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Biomedical Instrumentation

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Biomedical Instrumentation and its Fundamentals,Bio electric Signals(ECG, EMG ,EEG)and its Electrodes ,Physiological Transducers,Blood Pressure ,Blood Flow,Cardiac Output ,Patient Safety,Physiological Effects of Electric current on human body etc...

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Biomedical Instrumentation

  1. 1. Course Name: Biomedical Instrumentation Course Code: MC1652 Wednesday, March 30, 2016 1
  2. 2. Wednesday, March 30, 2016 2 Books/References  J. G. Webster , Medical Instrumentation: Application And Design, 3rd edition ,Wiley Publishers  D Reddy, Biomedical Signal Processing, Tata Mcgraw Hill Publications.  Sergio Cerutti Advanced Methods of Biomedical Signal Processing, Oxford Publications.  B. Jacobson, J.G. Webster, Medical and Clinical Engineering, Prentice Hall, International.  Cromwell, Biomedical Instrumentation and Measurements, Prentice Hall, International.  R.S. Khandupur, Handbook of Biomedical Instrumentation, - Tata McGraw Hill
  3. 3. Introduction Instrumentation : Instrumentation is the use of measuring instruments to monitor and control a process. It is the art and science of measurement and control of process variables within a production, laboratory, or manufacturing area. Wednesday, March 30, 2016 3
  4. 4. Introduction Biomedical Instrumentation : Biomedical Instrumentation is the field of creating such instruments that help us to measure, record and transmit data to or from the body Wednesday, March 30, 2016 4 COMPONENT OF MAN INSTRUMENT SYSTEM
  5. 5. Basic Objectives of Instrumentation System  Information Gathering  Diagnosis  Evaluation  Monitoring  Control Wednesday, March 30, 2016 5
  6. 6. Classification of Bio Medical Instrumentation System  Clinical Instrumentation Basically devoted to the area of  Diagnosis  Patient care  Treatment of Patients ( Therapeutic use ) Wednesday, March 30, 2016 6
  7. 7. Classification of Bio Medical Instrumentation System  Research Instrumentation  It is used primarily in the search for new knowledge related to various systems that compose the human organism.  Some instruments can be used in both areas. Wednesday, March 30, 2016 7
  8. 8. Classification of Instruments Used CLASSIFICATION OF INSTRUMENTS Engineering Indicating Recording Monitoring Data Logging Analysis Control Medical Diagnostic Therapeutic Supplementary Wednesday, March 30, 2016 8
  9. 9. Engineering Classification of Biomedical Instruments  Measuring Instruments.  Audiometer  Blood cell counter  Blood Pressure meter  Blood PH meter  Blood flow meter  Digital BP meter  GSR meter  Stethoscope Wednesday, March 30, 2016 9
  10. 10. Recording Instruments  Electrocardiograph  Electromyograph  Electro encephalograph  Expirograph  Phonocardiograph  Plethysmograph  Thermograph  Tomograph  Ultra sonograph  Radio graph ( x-ray) Wednesday, March 30, 2016 10
  11. 11. Monitoring Instruments  Bed – side monitor  Bio – monitor  Foetal monitor Wednesday, March 30, 2016 11
  12. 12. Analysing Instruments  Colorimeter  Spectrometer  Flame photo meter Wednesday, March 30, 2016 12
  13. 13. Data Logging and Controlling Instruments  Data Logging - Computer  Controlling - Defibrillator - Dialysis instrument - Heart lung machine Wednesday, March 30, 2016 13
  14. 14. A) Medical Classification of BMI  Diagnostic instruments  Endoscope  Stethoscope  Microscope Wednesday, March 30, 2016 14
  15. 15. B)Therapeutic Instruments  Shortwave diathermy  Ultrasound therapy  Electro surgery  Nuclear Medicine Wednesday, March 30, 2016 15
  16. 16. B)Supplimentary Instruments  Aid for blind  Hearing aid  Pace maker Wednesday, March 30, 2016 16
  17. 17. Functional Classification of Instruments A] BLOOD INSTRUMENTS 1. Blood Pressure meter 2. Blood PH meter 3. Blood flow meter 4. Blood cell counter 5. Calorimeter 6. Spectra – Photometer 7. Flame photometer 8. Digital BP meter Wednesday, March 30, 2016 17
  18. 18. Contd… B] HEART INSTRUMENT 1. ECG 2. Pace Maker 3. Defibrillator 4. Heart Lung Machine 5. Bed side monitor 6. Plethysmograph 7. Electronic stethoscope 8. Phonocardiograph Wednesday, March 30, 2016 18
  19. 19. Contd…. C] BRAIN INSTRUMENTS 1. EEG 2. Tomo-graph D] MUSCLE INSTRUMENTS 1. EMG 2. Muscle Stimulator Wednesday, March 30, 2016 19
  20. 20. Contd…. E) KIDNEY INSTRUMENTS 1. Dialysis Instrument 2. Lithotripsy F] EAR INSTRUMENTS 1. Audiometer 2. Hearing aid Wednesday, March 30, 2016 20
  21. 21. Contd…. G) EYE INSTRUMENTS 1.Occulometer 2.Aid for blind H] LUNG INSTRUMENT 1. Spirometer Wednesday, March 30, 2016 21
  22. 22. Contd…. I) BODY INSTRUMENTS 1. Ultra Sonography 2. Thermograph 3. Radiograph 4. Endoscope Wednesday, March 30, 2016 22
  23. 23. Contd…. J) PHYSIOTHERAPY INSTRUMENTS 1. Diathermy, Short wave 2. Vibrator ( Massage type ) 3. U.V. Lymph 4. Microwave diathermy Wednesday, March 30, 2016 23
  24. 24. Anatomy and Physiology The science of structure of the body is known as ANATOMY Classification : Gross ANATOMY Topographical ANATOMY Microscopic ANATOMY Wednesday, March 30, 2016 24
  25. 25. Anatomy and Physiology Physiology which relates to the normal function of the organs of the body . Example :  Cell Physiology  Pathaphysiology - Circulatory Physiology - Respiratory Physiology Wednesday, March 30, 2016 25
  26. 26. Physiological Systems of the body  Human body contains various systems such as electrical ,mechanical, hydraulic, pneumatic, chemical and thermal etc.  Systems communicate internally with each other and with external environment.  With this, enable to perform useful tasks, sustain life and reproduce itself. Wednesday, March 30, 2016 26
  27. 27. Major Subsystems of the body 1. Cardiovascular System  Cardio = “heart” Vascular = “vessels” It performs the essential service of transportation of oxygen, carbon dioxide numerous chemical compounds and the blood cells.  System made up of “heart” , “vessels and “blood” Wednesday, March 30, 2016 27
  28. 28. Major Subsystems of the body Function of Cardiovascular System  Delivering materials to cells  Carrying wastes away  In addition, blood contains cells that fight disease. Wednesday, March 30, 2016 28
  29. 29. Major Subsystems of the body Heart  Heart is divided into two parts right and Left-each part has two chambers called atrium and ventricle.  Heart has four valves: -Tricuspid valve or Right Ventricle valve - Bicuspid Mitral or Left Ventricle Valve - Pulmonary Valve - Aortic Valve  Heart wall consist of three layers: - Pericardium - Myocardium - Endocardium Wednesday, March 30, 2016 29
