Telemedicine and remote patient monitoring systems

medical

1. EC6001 MEDICAL ELECTRONICS

2. OBJECTIVES To gain knowledge about the various physiological parameters both electrical and non electrical and the methods of recording and also the method of transmitting these parameters. To study about the various assist devices used in the hospitals. To gain knowledge about equipment used for physical medicine and the various recently developed diagnostic and therapeutic techniques.

3. MEDICAL ELECTRONICS A branch of electronics in which electronic instruments and equipment are used for such medical applications as diagnosis, therapy, research, anesthesia control, cardiac control, and surgery.

4. Factors to be considered for the design of medical instrumentation system Range Sensitivity linearity Hysteresis Frequency response Accuracy Signal to noise ratio Stability Isolation Simplicity

5. Categories of instrumentation Information gathering Diagnosis Evaluation Monitoring Control

6. Components of the Man-Instrumentation system The subject Stimulus The transduce Signal conditing equipment Display equipment Recording ,data processing and transmission equipment Control devices

7. Physiological system of the body Biochemical System Cardiovascular System Respiratory System Nervous System

8. Cell and its structure

9. UNIT I ELECTRO-PHYSIOLOGY AND BIO-POTENTIAL RECORDING

10. List of contents in unit-1 The origin of Bio-potentials; biopotential electrodes, biological amplifiers, lead systems and recording methods, typical waveforms and signal characteristics for ECG EEG EMG PCG

11. Origin Of Biopotentials Electrodes Nerve cells or neurons are excitable. When stimulated, they undergo chemical changes that produce tiny traveling waves of electricity.- nerve signals or impulses. These pass to other neurons, eliciting similar response from them. Throughout the nervous system, information is conveyed as tiny electrical signals called nerve impulses or action potentials. These impulses are the same all over the body about 100 milli volts in strength and lasting just 1 millisecond. Resting Potentials And Action Potentials

12. RESTING POTENTIALS AND ACTION POTENTIAL

13. RESTING POTENTIALS AND ACTION POTENTIAL( cotd ,.) Resting potential is defined as the electrical potential of an excitable cell relative to its sur-roundings when not stimulated or involved in passage of an impulse.   It ranges from -60mV to -100mV   The nerve and muscle cells permit the entry of potassium and chloride ions. It blocks the entry of sodium ions.   The permeability of sodium ions is about 2 x 10 -8 cm/s and for potassium and chloride ions is 4 x 10 -6 cm/s.    

14. Resting potential The resting potential is derived by Gold-man's equation     The subscript o=outside the cell   The subscript i =inside the cell   V R = Resting Potential  

15. Resting potential ( cotd ,.) K= Boltzman constant   T=Absolute temperature in Kelvin   q=1.602x10 -19 coulombs   P k =Permeability of potassium ion   P na = Permeability of sodium ion   P Cl =Permeability of chloride ion

16. Waveform of action potential

17. Action potential ( cotd ,.) Absolute refractory period is the time dura-tion of the cell not responding to further stimuli. It is about 1 millisecond in nerve cell.   Relative Refractory Period   Following the absolute refractory period there is a brief period of time during which another action potential can be triggered but a much stronger stimulation is required.   Propagation Rate Or Conduction Velocity   The rate at which an action potential moves down a fiber of a nerve cell or is propagated from cell to cell . The conduction velocity var-ies in nerves depending on the type and diame-ter of the fiber and is from 20 n/s to 140 m/s. But in heart muscle, it is very slower ranging from 0.2 to 0.4 m/s.

18. Action potential ( cotd ,.) Net Height The net height of the action potential is defined as the difference between the potential of the depolarised membrane at the peak of the action potential and resting potential.

19. Bioelectric potentials ECG(Electro Cardiogram) EEG(Electro Encephalogram) EMG(Electro Myogram ) ERG(Electro Radiogram) EGG(Electro Gastro Gram)

20. Biopotential electrodes Device that conver ionic potential into electronic potentials are called electrodes. The interface of metalic ions in solution with their associated metals results in an electrical potential that is called the electrode potential.

21. Biopotential electrodes( Cotd .,) Nerst equation R=gas constant T=absolute Temperature,degrees Kelvin n=valence of the ion(the number of electrons added or removed to ionize the atom) C1,C2 =two concentrations of the ion on the two sides of the membrane f1,f2=respective activity coefficients of the ion on the two sides of the membrane

22. Half Cell Potential A characteristic potential difference established by the electrode and its surrounding electrolyte which depends on the metal, concentration of ions in solution and temperature (and some second order factors) . Half cell potential cannot be measured without a second electrode. The half cell potential of the standard hydrogen electrode has been arbitrarily set to zero. Other half cell potentials are expressed as a potential difference with this electrode. Reason for Half Cell Potential : Charge Separation at Interface Oxidation or reduction reactions at the electrode-electrolyte interface lead to a double-charge layer, similar to that which exists along electrically active biological cell membranes.

