BIOMED 10/17a Stim II

Question 1

define alternating current

Answer 1

1. uninterrupted and bidirectional flow of charged particles

Question 2

descriptive characteristics of AC

Answer 2

1. biphasic
2. symmetrical
3. balanced
4. varied shapes: sine wave, rectangular, triangular
5. zero net current flow

Question 3

what is pulsed current?

Answer 3

1. interrupted (Break) bidirectional flow of charged particles
2. flow ceases for a finite period

Question 4

descriptive characteristics of pulsed current?

Answer 4

1. mono or biphasic
2. symmetrical or asymmetrical
3. balanced or unbalanced
4. various shapes (waveforms)

Question 5

Burst modulation

Answer 5

russian current

• AC current with a break
• both ac and biphasic pulsatile (electrons move in one direction and then the other)

Question 6

what are different pulse characteristics?

Answer 6

1. wave form
2. pulse/phase duration
3. current amplitude
4. pulse/phase charge
5. frequency
6. frequency modulation
7. carrier frequency modulation

Question 7

what are different kinds of wave forms?

Answer 7

1. mono/biphasic
2. symmetrical/asymmetrical
3. balanced/unbalanced
4. shape

Question 8

what are the most common types of e stim wave forms?

Answer 8

1. symmetrical

2. balanced

Question 9

what is phase duration?

Answer 9

time elapsed from beginning to end of one phase (crosses 0) (microseconds)

Question 10

what is pulse duration?

Answer 10

whole pulse duration, time elapsed from beginning to end of all phases,

• how long the wave comes on for
• should have the ability to change

Question 11

what is current amplitude?

Answer 11

the peak amplitude

Question 12

what is pulse charge in terms of duration and amplitude?

Answer 12

Q = Pulse Duration x Pulse Amplitude

Question 13

what is pulse charge vs phase charge?

Answer 13

area under curve for current on y and microseconds on x

1. phase = half
2. pulse = whole thing

Question 14

what does pulse duration have a direct impact on?

Answer 14

direct impact on the voltage that is created through the phase/charge

Question 15

modifying what parameters makes them more excitable?

Answer 15

1. duration

2. intensity

Question 16

when you have a longer pulse _____, you need less ______ to stimulate the nerve

Answer 16

duration, intensity

Question 17

what is the pulse frequency?

Answer 17

the IPI (interpulse interval)
is time between successive pulses can be for monophasic or biphasic pulses
frequency = 1/period

units: 1/second or hertz

Question 18

what triggers a tetanic contraction?

Answer 18

greater than 50 pulses per second

Question 19

what is a tetanic contraction?

Answer 19

isometric/continuous contraction

Question 20

is period is 1 millisecond, what is the frequency?

Answer 20

frequency = 1/0.001s = 1,000 Hertz

Question 21

if pulse duration is 8msec and IPI is 2msec, what is frequency?

Answer 21

T = pulse duration + IPI
Frequency = 1/T

T = 0.008 s + 0.002s = 0.01

F = 1/0.01 = 100

Question 22

what is frequency modulation?

Answer 22

requires a lot of pulses with a high frequency to generate tetany

-AC current with a break, how fast you put the bursts together is the frequency modulation

Question 23

what is carrier frequency?

Answer 23

• used only for burst modulated AC currents

- interferential waveforms

Question 24

ion response around the nerve membrane/characteristics of a pulse that are most important for nerve recruitment?

Answer 24

1. AC and DC current affect the polarity of the membrane
2. Capacitance is the ability for systems to store charge
3. neuron activation
4. membrane time constant

Question 25

how do AC and DC charge affect the polarity of the nervous tissue?

Answer 25

positive paticles go to negative electrode and can cause depolarization of the membrane if the charge is sufficient

Question 26

how does the capacitance impact the ion response around nerve membrane

Answer 26

- property of a system of conductors and insulators that allows them to store charge - very similar to the cell membrane in the sense that it acts like a resistor and a capacitor to block easy movement of charged particles

Question 27

how does estim trigger neuron activation

Answer 27

local current produced increased Na conductance which depolarizes the membrane and further depolarizes. - when Na influx is greater than potassium efflux, threshold is reached * *** if amplitude and duration aren't enough, then the AP won't be generated

Question 28

what is the membrane time constant?

Answer 28

tau = resistance x capacitance = slope of time vs voltage - determines how easily a nerve is excited - since size impacts resistance, the smaller the diameter the higher the time constant and the harder it will be to stimulate

Question 29

do all nerves have the same time constant?

Answer 29

NO! different nerves have different time constants -the bigger the nerve, the less resistance, so the more easily it will be stimulated -the smaller the nerve, the more resistance, so the harder it will be to stimulate it

Question 30

different nerve fiber activations

Answer 30

1. Largest diameter lowest internal resistance are the most easily excitable - Requires shorter pulse durations to get stimulated - Requires less intensity to get stimulated 2. Denervated muscles - SCI or cut peripheral nerve, you're really trying to stimulate the muscle membrane rather than the nerve - That individual will require longer duration and larger intensity of the charge 3. Aα—muscle spindle primary afferent; GTO (golgi tendon) afferent; skeletal muscle efferent 4. Aβ—touch pressure receptor afferent; muscle spindle secondary afferent 5. Aδ—mechanical and thermal afferents 6. C—mechanical and thermal afferents

Question 31

why does one feel sensory tingling when stim is started?

Answer 31

1. This is because there are sensory receptors closer to the surface even though they are smaller 2. You have to jack up the stim even more to get motor contractions 3. Unfortunately, you start to get the pain receptors as well as you jack it up which may yield to a dosing problem

Question 32

what are key device characteristics that should be known for your stim faciltation?

Answer 32

1. Allow control on:off times 2. Allow control of pulse frequency (2-150pps) 3. Allow control of pulse duration (50 - at least 400microseconds) 4. Has adequate power (up to 100mA through 100 ohm resistor)

Question 33

What are possible mechanisms for stim to reduce edema?

Answer 33

1. Reduction in microvasculature permeability 2. Motor-level contractions -> improve venous and lymphatic drainage (stimulate contractions that moves fluid) 3. Pain reduction -> improve/increase limb use that will accelerate venous and lymphatic drainage and return to function (secondary effect on swelling because you get patient moving and more active by reducing their pain)

Question 34

results for animal model using stim for edema reduction on hamsters

Answer 34

used High Voltage pulsed current (HVPC) in hamsters - Monophasic - Work on reducing microvasculature of permeability - Different types of anodal and cathodal current were successful in halting edema in the hamster cheek pouch

Question 35

results for animal model using stim for edema reduction on different kinds of rats

Answer 35

HVPC (High Voltage Pulsed Current) was used □ Looked at swelling in hind limb □ 3 different strains of rats □ In 2 of the 3 there was evidence that high volt pulse current retarded swelling/edema

Question 36

what were the findings in the systematic review about using stim for edema reduction in humans

Answer 36

- | All over the place, after acute ankle sprain there isn't positive evidence on reducing swelling

Question 37

what were the findings in the systematic review about using stim for pain reduction in humans

Answer 37

small study, but found that there was a moderate effect

Question 38

what were the findings in the systematic review about using stim for function improvement in humans

Answer 38

2 studies, 4 different kinds of settings, all crossing 0 and stim was not really effective