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Physical Agents > Electrotherapeutic Basics > Flashcards

Electrotherapeutic Basics Flashcards

1
Q

To have current, there must be:

A
  • a source of electrons
  • a conductor of the electrons
  • a driving force of electrons
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2
Q

ions

A

atoms that possess a charge

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3
Q

ions move from ___ concentration to ____ concentration

A

high; low

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4
Q

Electric current

A

the net movement of charged particles (ex ions or electrons) along a conductor

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5
Q

Electromotive force

A

The amount of potential (electrical) difference between two points ( conc of ions or electrons) in an electrical field that drives the charged particles
-measured in Volts

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6
Q

Driving force

A
  • Commercial current flowing from a wall outlet produces an electromotive force of either 110-115 V or 220-240 V
  • electrotherapeutic modalities then modify this voltage for specific therapeutic purposes
  • in human system, the electric stimulator generates a voltage to overcome resistance (wires, tissues) allowing a current to flow along the path of least resistance
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7
Q

Low voltage generators

A

-Electrotherapeutic modalities that produce a voltage less than 150V

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8
Q

Coulomb (C)

A

The measure of electric charge equal to 6.25 x 10^18 electrons

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9
Q

Ampere (A)

A

Measure of current flow equal to 1 Coulomb (C) per second

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10
Q

ohm

A

Measure of resistance to current flow

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11
Q

Voltage (V)

A
  • Measure of potential difference of EMF required to move 1 Amp (A) of current across 1 ohm of resistance
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12
Q

Resistance

A
  • The ability of a medium to resist the flow of electrons through direct current
  • expressed in ohms
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13
Q

Inductance

A

opposition to electron flow created by electromagnetic eddy currents generated when current is passed through a wire

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14
Q

Capacitance

A

Ability of a material to store an electrical charge

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15
Q

Impedance

A

-Resistance + inductance + capacitance

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16
Q

Conductors

A

materials that offer little resistance and allow current to flow easily

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17
Q

Insulators

A

Materials that offer high resistance to current flow

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18
Q

semiconductors

A

Materials that offer neither high nor low resistance to current flow

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19
Q

Electron flow

A
  • Volt
  • Ampere
  • Resistance (ohm)
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20
Q

Water flow

A
  • Pump
  • Gallon of water/min
  • length and diameter of pipe
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21
Q

Energy created by water flowing is dependent upon..

A
  • pressure in the pipe

- # of gallons flowing per unit of time

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22
Q

Electrical power is measured in…

A

Watts

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23
Q

Watts=

A

Volts X Amps

W=V x A

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24
Q

Power (watts)=

A

EMF x current
(P= V x I)
- One watt is the power needed to move ( produce a current flow) one ampere of current with a force (pressure) of one volt

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25
Q

ohms law

A
  • The amount of electromotive force (volts) in a circuit is equal to the current intensity (amps) multiplied by the resistance (ohms)
  • V= I (amps) x R (ohms)
  • I = V/R
  • increase resistance = increased voltage needed to move current (I)
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26
Q

Series circuit

A
  • When the same current flows through each resister, they are said to be in series
  • RT=R1+ R2 + R3
  • skin and fat in series
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27
Q

Parallel circuit

A
  • When current flowing through a circuit has multiple pathways to follow through or around each resister
  • 1/RT= 1/R1 + 1/R2 + 1/R3
  • muscle, blood, tendon, ligament, bone in parallel
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28
Q

Types of currents capable or producing specific biological effects

A
  • Direct (DC)
  • alternating (AC)
  • pulsatile or pulsed
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29
Q

Direct/galvanic/ or monophasic current types

A
  • Continuous
  • reversed DC current
  • interrupted DC current
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30
Q

Continuous direct current

A

Unidirectional flow of electrical charges for at least one second

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31
Q

Reversed direct current

A

unidirectional flow of electrical charges for at least one second that then changes polarity

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32
Q

Interrupted direct current

A

unidirectional flow of electrical charges for at least one second that then stops for at least one second then resumes

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33
Q

direct current is generally used for:

A
  • iontophoresis
  • stimulating denervated muscle directly
  • stimulate wound healing
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34
Q

Alternating/faradic/ biphasic current (AC)

A
  • A continuous, bidirectional flow of charged particles where each cycle duration occurs in less than one second
  • equal ion flow in each duration ( no net charge)
  • wavelength= one cycle
  • wavelength and frequency are inversely related
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35
Q

Rate of rise

A

Amount of time it takes to reach peak flow (when alternating current begins to flow in + direction)
-time dependent

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36
Q

Rate of fall

A

amount of time it takes to go from peak flow back to zero (isoelectric line)

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37
Q

Frequency

A
  • # of pulses per second

- in alternating current frequency and duration (time) inversely related

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38
Q

AC current generally used for

A
  • muscle strengthening
  • muscle re-education
  • pain modulation
  • functional training (ie gait)
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39
Q

Pulsed/pulsatile currents

A
  • unidirectional or bidirectional flow of electrical current that lasts less than one second and stops for a finite period (usually between 5 and 999 milliseconds) before the next pulse
  • electrical current delivered discontinuously separated by a finite period of time
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40
Q

