Electrotherapeutic Modalities Flashcards
Purposes of EStim
muscle strengthening enhancing transdermal drug delivery wound healing decreasing edema/preventing edema muscle re-educatoin decrease muscle atrophy
describe polarity of cell membranes and polarization and action potentials
- 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
Ohm’s Law
I=V/R
capacitance
ability of a body to store an electric charge (example-static shock)
impedance
form of resistance that is frequency dependent (gels and adhesives on electrodes decrease impedence)
What are the 3 types of current?
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
What’s a clinical use for DC?
iontophoresis
wound care
What’s a clinical use for AC?
most therapeutic applications use AC
- burst modified AC-russian current
- amplitude modulated AC- interferential current
- contraction for denervated muscle
What’s a clinical use for PC?
most common type of Estim used for therapy
- monophasic PC = interrupted DC
- biphasic PC = interrupted AC
When is monophasic current used?
high voltage pulsed stimulation
When is biphasic current used?
NMES
What are the 3 types of biphasic current?
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.
What is pulse duration?
the time from when the pulse rises from the baseline to the point where it terminates on the baseline.
what is phase duration?
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
what type of phase duration depolarizes the following types of nerves:? sensory motor pain muscle fibers
sensory-short
motor-medium
pain- long
muscle fibers-DC
What is an interpulse interval?
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
what is an intrapulse interval?
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
What is a pulse period?
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.
what is pulse frequency?
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
What are pulse trains (bursts)?
contain individual pulses.
pulses in the train still have time-dependent characteristics.
each train is separated by “off” times - the intertrain/interburst interval
what is a pulse?
an electrical event separated from the next by a period of time called the interpulse interval
what is a phase?
flow of current in ONE direction for a short time
How are these ionic effects used therapeutically?
iontophoresis
edema
wound healing
What is the mechanism by which electrotherapy aids tissue healing?
- 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
in general, when would you use - electrodes? +?
-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)
What are the tissue healing parameters? placement? pulse freq? pulse duration? amp? time?
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
Electrotherapy for edema control:
should be used in conjunction with what?
how does it work?
- 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)
What are parameter to decrease the formation of edema (HVPC)?
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
What are parameters to decrease existing edema (NMES)?
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!
What is Rheobase?
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
What is chronaxie?
the duration (microsecond/ millisecond) of a stimulus 2x the rheobase strength
What is the difference between physiologically generated recruitment and electrically stimulated recruitment?
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.
what is the overload principle?
the greater the load placed on a muscle, the higher force contraction it produces, the more strength that muscle will gain.
What type of force should be used to increase muscle strength? to increase muscle endurance?
strength- high force contractions
endurance- prolonged stimulation with more lower force contractions
