Diathermy Flashcards
Define electron.
-a small fundamental particle of matter that has a negative charge.
How do electrons work?
- they travel in orbit around the central nucleus (+) and are held in place by the attraction of the positive protons.
- can be dislodged and moved to an outer orbit of an adjacent atom
- when electrical force (voltage) applied to a circuit electrons become organized and directional from negative to positive
- when an electron leaves an atom that atom becomes more positively charged and the atom receiving the electron becomes more negative
What is static electricity?
- Two surfaces involved: An excessive amount of electrons on one surface and a deficit of electrons on the other surface after being rubbed together
- The electrical current is beacuse electrons are moving successively from one atom to another NOT moving along a conductor
What is true about two objects with the same polarity?
the objects will repel each other
What is true about two objects with the opposite polarity?
the objects attract each other
Define conductor.
Any material which permits the easy movement of electrons in a circuit.
Ex: metal, liquid, body tissue
-usually good conductors of electricity are good conductors of heat
Define ohm.
-the unit of measurement of resistance and defined as one (1) volt applied across a resistance that causes 1 ampre (amp) of current to flow
Why is resistance important?
-different electrical conductors have different amounts of resistance to the flow current
Define ampre.
the measurement of the intensity of the electrical current
Define volt.
the measurement of pressure or potential of electrical current
Define resistance.
impedence or opposition which is dependent upon the intensity and potential of the electrical current
How does resistance, ampre, conductors, and volt work together?
- Conductors have different amounts resistance to the flow current.
- Resistance to the flow of electrons dependent on the ampres, and volts (ohm’s law: Voltage= Current x Resistance)
- ampres and volts are used to measure output of many electrotherapy machines
- as electrical current flows through a conductor, part of the current is dissipated due to the resistance of the conductor to the flow of the current
What are the local effects of shortwave diathermy?
Local = at the site of healing tissue
- Marked hyperemia
- marked increase in lymph flow
- increase in the volume of the area treated due to increase in blood and lymph in the area
- increase in glandular secretion if a gland is treated
- increased extensibility of connective tissue structures
What are the general effects of shortwave diathermy?
General = remote to area treated
- rapid dilation of peripheral blood vessels
- rise in body temperature and in the operation of all mechanisms of heat loss
- marked sedative effect
- general perspiration
- consensual vasodialtion
What are the selective effects of heating tissues?
- depends upon the presence of charged particles called ions held in solution in the body fluids
- body tissues with high fluid content = blood vessels and muscles
- areas of fatty accumulation = danger for producing burns because low conductivity and high resistance
- lack of vascular network to dissipate heat in these areas
What are the indications for shortwave diathermy?
- subacute and chronic traumatic and inflammatory conditions such as sprains, strains, fibrositis, tendonitis, and bursitis
- Neuritis and neuralgia
- Muscle spasms or joint contractures
What are the contraindications for shortwave diathermy (SWD)?
- Epiphyseal areas of growing bone
- over dressings or adhesive tape
- metal implants or any metal in the treatment area
- Cardiac pacemakers
What are the precautions for shortwave diathermy (SWD)?
- Cardiac conditions (take pulse frequently)
- areas of diminished circulation
- over bony prominences
- elderly population and children
Body tissues from lowest conductivity to highest conductivity.
(list adapted from the internet)
- adipose tissue (low conductivity)
- bone
- skin
- muscle
- blood (high conductivity)
How does diathermy transfer heat?
conversion of electricity- causes DEEP heat
What is the frequency of SWD?
high frequency electrical current
What is an electromagnetic field?
- occurs as electric current flows through a wire conductor and electromagnetic field surrounds the wire.
- strength of the field depends on the intensity (amps) of the current flowing through the wire
- when magnetizable substance in the magnetic field becomes magnetized
- shape of electromagnetic field depends on the shape of the conductor
How does SWD and electromagnetic field relate?
- 1 of 2 types of electro fields involved in SWD
- SWD uses electromagnetic field to INDUCE electrical energy into the body
- electrical energy is CONVERTED to heat the body
What is it called when you use electromagnetic field to heat the body?
Inductive heating
What is an electrostatic field?
- electrical field that exists between two electrified plates
- When an electrical conductor placed withing an electrostatic field the conductor becomes electrified
How does SWD and electrostatic field relate?
- 2nd type of electro field involved in SWD
- electrical current applied to two plates causing an electrostatic field
- two electrified plates (air-spaced electrodes) placed around the body part
- body part becomes electrified, then electrical energy converted into heat, thus heating the tissues
- this type of heating is good for tendons, ligaments, and capsular tightness
What is it called when you use electrostatic field to heat the body?
- Condensive or capacitive heating.
- Capacitive (capacitance) refers to the ability to store an electrical charge.
Define capacitance.
The ability to store an electrical charge
What is inductance?
property of an electric circuit in which a varying current induces an electromotive (motion producing) force in either that circuit or a neighboring one
What are the three methods of heating using radio waves?
- Long wave diathermy- outlawed by FCC because interferes with commercial communication systems
- short wave diathermy
- microwave diathermy- rarely seen in PT clinics today
What is the wavelength and frequency of long wave diathermy?
wavelength: 300 meters
frequency: 1,000,000 cycles/sec (1 megacycle)
What is the wavelength and frequency of short wave diathermy?
wavelength: 3 to 30 meters
frequency: 10-100 megacycles; 27.12 MHz most common
What is the wavelength and frequency of microwave diathermy?
wavelength: 10cm to 1 meter
Frequency: 300-3,000; 2450 Mhz most common