  30. 30. 4) Right Ventricle The right ventricle pumps oxygen-poor blood to the lungs. 3) Right Atrium The right atrium receives blood from the body that is low in oxygen and high in carbon dioxide. The Heart 1 2 3 5 6 7 8 94 1) Major vessel from upper body to heart 2) Vessels from lung to heart 5) The. aorta carries blood from the left ventricle to the body 6) Vessel from heart to lungs 7) Vessels from lung to heart 8) Left Atrium Oxygen-rich blood is carried from the lungs to the left atrium. 9) Left Ventricle The left ventricle pumps oxygen-rich blood from the heart. Pathways of Blood Wednesday, March 30, 2016
  31. 31. Major Subsystems of the body Three types of blood vessels  Arteries - move blood away from the heart -Most arteries carry oxygen-rich blood -The largest artery in the body is the Aaorta have thick walls that are both strong and flexible. Veins - move blood toward the heart  Capillaries - tiny blood vessels that connect arteries and veins -Branching from the smallest arteries are capillaries, the smallest blood vessels in your body. -As blood flows through the capillaries, oxygen and dissolved nutrients diffuse through the capillary walls and into your body’s cells. -Capillaries are involved in temperature regulation. Wednesday, March 30, 2016 31
  32. 32. Major Subsystems of the body Function of the blood  Carries oxygen from lungs to all body cells and removes carbon dioxide from the cells Carries waste products of cell activity to the kidneys to be removed from the body Transports nutrients from the digestive system to body cells Red blood cell White blood cell Wednesday, March 30, 2016 32
  33. 33. Major Subsystems of the body Conduction System of the heart  Cardiac conduction system: The electrical conduction system controls the heart rate  This system creates the electrical impulses and sends them throughout the heart. These impulses make the heart contract and pump blood. Wednesday, March 30, 2016 33
  34. 34. Major Subsystems of the body 2. Respiratory System  The Primary function of respiratory system is to supplies the blood with oxygen so that the blood can deliver oxygen to all parts of the body.  It also removes carbon dioxide waste that cells produce. Wednesday, March 30, 2016 35
  35. 35. Amazing Facts About the Respiratory System Did you know that...  Your right lung has three lobes and your left lung only has two?  The right lung is a little larger than the left lung?  A person sleeping almost always breathes twelve or fifteen times a minute?
  36. 36. More Amazing Facts About the Respiratory System Did You Know That...  The exhaling rate is faster in kids than in adults?  The trachea is made out of cartilage shaped rings?  The fastest recorded “ sneeze speed” is 165 km per hour?  It is healthier to breathe through your nose than your mouth, because your nose hairs and mucus clean the air.
  37. 37. Major Subsystems of the body 3. Nervous System  Control center for all body activities.  Responds and adapts to changes that occur both inside and outside the body (Ex: pain, temperature, pregnancy) Wednesday, March 30, 2016 38
  38. 38. Wednesday, March 30, 2016 39 your nervous system is divided into the central nervous system (CNS) and the peripheral nervous system (PNS) which is the brain and spinal cord which connects everything to the brain and spinal cord
  39. 39. Central Nervous System Wednesday, March 30, 2016 40  Brain : a mass of 100 billion neurons located inside the skull. - Cerebrum : largest part of human brain - Cerebellum : at base of brain - Brain Stem : connects brain to spinal cord  Spinal Cord : Column of nerves from brain to tailbone – protected by vertebrae of spine -Responsible for: - Conducting impulses between the brain and the rest of the body *Impulses may travel as fast at 268 miles/hr.  Neurons
  40. 40. Credit:MarkLythgoe&ChloeHutton,WellcomeImages different regions have different functions Cerebral cortex Functions include: planning; reasoning; language; recognising sounds and images; memory. Corpus callosum connects the brain’s right and left hemispheres Cerebellum important for coordination, precision and timing of movement Brain stem regulates heart rate, breathing, sleep cycles and emotions
  41. 41. Peripheral Nervous System Wednesday, March 30, 2016 42 Nerves : visible bundles of axons and dendrites that entend from the brain and spinal cord to all other parts of the body - Motory Nerves - Sensory Nerves
  42. 42. the cells of the nervous system are called neurones cell body axon myelin sheath dendrites nerve endings nucleus structure of a neurone
  43. 43. there are different typesof neurone sensory neuronemotor neurone relay neurone direction of electrical signal sends signals to your muscles to tell them to move sends signals from your sense organs connects neurones to other neurones dendrites cell body axon myelin sheath nerve endings
  44. 44. neurones communicate with each other using a mixture of electrical & chemical signals cell body axon myelin sheath dendrites nerve endings nucleus an electrical signal is transmitted along the axon But what happens when the signal reaches the end of the axon?
  45. 45. What do you think can change neurons and their connections? • Accidents • Drugs • Alcohol • Disease
  46. 46. Accidents • Physical injury of your neurons
  47. 47. Drugs and alcohol bind important receptors on neurons
  48. 48. Drugs = neuron death
  49. 49. Alcohol damages dendrites - can repair after abstinence Alcohol blocks receptors and slows down transmission
  50. 50. •Parkinson's Disease •ALS - Lou Gehrig’s Disease •Huntington’s Disease •Multiple Sclerosis •Alzheimer's •Cerebral Palsy •Epilepsy •? SIDS
  51. 51. Facts-Did you know Wednesday, March 30, 2016 52 There are around 47 miles of nerves in your body. One nerve cell may be connected to 1000 more. Your nerve impulses can travel up to 390 feet per second. Thousands of nerve cells die each day
  52. 52. What if neurons die here? or hereor here or here or here
  53. 53. Transducers • Transducer – a device that converts primary form of energy into other different energy form only for measurement purposes. • Primary Energy Forms: mechanical, thermal, electromagnetic, optical, chemical, etc. • Sensor – It is a wide term which covers almost everything from human eye to trigger of a pistol. – Senses the change in parameter(specific).
  54. 54. CLASSIFICATION OF TRANSDUCERS  Active & Passive Transducers  Analog & Digital Transducers  Primary & secondary Transducers  On the basis of principle used
  55. 55. Active vs Passive Transducers: Passive Transducers:  Add energy to the measurement environment as part of the measurement process.  Requires external power supply. Strain gauge, potentiometer & etc. Active Transducers :  Do not add energy as part of the measurement process but may remove energy in their operation.  Does not require external power supply Thermocouple, photo-voltaic cell & etc.
  56. 56. ANALOG & DIGITAL TRANSDUCERS ANALOG TRANSDUCER - The transducers which convert the input quantity into an analog output which is a continuous function of time. DIGITAL TRANSDUCERS - The transducers which convert the input quantity into digital form means in the form of pulses.
