MOTOR effects
- Muscle re-education
- Muscle strengthening
Sensory Effects
- Pain management
- Reducing muscle spasticity
Other effects
- Promote blood flow
- Facilitate wound & fracture healing
- reduce oedema
Voltage
difference in electric potential energy between two points in a circuit (measured in Volts)
Current
amount of electrical charge flowing through the circuit (measured in Amps)
Resistance
a material’s tendency to resist the flow of electrical charge
Pulse amplitude
strength of stimulus (mA or V)
Frequency
the number of pulses delivered per second (Hz)
Pulse duration/width
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
Sensory electrical stimulation methods
- Interferential Therapy (IFT)
- Portable Transcutaneous Electrical Nerve Stimulation (TENS) machines
Any electrical stimulation device will have 3 components:
- Power source
- Stimulator
- Electrodes and leads
General safety considerations
- 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.
Contraindications
- 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)
Safety Skin check
Sharp/blunt discrimination test using a toothpick, paperclip or sharp pen.
Effects of TENS
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).
TENs Application
- Test machine prior to a
ttaching to patient - Clean the area thoroughly
with alcowipes - Adhesive gel electrodes
TENS Parameters
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)
Tolerance to TENS
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.
