Electrical Modalities

Question 1

purpose of electrical modalities

Answer 1

1. Provide sensory input to sensory receptors (a different stimulation to receive)
2. Excite a motor unit (make muscle work harder)

Question 2

Clinically Common types of electrical stimulation:

Answer 2

Iontophoresis
TENS
NMES

Question 3

current

Answer 3

Current: Flow or movement of ions or charged particles from one point to another in order to equalize the charge: often from positive to negative.

Question 4

DC Current: Direct Current

Answer 4

DC Current: Direct Current: unidirectional. Also called galvanic current. Used clinically to facilitate the ionization of medication through the skin (Iontophoresis)

Question 5

AC Current

Answer 5

AC Current: Alternating Current: Periodically changes the direction of flow. Clinically this could be interferential or Russian Stim

Question 6

PC Current: Pulsatile Current

Answer 6

Used in TENS, NMES, FES. Electron flow in one direction however is interrupted.
Symmetrical Biphasic – pulse is bi-directional. The two phases deviate equally from baseline – more comfortable
Asymetrical Biphasic – pulse is bi-directional. The two phases are not identical. Creates greatest nerve excitation under the negative electrode. Generally less comfortable but used when unable to elicit response with symmetrical.

Question 7

Voltage:

Answer 7

The pressure or force that moves the electrons. This is built into the device. Ie. Plug into wall or 9 volt battery.

Question 8

Amplitude

Answer 8

Intensity. This is the knob we turn up slowly on the device. Determines the magnitude of the response (sensory or motor). Most devices are measured in milliamps. mAmp (low volt devices)

Question 9

Resistance

Answer 9

Factors that prevent or reduce the ability of the current to pass through the tissue. (adipose, scar, dry skin, hair, not adequate medium). Effects comfort level of unit.

Question 10

Ohms Law

Answer 10

I = V/R Intensity (amplitude) = Voltage/ resistance

Question 11

Pulse Duration

Answer 11

the amount of time that a stimulus (pulse) is on. Measured in mili-seconds. Often called Width (although this really does NOT describe what we are talking about here). May be fixed on the unit to 200 – 400 m-sec.

Question 12

Pulse Frequency

Answer 12

Also called Rate: pulses delivered per second. Expressed as pps (pulse per second). Can also be expressed in Hz (Hertz) Effects 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 results in fatigue

Question 13

Ramp

Answer 13

Rise time: gradual build up or amount of time it takes to reach the amplitude. Slower ramp time provides increased comfort. Also affects spastic response, stretch reflex (Important for patients who may be guarding or who have tone issues).

Question 14

Fall time

Answer 14

amount of time it takes for current to return to off.

Question 15

Duty Cycle

Answer 15

On/Off Time – cycle of work vs. rest time. Effects fatigue of muscle. Recovery time needed to benefit from next contraction. Generally a 1:2 ratio is adequate. ie. 10 seconds on and 20 seconds off. => Ramp on 2 seconds, 6 second hold, ramp off 2 seconds (2+6+2 = 10 seconds on)

Question 16

Contraindications for Electromodalities:

Answer 16

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

Question 17

precautions

Answer 17

1. Polio, MS, Peripheral Vascular Disease
2. Seizure
3. Decrease sensation
4. Over bony area
5. Over excess adipose tissue/obesity
6. Over superficial metal implants
7. Skin irritation or wound
8. Use of machinery or sleep while unit on
9. Around microwave or cell phone use
10. Cognitive, esp when planning home use.