  57. 57. PRIMARY vs SECONDARY TRANSDUCERS  PRIMARY TRANSDUCERS - Some transducers contain the mechanical as well as electrical device. The mechanical device converts the physical quantity to be measured into a mechanical signal. Such mechanical device are called as the primary transducers.  SECONDARY TRANSDUCERS - The electrical device then convert this mechanical signal into a corresponding electrical signal. Such electrical device are known as secondary transducers
  58. 58. CLASSIFICATION ON THE BASIS OF PRINCIPLE USED  Capacitive  Inductive  Resistive  Electromagnetic  Piezoelectric  Photoconductive  Photovoltaic
  59. 59. Selecting a Transducer  What is the physical quantity to be measured?  Which transducer principle can best be used to measure this quantity?  What accuracy is required for this measurement?  Fundamental transducer parameters  Physical conditions  Environmental conditions  Compatibility of the associated equipment  Reducing the total measurement error :  Using in-place system calibration with corrections performed in the data reduction  Artificially controlling the environment to minimize possible errors
  60. 60. Transducers for Physiological Variable Measurements • A variable is any quantity whose value changes with time. A variable associated with the physiological processes of the body is known as a physiological variable. • Physiological variables occur in many forms: as ionic potential, mechanical movements, hydraulic pressure ,flows and body temperature etc. • Different transducers are used for different physiological variables.
  61. 61. Bio-Electric Potential Wednesday, March 30, 2016 62
  62. 62. Electrical Activity Measurement • Electrodes: – Electrodes convert ionic potential into electrical signals. – Used for EEG, ECG, EMG, ERG and EOG etc. – Different types of Electrodes are: 1) Surface Electrodes(no. Of muscles) These electrodes are used to obtain bioelectric potentials from the surface of the body. 2) Needle electrodes(specific to a muscle) These electrodes are inserted into body to obtain localized measurement of potentials from a specific muscle. 3) Microelectrodes(cellular level record) Electrodes have tips sufficiently small to penetrate a single cell in order to obtain readings from within cell.
  63. 63. Electrical Activity Measurement(cont.) • Working of Electrodes: • When metal electrodes come in contact with electrolyte then ion-electron exchange takes place as a result of electro-chemical reaction. One cation M+ out of the electrolyte becomes one neutral atom M taking off one free electron from the metal One atom M out of the metal is oxidized to form one cation M+ and giving off one free electron e- to the metal.
  64. 64. Half-cell potential Oxidation and reduction processes take place when metal comes in contact with Electrolyte . Net current flow is zero but there exists a potential difference depends upon the position of equilibrium and concentration of ions. That p.d. is known as half-cell potential. Over-potential If there is a current between the electrode and electrolyte then half-cell potential altered due to polarization is known as over-potential. Electrical Activity Measurement(cont.)
  65. 65. Electrical Activity Measurement(cont.) Types of Electrodes:  Perfectly Polarizable Electrodes - only displacement current, electrode behave like a capacitor example: noble metals like platinum Pt  Perfectly Non-Polarizable electrode - current passes freely across interface, - no overpotential examples: - silver/silver chloride (Ag/AgCl), - mercury/mercurous chloride
  66. 66. ECG Wednesday, March 30, 2016 67
  67. 67. EEG Wednesday, March 30, 2016 68
  68. 68. Electrode Placement Wednesday, March 30, 2016 69
  69. 69. Block Diagram of ECG Wednesday, March 30, 2016 70
  70. 70. Effects of Artefacts on ECG Recording Wednesday, March 30, 2016 71  Power Line Interference Shifting of the baseline Muscle tremors
  71. 71. Types of ECG Recorder Wednesday, March 30, 2016 72  Single-channel Recorders  Three –channel Recorders  Vector electrocardiographs( vector-cardiography)  Electrocardiograph systems for stress testing  Electrocardiographs for computer processing  Continuous ECG recording (Holter Recording )
  72. 72. Phonocardiograph (PCG) Wednesday, March 30, 2016 73 • A Phonocardiogram is a recording of the heart sounds and murmurs. • Eliminates subjective interpretation of the heart sounds • Enables evaluation of the heart sounds and murmurs with respect to the electric and mechanical events in the cardiac cycle. • Evaluation of the result is based on the basis of changes in the wave shape and various timing parameters.
  73. 73. 74 • S1 – onset of the ventricular contraction • S2 – closure of the semilunar valves • S3 – ventricular gallop • S4 – atrial gallop • Other – opening snap, ejection sound • Murmurs Heart Sounds
  74. 74. 75 • The phonocardiograph transducer is a contact or air- coupled acoustical microphone held against the patient's chest (shown in fig). • Various types of microphones are used, but most are the piezoelectric crystal or dynamic type of construction. Microphones for Phonocardiography
  75. 75. 76 • The crystal microphone generally costs less and is more rugged than the dynamic type. • Also, the crystal microphone produces a larger output signal for a given level of stimulus • The dynamic microphone uses a moving coil coupled to the acoustical diaphragm. • The dynamic microphone is used when it is desirable to have a signal frequency response similar to that of the medical stethoscope. • An air-coupled microphone with a 2-s time constant is often used in apex phonocardiography. Microphones for Phonocardiography
  76. 76. EEG Wednesday, March 30, 2016 77  Electrical Activity of the brain EEG electrodes are smaller than ECG It is an Effective method for diagnosing many neurological, disorder such as epilepsy, tumour etc.
  77. 77. EEG Electrode Placement Wednesday, March 30, 2016 78
  78. 78. Brain Wave Classification Wednesday, March 30, 2016 79 EEG rhythms correlate with patterns of behavior (level of attentiveness, sleeping, waking, seizures, coma). Rhythms occur in distinct frequency ranges: Gamma: 20-60 Hz (“cognitive” frequency band) Beta: 14-20 Hz (activated cortex) Alpha: 8-13 Hz (quiet waking) Theta: 4-7 Hz (sleep stages) Delta: less than 4 Hz (sleep stages, especially “deep sleep”) Higher frequencies: active processing, relatively de-synchronized activity (alert wakefulness, dream sleep). Lower frequencies: strongly synchronized activity (nondreaming sleep, coma).
  79. 79. Brain Wave Classification Wednesday, March 30, 2016 80 The period of High Frequency EEG that occurs during sleep is called Paradoxical sleep or REM (Rapid Eye Movement).
  80. 80. Effects of Artefacts on EEG Wednesday, March 30, 2016 81  Biological Artefacts  Eye Induced Artefacts  Cardiac Artefacts  Muscle Artefacts  Respiration Artefacts Physiological Artefacts  60 Hz Interference  EEG Electrodes  Environmental Artefacts Non Physiological Artefacts
  81. 81. Block Diagram of EEG Wednesday, March 30, 2016 82
  82. 82. Evoked Potential Wednesday, March 30, 2016 83 If an external stimulus is applied to the sensory area of brain, it responds by producing a electrical potential known as Evoked Potential.  Classification: Visual Evoked Potential Auditory Evoked Potential SomatoSensory Evoked Potential
  83. 83. Blood Pressure Wednesday, March 30, 2016 84 Blood pressure is indicates your heart health It is determined by the contractions of the heart Your pressure varies depending on the condition of your heart and blood vessels Pressure is measured in millimeters of mercury (mm Hg)
  84. 84. Blood Pressure Wednesday, March 30, 2016 85
  85. 85. 86 Blood Pressure Risks 12/3/2013 • High blood pressure (hypertension) increases the risk of:  Chest pain (angina).  Heart attack.  Heart failure.  Kidney failure.  Stroke.  Blocked arteries in the legs or arms (peripheral arterial disease.  Eye damage .  Aneurysms (permanent cardiac or arterial dilatation).