23. Measuring Half Cell Potential Note: Electrode material is metal + salt or polymer selective membrane

24. Equivalent Circuit C d : capacitance of electrode-eletrolyte interface R d : resistance of electrode-eletrolyte interface R s : resistance of electrode lead wire E cell : cell potential for electrode Frequency Response Corner frequency Rd+Rs Rs

25. Body Surface Recording Electrodes Metal Plate Electrodes (historic) Suction Electrodes (historic interest) Floating Electrodes Flexible Electrodes Electrode metal Electrolyte Think of the construction of electrosurgical electrode And, how does electro-surgery work?

26. Commonly Used Biopotential Electrodes Metal plate electrodes Large surface: Ancient, therefore still used, ECG Metal disk with stainless steel; platinum or gold coated EMG, EEG smaller diameters motion artifacts Disposable foam-pad: Cheap! (a) Metal-plate electrode used for application to limbs. (b) Metal-disk electrode applied with surgical tape. (c)Disposable foam-pad electrodes, often used with ECG

27. Commonly Used Biopotential Electrodes Suction electrodes No straps or adhesives required precordial (chest) ECG can only be used for short periods Floating electrodes metal disk is recessed swimming in the electrolyte gel not in contact with the skin reduces motion artifact Suction Electrode

28. Double-sided Adhesive-tape ring Insulating package Metal disk Electrolyte gel in recess (a) (b) (c) Snap coated with Ag-AgCl External snap Plastic cup Tack Plastic disk Foam pad Capillary loops Dead cellular material Germinating layer Gel-coated sponge Commonly Used Biopotential Electrodes Floating Electrodes Reusable Disposable

29. Microelectrodes Why Measure potential difference across cell membrane Requirements Small enough to be placed into cell Strong enough to penetrate cell membrane Typical tip diameter: 0.05 – 10 microns Types Solid metal -> Tungsten microelectrodes Supported metal (metal contained within/outside glass needle) Glass micropipette -> with Ag-AgCl electrode metal Intracellular Extracellular

30. Metal Microelectrodes Extracellular recording – typically in brain where you are interested in recording the firing of neurons (spikes). Use metal electrode+insulation -> goes to high impedance amplifier…negative capacitance amplifier! Microns! R C

31. Metal Supported Microelectrodes (a) Metal inside glass (b) Glass inside metal

32. Glass Micropipette A glass micropipet electrode filled with an electrolytic solution (a) Section of fine-bore glass capillary. (b) Capillary narrowed through heating and stretching. (c) Final structure of glass-pipet microelectrode. Intracellular recording – typically for recording from cells, such as cardiac myocyte Need high impedance amplifier…negative capacitance amplifier ! heat pull Fill with intracellular fluid or 3M KCl Ag-AgCl wire+3M KCl has very low junction potential and hence very accurate for dc measurements (e.g. action potential)

33. BIOLOGICAL AMPLIFIERS Need of bioamplifier Used to amplify low amplitude and low frequency signals. Output Displayed as EEG or ECG

34. Differential amplifier

35. OPERATIONAL AMPLIFIER

36. Ideal Op-Amp Properties Infinite input impedance Zero output impedance Infinite open loop voltage gain Zero noise level Infinite frequency response

37. INSTRUMENTATION AMPLIFIER Advantages: High gain Extremely high input impedance CMRR is good

38. CHOPPER AMPLIFIERS Analog signal is sampled in this amplifier cir- cuit . Hence this circuit is known as chopper amplifier.   Chopper amplifiers are classified into mechan-ical and non-mechanical choppers Advantages: Stable gain Provides low noise operation

39. ELECTROCARDIOGRAPHY(ECG) ECG shows the electrical activity of the heart muscles. The recorded ECG waveform is known as ElectroCardioGraph and the instrument is termed as electrocardiogram. It gives the valuable information about the cardiac disorders. A very widely used medical instrument, which is utilized to diagnose and monitor cardiac beat abnormalities.

40. Structure of Heart

41. Structure of Heart( cotd ,.) TRICUSPID VALVE [Right Atrio Ventricular Valve]: It is located in between the right atrium and right ventricle. It is located in between the right atrium and right ventricle. It prevents backward blood flow from right ven-tricle to right atrium.   BICUSPID VALVE [Left Atrio Ventricular Valve]: It is located in between left atrium and left ventricle. It prevents backward blood from left ventricle to left atrium.   PULMONARY VALVE: It is located at the right ventricle. It has half moon shaped cusps. It does not allow blood to come back to the right ventricle.   AORTIC VALVE: It is located between left ventricle and aorta. It does not allow the blood to come back to the left ventricle. Heart consists of 3 layers namely,   Pericardium   Endo cardium Myocardium   Pericardium: It is the outer layer of heart. It keeps the outer surface and prevents the heart from friction.

