Electrotherapy Flashcards
What is the fundamental underlying property of electromagnetic force?
Charge
What is the mechanism by which living cells communicate with one another?
Charge
What is the unit of measurement for charge?
Coulombs or microcoulombs
How is charge obtained?
By the addition or removal of electrons when atoms of elements are acted upon by external forces like friction, chemicals, heat,, and electricity
The net gain of electrons leads a _____ charge
Negative
The met loss of electrons leads to a _____ charge
Positive
What is an ion?
An ion or molecule that adds or looses an electron
What is ionization?
Process of addition or removal of electrons
What are the 4 fundamental properties of electrical charge?
1) 2 types of charge, positive and negative
2) like charges repel, opposites attract
3) charge is neither created nor destroyed
4) charge can be transferred from one object to another
What is electrical current?
The flow of electrons
What is the source of electrons?
Electrical current
What is a conductor?
A material that allows the passage of electrons
What is the driving force of electrons?
Voltage
What is polarity?
The net charge of an object (positive or negative)
What is a cathode?
An electrode with a net negativity
What is an anode?
An electrode with a net positivity
What kind of ions does a cathode attract?
It attract positive ions (cations)
What kind of ions does an anode attract?
Negative ions (anions)
What is the equation for charge?
Current x time
What electrolyte goes to the cathode to form NaOH?
Sodium
What electrolyte goes to the anode to form HCl?
Chloride
What is the electrothermal effect of ES?
Heat is created as a product of kinetic energy of molecules secondary to friction and vibration as charged particles move through a conductor
What are the electrochemical effects of ES?
Creation of sodium hydroxide from Na to a cathode
Creation of hydrochloric acid from Cl to an anode
Do we generally want energy to flow from the cathode to the anode or the anode to the cathode?
From the cathode to the anode
What is the electrical field?
The force created by the separation of charge (attraction or repulsion)
What is voltage?
The measure of force of attraction or repulsion created by an electric field
What is voltage sometimes referred to as?
The electrical potential difference
For electrons to flow, there must be a difference in the quantity of what bw two points?
Electrons
What is a volt?
The unit of electrical force (V or mV)
When is voltage created?
Whenever oppositely charged particles are separated or brought together
Electron/ion movt requires what?
Material that permits that movt
What are conductors?
Materials in which electrons and ions move freely
What are conductors in the real world? What are conductors in the body?
Metals and water in the real world
Muscles, nerves, and bodily fluids in the body
What are insulators?
Materials in which electrons and ions aren’t free to move
What are insulators in the real world? In the human body?
Plastics and rubbers in the real world
Fat and bone in the human body
T/f: adipose tissue holds heat
True
What is the current?
The movt of ions/electrons in response to a voltage force
Designated by the symbol I
What is the quantity/amount of ions/electrons flowing at a given time?
Current
Electrons flow from ____ to ____
Negative to positive
T/f: the flow of current (I) is directly proportional to the magnitude of the driving force (voltage)
True
What is amperage?
The measure of current
Rate of electron flow past a given point
Current measured in amps (A), milliamps (mA), or microamps
What things on the body can cause resistance to flow?
Skin, hair, fascia, ligaments, calluses, fat, bone, tendons, scars
What is resistance?
Measure of difficulty or opposition to current flow by the material through which the current travels
When there is an increase in resistance there is a _____ in voltage
Increase
With increased resistance there is _____ ability to generate heat
Increased
What is the measure of resistance?
Ohm
Why is there an increased burn risk when laying on a heating pad?
Bc there is increased resistance which creates greater potential for heating
T/f: when the voltage is present, the amount of resistance determines the amount of current flow
True
Why is icy hot a burn risk with ESTIM?
Bc it creates a numbing effect
What is Ohm’s law?
The current (I) in amperes is directly proportional to the voltage force (V) pushing the current and inversely proportional to the resistance (R) to the voltage force (V)
What is the equation of Ohms law?
I=V/R
T/f: the more resistance there is to the current flow, the less current there will be
True
T/f: when there is less current, there is less physiologic or therapeutic effect
True
As resistance increases, ____ voltage is required to pass the same current through
Greater
T/f: if resistance is held constant, a greater voltage will result in a greater current
True
What is capacitance?
The degree to which electrical charge is stored in a system of conductors and insulators
What arises from the storage of charge in an insulator within a field of current?
Capacitance
T/f: when flow of current ceases, energy stored in the insulator flows back through the conductor
True
What is impedance?
A form of resistance to the flow of current that is frequency dependent
What is the resistance to flow of AC?
Impedance
T/f: resistance is specific to DC
True
T/f: current passes through the body along the path of least resistance
True
Do gels, adhesive conductive agents on electrodes serve to increase or decrease impedance?
Decrease
Do gels, adhesive agents on electrodes serve to increase or decrease conductivity bw electrodes and skin?