Types of pulsed/pulsatile currents

A

-Monophasic pulsed current
-biphasic pulsed current
* symmetric
* asymmetric
+ balanced
+ unbalanced

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41
Q

Monophasic pulsed current

A
  • flowing only in one direction

- separated by finite amount of time before next pulse becomes active

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42
Q

Biphasic pulsed current

A
  • current flowing in + and - direction

- separated by finite amount of time before next pulse becomes active

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43
Q

symmetric biphasic pulsed current

A
  • both positive and negative phases have same amplitude and are on for same amount of time
44
Q

balanced asymmetric biphasic pulsed current

A
  • waves look different but the area under the waves are equal
  • balanced relative to amount of charge
45
Q

Unbalanced asymmetric biphasic pulsed current

A
  • positive phase and negative phase look different and have different area under the waves
  • unbalance charge which leads to build up of one charge on one side
46
Q

Waveform

A

the shape of the current intensity vs time graph

47
Q

number of phases

A
  • Monophasic
  • biphasic
  • triphasic
  • polyphasic
48
Q

symmetry of phases

A
  • Symmetric

- asymmetric

49
Q

balance of phase charge

A

-Balanced/unbalanced

50
Q

waveform or phase shape

A
  • Rectangular
  • square
  • triangular
  • saw toothed
  • sinusoidal
51
Q

descriptive characteristics of waveforms

A
  • waveform
  • number of phases
  • symmetry or phases
  • balance of phase charge
  • waveform or phase shape
52
Q

Amplitude-Dependent characteristics of pulsed and AC currents

A
  • Peak amplitude
  • peak to peak amp
  • root mean square amp
  • average amp
53
Q

Peak amplitude

A
  • the max current reached for a single phase
54
Q

peak-to-peak amplitude

A

the max current measured from the peak of the first phase to the peak or the second phase

55
Q

Root mean square amplitude

A

-Most common mathmatical method of defining the effective voltage or current of an AC wave

56
Q

Average amplitude

A

the mean voltage under the sine wave curve

57
Q

Time dependent characteristics of Pulsed and AC currents

A
  • phase duration
  • pulse duration
  • rise time
  • decay time
  • interpulse interval
  • intrapulse interval
  • Period
  • Frequency
58
Q

Phase duration

A

time from beginning of a phase to the end of a phase

59
Q

Pulse duration

A

time from beginning of a pulse to the end of a pulse

60
Q

rise time

A

time required from the beginning of a phase to the peak of the phase

61
Q

decay time

A

time from the peak of the phase to the end of the phase

62
Q

interpulse interval

A

time from the end of one pulse to the beginning of the next pulse

63
Q

intrapulse interval

A

time from the end of one phase to the beginning of the next phase

64
Q

Period

A

the time to complete one pulse

65
Q

frequency

A

1/period

66
Q

Amplitude modulation

A
  • vary amplitude up and down
67
Q

Pulse duration modulation

A

vary how much time each pulse takes

68
Q

frequency modulation

A

modulate how many pulses per second

69
Q

Ramp modulation

A

modulate how much time it takes to get to peak of the individual phase or pulse

70
Q

Timing modulation

A

-Burst: a series of pulses for a finite period of time followed by a period of no current flow

71
Q

Burst duration

A

the length of time from the beginning of the burst to the end
- usually expressed in milliseconds (msec)

72
Q

interburst interval

A

time from the end of one burst to beginning of the next burst

73
Q

burst frequency

A

the number of bursts per unit of time

74
Q

Electrode systmes

A
  • carbon rubber
  • carbon rubber with conducting gel
  • vinyl covered metal plate
75
Q

Electrode considerations current density: depends on size of electrodes

A
  • smaller electrode has higher current density
76
Q

Electrode considerations current density: depends on electrode placement

A
  • Electrodes placed closer together have higher current density superficially
  • electrodes placed further apart have higher current density deeper in the tissues
77
Q

Electrode placement

A
  • monopolar:
  • Bipolar
  • quadrapolar
    • intersecting
    • non-intersecting
78
Q

Tap key electrode

A
  • to identify motor points

- to stimulate small muscles (esp face muscles)

79
Q

Monopolar electrode placement

A
  • Negative electrode= active electrode placed near tissue we are trying to stimulate
  • Positive electrode= non active electrode; usually larger dispersive electrode
80
Q

Bipolar electrode placement

A
  • positive and negative electrodes equal in size
  • put both over tissue you are trying to stimulate
  • one wire with +/- plugs
  • or one +, and one - wire
81
Q

quadrapolar electrode placement

A
  • 4 electrodes
  • non-intersecting> straight across
  • intersecting> diagonal from each other
82
Q

Interferential current history

A
  • The research and use of IFC: primarily in Europe
  • Ho Nemec- Austrian- introduced IFC (1950)
  • came to N. America in 1980s
  • surveys of PTs in England, Ireland, Australia, and Canada find IFC in the top 5 therapeutic modalities used
83
Q