42. Structure of Heart( cotd ,.) Endocardium : It is the inner layer of the heart. It provides smooth path for blood flow.   Myocardium: It is the middle layer of the heart. It acts as the main muscle of the heart and it is made up of short cylindrical fibers.   Normal ECG amplitude ranges between 0.5-4 mV. Normal frequency content of ECG (for diagnostic purposes) is 0.05-100 Hz

43. ECG LEAD SYSTEMS: Types of ECG lead systems are ( i ) Limb lead systems and (ii) Chest lead sys- tems ( i ) Limb lead systems:   Bipolar limb lead systems Unipolar or augmented limb lead systems.   (a)Bipolar limb lead systems:   Potential between any two limb leads is measured with RL grounded.

44. ( i ) LeadI : Potential between LA & RA with RL grounded.

45. ii) Lead II: Potential between RA & LL with LA tied to RL & RL grounded.

46. (iii) Lead III: Potential between LA & LL with RA tied to RL & RL grounded.

47. Unipolar or augmented limb lead systems: Potential at a particular limb lead with other two limb leads augmented is known as Unipolar or augmented limb lead systems . This increases the amplitude of the ECG signal without changing its waveform.

48. ( i )Lead aVR : Potential at RA with LA & LL augmented & RL grounded

49. (ii)Lead aVL : Potential at LA with RA & LL augmented & RL grounded..

50. (iii)Lead aVF : Potential at LL with RA & LA augmented & RL grounded

51. Chest leads systems:

52. EINTHOVAN TRIANGLE

53. EINTHOVAN TRIANGLE An imaginary equilateral triangle having the heart at its center and formed by lines that represent the three standard limb leads of the electrocardiogram.

54. ECG WAVEFORM

55. ECG RECORDING METHOD

56. ECG RECORDING METHOD( cotd ,.) Electrode system: Metal plate electrodes made of Ag/ AgCl are placed atthe desiredlimb posi-tions . Good contact between electrodes & skin is ensured with the helpof gel and belts.   Lead fault detect: The function of this block is to detect the improper connection ofthe elec-trodes on to the skin by continually measuring the contact resistance andto warn the operator of this via either an audible tone or a visual indi-cation .   Amplifier protection circuitry: The function of this block is to protect the remainingpart of the circuit from large electrical discharges result- ing from defibrillationprocess .   Lead selector: The function of this block is to select a desired lead system from 12possible lead systems. This can be carried out either man- ually by an operator orautomatically by micro-processor or microcontroller or microcomputer   Preamplifier: The function of this block is to eliminate noise such as otherbiopotentials and various electromagnetic interferences resulting from nearbycommunication links etc. Gener -ally a differential amplifier with high inputimpedance and CMRR is used for this pur -pose.   Calibration signal: The function of this block is to calibrate the display or therecorder for prede-termined amplitude. A sine wave of 1 mV is gen- erally used forthis purpose.

57. ECG RECORDING METHOD( cotd ,.) Baseline restoration: The function of this block is to restore any baseline shift resulting from the low operating frequency of the amplifier.   Right leg driven system: The function of this block is to provide a reference point on the patient generally at ground potential.   Isolation circuitry: The function of this block is to provide electrical isolation between the high power section that is generally driven by 230 V 50 Hz ac mains and the low power patient section that is generally driven by a low power battery. This is required to protect the patient from any electrical hazards resulting from leakage currents.   Driver amplifier: The function of this block is to amplify the ECG signal sufficiently to   level required for the display or the recorder.   ADC & memory: The ECG signal can be digitized and stored for future analysis.  

58. ECG RECORDING METHOD( cotd ,.) Microcomputer: A microcomputer along with a user-friendly software package developed on a high-level language such as VC++ can be used (I) to control the entire process of acquiring the ECG and (ii) to analyze it automatically for various parameters such as heart rate, PR interval, QRS interval etc using sophisticated digital signal processing techniques. Recorder-printer/display: A heat sensitive paper can be used to get a hard copy of the ECG signal obtained or a CRO can be used to display the ECG signal obtained for visual analysis.

