flow measurements, muscle movement (LVDT) Capacitive Transducers - Heart sound measurement, Pulse pick up Photoelectric Transducers - Pulse transducers, Blood pressure, oxygen Analyses Piezoelectric Transducers - Pulse pickup, ultrasonic blood flowmeter Chemcial Transducer - Ag-Agfallas (Electrodes, PH electrode DEEPAK.P

121 pH Electrode DEEPAK.P

122 pH Electrode This is a device for measuring the concentration of hydrogen ions and hence the degree of acidity of a solution. pH is defined as the negative logarithm of the hydrogen ion concentration. pH=7 means a concentration of 1x10-7 moles per litre. The most essential component of a pH electrode is a special, sensitive glass membrane which permits the passage of hydrogen ions, but no other ionic species. DEEPAK.P

123 pH Electrode When the electrode is immersed in a test solution containing hydrogen ions the external ions diffuse through the membrane until an equilibrium is reached between the external and internal concentrations. Thus there is a build up of charge on the inside of the membrane which is proportional to the number of hydrogen ions in the external solution. The potential difference developed across the membrane is in fact directly proportional to the Logarithm of the ionic concentration in the external solution. DEEPAK.P

124 pH Electrode The relationship between the ionic concentration (activity) and the electrode potential is given by the Nernst equation: E = E0 + (2.303RT/ nF) x Log(A) Where  E = the total potential (in mV) developed between the sensing and reference electrodes. E0 = is a constant which is characteristic of the particular ISE/reference pair. (It is the sum of all the liquid junction potentials in the electrochemical cell, see later) 2.303 = the conversion factor from natural to base10 logarithm. R = the Gas Constant (8.314 joules/degree/mole). T = the Absolute Temperature. n = the charge on the ion (with sign). F = the Faraday Constant (96,500 coulombs). Log(A) = the logarithm of the activity of the measured ion. DEEPAK.P

125 pH Electrode DEEPAK.P

126 Agcl Electrode DEEPAK.P

127 Ag-Agcl Electrode DEEPAK.P

128 Ag-Agcl Electrode A silver chloride electrode is a type of reference electrode, commonly used in electrochemical measurements. The silver/silver chloride reference electrode is a widely used reference electrode because it is simple, inexpensive, very stable and non-toxic. Typical laboratory electrodes use a silver wire that is coated with a thin layer of silver chloride either by electroplating or by dipping the wire in molten silver chloride. DEEPAK.P

129 Ag-Agcl Electrode The electrode functions as a redox electrode and the reaction is between the silver metal (Ag) and its salt — silver chloride (AgCl, also called silver(I) chloride). DEEPAK.P

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