  86. 86. 87 Cont. Blood Pressure Risks
  87. 87. BMTS 353 88 Cont. Blood Pressure Risks 12/3/2013 • Low blood pressure (hypotension) increases the risk of:  Reduces the blood flow to the brain and other vital organs.  Dizziness or fainting.  Lack of concentration.  Blurred vision.  Fatigue.  Cold and clammy skin.  Rapid shallow breathing.
  88. 88. Blood Pressure Measurement  Blood pressure measurement techniques are generally put into two broad classes: 1) DIRECT TECHNIQUES Direct techniques of blood pressure measurement, which are also known as invasive techniques, involve a catheter to be inserted into the vascular system. eg. Percutaneos insertion, Catheterization etc 2) INDIRECT TECHNIQUES The indirect techniques are non-invasive, with improved patient comfort and safety, but at the expense of accuracy. eg. Sphygmomanometer, Rheographic Method, Oscillometric Method, Ultrasonic Doppler Method etc
  89. 89. Blood Pressure (Sphygmomanometer/ Auscultatoy Method) Wednesday, March 30, 2016 90
  90. 90. Auscultatory Method (cont.) -) The observations differ from observer to another -) A mechanical error might be introduced into the system e.g. mercury leakage, air leakage, obstruction in the cuff etc. -) The observations do not always correspond with intra-arterial pressure -) Auscultatory tecnique cannot be used in noisy environment +) Auscultatory technique is simple and does not require much equipment ADVANTAGES DISADVANTAGES -) The technique does not give accurate results for infants and hypotensive patients
  91. 91. March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 15 How to measure?  Non-invasive blood pressure  Auscultation  Oscillometry Mercury sphygmomanometer + stethoscope Mechanical manometer + stethoscope
  92. 92. March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 17 The auscultation method
  93. 93. March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 18 The auscultation method
  94. 94. March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 19 The auscultation method Systolic BP Diastolic BP
  95. 95. March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 20 The oscillometric method
  96. 96. March 30, 2016 Blood Pressure - Biomedical Signal Processing Page 21 The oscillometric method  It is based on the change of the magnitude of oscillation  MAP – Mean Arterial Pressure
  97. 97. Oscillometric Method http://colin-europe.com/docpdfdemos/oscillo0104.wmv The intra-arterial pulsation is transmitted via cuff to transducer (e.g. piezo-electric) The arterial pressure oscillations (which can be detected throughout the measurement i.e. when P > SP and P < DP) are superimposed on the cuff pressure SP and DP are estimated from the amplitudes of the oscillation by using a (proprietary) empirical algorithm. cuff cuff The cuff pressure is deflated either linearly or stepwise
  98. 98. Oscillometric Method (cont.) DISADVANTAGE -) Many devices use fixed algorithms leading to large variance in blood pressures +) In the recent years, oscillometric methods have become popular for their simplicity of use and reliability. ADVANTAGES +) MP can be measured reliably even in the case of hypotension
  99. 99. Ultrasonic Method A transcutaneous (through the skin) Doppler sensor is applied here. The motion of blood-vessel walls in various states of occlusion is measured. The frequency difference between transmitted (8 MHz) and received signal is 40-500 Hz and it is proportional to velocities of the wall motion and the blood. The vessel opens and closes with each heartbeat when DP < P < SPcuff
  100. 100. Ultrasonic Method (cont.) +) Can be also used in noisy environment ADVANTAGES & DISADVANTAGES +) Can be used with infants and hypotensive individuals -) Subject’s movements change the path from sensor to vessel As the cuff pressure is increased, the time between opening and closing decreases until they coincide Systolic pressure Again as the cuff pressure is decreased, the time between opening and closing increases until they coincide Diastolic pressure
  101. 101. Direct Methods in Blood Pressure Measurements
  102. 102. General Facts Direct measurement = Invasive measurement Used only when essential to determine the blood pressure continuously and accurately in dynamic circumstances A vessel is punctured and a catheter (a flexible tube) is guided in The most common sites are brachial and radial arteries but also other sites can be used e.g. femoral artery A division is made into extravascular and intravascular sensor systems This method is precise but it is also a complex procedure involving many risks….
  103. 103. Extravascular Sensor The sensor is located behind the catheter and the vascular pressure is transmitted via this liquid-filled catheter. The ’normal’ measuring system The actual pressure sensor can be e.g. strain gage variable inductance variable capacitance optoelectronic piezoelectric, etc…
  104. 104. Extravascular Sensor (cont.) The hydraylic link is the major source of errors. The system’s natural frequency may be damped and degraded due (e.g.): too narrow catheter too long tubing various narrow connections air bubbles in the catheter The catheter-sensor system must be flushed with saline-heparine solution every few minutes in order to prevent blood from clotting at the tip. .
  105. 105. Extravascular Sensor (cont.) Normally the interesting frequency range is 0 – 100 Hz. If only MP is measured the bandwidth is 20 Hz (harmonics > 10 are ignored)
  106. 106. Intravascular Sensor The sensor is located in the tip of the catheter. This way the hydraulic connection is replaced with an electrical or optical connection +) The frequency response is not limited by the hydraulic properties of the system. No time delay. -) Breaks easily -) More expensive +) Electrical safety and isolation when using fiber optics The dispacement of the diaphragm is measured
  107. 107. Blood Pressure Blood pressure is an important signal in determining the functional integrity of the cardiovascular system. Scientists and physicians have been interested in blood pressure measurement for a long time.
  108. 108. Transducers for Blood Pressure Measurement Strain Gauges Resistance is related to length and area of cross-section of the resistor and resistivity of the material as By taking logarithms and differentiating both sides, the equation becomes Dimension al piezoresistanc e Strain gage component can be related by poisson’s ratio as
  109. 109. Transducers for Blood Pressure Measurement(cont.) Gage Factor of a strain gage G is a measure of sensitivity Think of this as a Transfer Function! Input is strain  Output is dR Put mercury strain gauge around an arm or chest to measure force of muscle contraction or respiration, respectively  Used in prosthesis or neonatal apnea detection, respectively Strain Gauges
  110. 110. Transducers for Blood Pressure Measurement(cont.) Strain Gauges
  111. 111. Transducers for Blood Pressure Measurement(cont.) An inductor is basically a coil of wire over a “core” (usually ferrous) It responds to electric or magnetic fields A transformer is made of at least two coils wound over the core: one is primary and another is secondary Primary Secondary Displacement Sensor Inductors and tranformers work only for ac signals Inductive Pressure Sensors ( LVDT)
  112. 112. Transducers for Blood Pressure Measurement(cont.) Capacitive Pressure Sensors When there is difference in P1 & P2 then diaphragm moves toward low pressure side and accordingly capacitance varies. So, capacitance becomes function of pressure and that pressure can be measured by using bridge ckt. It can be used for blood pressure measurent.
