Electrical Modalities Background/Terminology Flashcards
2 Purposes of Electrical Modalities
1) Provide sensory input to sensory receptors (a different stimulation to receive)
2) Excite a motor unit (make muscles work harder)
Flow or movement of ions or charged particles from one point to another in order to equalize the charge: often from + to -
Current
Used clinically to facilitate the ionization of medication through the skin (iontophoresis)
DC - Direct Current (unidirectional) also called galvanic current.
Periodically changes the direction of flow
AC- Alternating current. Clinically this could be interferential or Russian Stim
Used in TENS, NEMS, FES. Electron flow in one direction however it is interrupted.
PC- Pulsatile Current
PC Current which the two phases deviate equally from the baseline
Symmetrical Biphasic- pulse is bi-directional (more comfortable)
PC Current which the two phases are not identical. Creates greatest nerve excitation under the negative electrode
Asymmetrical Biphasic- pulse is bi-direction (less comfortable) it is used when unable to elicit a response with symmetrical.
The pressure or force that moves the electrons
Voltage (this is built into the device)
Determines the magnitude of the response
Amplitude- Intensity. This is the knob we turn up slowly on the device. Most are measures in millamps (mAmp)
Factors that prevent or reduce the ability of the current to pass through the tissue
Resistance: (adipose, scar, dry skin, hair, not adequate medium) effect the comfort level of the unit.
Ohms Law
I = V/R Intensity (amplitude) = Voltage/Resistance
The amount of time that a stimulus (pulse) is on
Pulse Duration - Measured in mili-seconds. (often called width) May be fixed on the unit to 200-400 m-sec.
Pulses delivered per second: Expressed as pps (pulse per second) Can also be expressedin Hz (Hertz)
Pulse Frequency also called rate: Effects the rate of fatigue
1-25 pps
may get twitch generally used for increased blood flow or sensory input .
30 pps and up
Need at least 30 for tetanic contraction
50 pps and up
For much larger muscles - generally relates in fatigue
Gradual build up or amount of time it takes to reach the amplitude.
Ramp-Rise time.
Slower ramp time provides increased comfort.
Also affects spastic response, stretch reflex (important for pts. who may be guarding or who have tone issues)
Amount of time it takes for current to return to off
Fall time
Cycle of work vs. rest time
Duty Cycle- On/Off Time.
Effects the fatigue of muscles. Recover time needed to benefit from next contraction.
Adequate Ratio for a duty cycle
1: 2 ratio.
i. e. 10 seconds on and 20 off, -> ramp on 2 seconds, 6 second hold, ramp of f2 seconds
7 Contraindication for electromodalities
1) Demand Pacemaker
2) Over Carotid Artery/Anterior neck triangle
3) Trans-cerebral electrode placement - seizures
4) Undiagnosed pain- unknown etiology
5) Over pregnant uterus
6) Infection (except when used in wound healing)
7) Cancer
10 Precautions for electromodalities
1) Polio, MS, Peripheral Vascular Disease
2) Seizure
3) Decrease Sensation
4) Over bony area
5) Over excess adipose tissue/obesity
6) Over superfical metal implants
7) Skin irritation or wounds
8) Use of machinery or sleep while unit on
9) Around microwave or cell phone use
10) Cognitive, esp. when planning home use