Principles of Electrotherapy Flashcards
1
Q
What is NMES used for?
A
- muscle re-education
- pain modulation
- used in place of prosthetic device
- tactile stimulation
- strengthening
- ROM
- improved function
- contraction of denervated tissue
- wound healing
- edema control
2
Q
What is charge measured in?
A
Coulombs (C) or micro coulombs
3
Q
Net gain of electrons =
A
negative charge
4
Q
Net loss of electrons =
A
postive charge
5
Q
do like charges repel or attract?
A
repel
6
Q
do opposite charges repel or attract?
A
attract
7
Q
can charges be created or destroyed?
A
nope - neither
8
Q
can charges be transferred from one object to another?
A
yep
9
Q
anode =
A
net positive pole
attracts (-) ions
10
Q
cathode =
A
net negative pole
attracts (+) ions
11
Q
what is voltage?
A
- potential difference in distribution of ions
- also referred to as electromotive force
- a force that PUSHES charge
12
Q
what is voltage measured as?
A
- volts or millivolts
13
Q
What is current flow?
A
the flow of charged particles (ions or electrons)
14
Q
what is current flow measured as?
A
- the number of electrons or ions that pass a certain point in a specified period of time
15
Q
what is current flow measured in?
A
amperes or microamperes or as a rate (coulombs per second)
16
Q
current flow moves from …
A
anode to cathode
17
Q
current flow and electron flow are …
A
opposite
18
Q
what is resistance/capacitance/impedance?
A
opposition to flow of charged particles
19
Q
Formula for intensity
A
I = V/R
- which means that there is an inverse relationship between resistance and intensity
20
Q
in an alternating current, what is the formula for intensity?
A
I = V/Z
- Z is the resistance stated above + any additional resistance found in the capacitance and inductance of an alternating current generator
21
Q
what does resistance/ capacitance/ impedance depend on?
A
- nature of the material
- length of the pathway
- cross-sectional area of the pathway
22
Q
what is skin impedance?
A
- a form of resistance
- resistance offered by the skin
- highly variable throughout the body
23
Q
Skin impedance - Variables
A
- water content
- blood flow
- patient activity or position
- conducting medium
- hair
24
Q
skin impedance - fixed factors
A
- distance between electrodes
- what is under the electrodes
25
Three types of currents
- Direct Current
- Alternating Current
- Pulsed Current
26
What is direct current?
- unidirectional current flow lasting for at least 1 second
- since current flow is only in one direction will lead to an accumulation of ions under the electrodes (OUCH!)
27
What is direct current used in?
- iontophoresis
- wound healing
- stimulation to denervated tissue
28
direct current - cathode
- depolarized membrane of excitable cells
- alkaline effect (hurts more)
- attracts hydrogen
- liquifies protein
- promotes fibroblastic migration (scarring)
29
direct current - anode
- hyper polarizes membrane of excitable cells
- acid effect
- attracts oxygen (bubbles)
- coagulates protein
- kills bacteria
30
What is alternating current
- continuous current flow alternating direction of at least once each second
- the number of electrons that pass in each direction is generally equal
31
what is alternating current used for?
- stimulation of nervous and muscular tissue
- may be used for denervated tissue (but nothing in US is strong enough)
32
how can alternating current be identified?
by waveform
33
what is pulsed current?
- unidirectional or bi-directional current flow with periodic interruptions
- current flow lasts for only a few milliseconds or less
34
what is the most common form of therapeutic e-stim used?
pulsed current
35
what **isnt** pulsed current used for?
iontophoresis
36
constant current
- current stays fixed even if resistance or impedance changes
- voltage varies
- how the generator is going to react to resistance
- typically dont want constant current in smaller area
37
Constant voltage
voltage will remain constant and current will change in proportion to resistance or impedance changes
38
Current parameters
- amplitude
- rise time and decay time
- pulse duration
- interphase and interpulse intervals
- total current and pulse charge
- frequency (rate)
39
What is amplitude?
- same as intensity
40
what is amplitude measured in?
Amperes
More often milliamperes
Sometimes expressed in voltage (# would be higher)
41
peak amplitude
highest intensity reached during one stimulus
42
rise time
elapsed time from onset of stimulus to peak amplitude of stimulus
43
decay time
elapsed time from peak amplitude to termination of stimulus
44
what is rise/decay time measured in?
- milliseconds or microseconds
- different from "ramp and fall" time which are modulations to an individual stimulus
45
Pulse duration
- length of time one pulse lasts
46
Phase duration
- in biphasic pulse
- length of time current flows in one phase of a pulse
47
interphase interval
- brief interruption between phases
48
interpulse interval
elapsed time between consecutive pushes in a pulsed current
49
what are interphase and interpulse intervals measured in?
microseconds
50
frequency (rate)
number of pulses or cycles per second
51
what is frequency measured as in pulsed current
pps
52
what is frequency measured as in alternating current?
