Introduction to Electrotherapy Flashcards
Ohm’s Law
V = IR
Voltage = Current x Resistance
Define impedance
- impedance is the resistance of the tissue to the passage of electrical current
What tissues have low impedance
- nerves
- muscles
What tissues have high impedance
- bones
- fat
Define cathode
- negative electrode
- high electron concentration
- attracts positive ions
- alkaline reaction
Define anode
- positive electrode
- low electron concentration
- attracts negative ions
- acidic reaction
When does the placement of the cathode and anode matter
- with monophasic/direct current only
Define series circuit
- one pathway is available for travel
- this is how current enters the body
Define parallel circuit
- two or more routes exist for the current to pass between the two terminals
- this is how current moves in the body
Is skin a conductor or an insulator/non-conductor
- considered an insulator
- offers the chief resistance to current flow
Is blood a conductor or an insulator/non-conductor
- considered the best electrical conductor of all tissues
Is muscle a conductor or an insulator/non-conductor
- considered a relatively good conductor
Is fat a conductor or an insulator/non-conductor
- considered a poor conductor
Are tendons a conductor or an insulator/non-conductor
- considered poor conductors
Is bone a conductor or an insulator/non-conductor
- considered the poorest biological conductor
What are the effects of electrical stimulation
- electrical currents exert physiological effects by depolarizing the nerve membranes resulting in production of an action potential
- electrical currents reverse the electrical gradient of the nerve to create a depolarization
Define amplitude
- lower setting=sensory stimulation
- higher settings=motor level stimulation
- provides current to deeper tissues
What parameters have the most impact on how a patient feels & responds to electrical currents
- amplitude
- pulse duration (pulse width)
Define pulse duration
- the time to complete two phase durations
- short duration with low amplitude=depolarize sensory nerves
- long durations are required to stimulate motor nerves
- very long duration with high amplitude stimulates denervated muscle
Define interpulse interval
- the time between the end of one pulse & the start of the next pulse
- increasing the pulse frequency decreases the interpose interval & vice-versa
Define pulse frequency
- indicates the pulse rate or number of pulses per second (Hz)
-normal physiological contraction is asynchronous firing or motor units while Estim induced=synchronous
What pulse frequency will contribute to the different types of contraction
- 1-10pps = twitch contraction
- > 30 = tetanic contraction
- 30-70 = non fatiguing tetanic contraction
- 100-1000 = fatiguing tetanic contraction
Define monophasic/direct current
- unidirectional flow of electrons towards positive pole
- can create a pulse charge
Define biphasic/alternating current
- flow of electrons constantly changes direction/reverses polarity
- most often results in a neutral pulse charge
Define pulsed current
- can be monophasic or biphasic
- contains 3 or more pulses grouped together that are interrupted for short periods of time & repeat regularly
Define polyphasic current
- bidirectional current with 3 or more phases in a burst pattern
Examples of monophasic/direct current
- iontophoresis
- wound healing
- stimulation contraction in denervated muscle
- microcurrent
Example of monophasic/direct current pulsed
- high voltage pulsed current (HVPC) used for tissue healing & acute edema control
Examples of biphasic/alternating current
- used for pain control
- interferential
- premodulated
- TENS
- russian protocol
- NMES
Define Rheobase
- minimum current amplitude at a long duration required to produce an action potential (intensity)
Define Chronaxie
- minimum duration (time) it takes to stimulate tissue at twice rheobase intensity (duration)
In what order are the different nerve types stimulated on the strength (amplitude) duration (pulse duration) curve from the lowest duration to highest duration
1) a-beta sensory
2) motor
3) a-delta sharp pain
4) c-dull pain
5) denervated muscle
Define motor point
- area of greatest excitability on the skin surface at which a small amount of electrical current generates a strong muscle response
Where can you find the motor point in innervated and denervated muscles
Innervated muscle: where motor nerve enters the muscle, over the belly
Denervated muscle: over the muscle distally toward the insertion
Define current modulation
- any alteration or any variation of the pulses of various waveforms to limit neural adaptation
Define scan
- amplitude modulation (IFC)
- creates different patterns of amplitude
- prevents accommodation
Define sweep
- frequency modulation (IFC)
- creates different patterns of frequency
-prevents accommodation
Define burst mode
- a pulse train of individual patterns of waveforms, durations, and/or frequencies that are linked together
- repeat at regular intervals
Characteristics of small electrodes
- high density
- low current spread
- more selective & discriminatory=small muscles
Characteristics of large electrodes
- less density
- increased current spread
- low selectivity & discrimination=large muscles
Why is electrode placement important
- closer together electrodes are configured, the more superficial the current travels
- farther apart the electrodes are, the deeper the current travels
Indications for e-stim
- pain relief = TENS
- reduce edema = monophasic/NMES
- wound healing = monophasic
- decrease atrophy, increase strength & endurance = NMES, FES
- muscle reeducation = NMES, FES
- improve circulation = monophasic, NMES
- administer medication = monophasic
- stimulation of denervated muscle = monophasic
- fracture healing = monophasic, microcurrent
Contraindications for E-stim
- demand cardiac pacemaker or implanted defibrillator
- unstable arrhythmias (common is a-fib)
- placement of electrodes over carotid sinus
- areas where venous or arterial thrombosis or thrombophlebitis is present
- pregnancy: over or around the abdomen/low back
Precautions for E-stim
- cardiac disease
- patients with impaired mentation or in areas of impaired sensation
- malignant tumors
- areas of skin irritation or open wounds
- adverse events: burns, skill irritation, & pain
Basic set-up for E-stim
- position patient comfortably
- clean body area & electrodes with alcohol or soap & water
- shave or clip hair prior
- electrotherapy unit must be plugged into a ground fault interrupter (3 prong cord/outlet)
- make sure electrode leads are not tangled & inspect integrity
- make sure all dials are off/at zero
