Electrotherapy Flashcards
What is charge?
The mechanism through which a living cell communicates with another cell.
There are four properties of electric charge. Name them.
- There is + and - charge
- Like charges repel while opposites attract
- Charge is neither created or destroyed
- Charge can be transferred from one object to another
Explain polarity.
Electrons flow from negative to positive poles.
What surrounds charged particles?
An electric force field.
Define voltage.
An electromotive force or potential difference expressed in volts.
True or False
Conductors store electricity.
False.
Conductors allow for the free movement of the electrons and transfer of charge.
What is an insulator?
Insulators impede the movement of electrons and the transfer of charge.
What does resistance denote about a charge?
Normally, it denotes the direction. Resistance is whether something will slow down the current or not.
True or False
Capacitance is the storage of particles.
True
What is impedence?
How much resistance it takes to get through the material. Skin will have a certain amount of impedance, and muscle will have a different amount of impedence.
If the voltage stays the same but the impedance changes, what will happen to the current?
The current will become more or less intense.
Which is safer, constant current or constant voltage?
Constant current is safer than constant voltage.
What are the three types of current and waveforms?
- AC
- DC
- Pulsed
What defines direct current?
Continuous stream of charged particles flowing in 1 direction for at least 1 second.
What is direct current used for?
Iontophoresis, wound care, and stimulating contractions in denervated muscle
Is direct current comfortable?
No
What charge does the anode hold?
Positive.
The cathode is negative.
Describe interrupted DC current.
On for one second. Off for a bit. Then on for another second.
Describe reversed DC current.
Flows negative to positive for a second. Then positive to negative for a second.
What kind of current flows from negative to positive for one second, stops for a bit, and then flows positive to negative for a second?
Interrupted reversed DC current
Continuous, sinusoidal, bidirectional flow of charged particles are characteristics of which type of current?
Alternating current (AC)
Clinically, what is AC used for?
Pain control and muscle contraction. It normally feels better than direct current.
True or False
Frequency = rate at which AC switches direction (Hz)
True!
What are two examples of AC?
Russian current and IFC.
What are the characteristics of pulsed current?
- Interrupted flow of charged particles
- Current flows in a series of pulses separated by periods where no current flows
What does the carrier frequency have to do with?
It has to do with the underlying wave form of the bursts in pulsed current.
The time in between the pulses in PC is…
The interburst interval
What is a burst?
A group of little pulses
Five little pulses together would make up what?
The burst frequency
In PC what would a square, rectangle, or triangle denote?
It would show how fast the burst goes up in amplitude.
True or False
In monophasic PC, a phase does not equal a pulse.
False
In monophasic, a phase equals a pulse.
What is the difference between monophasic PC and biphasic PC?
Monophasic flows in one direction. Biphasic flows in both directions and is the most common.
What makes up a pulse in biphasic PC?
There is a positive phase and a negative phase, and those added together make up the pulse.
Why does the phase duration in PC have to be under 1 second?
If it was one second or more, it would be DC.
What is the intra-pulse interval?
It is the time between the positive phase and negative phase of a biphasic pulse.
Which types of current can be modulated?
Any of them. AC, DC, or PC
What is modulation?
It is a process where one or more characteristics of a wave are changed.
What is the difference between regular and irregular modulation?
Regular modulation repeats the same pattern. Irregular modulation is harder for the patient to get used to and stop feeling it.
What are aspects you can modulate in a current?
- Amplitude
- Frequency
- Pulse/phase duration
If you have the amplitude varying, you don’t want to turn the machine up when the amplitude is at its low point. Turn it up when it is at the high point, or it might be too high at the top.
True or False
Symmetrical currents are also balanced.
True!
Define symmetrical current.
The positive phase looks exactly like the negative phase.
What is more likely with an unbalanced wave?
Skin irritation is more likely.
Define asymmetrical current.
In asymmetrical current, the pulses do not look the same.
What is a balanced current?
The amount of positive phase charge = the amount of negative phase charge
Explain the electrochemical effects of electrotherapy.
Extracellular fluid is mostly salf water. Na is positive, and Cl is negative. Na will go toward the cathode which is negative. Cl will go toward the anode which is positive. Water tends to move towards the Na which reduces the protein density in that tissue. This softens the tissues at the cathode. The opposite happens at the anode, so the tissues harden at the anode because the water is being pulled towards the cathode.
The pH at the cathode increases, and the pH at the anode decreases.
Explain the electrothermal effects of electrotherapy.
Some energy will be lost in the form of heat, so you get some thermal effects. The amount depends on the voltage. If you are doing it with heat or over an area that is calloused, you can get a larger build up of heat because there is more resistance.
Explain the electrophysical effects of electrotherapy.
The electrophysical effects are due to changes in the permeability of the cell.
What needs to be high enough to depolarize the cell and elicit an action potential?
Must have sufficient strength (current amplitude) and duration (pulse duration).
What order are the nerves stimulated in?
- A beta sensory
- Motor
- A delta sharp pain
- C dull pain
- Denervated muscle
How many mA do you need to stimulate A beta sensory nerves?
It needs to be turned to at least 20 mA
How many mA do you need to stimulate motor neurons?
At least 30 mA
How many mA do you need to stimulate A delta sharp pain?
At least 40 mA