Download - Electrotherapy- Dr. Rashi Goel
Dr. Rashi Goel (PT)
Assistant Professor
DY Patil College of Physiotherapy
Pimpri, Pune
Definition
Use of electrical energy as a medical treatment
Electricity is an element of PT modalities most frightening and least understood
12/19/14 Dr. Rashi Goel 2
12/19/14 3Dr. Rashi Goel
Matter
Mass + occupies space Basic unit of matter- atom
12/19/14 Dr. Rashi Goel 4
12/19/14 Dr. Rashi Goel 5
States of matter
Solid- lattice formation Liquid Gas
12/19/14 6Dr. Rashi Goel
Cohesive force- attracts molecules of the substance to one another
Kinetic force- force of movement of the molecules
12/19/14 7Dr. Rashi Goel
Properties of matter
Adhesion Surface tension Viscosity Density Elasticity
12/19/14 8Dr. Rashi Goel
Adhesion
Attachment of a substance to the surface of another substance
12/19/14 Dr. Rashi Goel 9
Surface Tension
The cohesive forces between liquid molecules
12/19/14 Dr. Rashi Goel 10
Viscosity
Quantity that describes a fluid's resistance to flow
12/19/14 Dr. Rashi Goel 11
Density
Mass per unit volume
12/19/14 Dr. Rashi Goel 12
Elasticity
Tendency of solid materials to return to their original shape after being deformed
12/19/14 Dr. Rashi Goel 13
ATOM
A central nucleus surrounded by a cloud of electrons revolving in definite orbits
12/19/14 14Dr. Rashi Goel
Structure of atom
12/19/14 15Dr. Rashi Goel
Nucleus
Proton Neutron
Electron
12/19/14 16Dr. Rashi Goel
12/19/14 Dr. Rashi Goel 17
12/19/14 18Dr. Rashi Goel
Molecule
Electrically neutral group of two or more atoms held together by chemical bonds
A substance that is the smallest particle of a compound and still contains all the characteristics of that compound
12/19/14 19Dr. Rashi Goel
Elements
a substance that is made entirely from one type of atom
12/19/14 20Dr. Rashi Goel
12/19/14 Dr. Rashi Goel 21
Compounds
Substance formed by the union of two or more elements, the union taking place via the electrons of the atoms involved to form a molecule of the compound
12/19/14 Dr. Rashi Goel 22
Compounds
Covalent Electrovalent
12/19/14 23Dr. Rashi Goel
12/19/14 Dr. Rashi Goel 24
Molecule/Compound
A molecule is formed when two or more atoms join together chemically
A compound is a molecule that contains at least two different elements
All compounds are molecules but not all molecules are compounds
12/19/14 Dr. Rashi Goel 25
Electron theory
Electric Charges:
Electrons have a –ve charge Protons- =+ve Neutrons- no charge
12/19/14 26Dr. Rashi Goel
An electrically neutral atom has the same number of protons and electrons
12/19/14 Dr. Rashi Goel 27
Atomic no.= no. of protons in the nucleus
Atomic mass= no. of protons + no. of neutrons
Isotopes eg. Carbon
12/19/14 28Dr. Rashi Goel
12/19/14 29Dr. Rashi Goel
Electricity
Electricity is the force created by an imbalance in the number of electrons at two points
12/19/14 Dr. Rashi Goel 30
Static electricity
Simplest form of electricity
12/19/14 Dr. Rashi Goel 31
Causes of static electricity
Static electricity is usually caused when certain materials are rubbed against each other, like wool on plastic or the soles of your shoes on the carpet
This causes electrons to be pulled from the surface of one material and relocated on the surface of the other material
12/19/14 Dr. Rashi Goel 32
Try-
run a comb through your hair to charge the comb with static electricity
The comb can then be used to attract neutral pieces of tissue
12/19/14 Dr. Rashi Goel 33
The material that loses electrons ends up with an excess of positive (+) charges
The material that gains electrons ends up an excess of negative (-) charges on its surface
12/19/14 Dr. Rashi Goel 34
Electric field of a charged body
A zone of influence
Lines of force
