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Physical Agents II > Principles of Electrotherapy > Flashcards

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
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2
Q

What is charge measured in?

A

Coulombs (C) or micro coulombs

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3
Q

Net gain of electrons =

A

negative charge

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4
Q

Net loss of electrons =

A

postive charge

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5
Q

do like charges repel or attract?

A

repel

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6
Q

do opposite charges repel or attract?

A

attract

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7
Q

can charges be created or destroyed?

A

nope - neither

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8
Q

can charges be transferred from one object to another?

A

yep

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9
Q

anode =

A

net positive pole
attracts (-) ions

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10
Q

cathode =

A

net negative pole
attracts (+) ions

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11
Q

what is voltage?

A
  • potential difference in distribution of ions
  • also referred to as electromotive force
  • a force that PUSHES charge
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12
Q

what is voltage measured as?

A
  • volts or millivolts
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13
Q

What is current flow?

A

the flow of charged particles (ions or electrons)

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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
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15
Q

what is current flow measured in?

A

amperes or microamperes or as a rate (coulombs per second)

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16
Q

current flow moves from …

A

anode to cathode

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17
Q

current flow and electron flow are …

A

opposite

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18
Q

what is resistance/capacitance/impedance?

A

opposition to flow of charged particles

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19
Q

Formula for intensity

A

I = V/R
- which means that there is an inverse relationship between resistance and intensity

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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

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21
Q

what does resistance/ capacitance/ impedance depend on?

A
  • nature of the material
  • length of the pathway
  • cross-sectional area of the pathway
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22
Q

what is skin impedance?

A
  • a form of resistance
  • resistance offered by the skin
  • highly variable throughout the body
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23
Q

Skin impedance - Variables

A
  • water content
  • blood flow
  • patient activity or position
  • conducting medium
  • hair
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24
Q

skin impedance - fixed factors

A
  • distance between electrodes
  • what is under the electrodes
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25
Q

Three types of currents

A
  • Direct Current
  • Alternating Current
  • Pulsed Current
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26
Q

What is direct current?

A
  • 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!)
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27
Q

What is direct current used in?

A
  • iontophoresis
  • wound healing
  • stimulation to denervated tissue
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28
Q

direct current - cathode

A
  • depolarized membrane of excitable cells
  • alkaline effect (hurts more)
  • attracts hydrogen
  • liquifies protein
  • promotes fibroblastic migration (scarring)
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29
Q

direct current - anode

A
  • hyper polarizes membrane of excitable cells
  • acid effect
  • attracts oxygen (bubbles)
  • coagulates protein
  • kills bacteria
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30
Q

What is alternating current

A
  • continuous current flow alternating direction of at least once each second
  • the number of electrons that pass in each direction is generally equal
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31
Q

what is alternating current used for?

A
  • stimulation of nervous and muscular tissue
  • may be used for denervated tissue (but nothing in US is strong enough)
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32
Q

how can alternating current be identified?

A

by waveform

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33
Q

what is pulsed current?

A
  • unidirectional or bi-directional current flow with periodic interruptions
  • current flow lasts for only a few milliseconds or less
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34
Q

what is the most common form of therapeutic e-stim used?

A

pulsed current

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35
Q

what isnt pulsed current used for?

A

iontophoresis

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36
Q

constant current

A
  • 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
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37
Q

Constant voltage

A

voltage will remain constant and current will change in proportion to resistance or impedance changes

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38
Q

Current parameters

A
  • amplitude
  • rise time and decay time
  • pulse duration
  • interphase and interpulse intervals
  • total current and pulse charge
  • frequency (rate)
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39
Q

What is amplitude?

A
  • same as intensity
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40
Q

what is amplitude measured in?

A

Amperes
More often milliamperes
Sometimes expressed in voltage (# would be higher)

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41
Q

peak amplitude

A

highest intensity reached during one stimulus

42
Q

rise time

A

elapsed time from onset of stimulus to peak amplitude of stimulus

43
Q

decay time

A

elapsed time from peak amplitude to termination of stimulus

44
Q

what is rise/decay time measured in?

A
  • milliseconds or microseconds
  • different from “ramp and fall” time which are modulations to an individual stimulus
45
Q

Pulse duration

A
  • length of time one pulse lasts
46
Q

Phase duration

A
  • in biphasic pulse
  • length of time current flows in one phase of a pulse
47
Q

interphase interval

A
  • brief interruption between phases
48
Q

interpulse interval

A

elapsed time between consecutive pushes in a pulsed current

49
Q

what are interphase and interpulse intervals measured in?

A

microseconds

50
Q

frequency (rate)

A

number of pulses or cycles per second

51
Q

what is frequency measured as in pulsed current

A

pps

52
Q

what is frequency measured as in alternating current?