IFC description

A
  • a medium frequency (1000 to 10,000 Hz) current that produces unmodulated sinusoidal waves of similar amplitude that cross
  • these two different carrier frequencies interfere with each other to generate an amplitude modulated beat frequency
  • this beat frequency is the net difference between the two superimposed frequencies and is the stimulation frequency of the waveform
84
Q

Interference

A

-When two waves are brought into the same location, the amplitudes combine and are increased or summative

85
Q

Constructive interference

A

two waves produced in phase or originate at the same time

- amplitudes combine with resultant amplitude increased

86
Q

Destructive interference

A

Two waves produced out of phase or originate at different times

  • amplitudes combine with resultant amplitude decreased
  • if perfectly out of phase, amplitudes will cancel each other with resultant amplitude of 0
87
Q

beat effect

A

produced by waveforms that have two different frequencies but combine at the same location

  • the blending of waves results in both constructive and destructive interference and is termed heterodyne (different power-greek)
  • the heterodyne effect is seen as rising and falling waveform
  • the peaks correspond to the beat frequency and is the stimulation frequency of the waveform
  • the beat frequency is the difference between the two original frequencies
88
Q

four petal effect

A
  • IFC : 4 electrodes crossing causing this effect

- electric field lines flowing perpendicular to generator 1 and generator 2

89
Q

IFC: stimulating current pattern

A
  • when electrodes are placed in a square pattern, electric field is produced that looks like a four petal flower
  • maximum interference is at the center
90
Q

Constant (bipolar) IFC

A

-Both carrier frequencies are fixed

91
Q

Variable (quadripolar) IFC

A
  • One carrier frequency is fixed while the other varies in frequency creating a variable or sweep frequency
  • This is used to minimize pt accommodation to the current
92
Q

Scanning IFC (quadripolar with vector scanning)

A

-The ability to move the entire petal of stimulation so as to effect a larger treatment area

93
Q

Stereodynamic IFC

A

Three distinct circuits that blend and create a distinct wave

94
Q

High voltage pulsed current: history

A
  • Lehmann- “high-voltage electro galvanic stimulator”
  • Term “ galvanic” was erroneuous in that current was not direct or continuous current but rather pulsed
  • Proper term should be high-voltage pulsed current (APTA, 1990)
95
Q

HVPC: biophysical characteristics

A
  • Twin peaked, monophasic, pulsed current
  • driven by characteristically high EMF (current) from 150-500 volts
  • 150 volts= high volt stimulator
  • HVPC pulses generally fixed
  • some allow for adjustment of interspike interval
  • pulse frequency: 1-200 pps (pair of monophasic spike like waveforms
96
Q

HVPC: twin-peak monophasic pulse

A
  • pair of monophasic spike-like waveforms
  • almost instantaneous rise followed by exponential decline
  • pulse duration: short
  • 100-200 usec
97
Q

HVPC: Tissue impedence

A
  • capacitance= charge/voltage
  • high volt source > less capacitance
  • low capacitance > low tissue impedance > more comfortable
98
Q

HVPC: strength duration curve

A
  • need for high voltage output due to extreme shortness of pulse duration at its peak in keeping with classic strength duration curve
  • shorter pulse duration- higher current amplitude
99
Q

HVPC: versatility

A

High voltage output and monophasic pulsed waveform allows for

  • electric nerve/muscle stim
  • wound healing
100
Q

Russian current history

A

-Yakov Kots – Russian physiologist
1977 – Russian – Canadian exchange symposium
-Revolutionary claims
*An electrically produced human muscle contraction, using this new type of stimulation, could generate up to 30% more force then that generated by a MVC
*Application of such current is painless
*Short-term training could produce lasting gains in mm strength of up to 40% in healthy subjects
-1980s -first russian current stimulator electro-stim 180 produced in US and canada
-Clinical importance:
* if kot’s claim is correct, could train individuals without need of voluntary contractions

101
Q

Russian current: biophysical characteristics

A
  • Time modification of continuous sine-wave having carrier frequency of 2,500 pps
  • burst modulated for fixed 10 msec periods
  • Fixed IPI of 10 msec
  • Burst frequency of 50 bursts per second (bps)
102
Q

Russian current: net physiological effects

A
  • total number of bursts/sec (burst frequency) determine magnitude of effect
  • at nerve/muscle memebrane level, each bursts leads to motor nerve depolarization and tetanic contraction
103
Q

Russian current: physiological and therapeutic effects

A
  • depolarizes both motor and sensory neurons simultaneously
  • muscle contraction will be painless
  • higher current amplitudes can be used
  • will stimulate deeper motor neurons
104
Q

Russian current: motor unit activation

A
  • preferential activation of type II motor units
105
Q

Russian current: motor unit recruitment deficiency

A
  • during max voluntary muscle contraction
    • unable to recruit large #s of large, type II fast-twitch motor units or get them to fire fast enough to develop max muscle force
  • with Russian stimulation, higher current amplitudes that are painless stimulate larger pool of type II motor units

Physical Agents (21 decks)

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