12/19/14 Dr. Rashi Goel 35
Properties of lines of force
I. Straight lines
II. Repel one another
III. Pass more easily through conductors than insulators
IV. Concentrate over that part of the surface over which they can exert an influence
12/19/14 Dr. Rashi Goel 36
Electrical Potential
When compared to neutral potential of the earth
Unit- Volt High potential= strong repelling power
12/19/14 Dr. Rashi Goel 37
Capacitance
The ability of tissue (or other material) to store electricity
Unit is Farad, microfarad
12/19/14 38Dr. Rashi Goel
Potential Difference
Difference in concentration of electrons between two points
Electrons will not move unless a potential difference exists
12/19/14 39Dr. Rashi Goel
EMF
Force producing the force
Electrons flow from more negative to less negative body until both are at same potential
Unit is Volts
12/19/14 Dr. Rashi Goel 40
Current electricity
An electric current occurs when there is a flow of charged particles in a conductor
12/19/14 41Dr. Rashi Goel
Conductors
Materials that permit free movement of electrons
Composed of large numbers of free electrons
Offer little resistance to current flow Good conductors
Metals (copper, gold, silver, aluminum)Electrolyte Solutions
12/19/14 42Dr. Rashi Goel
Insulators
Materials that resist the flow of electrons Contain few free electrons Insulator materials
Air, Wood, Glass
12/19/14 43Dr. Rashi Goel
Electromagnetic Radiation
Produced by movement of electrons within the atom
Excited state
12/19/14 Dr. Rashi Goel 44
Resistance
The opposition to flow of current
Measured in Ohms
12/19/14 45Dr. Rashi Goel
Intensity
Magnitude of current- rate of flow of electrons through the conductor per second
Measured in Amperes
12/19/14 46Dr. Rashi Goel
Ohm’s law
V = IR (V is voltage, a measure of the driving
force which is equal to the I x R where I is the Ampere (the amount of current flow) and R is the resistance
The Ampere is equal to the Voltage divided by the Resistance.
12/19/14 47Dr. Rashi Goel
Application of Ohm’s law to AC and DC currents Thermal effects of an electrical current
Joule’s law: Q= I2RT
I= current in amperes R= Resistance in ohms T= time in seconds
12/19/14 48Dr. Rashi Goel
Main supply
Produced by Dynamo Principal of Dynamo
Live wire- at high potential Neutral wire- at zero potential connected
to earth
12/19/14 Dr. Rashi Goel 49
12/19/14 Dr. Rashi Goel 50
Electrical supply
Alternating sinusoidal current of 50 Hz at 220- 240 voltage
GRID SYSTEM
12/19/14 Dr. Rashi Goel 51
12/19/14 Dr. Rashi Goel 52
Wiring in houses
Light and power circuits In parallel or in ring main Sub-circuits
12/19/14 Dr. Rashi Goel 53
12/19/14 Dr. Rashi Goel 54
12/19/14 Dr. Rashi Goel 55
Numericals
2 formulae
EMF= VI V= IR
12/19/14 Dr. Rashi Goel 56
Watt= 100W V= 240V R=?
Watt= 2000W V=240V R=?
12/19/14 Dr. Rashi Goel 57
Results
1. I= 0.417A R= 576 ohm
2. I= 8.333A R=28.9ohm
12/19/14 Dr. Rashi Goel 58
Over current/Excess current
A situation where a larger than intended electric current exists through a conductor, leading to excessive generation of heat, and the risk of fire or damage to equipment
12/19/14 Dr. Rashi Goel 59
Causes for over current
Short circuits Excessive load Incorrect design
12/19/14 Dr. Rashi Goel 60
Short Circuit
Resistance of circuit reduces- due to:
If insulation becomes worn out 2 supply wires come in contact Connection between live wire and earth
12/19/14 Dr. Rashi Goel 61
Fuse
Weak point in the circuit which blows if a very high intensity of current is passed
Low melting point
Safety device
Live wire
12/19/14 Dr. Rashi Goel 62
Fuse
Silver wire- fusible material Metal caps Glass tube Metal clips
12/19/14 Dr. Rashi Goel 63
Cartridge fuse
12/19/14 Dr. Rashi Goel 64
Why a fuse blows off?