A

Hz

53
Q

low frequency

A

0-1,000 Hz

54
Q

Medium frequency

A

1,000 - 10,000 Hz

55
Q

High frequency

A

> 10,000 Hz

56
Q

what does a change in frequency in alternating current lead to?

A

an automatic change in cycle duration

57
Q

does a change in pulsed current frequency necessitate a change in pulse duration?

A

no
due to an interpulse interval

58
Q

what decreases with decreasing pulse or cycle duration?

A
  • skin impedance
  • increasing frequency may increase current penetration
59
Q

what is perceived as being more comfortable and why?

A
  • higher frequency
  • because skin impedance is reduced in AC current
60
Q

When is more fatigue seen over time?

A
  • with higher frequency
  • varying the rate may reduce this fatigue
61
Q

relationship between frequency and recruitment of fiber type

A

Type I: 10-20 Hz
Type II: 30-60 Hz

62
Q

What is a modulation?

A
  • any parameter that is altered or varied during a series of pulses or cycles
  • usually seen in amplitude, frequency, phase duration, or waveform
63
Q

Burst Modes

A
  • multiple pulses or groups of cycles carried out in bursts
  • modulation in AC
64
Q

Carrier Frequency

A
  • number of cycles/second before burst modulation in AC current
65
Q

Burst Frequency

A

Burst occurring to deliver the carrier frequency

66
Q

resting membrane potential

A

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
Q

Where is there more Na? Where is there more K?

A
  • There is more Na+ on the outside
  • There is more K+ on the inside of the cell
68
Q

Resting membrane potential

A

-70 mV

69
Q

Action potential

A

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
Q

local excitatory response

A

allows cell membrane to increase its permeability to Na+

71
Q

depolarization

A
  • reduction in negative charge caused by Na+ entering the cell
72
Q

what occurs when threshold is reached?

A

a rapid reversal of electrical potential (action potential)

73
Q

what does the resting membrane potential change from during the action potential?

A

it changes from -70 mV to +30 mV

74
Q

What causes the membrane to become hyper polarized?

A

As the permeability to Na+ begins to shut down, the slower movement of K+ is just reaching its equilibrium

75
Q

Absolute refractory period

A
  • depolarization phase
  • another AP cannot occur under any circumstance
76
Q

relative refractory period

A

during hyper polarization another AP could occur if a stimulus of a much greater magnitude occurs

77
Q

voluntary contraction

A

small, slow deeper units are recruited first in all or non fashion

78
Q

electrically stimulated contraction

A

larger, faster motor units fire first

79
Q

what is the biggest factor of motor unit recruitment?

A
  • electrode placement
  • the closer the motor unit is to the electrode, the faster it will be recruited
80
Q

cell type recruitment

A

sensory n > motor n > deep pain n > muscle fibers

81
Q

What do you need in order to get a response?

A
  • adequate total current
  • either have to increase amplitude or pulse duration to get the desired response
  • all or nothing
82
Q

what does a strength duration curve show?

A

the relationship between the amplitude and pulse duration to produce a threshold stimulus for different nerve types and skeletal muscle

83
Q

Rheobase

A

minimal amplitude needed to create an action potential given an infinite pulse duration

84
Q

Chronaxie

A

Minimal pulse duration that will cause an action potential at two times rheobase

85
Q

Contraindications

A
  • 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
Q

Precautions

A
  • sensory loss
  • Areas of scarring
  • Thick adipose tissue
  • Severe edema
  • Over malignancy/neoplasm
  • Open wounds
  • Severe depression
  • Disoriented patients
  • Superficial metal
87
Q

Verbal preparation

A

explain what, why, how it will feel, the patients responsibility, encourage open conversation

88
Q

should you demonstrate e stimulation

A

yep

89
Q

positioning

A

thing about patient comfort, goals for use, good visibility for patient and you

90
Q

skin impedance

A

clean with alcohol, abrade, hydrate, heat, dont shave

91
Q

canvas conductive medium

A

clean with water, cover with gauze, make conductive with water

92
Q

carbon/silicon rubber

A

use of conductive gel or sponges, clean electrodes by washing

93
Q

carbon/silicon self-adhesive

A

disposable, requires slight film of water to make tacky

94
Q

probe

A

cover with gauze, soak button, check that switch is in good working order

95
Q

size of electrode

A
  • make as large as target area but not larger
  • large electrodes decrease skin impedance
  • can cut some electrodes to shape and size desired
96
Q

location of electrodes

A
  • 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
Q

Unipolar or Monopolar

A
  • 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
Q

what are unipolar/monopolar leads used for?

A
  • usually for isolating single or small muscle groups whether innervated or denervated and for training functionally after transplant or repair
99
Q

Bipolar

A
  • 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
Q

what are bipolar leads used for?

A

primarily to stimulate larger muscles and muscle groups for functional activities

101
Q

quadripolar

A
  • specific to iaterfererntial stimulation
  • circuits are crossed

Physical Agents II (8 decks)

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