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Unit 2 > 10-17a Introduction to Electrotherapy II > Flashcards

10-17a Introduction to Electrotherapy II Flashcards

1
Q

DC is always flows from

A

positive to negative

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2
Q

Define AC

A

uninterrupted bidirectional flow of charged particles

no net change in polarity at either electrode = no chemical effects = zero net current flow

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3
Q

What are the descriptive characteristics of AC?

A

biphasic

symmetrical (or asymmetrical): same shape on top and bottom

balanced (or unbalanced): top as big as bottom

varied shapes: largely sine and rectangular

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4
Q

What are the characteristics of pulsed current?

A

mono (only on top) or biphasic pulses

symmetrical (or asymmetrical): same shape on top and bottom

balanced (or unbalanced): top as big as bottom

varied shapes: rectangular, twin peak

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5
Q

Define pulsed current

A

interrupted uni or bidirectional flow of charged particles

interpulse interval/stop in current

uni or bidirectional flow of charged particles

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6
Q

How long does direct current have to last for?

A

at least 1 second

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7
Q

What is burst modulated AC current?

A

AC current with an interpulse interval

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8
Q

What is phase duration

A

time elapsed from beginning to end of one phase

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9
Q

What is pulse duration?

A

time elapsed from beginning to end of all phases

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10
Q

What is peak current?

A

The amplitude of each phase

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11
Q

How can AC cause an ion response around the nerve membrane

A

migration of negative particles and ions to the surface of the positively charged electrode to change polarity

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12
Q

How can electrodes cause an AP?

A

if the amplitude and duration of the current is sufficient enough to change the polarity of negative 70

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13
Q

What is capacitance?

A

The property of a system of conductors and insulators to store charge

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14
Q

How is the cell membrane similar to a capacitor?

A

phospholipid bilayer partially acts as a resistor by blocking flow of charged ions from moving in and out of the cell

also acts as a capacitor since the cell is more negative intracellularly and positive extracellulary = stores energy by having a different voltage on either side to cause a change in polarity > depolarization

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15
Q

What is the membrane time constant?

A

membrane Resistance * membrane capacitance

different n. have diff time constants due to diff resistances (larger diameter, less resistance)

some n. are easily excited & some are less easily excited

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16
Q

What is a pulse charge? What is it important for?

A

area under both positive and negative phases
amps times micro seconds
important for det. excitation of tissue

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17
Q

what is phase charge?

A

area under half of the phase

Amps times micro seconds

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18
Q

can two pulses w diff amplitudes and durations have the same pulse/phase charge?

A

yes

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19
Q

What two factors affect tissue excitation?

A

pulse charge/phase charge and duration

20
Q

What is the relationship between pulse duration and excitability

A

the longer the pulse duration, the less intensity (pulse amplitude (mA)) required to excite it

21
Q

Which neurons are the largest? What do they innervate? What is its level of resistance and excitability?

A

alpha motor neurons (m. tendons, m.spindles)

largest diameter, lowest internal resistance, most easily excitable

22
Q

Which neurons are the second largest? What do they innervate? What is its level of resistance and excitability?

A

beta motor n. (sensory n.) medium resistance and medium excitability

23
Q

Which neurons are the smallest? What do they innervate? What is its level of resistance and excitability?

A

Gamma n. (pain n.), highest resistance and lowest excitability

24
Q

What is the relationship between n. size and excitability?

A

larger the n., less internal resistance, shorter durations and smaller intensity to become stimulated

25
Q

What kind of intensity and duration does it take to activate deinnervated m.?

A

RMP is less, takes longer and higher pulses to get stimulation

26
Q

What is the first n. type to sense Estim? Why?

A

sensory n. (beta) due to them being much closer to the skin surface/electrode (so are pain n. fibers)

27
Q

What is noxious threshold?

A

when it starts to become painful

28
Q

What is the period of pulse frequency?

A

time elapsed from one point in the waveform to identical point in the next waveform

29
Q

What is frequency of the pulse?

A

of pulses/cycles per second (Hz)

1/period

30
Q

What does frequency determine for a pulse?

A

whether the contraction stays on or not

the type of stimulation/effect from Estim

determines tetany

31
Q

What is pulse charge?

A

how high and how long the wave is

32
Q

What is the period the sum of?

A

pulse duration and IPI

33
Q

what are the units for frequency

A

pulse per second

34
Q

When would a low frequency be appropriate?

A

pain relief

35
Q

What freq. is needed for m. stimulation?

A

high frequency

36
Q

how can freq. be modulated with burst modulated?

A

how close bursts are together determines frequency

37
Q

What are key device characteristics needed

A

Allow control of ON:OFF times
Allow control of pulse frequency (2-150pps)
Allow control of pulse duration (50- at least 400µs)
Has adequate power (up to 100mA through a 1000Ω resistor)

38
Q

What’re the possible mechanisms for edema reduction

A
  1. Reduction in microvascular permeability
  2. Motor-level contractions > improve venous and lymphatic drainage (create ankle pump)
  3. Pain reduction > improve/increase limb use that will accelerate venous and lymphatic drainage and return to function
39
Q

Which mechanism can reduce microvascular permeability?

A

high voltage pulsed current (monophasic to create charge on tissue)

40
Q

What do animal studies show about what stimulation can reduce swelling?

A

high voltage pulsed current

41
Q

What do human trials show for Estim on swelling?

A

no evidence showing positive effect in swelling

42
Q

What do human trials show for Estim on decreasing pain?

A

moderate

43
Q

effect on estim on function for humans?

A

no support

44
Q

What does the animal research indicate?

A

decreased formation of edema after injury, use of cathode (-) with monophasic current (HVPC) 90% of motor threshold

45
Q

What is the timing for estim for edema?

A

on site field management

following interventions/exercise

46
Q

What is needed for iontophoresis? What can it not be?

A

1 sec duration

biphasic

Unit 2 (29 decks)

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