Increase
What are the three fundamental electrical currents?
Direct current
Alternating current
Pulsed current
What is the most common current used in electrotherapy?
Pulsed current
What is a waveform?
Graphic representation of current used to describe shape, magnitude, and duration of the current
What characteristic is represented by the horizontal X axis?
Time or duration
What characteristic is represented by the vertical y axis?
Magnitude of intensity
What is direct current?
Continuous unidirectional flow of electrons or ions for at least one second
T/f: direction implies the current flowing from positive to negative or negative to positive
True
Is positive or negative direction deviation from the isoelectric baseline in the upwards direction?
Positive direction
Is positive or negative direction deviation from the isoelectric baseline in the downward direction?
Negative direction
What is interrupted DC?
Current flow that ceases after one or more seconds b4 resuming in the same direction for one or more seconds
What is reversed DC?
Flow that ceases after one or more seconds b4 resuming in the opposite direction from one or more seconds
What is interrupted reversed DC?
A combo of interrupted and reversed DC
What is alternating current (AC)?
Uninterrupted bidirectional flow of ions or electrons that must change direction at least once per second
T/f: the clinical use of pure sinusoidal AC is common
False
What is burst modulated AC?
Russian current
What is amplitude modulated AC?
Interferrential current
What is pulsed current (PC)?
Uni or bidirectional flow of ions or electrons that periodically cease for a period of time b4 the next electrical event
What kind of currents can be hazardous for clinical uses?
AC/DC
How can we use AC/DC currents?
Currents are modulated within the electrical stimulator to produce safe, comfortable stimulation (pulsatile current)
What are the two major classifications of waveforms?
Monophonic and biphasic currents
What are monophonic currents?
Pulse that deviates from the isoelectric line in one direction before ceasing and returning to the isoelectric line
What type of currents have uniquely positive and negative electrodes?
Monophasic currents
What is monophasic pulsed current?
Delivery of repeated monophasic pulses separated from each other by an interpulse interval
What are biphasic currents?
Pulse that deviates from the isoelectric line first in one direction then in the other direction
What type of current shifts continually, with each electrode having identical effects?
Biphasic currents
What type of current results in polarity effects to the tissues that are minimized/eliminiated?
Biphasic currents
What is a symmetrical biphasic waveform?
When the sum of current amplitude and duration of the first phase are identical to the second phase
What is an asymmetrical biphasic waveform?
When the amplitude and duration characteristics bw the 2 phases differ
What is a balanced biphasic waveform?
When the area under the curve of the first and second phases are equal and the average charge is zero
What is an unbalanced biphasic waveform?
When the phases aren’t equal and the average charge isn’t zero
What is a burst?
The generation of two or more consecutive pulses separated from the next series of consecutive pulses
What is the burst frequency?
The frequency at which bursts are generated
What is the carrier frequency?
The frequency of the underlying waveform
What is the interburst interval?
The time bw bursts
If there are 25 cycles of bursts in 10 msec, what is the carrier frequency?
2500 Hz
If there are two bursts in 40 msec, what is the bursts per sec?
50 bursts per sec
What is the amplitude?
The magnitude of the current
What is the peak current?
The max amplitude reached during the pulse
What is the average current?
The amount of current supplied over time
What is the phase/pulse charge?
The total amount of current or electrical energy delivered to the pt
What is the integrated sum of current amplitude and duration?
Phase/pulse charge
What is the measure of the waveform “area under the curve”
Phase/pulse charge
What is a ramp?
Progressive increase/decrease in amplitude
What is a ramp up?
A progressive increase in amplitude
What is a ramp down?
A progressive decrease in amplitude
Why is a ramp up/down in ES important in stroke populations.
Bc sudden on/off will induce an increase in tone
What is the rise time?
The time for the leading edge of a single phase to reach the peak amplitude
What is the fall time?
The time for the trailing edge of a single phase to reach the isoelectric line
T/f: long ramp times can reduce the total amount of current delivered
True
What is the phase duration?
The time is takes the current to leave the isoelectric line and return to the isoelectric line
Which type of phase duration has 2 phase durations for each pulse?
Biphasic
Which type of phase duration has a phase duration that is the same as the pulse duration?
Monophasic
Do tissues only respond to the phase duration or the pulse duration.
The phase duration
T/f: the phase duration must be long enough to overcome the capacitance of the nerve to cause an action potential
True
What is capacitance?
The ability of the nerve to store electrical charge
Large diameter nerve fibers have ____ capacitance
Low
Small nerve fibers have ____ capacitance
Higher
Do large diameter fibers result in fast or slow action potentials?
Fast
Do smaller nerve fibers require longer or shorter duration to elicit an action potential?
Longer
What is the strength duration curve?
The curve that describes the relationship of the amplitude of the electrical current to the duration
What are the two parameters linked to phase charge?
