Electrotherapeutic Modalities

Question 1

Purposes of EStim

Answer 1

muscle strengthening
enhancing transdermal drug delivery
wound healing
decreasing edema/preventing edema
muscle re-educatoin
decrease muscle atrophy

Question 2

describe polarity of cell membranes and polarization and action potentials

Answer 2

• more negative inside than outside because positive Na ions outside, positive K ions and other negative ions inside
• resting membrane potential of -70mV, AP evoked around -55mV.
• Na channels open and flood in cell
• nerve AP either sends an ascending sensory impulse to the brain OR a descending muscle action potential which causes a muscle contraction
• nerve repolarized quickly (.4-2 msec depending on the nerve)
• larger nerves and more superficial nerves are easier to stimulate
• nerve cell RMP = -70mV
• skeletal muscle RMP= -90mV

Question 3

Ohm’s Law

Answer 3

I=V/R

Question 4

capacitance

Answer 4

ability of a body to store an electric charge (example-static shock)

Question 5

impedance

Answer 5

form of resistance that is frequency dependent (gels and adhesives on electrodes decrease impedence)

Question 6

What are the 3 types of current?

Answer 6

DC- continuous unidirectional flow of ions or electrons for AT LEAST 1 second

AC- continuous (uninterrupted) bidirectional flow of ions or electrons that CHANGE DIRECTION AT LEAST 1time per second

Pulsed Current- uni or bidirectional flow of ions or electrons that ceases (INTERRUPTED) for a small period of time

Question 7

What’s a clinical use for DC?

Answer 7

iontophoresis

wound care

Question 8

What’s a clinical use for AC?

Answer 8

most therapeutic applications use AC

• burst modified AC-russian current
• amplitude modulated AC- interferential current
• contraction for denervated muscle

Question 9

What’s a clinical use for PC?

Answer 9

most common type of Estim used for therapy

• monophasic PC = interrupted DC
• biphasic PC = interrupted AC

Question 10

When is monophasic current used?

Answer 10

high voltage pulsed stimulation

Question 11

When is biphasic current used?

Answer 11

NMES

Question 12

What are the 3 types of biphasic current?

Answer 12

symmetrical- mirror images on each side of the baseline, no net +/- charges under the electrodes

balanced asymmetrical- shape of the pulse allows for anodal (+) or cathodal (-) effects, no net +/- charge

unbalanced asymmetrical- +/-effects, imbalance in + and - charges results in a net charge over time. can cause irritation if used for long durations.

Question 13

What is pulse duration?

Answer 13

the time from when the pulse rises from the baseline to the point where it terminates on the baseline.

Question 14

what is phase duration?

Answer 14

individual portions of the pulse that appear on one side of the baseline.
for monophasic currents, pulse duration and phase duration are synonymous.
for biphasic pulses have 2 phase durations.
phase duration determines which nerve type is affected

Question 15

what type of phase duration depolarizes the following types of nerves:?
sensory
motor
pain
muscle fibers

Answer 15

sensory-short
motor-medium
pain- long
muscle fibers-DC

Question 16

What is an interpulse interval?

Answer 16

time between the end of one pulse and the start of the next pulse.
allows for mechanical changes in the tissue, such as when eliciting muscle contractions.
increasing the pulse frequency decreases the interpulsed interval and vice versa

Question 17

what is an intrapulse interval?

Answer 17

brieft interruptions of current flow.
always shorter than the interpulse interval.
allow for physiological adaptations to the current and/or to decrease the total charge delivered by the pulse.
normally not adjustable on the unit.
can apply to biphasic and monophasic currents

Question 18

What is a pulse period?

Answer 18

amount of time from the start of one pulse to the start of the next pulse.
includes phase durations, intrapulsed interval, and interpulsed interval.
inversely proportional to pulse frequency.

Question 19

what is pulse frequency?