1. Resistance too low
2. Wattage too high
3. Several parallel circuits from one supply point eg. Adaptors
To prevent overheating and fire
12/19/14 Dr. Rashi Goel 65
When a fuse blows what to do?
1. Disconnect the apparatus
2. Switch off the main supply
12/19/14 Dr. Rashi Goel 66
Dangers
Short circuits Electric shocks
12/19/14 Dr. Rashi Goel 67
3 Pin Plug & Socket
Earth pin- longest
Live- brown Neutral- blue Earth- yellow and green
Easily distinguished
12/19/14 Dr. Rashi Goel 68
One way to enter One way to exit
12/19/14 Dr. Rashi Goel 69
Earthing
Precaution against earth shock
12/19/14 Dr. Rashi Goel 70
Earth shock
Connection between live wire of the mains and earth
Earth circuit Eg.
12/19/14 Dr. Rashi Goel 71
Precautions for earth shock
Water and gas pipes- out of reach of apparatus & patients getting treatment
Floor should be dry Floor of insulating material/mat placed Fuses on live wire
12/19/14 Dr. Rashi Goel 72
Electric shock
Physiological reaction or injury caused by electric current passing through the human body
Painful stimulation of sensory nerves caused by a sudden flow, cessation or variation in the current passing through the body
12/19/14 Dr. Rashi Goel 73
Causes of electric shock
Sudden increase in the current
12/19/14 Dr. Rashi Goel 74
Effects of electric shock
Minor- frightened and distressed Major- Fall in BP, Loss of consciousness,
stoppage of respiration, cardiac arrest, ventricular fibrillation due to electrical stimulation of the heart
Death caused by an electric shock is called electrocution/ electrical execution
12/19/14 Dr. Rashi Goel 75
Electrical currents flowing at <1mA will not be felt and is referred to as microshock
Shock from a current flow >1 mA is called macroshock
Currents b/w 1 - 15 mA: a tingling sensation or perhaps some muscle contraction
Currents b/w 15-100 mA: a painful electrical shock
Currents b/w 100 and 200 mA may result in fibrillation of cardiac muscle or respiratory arrest
Current flow > 200 mA: rapid burning and destruction of tissue12/19/14 Dr. Rashi Goel 76
Severity of shock-
1. High voltage/ High current
2. Duration
3. Resistance of the body
4. Path taken by current- lethal if current flows through the heart muscle
5. Type of current
12/19/14 Dr. Rashi Goel 77
Under dry conditions, resistance offered by the human body is- 100,000 Ohms
Wet or broken skin- body's resistance is 1,000 Ohms
high-voltage electrical energy quickly breaks down human skin, reducing the human body's resistance to 500 Ohms
12/19/14 Dr. Rashi Goel 78
Treatment of electric shock
Disconnect the person from the source of supply
Switch off the current at once
12/19/14 Dr. Rashi Goel 79
Precautions to be taken
Self test all equipments before using on patients
Check all connections Check all control knobs Intensity to be increased slowly Regular servicing of the equipments Patient should not touch electrical
equipments
12/19/14 Dr. Rashi Goel 80
Electric shock as a medical therapy
Electroconvulsive therapy/ ECT- psychiatric illness
Defibrillation– for fibrillation/ irregular heart rhythms
For pain relief- TENS For hyperhidrosis- Iontophoresis
12/19/14 Dr. Rashi Goel 81
12/19/14 Dr. Rashi Goel 82