  113. 113. Transducers for Blood Pressure Measurement(cont.) Capacitive Pressure Sensors Pressure An example of a capacitive sensor is a pressure sensor. In parts a, the thin sensor diaphragm remains parallel to the fixed electrode and in part b, the diaphragm deflects under applied pressure resulting in capacitance change
  114. 114. Transducers for Blood Pressure Measurement(cont.) The other pressure sensing approach, characterized by a diaphragm in front of the fibre optic link, is based on the light intensity modulation of the reflected light caused by the pressure-induced position of the diaphragm. Fibre-optic pressure sensor
  115. 115. 116 Blood Flow • Blood flow helps to understand basic physiological processes and e.g. the dissolution of a medicine into the body. • Blood flow and changes in blood volume, are usually correlated with concentration of nutrients and other substance in the blood. • Also, Blood Flow measurement reflects the concentration of O2.
  116. 116. Blood Flow • A measure of the velocity of blood in a major vessel. In a vessel of known diameter , this can be calibrated as flow and is most successful accomplished in arterial vessels. Used to estimate heart output and circulation. Requires exposure of the vessel. Flow transducer surrounds vessel. Methods of measurement include • Electro-magnetic • Ultrasonic principles • Fibre-optic laser Doppler flowmetry • Thermal Convection • Blood Flow Determination by Radiographic Method
  117. 117. Blood Flow Measurement • Based on Faraday’s law of induction that a conductor that moves through a uniform magnetic field, or a stationary conductor placed in a varying magnetic field generates emf on the conductor: • When blood flows in the vessel with velocity u and passes through the magnetic field B, the induced emf e measured at the electrodes is.   L de 0 LBu For uniform B and uniform velocity profile u, the induced emf is e=BLu. Flow can be obtained by multiplying the blood velocity u with the vessel cross section A. Electromagnetic Flow meters
  118. 118. Blood Flow Measurement(cont.) Electromagnetic Flow meter Probes • Comes in 1 mm increments for 1 ~ 24 mm diameter blood vessels • Individual probes cost $500 each •Only used with arteries, not veins, as collapsed veins during diastole lose contact with the electrodes • Needless to say, this is an INVASIVE measurement!!! • A major advantage is that it can measure instantaneous blood flow, not just average flow.
  119. 119. Blood Flow Measurement(cont.) Ultrasonic Flow meters  Based on the principle of measuring the time it takes for an acoustic wave launched from a transducer to bounce off red blood cells and reflect back to the receiver.  All UT transducers, whether used for flowmeter or other applications, invariably consists of a piezoelectric material, which generates an acoustic (mechanical) wave when excited by an electrical force (the converse is also true)  UT transducers are typically used with a gel that fills the air gaps between the transducer and the object examined
  120. 120. Blood Flow Measurement(cont.) Ultrasonic Flow meters The Doppler blood-flow measurement Doppler blood flow detectors operate by means of continuous sinusoidal excitation. The frequency difference calibrated for flow velocity can be displayed or transformed by a loudspeaker into an audio output.
  121. 121. 122 Cont. Blood Flow Normal blood flow velocity 0,5 m/s 1 m/s (Systolic, large vessel)
  122. 122. 123 Blood Flow Measurement Blood Pressure
  123. 123. 124 Ultrasonic Doppler Method Blood Pressure • The blood cells in the fluid reflects the ultrasound signal with a shift in the ultrasonic frequency due to its movement. • In the recent years ultrasound contrast agents have been used in order to increase the echoes. c v ff cd 2 f = 2 – 10 MHzc c = 1500 - 1600 m/s (1540 m/s) f = 1,3 – 13 kHzd
  124. 124. 125 Laser Doppler Flowmetry Blood Pressure • The principle of measurement is the same as with ultrasound Doppler. • The laser parameter may have e.g. the following properties: 5 mW He-Ne-laser 632,8 nm wavelength • The method is used for capillary (microvascular) blood flow measurements.
  125. 125. (1) Bios current => Thermister heating (2) T2 Thermister is cooled by thermal convection. Invasive, probe positioning is difficult. The stronger F gets, The sharper the temperatur is decreased. (cf.) respiratory monitoring by thermister Temp. of inspiration is 25˚C. Temp. of expiration is 36.5˚C. Thermal convection flowmeter
  126. 126. Radiographic Method  Blood is not normally visible on an X-ray image because it has about the same radio density as the surrounding tissue.  By the injection of a medium into the blood vessel, the circulation pattern can be made locally visible.  On a sequential record of the X- ray image, the progress of the contrast medium can be followed,obstructions can be detected and the blood flow in the blood vessels can be estimated known as CINE or ANGIOGRAPHY.
  127. 127. 128 Plethysmography Method (Strain Gage) Blood Pressure Plethysmography means the methods for recording volume changes of an organ or a body part. • Strain gage is made of silicone rubber tubes, which are filled with conductive liquid (e.g. mercury) whose impedance changes with volume. • Venous occlusion cuff is inflated to 40 – 50 mmHg. In this way there will be the arterial inflow into the limb but no venous outflow.
  128. 128. 129 Plethysmography Method (Electric-Impedance) Blood Pressure • Different tissues in a body have a different resistivity. Blood is one of the best conductors in a body. • A constant current is applied via skin electrodes. • The change in the impedance is measured. • The accuracy is often poor.
  129. 129. 130 Plethysmography Method (Photoelectric) Blood Pressure • A beam of IR-light is directed to the part of the tissue which is to be measured for blood flow (e.g. a finger or ear lobe). • The blood flow modulates the attenuated / reflected light which is recorded. • The light that is transmitted / reflected is collected with a photo detector. Poor measure for changes in volume Very sensitive to motion artefacts Method is simple Heart rate is clearly seen
  130. 130. Pulse sensors Heart rate measurement is one of the very important parameters of the human cardiovascular system. The heart rate of a healthy adult at rest is around 72 beats per minute (bpm). Basically, the device consists of an infrared transmitter LED and an infrared sensor photo-transistor. The transmitter-sensor pair is clipped on one of the fingers of the subject. The LED emits infrared light to the finger of the subject. The photo-transistor detects this light beam and measures the change of blood volume through the finger artery. This signal, which is in the form of pulses is then amplified and filtered suitably and is fed to a low-cost microcontroller for analysis and display
  131. 131. Pulse Sensor(cont.) The microcontroller counts the number of pulses over a fixed time interval and thus obtains the heart rate of the subject. Several such readings are obtained over a known period of time and the results are averaged to give a more accurate reading of the heart rate. The calculated heart rate is displayed on an LCD in beats-per-minute in the following format: Rate = nnn bpm
  132. 132. 133 Blood Flow Measurement Blood Pressure
  133. 133. 134 Indicator Dilution Methods (Dye Dilution) Blood Pressure • A bolus of indicator, a colored dye (indocyanine green), is rapidly injected in to the vessel. • The concentration is measured in the downstream • The blood is drawn through a colorimetric cuvette and the concentration is measured using the principle of absorption photometry.
