Lecture 9 - sensory electrical stimulation and therapeutic ultrasound Flashcards
Use of electrical stimulation
Motor:
- muscle re-educating
- muscle strengthening
Sensory:
- pain management
- reducing muscle spasticity
Other:
- promote blood flow
- facilitate wound and fracture healing
- reduce oedema
Voltage
difference in electrical potential energy between two points in a circuit (volts)
Current
amount of electrical charge flowing through the circuit (amps)
Resistance
a materials tendency to resist the flow of electrical charge
Types of currents
Direct currents (DC)
Pulsed currents
Alternating current
Electrical stimulation parameters
- pulse amplitude
- frequency
- pulse duration
Pulse amplitude
strength of stimulus (mA or V)
Frequency
the number of pulses delivered per second
Pulse duration/width
length of each electrical impulse (us or ms)
Selective stimulation of nerves fibres - order of stimulation
- non-noxious sensory
- Motor
- Noxious sensory
Sensory electrical stimulation methods/ 3 components
Interferential therapy (IFT) Portable transcutaneous electrical nerve stimulation (TENS) machine
components:
- power source
- stimulator
- electrodes and leads
Contraindications of electrical stimulation
- within 3m of operating shortwave diathermy (SWD)
- transthoracic application
- cardiac pacemaker
- pregnant
- inability to communicate
- sensory loss
Precautions of electrical stimulation
- broken skin
- metal implants
- circulatory insufficiency
- exacerbation of existing conditions
- risk of dissemination
Safety skin check
sharp/blunt discrimination test using pen
Portable TENS
portable, battery operated type of sensory electrical stimulation
- uses pulsed currents
Effects of TENS
Stimulating AB fibres - can reduce the transmission of nociceptive signals by activating inhibitory interneurons in dorsal horn
Stimulating AD fibres - reduce transmission of nociceptive signals through the release of endogenous opioids that inhibit C-fibres
TENS parameters
longer pulse durations stimulate AD fibres
High frequency (>50Hz) - pain gate mechanism
Low frequency (1-10Hz) - endogenous opioid mechanism
Treatment time
30 mins or more
Current intensity
- strong tingling but below motor threshold (high frequency TENS)
- At or above motor threshold (low frequency TENS)
Mode
B: burst stim
N: constant stim
M: modulation stim
Tolerance to TENS
Because the effects are opioid mediated, repeated use of TENS can produce tolerance to analgesic effects’
can be delayed by alternating between high frequency and low frequency
Interferential therapy (IFT)
application of two medium frequency (kHz) alternating currents (AC) by 2 pairs of electrodes to the surface of the skin, positioned diagonally opposed to each other
Two currents have slightly different frequency, and so “interfere” or intersect deep within the tissues
What is ultrasound?
- a type of mechanical vibration
- longitudinal waves made up of a series of mechanical compressions and rarefactions
- requires a medium to travel
ultrasound reflection
some of the energy is reflected back and the remainder is refracted
