Electrical Stimulation

Question 1

MOTOR effects

Answer 1

• Muscle re-education
• Muscle strengthening

Question 2

Sensory Effects

Answer 2

• Pain management
• Reducing muscle spasticity

Question 3

Other effects

Answer 3

• Promote blood flow
• Facilitate wound & fracture healing
• reduce oedema

Question 4

Voltage

Answer 4

difference in electric potential energy between two points in a circuit (measured in Volts)

Question 5

Current

Answer 5

amount of electrical charge flowing through the circuit (measured in Amps)

Question 6

Resistance

Answer 6

a material’s tendency to resist the flow of electrical charge

Question 7

Pulse amplitude

Answer 7

strength of stimulus (mA or V)

Question 8

Frequency

Answer 8

the number of pulses delivered per second (Hz)

Question 9

Pulse duration/width

Answer 9

length of each electrical pulse (μs or ms)
At short pulse durations, it is easier to selectively excite
sensory or motor nerves without eliciting pain

Question 10

Sensory electrical stimulation methods

Answer 10

• Interferential Therapy (IFT)
• Portable Transcutaneous Electrical Nerve Stimulation (TENS) machines

Question 11

Any electrical stimulation device will have 3 components:

Answer 11

1. Power source
2. Stimulator
3. Electrodes and leads

Question 12

General safety considerations

Answer 12

• Check machine on yourself first
• Any metal parts of electrode should NOT touch patient
• Careful with cuts & abrasions due to low skin impedance, which could cause large currents and lead to skin burns
• Patients should be positioned on non-metallic surfaces
  ▪ Ensure mains-operated equipment is electrically safe i.e. properly earthed & isolated
• Turn intensity down first when changing parameters (e.g. pulse rate)
• Use electrodes that are clean, moist and well secured.

Question 13

Contraindications

Answer 13

• Within 3 metres of operating shortwave diathermy (SWD)
• Transthoracic application
• Cardiac pacemaker or any other inbuilt stimulator
• Over pregnant uterus
• Inability to communicate
• Sensory loss - sharp/blunt discrimination skin test
• Broken skin
• Metal implants
• Circulatory insufficiency
• Exacerbation of existing conditions (e.g. acute infections, recent radiotherapy, etc)
• Risk of dissemination (e.g. acute infections, tumours, etc)

Question 14

Safety Skin check

Answer 14

Sharp/blunt discrimination test using a toothpick, paperclip or sharp pen.

Question 15

Effects of TENS

Answer 15

Stimulation of AB fibres using TENS can reduce the transmission of nociceptive signals through the release of endogenous opioids that inhibit c-fibres (conventionally associated with low-frequency TENS 1-10 Hz).

Question 16

TENs Application

Answer 16

• Test machine prior to a
  ttaching to patient
• Clean the area thoroughly
  with alcowipes
• Adhesive gel electrodes

Question 17

TENS Parameters

Answer 17

Pulse duration typically approx. 50 micro seconds
* Longer pulse durations (>200) stimulate Aδ fibres

High frequency: > 50 Hz (usually 80-150 Hz)
* Pain gate mechanism

Low frequency: 1-10 Hz
* Endogenous opioid mechanism

Treatment time – 30 min or more

Current intensity
* Strong tingling but below motor threshold
(high frequency TENS)
* At or above motor threshold
(low frequency TENS)

Question 18

Tolerance to TENS

Answer 18

Because the effects are opioid-mediated, repeated use of TENS can produce tolerance to analgesic effects.
* Tolerance can be delayed by alternating between high-frequency and low-frequency TENS.