  134. 134. 135 Indicator Dilution Methods (Thermal Dilution) Blood Pressure • A bolus of chilled saline solution is injected into the blood circulation system (right atrium). • This causes decrease in the artery temperature. • Catheter-tip probes are used to measure the change in tempreture.
  135. 135. Cardiac Output Whenthe heartcontracts
  136. 136. CardiacOutput Cardiac Output is the volume of blood pumped each minute, and is expressed by the following equation: • CO = SV xHR • Where: • CO is cardiac output expressed in L/min (normal ~5 L/min) • SV is stroke volume per beat • HR is the number of beats per minute
  137. 137. 140 Cardiac Output Measurement (Fick Technique) Blood Pressure
  138. 138. 141 Cardiac Output Measurement (Fick Technique) Blood Pressurehttps://www.youtube.com/watch?v=nAgmCoqAoPo
  139. 139. Echocardiogram • An echocardiogram is a test in which ultrasound is used to examine the heart. • Displaying a cross-sectional "slice" of the beating heart, including the chambers, valves and the major blood vessels that exit from the left and right ventricle • M-mode • two- dimensional (2-D) Echo • Doppler Examination • 3-D echo
  140. 140. What information does Echocardiography and Doppler provide? • Size of the chambers of the heart • Pumping function of the heart • Valve Function • Volume status • Other Uses: fluid in the pericardium, congenital heart diseases, blood clots or tumors within the heart
  141. 141. 3-D Echo
  142. 142. Electromyography(EMG) • Electromyogram (EMG) is a technique for evaluating and recording the activation signal of muscles. • EMG is performed by an electromyograph, which records an electromyogram. • Electromyograph detects the electrical potential generated by muscle cells when these cells contract and relax.
  143. 143. INTRODUCTION Contd. EMG Apparatus Muscle Structure/EMG
  144. 144. ELECTRICAL CHARACTERITICS • The electrical source is the muscle membrane potential of about -70mV. • Measured EMG potentials range between < 50 μV up to 20 to 30 mV, depending on the muscle under observation. • Typical repetition rate of muscle unit firing is about 7-20 Hz. • Damage to motor units can be expected at ranges between 450 and 780 mV
  145. 145. ELECTRODE TYPES Intramuscular - Needle Electrodes Extramuscular - Surface Electrodes
  146. 146. EMG PROCEDURE • Clean the site of application of electrode; • Insert needle/place surface electrodes at muscle belly; • Record muscle activity at rest; • Record muscle activity upon voluntary contraction of the muscle.
  147. 147. EMG Contd. • Muscle Signals are Analog in nature. • EMG signals are also collected over a specific period of time. Analog Signal
  148. 148. EMG Contd. EMG processing: Amplification & Filtering Signal pick up Conversion of Analog signals to Digital signals Computer
  149. 149. APPLICATION OF EMG • EMG can be used for diagnosis of Neurogenic or Myogenic Diseases. • You tube link of EMG
  150. 150. 155 Patient Care, Monitoring and Safety Measures Blood Pressure  The Patient Monitoring System (PMS) is a very critical monitoring systems, it is used for monitoring physiological signals including Electrocardiograph (ECG), Respiration , Invasive and Non-Invasive Blood Pressure, Oxygen Saturation in Human Blood (SpO2), Body Temperature and other Gases etc.  In PMS, the multiple sensor and electrodes is used for receiving physiological signals like as ECG Electrodes, SpO2Finger Sensor, Blood Pressure Cuff and Temperature Probe to measure the physiological signals.
  151. 151. 156 Patient Care, Monitoring and Safety Measures Blood Pressure  During treatment, it is highly important to continuously monitor the vital physiological signs of the patient. Therefore , patient monitoring systems has always been occupying a very important position in the field of medical devices.  The continuous improvement of technologies not only helps us transmit the vital physiological signs to the medical personnel but also simplifies the measurement and as a result raises the monitoring efficiency of patients.
  152. 152. 157 Classes of Patient Monitoring System Blood Pressure In the past, the dominant products manufactured by medical device manufacturers are mainly those for single parameter measurement. Nowadays however, a multi-parameter patient monitor is commonly used. 1.Single-Parameters Monitoring Systems 2.Multi-Parameter Patient Monitoring Systems
  153. 153. 158 Single Parameter Monitoring System Blood Pressure The single parameter monitoring system is available for measuring blood pressure of a human body, ECG (Electrocardiograph) monitor, SpO2 (Oxygen Saturation in Blood) monitor etc..
  154. 154. 159 Multi- Parameter Monitoring System Blood Pressure  A multi-parameter Patient Monitoring System (PMS) is used for multiple critical physiological signs of the patient to transmit the vital information like Electro cardiograph , Respiration Rate, Blood pressure etc. Therefore, multi parameter PMS has always been occupying a very significant position in the field of medical devices.  Most diseases of the heart and of the circulatory system , referred to as cardiovascular diseases, strike with out warning and prompt treatment is required .  Such treatment is best provided in a specialized area of hospital referred to as “intensive care unit.”(ICU).  These specialized hospital units provide constant observation of the subject, constant monitoring of the subject’s physiological condition and provide immediate emergency treatment whenever it is required.
  155. 155. 160 Three Important Intensive Care Units Blood Pressure  Coronary intensive care: units used for treatment of diseases of the heart such as the heart attacks  Stroke intensive care: Units used for treatment of diseases of the circulatory system such as stroke.  Pulmonary intensive care units: Pulmonary intensive care unit s are used for treatment of respiratory diseases.
  156. 156. 161 PHYSIOLOGICAL FUNCTIONS TO BE MONITOR DURING INTENSIVE CARE UNIT Blood Pressure  Cardiac monitoring  Hemodynamic monitoring,  Respiratory monitoring  Neurological monitoring  Blood glucose monitoring  Childbirth monitoring  Body temperature
  157. 157. ECG MONITORING • The principal physiological signal monitored in an intensive care unit is often the electrocardiogram. The electrocardiogram is usually monitored in the lead-II configuration with two active electrodes. • These two electrodes are placed approximately 12inches apart along the maximum potential axis of the subject’s heart. • A third electrode (ground) should be located elsewhere on the chest. This electrocardiogram monitoring configuration is referred to as three-lead chest cluster. • The electrodes used for ECG monitoring during intensive care must be suited for long term monitoring applications. • The set of leads used for monitoring purpose is called ‘rhythm’ • strip and its purpose is just to note the heart beat and not for analyzing it.