Answer 19

number of times a pulse occurs per second.
with altering currents, this measure it described as cycles/sec.
increasing pulse freq decreases pulse period and interpulse interval

Question 20

What are pulse trains (bursts)?

Answer 20

contain individual pulses.
pulses in the train still have time-dependent characteristics.
each train is separated by “off” times - the intertrain/interburst interval

Question 21

what is a pulse?

Answer 21

an electrical event separated from the next by a period of time called the interpulse interval

Question 22

what is a phase?

Answer 22

flow of current in ONE direction for a short time

Question 23

How are these ionic effects used therapeutically?

Answer 23

iontophoresis
edema
wound healing

Question 24

What is the mechanism by which electrotherapy aids tissue healing?

Answer 24

• attracts appropriate cell types to the area (neutrophils, macrophages, lymphoctes, fibroblasts)
• enhances fibroblast replication
• increases the synthesis of DNA and collagen by fibroblasts
• promotes cell and lymphocyte migration, proliferation, and function
• reduction of edema
• promotes circulation
• most effective for accelerating the healing of of pressure ulcers
• different types of current used for this applications

Question 25

in general, when would you use - electrodes? +?

Answer 25

-electrode should be used to promote healing of inflamed/infected wounds (usually the early stages)

+ electrodes should be used to promote healing of wounds without inflammation (later stages of healing)

Question 26

What are the tissue healing parameters?
placement?
pulse freq?
pulse duration?
amp?
time?

Answer 26

placement- tx electrode in the wound (electrode placed within a saline moistened sterile gauze) or around the wound- dispersive electrode of opposite polarity placed on intact skin close to the wound side (15-30cm)

waveform- MONOPHASIC PC (twin peaked monophasic)

Pulse freq= 100pps
Pulse duration= 4-100 microseconds
Amp= sensory response
Duration= 60 min; 5-7 days/week

Question 27

Electrotherapy for edema control:
should be used in conjunction with what?
how does it work?

Answer 27

• should be applied in conjunction with elevation followed by the use of a compression garmet
• decreases the FORMATION of edema, reduces the leaking of large plasma proteins from leaking through the pores by reducing the pore size in microvessel walls (uses monophasic pulsed current)
• can also reduce edema caused by poor peripheral circulation due to lack of motion (using biphasic or burst modulated AC-NMES, Russian)

Question 28

What are parameter to decrease the formation of edema (HVPC)?

Answer 28

electrode placement- treatment electrode over the area of edema with the dispersive electrode more proximal

pulse freq = 100-125 pps
pulse duration 2-100 micro seconds
amp= to comfortable sensory perception
time= 10-20 min but may be used > 1x per day

Question 29

What are parameters to decrease existing edema (NMES)?

Answer 29

electrode placement- treatment electrode over the area of edema with the dispersive electrode more proximal

pulse freq= 20-80 pps
pulse duration 10-600 microseconds
amp= tetanic contraction
time= 1:1 on:off ratio for 10-20 min

*more than 20 min may increase blood flow which may increase edema!

Question 30

What is Rheobase?

Answer 30

the minimum strength (current amp/mA) of a stimulus of very long pulse duration that is capable of eliciting an action potential or minimally detectable motor response

Question 31

What is chronaxie?

Answer 31

the duration (microsecond/ millisecond) of a stimulus 2x the rheobase strength

Question 32

What is the difference between physiologically generated recruitment and electrically stimulated recruitment?

Answer 32

physo:

• order = smaller fibers first
• asynchronous recruitment of motor units

electric:

• order= larger fibers first
• all motor units of a given size fire simultaneously once a threshold is reached.

Question 33

what is the overload principle?

Answer 33

the greater the load placed on a muscle, the higher force contraction it produces, the more strength that muscle will gain.

Question 34

What type of force should be used to increase muscle strength? to increase muscle endurance?

Answer 34

strength- high force contractions

endurance- prolonged stimulation with more lower force contractions