Hz
53
low frequency
0-1,000 Hz
54
Medium frequency
1,000 - 10,000 Hz
55
High frequency
> 10,000 Hz
56
what does a change in frequency in alternating current lead to?
an automatic change in cycle duration
57
does a change in pulsed current frequency necessitate a change in pulse duration?
no
due to an interpulse interval
58
what decreases with decreasing pulse or cycle duration?
- skin impedance
- increasing frequency may increase current penetration
59
what is perceived as being more comfortable and why?
- higher frequency
- because skin impedance is reduced in AC current
60
When is more fatigue seen over time?
- with higher frequency
- varying the rate may reduce this fatigue
61
relationship between frequency and recruitment of fiber type
Type I: 10-20 Hz
Type II: 30-60 Hz
62
What is a modulation?
- any parameter that is altered or varied during a series of pulses or cycles
- usually seen in amplitude, frequency, phase duration, or waveform
63
Burst Modes
- multiple pulses or groups of cycles carried out in bursts
- modulation in AC
64
Carrier Frequency
- number of cycles/second before burst modulation in AC current
65
Burst Frequency
Burst occurring to deliver the carrier frequency
66
resting membrane potential
resting electrical potential difference across a membrane of nerve or muscle cells caused by the difference in distribution of charged particles on either side of the membrane
67
Where is there more Na? Where is there more K?
- There is more Na+ on the outside
- There is more K+ on the inside of the cell
68
Resting membrane potential
-70 mV
69
Action potential
an electrical event that occurs when the cell is excited by a stimulus adequate to cause a decrease in the electrical potential across the membrane
70
local excitatory response
allows cell membrane to increase its permeability to Na+
71
depolarization
- reduction in negative charge caused by Na+ entering the cell
72
what occurs when threshold is reached?
a rapid reversal of electrical potential (action potential)
73
what does the resting membrane potential change from during the action potential?
it changes from -70 mV to +30 mV
74
What causes the membrane to become hyper polarized?
As the permeability to Na+ begins to shut down, the slower movement of K+ is just reaching its equilibrium
75
Absolute refractory period
- depolarization phase
- another AP cannot occur under any circumstance
76
relative refractory period
during hyper polarization another AP could occur if a stimulus of a much greater magnitude occurs
77
voluntary contraction
small, slow deeper units are recruited first in all or non fashion
78
electrically stimulated contraction
larger, faster motor units fire first
79
what is the biggest factor of motor unit recruitment?
- electrode placement
- the closer the motor unit is to the electrode, the faster it will be recruited
80
cell type recruitment
sensory n > motor n > deep pain n > muscle fibers
81
What do you need in order to get a response?
- adequate total current
- either have to increase amplitude or pulse duration to get the desired response
- all or nothing
82
what does a strength duration curve show?
the relationship between the amplitude and pulse duration to produce a threshold stimulus for different nerve types and skeletal muscle
83
Rheobase
minimal amplitude needed to create an action potential given an infinite pulse duration
84
Chronaxie
Minimal pulse duration that will cause an action potential at two times rheobase
85
Contraindications
- Severe cardiac condition; use of demand type pacemaker
- active bleeding or risk of hemorrhage
- active osteomyelitis
- pregnancy (over lumbar region and uterus)
- carotid bodies/ anterior neck
- phrenic nerve, eyes, gonads
- when active motion is contraindicated
86
Precautions
- sensory loss
- Areas of scarring
- Thick adipose tissue
- Severe edema
- Over malignancy/neoplasm
- Open wounds
- Severe depression
- Disoriented patients
- Superficial metal
87
Verbal preparation
explain what, why, how it will feel, the patients responsibility, encourage open conversation
88
should you demonstrate e stimulation
yep
89
positioning
thing about patient comfort, goals for use, good visibility for patient and you
90
skin impedance
clean with alcohol, abrade, hydrate, heat, dont shave
91
canvas conductive medium
clean with water, cover with gauze, make conductive with water
92
carbon/silicon rubber
use of conductive gel or sponges, clean electrodes by washing
93
carbon/silicon self-adhesive
disposable, requires slight film of water to make tacky
94
probe
cover with gauze, soak button, check that switch is in good working order
95
size of electrode
- make as large as target area but not larger
- large electrodes decrease skin impedance
- can cut some electrodes to shape and size desired
96
location of electrodes
- have current run longitudinally
- not too close together
- not too far apart
- try to use motor points
- be sure adhesion is firm to keep in place, but does not construct if motion is desired
- use straps, body weight, tape, sand bags to help keep in place
97
Unipolar or Monopolar
- One electrode is considered active based on its function or differences in size
- use over motor point
- delivery of medication
- one small active electrode and one large dispersive electrode so current density is greater under the active one
98
what are unipolar/monopolar leads used for?
- usually for isolating single or small muscle groups whether innervated or denervated and for training functionally after transplant or repair
99
Bipolar
- both electrodes are of equal size with equal current density under both
- place one over the motor point and one distally over the nerve
100
what are bipolar leads used for?
primarily to stimulate larger muscles and muscle groups for functional activities
101
quadripolar
- specific to iaterfererntial stimulation
- circuits are crossed