  158. 158. Blood Pressure Monitoring • The second physiological parameter often of prime importance in intensive care monitoring is blood pressure. • Korotkoff system-Riva-Rocci Method • Blood pressure can be monitored using the automatic cuff pump and Korotkoff microphone blood- pressure measurement system this system is occasionally used in intensive care units. , • It also possesses the disadvantage of it does not provide a continuous record of the subject’s blood pressure. • Thus, if for some reason the subjects blood pressure were to suddenly drop, this system may take some minutes or so to detect this pressure drop. •
  159. 159. Blood Pressure Monitoring…… • PLETHYSMOGRAPH • Blood pressure monitoring with plethysmograph offers the least discomfort to the subject; however, it provides only a relative indication of the well being of the circulatory system rather than providing absolute values for diastolic and systolic pressure. • Digital blood pressure monitors are now-a-days often used in many intensive care units. Any intensive care unit may employ one or more of these techniques and indeed all three may be available if required.
  160. 160. BLOOD PRESSURE MONITORING
  161. 161. RESPIRATION MONITORING • It is often desirable to monitor the subject’s respiratory activity during intensive care ; • this may be accomplished with thermistor pneumograph placed in the subject’s nostril. • BODY TEMPERATURE • • It is often also desirable to monitor body temperature in intensive care subjects via a rectal or armpit thermistor probe
  162. 162. CENTRAL NURSE’S STATION
  163. 163. CENTRAL NURSE’S STATION…. • Multi connector cable connects the output form the four subject- monitoring sites located beside each intensive care bed to the central nurse’s station. • Each subject’s ECG is continuously displayed via a four channel CRT display. And also these signals are being recorded continuously on a memory loop tape recorder. • This tape recorder contains the previous one-minute ECG history for each subject by recording the ECG on a tape loop“one minute” in length
  164. 164. Present Parameters in Patient Monitoring System • ECG 3/5/10 leads • Respiration • Invasive Blood Pressure (IBP) • Non Invasive Blood Pressure(NIBP) • Pulse Oxy Meter (SpO2)
  165. 165. Non invasive Blood pressure ECG MONITOR PULSE OXYMETER
  166. 166. Hemodynamic monitoring • Cardiac output and flow rate ; • The heart is the driver of the circulatory system, pumping blood through rhythmic contraction and relaxation. • The rate of blood flow out of the heart meaning literally "blood flow, motion and equilibrium under the action of external forces", is the study of blood flow or the circulation. It explains the physical laws that govern the flow of blood in the blood vessels.
  167. 167. Respiratory monitoring • Measurement of airway pressure (Paw), flow (F) and volume (Vol) during mechanical ventilation assists in the differential diagnosis of respiratory failure. Airway occlusion technique makes possible to carefully characterize the mechanics of the lung, chest wall, and the total respiratory monitoring system • Pulse oximetry ;which involves measurement of the saturated percentage of oxygen in the blood, referred to as SpO2, and measured by an infrared finger cuff, • Capnography ;, which involves CO2 measurements, referred to as (EtCO2) or end-tidal carbon dioxide concentration. The respiratory rate monitored as such is called AWRR or (airway respiratory rate).
  168. 168. Neurological monitoring - EEG • Intracranial pressure. Also, there are special patient monitors which incorporate the monitoring of brain waves • Blood glucose meter ; is an electronic device for measuring the blood glucose level • Childbirth; also known as labour, delivery, birth,
  169. 169. Body temperature monitoring • Body temperature" redirects here. For information regarding normal human body temperature,
  170. 170. Components of Medical monitor • Sensor • Translating component • Display device • Communication links • Alarm
  171. 171. Spo2 sensor
  172. 172. Spo2 sensor board
  173. 173. Invasive BP sensor
  174. 174. ECG sensor
  175. 175. ECG placement
  176. 176. ECG sensor board
  177. 177. Temp sensor
  178. 178. Hospitals may have ICUs that cater to a specific medical specialty below using all medical monitor Neonatal intensive care unit (NICU) Pediatric intensive care unit (PICU) Psychiatric intensive care unit (PICU) Coronary care unit (CCU): Medical intensive care unit (MICU) Neurological intensive care unit (Neuro ICU) Trauma intensive care unit (Trauma ICU). Post-anesthesia care unit (PACU): Surgical Intensive Care Unit (SICU): Mobile Intensive Care Unit (MICU)
  179. 179. Use of computers for patient monitoring real-time monitoring Wherever you are – in the hospital, at home, or on the road – you have access to the patient information you need to make informed clinical decisions viaWeb and iPad access. IntelliVue Information Center iX offers virtually anywhere, anytime access to key patient monitoring information.
  180. 180. Use of computers for patient monitoring Automatic control Patient equipment Computer DBMS Reports Mouse and keyboard Display Transducers Clinician
  181. 181. ICU Bed Bed BedBed Nurse station Telemetry WEB connection
  182. 182. FUTURE TRENDS IN PATIENT MONITORINGSY STEM • Blood Gas Analyzer • Drug Dosage calculator • Drug Management System • Wearable PMS • Telemetry / Telemedicine
  183. 183. 189 Patient Safety Blood Pressure  The main objective of any healthcare system should be the safe progress of the patients through all parts of the system.  Harm from their care as well as from the environment in which it is carried out, must be avoided and risk minimized in care delivery processes.  Electrical shocks, burns and fire hazards caused by medical equipment are one of the highest risks that may harm the patient.  Electric shock: When the human body comes in contact with the live wire and an uninsulated electric power, the power flows naturally and easily through the body and we experience it as an E-shock.
  184. 184. Electrical safety Medical procedures usually expose the patient to more hazards than the typical home or workplace, because :- 1. In medical environments the skin and mucous membranes are frequently penetrated or altered. 2. There are many sources of potentially hazardous substances and energy forms that could injure either the patient or the medical staff. These sources of hazards include:-  fire, air, earth, water, chemicals, drugs, microorganisms  Waste products  Sound and electricity  Natural and unnatural disasters surroundings, gravity, mechanical stress  People responsible for acts of omission and operation
  185. 185. Physiological effects of electricity  For a physiological effect to occur, the body must become part of an electric circuit. Current must enter the body at one point and leave at some other point  The magnitude of the current is equal to the applied voltage divided by the sum of the series impedances of the body tissues and the two interfaces at the entry points Three phenomena can occur when electric current flows through biological tissue: (1) Electric stimulation of excitable tissue (nerve and muscle) (2) Resistive heating of tissue (3) Electrochemical burns and tissue damage for direct current and very high voltages psychophysical and physiological effects of electrical current in humans:- 70 kg AWGNo.8copperwires
  186. 186. psychophysical and physiological effects of electrical current in humans:- Threshold of perception = the minimal current that an individual can detect. This threshold varies considerably among individuals and with the measurement conditions (wet or dry skin) Thresholds for dc current range from 2 to 10 mA, and slight warming of the skin is perceived (realized)
  187. 187. Let-go current:- Is defined as the maximal current at which the subject can withdraw voluntarily. Involuntary contractions of muscles or reflex withdrawals is occur The minimal threshold for the let-go current is 6 mA Respiratory paralysis, pain, and fatigue:-  respiratory arrest has been observed at 18 to 22mA  Strong involuntary contractions of the muscles and stimulation of the nerves can be painful and cause fatigue if there is long exposure. psychophysical and physiological effects of electrical curren in humans:-
  188. 188. Ventricular fibrillation Ventricular fibrillation:- Is a rapid and disorganized cardiac rhythm. If the magnitude of the current is sufficient to excite only part of the heart muscle and disrupted the heart rate The heart rate can rise to 300 beats/min The fibrillation does not stop when the current that triggered it is removed. Ventricular fibrillation is the major cause of death due to electric shock. The threshold for ventricular fibrillation for an average-sized human varies from about 75 to 400 mA Normal rhythmic activity returns only if a brief high-current pulse from a defibrillator is applied to depolarize all the cells of the heart muscle the cells relax together, a normal rhythm usually returns
  189. 189. Body weight and fibrillation, duration of the current Several studies using animals of various sizes have shown that the fibrillation threshold increases with body weight Fibrillating current increases from 50 mA rms for 6 kg dogs to 130 mA rms for 24 kg dogs.