Amplitude and duration
The phase charge must exceed the _____ to depolarize the nerve
Capacitance
Does increased amplitude and phase duration increase or decrease the phase charge?
Increase
Does increased amplitude and phase duration make depolarization more or less likely?
More likely
What is the reobase?
The minimum amplitude needed to depolarize a nerve fiber when the phase duration is infinite
What is the current needed to elicit a minimally detectable motor response?
Reobase
What is the chronaxie?
The time or phase duration required to depolarize a nerve fiber when the peak current is 2x reobase
When is chronaxie thought to occur?
During the break in the capacitance curve
T/f: the chonaxie can be used to assess tissue quality
True
What is the physiologic response to electrical current?
Depolarization of cells interrupting the resting concentration gradients
What depolarizes first, the muscle or the nerve?
The nerve, which is why we feel the current before we see muscle contractions
What are the levels of stimulation with ES?
Sensory, motor, and noxious stimulation
What fibers are elicited first, large or small fibers?
Large
What spot can we put electrodes over to get a quicker response?
Directly over the motor unit
Do fibers closer or farther from the electrode get excited first?
Closer
What fibers elicit tingling without muscle twitch?
A beta fibers
What fibers elicit tingling and muscle contraction?
A alpha fibers
What fibers elicit burning and needling sensation?
A delta fibers
What info do A alpha fibers carry?
Proprioception and motor info
What info do the A beta fibers carry?
Touch
What info do the A delta fibers carry?
Pain and temp
How can fibers deeper and farther away from the electrode be stimulated?
By increasing the amplitude of the stimulus
What is frequency?
The number of pulses generated per second (PPS or Hz)
What parameter of ES affects the number of APs elicited during the stimulation?
Frequency
What does higher frequency do?
Causes the nerve fibers to fire at a more rapid pace, increasing the tension generated in the muscle
What is the rate-limiting factor in the number of impulses that can be generated by a nerve?
The absolute refractory period
Why can’t we keep the stimulation at a muscle the same frequency?
Bc it will tire out the muscle
How do we classify current frequency?
Low, medium, and high frequency
What kind of frequency is 1000Hz
Low frequency
What kind of frequency is 1000-10,000 Hz?
Medium frequency
What kind of frequency is >10,000 Hz?
High frequency
What kind of current has an inverse relationship bw frequency and wave length?
AC current
What kind of current can control phase duration and pulse rate?
Pulsed current
T/f: with TENS, higher frequencies cause nerve fibers recruited to fire more rapidly, allowing summation of stimulation
True
If the frequency on ES is higher than 20 pps, what will it feel like?
Continuous sensory effect, the body can’t detected the pulses
What is felt on ES with frequencies bw 35-50 pps?
Tetonic muscle contractions
What is an intrinsic duty cycle?
Used to modulate the current waveform where pulses are packed into small clusters and the current is interrupted at specific intervals (burst mode)
What duty cycle reduces the high total current of medium frequency generators by introducing an off time in the current making the mode safer?
Intrinsic duty cycle
What duty cycle creates on-off timing to create rest time?
Extrinsic duty cycle
T/f: extrinsic duty cycle is often used when stimulating the alpha motor neuron for muscle contraction (NMES/FES)
True
What is the recommendation for max contractions with ES to prevent muscle fatigue?
Duty cycle of 1:5
What is duty cycle?
No genuinely I would love to know, I have to relook in the textbook
Google says “the percent of time a device or circuit is actively operating within a specific period”
The textbook equation: on time/total time x 100%
What is the Law of Dubois Reymond?
The effectiveness of a currrent to target specific excitable tissues is dependent on 3 major factors
1) adequate intensity to reach threshold
2) current onset fast enough
3) duration long enough to exceed the capacitance of the tissue
Fast enough, long enough, strong enough
What is the proper way to store the leads?
By hanging them
Is there more or less current with a bigger phase duration?
More current
What ES settings can be used for pain control?
Strong but tolerable
Or
Noxious where you want the pt to feel pain with the ES
What ES settings would be used for muscle strengthening?
Get the strongest contraction, then bump it up one
How long should ES ideally be applied?
15 minutes is ideal, but no more than 60 minutes
T/f: redness is normal with use of ES
True and false, for a few minutes it is normal but if it lasts any longer it can be a burn
If the ES pads are placed further apart, will the current go deeper or more shallow?
Deeper
If the ES pads are placed closer together, will the current go deeper or more shallow?
More shallow
What are some body composition factors to be aware of during ES?
Adipose tissue
Muscle
Bones
Skin fragility
Muscle size
Depth of the tissue we are targeting
What are some contraindications for ES?
Pregnancy
DVT
cancer
Pacemaker or electrical implants
Does increased width/duration increase or decrease the intensity?
Decrease