59.   ELECTROENCEPHALOGRAM [EEG] Electroencephalography is the study of electrical activity of the brain. Typical bandwidth: 0.1 – 100 Hz Typical amplitude: 10 – 100 mV Typical waveform: Highly random  

60.   Delta : 01 – 4 Hz; found in children; if found in alert adult it is abnormal Theta : 4 – 8 Hz; found in children of 2-5 year old; if found in alert adult it is abnormal   Alpha : 8 – 13 Hz; found in alert adult with eyes closed (under relaxed conditions) Beta : 13 – 22 Hz; found in alert adult with eyes open (under active conditions)

61. ACTION POTENTIAL OF THE BRAIN Inhibitory Post Synaptic Potential If the transmitter substance is inhibitory, then the membrane potential of the receptor neuron increases in a negative direction. So that it is less likely to discharge. Excitatory Post Synaptic Potential   If the transmitter substance is excitatory, then the receptor membrane potential will increase in a positive direction. So that,it is more likely to discharge and produces a spike potential.

62. EVOKED POTENTIAL These are the potentials developed in the brain as the responses to external stimuli like sound, light etc.

63. PLACEMENT OF ELECTRODES IN   EEG MEASUREMENT Frontal Pole (FP): 10% of Nasion & Inion dis-tance above Nasion Frontal (F): 20% of Nasion & Inion distance from FP. Central (C): 20% of Nasion & Inion distance from F. Parietal (P): 20% of Nasion & Inion distance from C (Central Point) Occipital (O): 10% of Nasion & Inion distance from Inion

64. Anterior-Posterior Measurement

65. Lateral Measurement

66. EEG RECORDING SETUP

67. Electrode system: Metal disc electrodes made of Ag/ AgCl are placed at scalp positions. Good contact between electrodes & skin is ensured with the help of gel and adhesive tapes.   Channel selector:   The function of this block is to select a desired combination of 19 possible electrodes. This can be carried out either manually by an opera-tor or automatically by microprocessor or microcontroller or microcomputer.   Preamplifier:   The function of this block is to eliminate noise such as other biopotentials and various electro-magnetic interferences resulting from nearby communication links etc. Generally a differential amplifier with high input impedance and CMRR is used for this purpose. A minimum gain of 1000 is required as typical amplitude range of EEG is from 1 to few micro volts.

68. Calibration signal: The function of this block is to calibrate the display or the recorder for predetermined amplitude. A sine wave of 1 mV is generally used for this purpose.

69. Isolation circuitry   The function of this block is to provide electrical isolation between the high power section that is generally driven by 230 V, 50 Hz ac mains and the low power patient section that is   generally driven by a low power battery This is required to protect the patient from any electrical hazards resulting from leakage currents.   Driver amplifier   The function of this block is to amplify the EEG signal sufficiently to level required for the display or the recorder.   ADC & memory   The EEG signal can be digitized and stored for future analysis.  

70. Microcomputer A microcomputer along with a user-friendly software package developed on a high-level language such as VC++ can be used to control the entire process of acquiring the EEG and to analyze it automatically for various parameters using sophisticated digital signal processing techniques. Recorder-printer/display A heat sensitive paper can be used to get a hard copy of the EEG signal obtained or a CRO can be used to display the EEG signal obtained for visual analysis.

71. ELECTROMYOGRAPH

72. APPLICATIONS It is used in Electrophysiology testing. It is used in Clinical neurophysiology. It is used in Neurology. It is used in Psychiatry.

73. PHONO CARDIOGRAM (PCG) The device which is used to measure heart sound is known as Phonocardiogram. These heart sounds are due to the vibrations set up in the blood inside the heart by the sudden closure of valves.   Record of heart sounds – 1st and 2nd heart

74. sounds are heard well but 3rd and 4th are not. Heart sounds are generally used for diagnosis of valve related diseases. Suchabnormal heart sounds are called murmurs   1st heart sound: due to closure of AV valves – long, soft & low-pitched sound – sounds like ' lubb ' – 0.14-0.2 sec – 30-40 Hz.   2nd heart sound: due to closure of semilunar valves – short, sharp & high-pitched sound – sounds like 'dub' – 0.08-0.1 sec – 50-70 Hz.   3rd heart sound: due to ventricular vibrations resulting from on-rush of blood immediately after the opening of AV valves – very short – 0.04 sec.   4th heart sound: due to atrial contraction

75. AUSCULTATION The technique of listening sound produced by organs and vessels of the body is known as Auscultation. CLASSIFICATION OF HEART SOUND Valve closure sound Ventricular filling sound Valve opening sound Extra cardiac sound

76. PCG RECORDING SYSTEM:

77. Types Of Microphones Used in PCG are as fol -lows: Air-Coupled Microphone Contact Microphone

78. PCG WAVEFORM

79. Beyond the syllabus

80. ELECTROOCULOGRAM [EOG] EOG is the recording of the biopotentials generated by the movement of eyes. Surface electrodes are used to measure EOG.

81. EOG ELECTRODES

82. EOG Recording System

83. APPLICATIONS It is used to analyze the state of semicircular canals Diagnoses of the neurologic disorders are possible. The level of anesthesia can be indicated by the characteristics of eye movement