  190. 190. 196 Types of Shocks Blood Pressure Gross Shock/Macro Shock: The current flows through the body of the subject ,e.g. as from arm to arm. Micro current Shock: The current passes directly through the heart wall. This is the case when cardiac catheters may be present in the heart chambers.
  191. 191. Point of entry (macroshock and microshock) Macroshock:- When current is applied at two points on the surface of the body, only a small fraction of the total current flows through the heart (macroshock). The magnitude of current needed to fibrillate the heart is far greater when the current is applied on the surface of the body than it would be if the current were applied directly to the heart Microshock:- All the current applied through an intracardiac catheter flows through the heart small currents called microshocks can induce Ventricle fibrillation Current of about 20 µA can cause microshock . The widely accepted safety limit to prevent microshocks is 10 mA.
  192. 192. Distribution of electric power Electric power is needed in health-care facilities for :- 1. The operation of medical instruments 2. Lighting, maintenance appliances 3. Patient conveniences (such as television, hair curlers, and electric toothbrushes) 4. Clocks, nurse call buttons, and an endless list of other electric devices • So the first step on providing electrical safety is to control the availability of electric power and the grounds in the patients’ environment Safe distribution of power in health-care facilities:- High voltage (4800 V) enters the building— usually via underground cables
  193. 193. Patients’ electrical environment  A shock hazard exists between the two conductors supplying either a 240 V or a 120 V appliance.  Because the neutral wire on a 120 V circuit is connected to ground, a connection between the hot conductor and any grounded object poses a shock hazard.  Microshocks can occur if sufficient potentials exist between exposed conductive surfaces in the patients’ environment THE maximal potentials permitted between any two exposed conductive surfaces in the vicinity of the patient are specified by the 2006 NEC, Article 517- 15: 1. General-care areas, 500 mV under normal operation 2. Critical-care areas, 40 mV under normal operation Things must be done:- 1. All exposed conductive surfaces in the vicinity of the patient must be grounded at a single patient grounding point. 2. Periodic testing for continuity between the patient ground and all grounded surfaces is required 3. Each patient-bed location in general- care areas must have at least four single or two duplex receptacles ,the receptacle must be grounded 4. At least two branch circuits with separate automatic overcurrent devices must supply the location of each patient bed. 5. For critical-care areas at least six single or three duplex receptacles are required for each location of a patient bed
  194. 194. Isolated-power systems Any ground faults can posses hazard . A ground fault :- Is a short circuit between the hot conductor and ground that injects large currents into the grounding system.  Isolation of both conductors from ground is commonly achieved with an isolation transformer isolation transformer + line isolation monitor Measures the total possible resistive and capacitive leakage current (total hazard current) that would flow through a low impedance if it were connected between either isolated conductor and ground. When the total hazard current exceeds 3.7 to 5.0 mA for normal line voltage, a red light and an audible alarm are activated Checking the lines by the LIM can interfere with (ECG,EEG ,ect.) ,or it can trigger synchronized defibrillators
  195. 195. Microshock hazards Leakage currents:- Small currents (usually on µA) that flow between any adjacent insulated conductors that are at different potentials The leakage current in line operated equipment flows through: 1. The stray capacitance between the two conductors. 2. Resistive leakage current flows through insulation, dust, and moisture. If the ground wire is broken, then the chassis potential rises above ground, and a patient who touches the chassis and has a grounded electric connection to the heart may receive a micro shock
  196. 196. Electrical-safety codes and standards A code is a document that contains only mandatory requirements. A standard also contains only mandatory requirements, but compliance tends to be voluntary, and more detailed notes and explanations are given. Standards are designed for voluntary use and do not impose any regulations. However, laws and regulations may refer to certain standards and make compliance with them compulsory. A manual or guide is a document that is informative and tutorial but does not contain requirements
  197. 197. Limits on Leakage Current Limits on Leakage Current for Electric Appliances one fault is applied to the equipment to see what happens
  198. 198. Basic approaches to protection against shock There are two fundamental methods of protecting patients against shock:- 1. The patient should be completely isolated and insulated from all grounded objects. 2. All sources of electric current and all conductive surfaces within reach of the patient can be maintained at the same potential, which is not necessarily ground potential  In practical neither of these approaches can be fully achieved so we used :-  Grounding system  Isolated power-distribution system  Ground-fault circuit interrupters (GFCI)  Reliable grounding for equipment  Reduction of leakage current  Double-insulated equipment  Operation at low voltages  Electrical isolation  Isolated heart connections For the power distribution  For the equipment
  199. 199. Protection: power distribution The patient equipment grounding point is connected individually to all :- receptacle grounds Metal beds Metal door and window frames Water pipes Any other conductive surface. These connections should not exceed resistance of 0.15 Ω The difference in potential between receptacle grounds and conductive surfaces should not exceed 40 mV
  200. 200. Chassis leakage current Chassis leakage current:- Leakage current emanating from the chassis should not exceed :- 500 mA for appliances with single fault not intended to contact patients . 300 mA for appliances that are intended for use in the patient care vicinity. These are limits on rms current for sinusoids from dc to 1 kHz, and they should be obtained with a current-measuring device of 1000 Ω or less Chassis leakage-current test
  201. 201. Leakage current in patient leads Limits on leakage current in patient leads should be 50 µA. Isolated patient leads must have leakage current that is less than 10 µA. leakage current between any pair of leads or between any single lead and all the other patient leads should be measured. Test for leakage current from patient leads to ground
  202. 202. Test for leakage current between patient leads Test for leakage current between patient leads leakage current between any pair of leads or between any single lead and all the other patient leads should be measured
  203. 203. PACEMAKERS
  204. 204. ELECTRICAL SYSTEM IN THE HEART
  205. 205. WHEN DO WE NEED A PACEMAKER ??? • Bradycardia – a condition in which the heart beats too slowly – less than 60 beats per minute • Tachycardia – a condition in which the heart beats too fast – more than 80 beats per minute • Atrial fibrillation – the upper chambers of the heart beat rapidly
  206. 206. WHAT IS A PACEMAKER The basic parts : • Power source • Pulse generator • Electrodes

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