Interferential Current (IFC) (WEEK 10) Flashcards
IFC: how does it work/goal
electrical current delivered to the surface of the skin to stimulate nerves to fire (sensory, motor, nociceptors) to manage pain control
pain control**
IFC vs TENS: mechanism
IFC: transcutaneous application of two alternating media,-frequency electrical currents
TENS: one alternating current at a low frequency
IFC carrier frequency range
3000-5000Hz
IFC: Therapeutic Effects
main therapeutic benefit: PAIN MODULATION
pain modulation by
- pain gate mechanism
- DEOS
- endogenous opioid release at the level of the spinal cord
IFC: other therapeutic effects
- oedema control
- muscle retraining
IFC vs. TENS
- frequency
- comfort
- depth
- frequency
IFC: Medium
TENS: low - comfort
high frequency IFC is more comfortable - depth
IFC penetrates deeper into tissue and therefore can stimulate deeper nerves
IFC: depth
IFC uses 2 oscillating currents and when the currents and crossed and synchronized they superimpose on one another and we get summation of their amplitudes
- current travels from one electrode to another in an arched path, the further apart the electrodes the deeper the arc.
IFC: currents cancel out
If two oscillating currents are a half cycle out of sync then they cancel each other out completely - 100%
IFC: currents slightly out of sync
When two oscillating waves are slightly out of sync (5000Hz and 5100Hz), the resulting wave pattern is a series of “BEATS”
IFC: Beats
currents slightly out of sync
1. Perfect summation: every few beats circuit 1 and 2 are in sync and summate
- Perfect cancelation: every few beats circus 1 and 2 are half cycle out of sync and cancel out
- Partial summation or cancellation: majority of the time the beats partially summate or cancel
Beat frequency - what is it?
- beats per second, also known as amplitude modulated frequency (AMF)
- equal to the frequency difference between the two carrier frequency of oscillating waves. For example:
- Circuit 1: carrier frequency = 5100Hz
- Circuit 2: carrier frequency = 5000Hz
when circuit 1 and 2 cross we get beat frequency (AMF) of 100Hz
Beat frequency - significance
Amplitude of the beats has a stronger amplitude than the original currents
- stronger beat deep in tissue
- at the location where the currents cross, we get our beat frequency which is of a stronger intensity than the carrier frequency
IFC pattern
clover-leaf pattern of current
True IFC: how does this work?
- cross-fire arrangement of 4 electrodes to create 2 separate currents
- interference of two currents occurs within the tissue
- stimulation: superficial and deeper tissue
Pre-modulated ICF
- 2 currents are mixed within the machine so that the frequency is delivered by a single circuit
- no crossing and summation of currents within tissue, therefore we are not creating a stronger beat deeper in the tissue
- beat frequency pattern is delivered to the surface of the skin
Pre-modulated ICF: stimulation location
most of the nerve stimulation occurs directly under the electrodes as we do with tens but since we are using a medium frequency then it may be more comfortable than TENS
True vs. Pre-modulated ICF
- no difference own clinical outcome when it comes to stimulating sensory, motor, or pain thresholds
- True: more effective at targeting deeper tissues
- pre-mod: more comfortable
ICF vs. TENS: Beat frequency/AMF
when setting frequency we do not consider pulse width directly, rather we are setting the beat frequency
Beat frequency/AMF
- sensory
- motor
- pain
- sensory: 50-80Hz
- motor: <10Hz
- pain: >120Hz
Intensity:
- sensory
- motor
- pain
- sensory: comfortable
- motor: less comfortable
- pain: uncomfortable/painful
Proposed mechanism
- sensory: pain gate
- motor: DEOS, opioid release at SC
- pain: DEOS, opioid release at SCI
Onset/Duration of pain relief
- sensory: fast and short
- motor: slow and long
- pain: fast and long
Treatment times
- sensory: 15-20 mins
- motor: at least 30 mins to stimulate opioid release
- pain: depends on pt tolerance (15-30 mins)
AMF: frequency - beat relationship
- high beat frequency, we get shorter beats (shorter “pulse duration”)
- lower beat frequency, we get longer beats
- increase frequency, decrease pulse duration
AMF - strength duration curves
lower beat frequency would move us to the right of the graph (just as longer pulse duration would)
AMF parameter
changing AMF does not differentially stimulate different nerves and tissues
- change to pain threshold were similar with AMF settings 0-100Hz
- sensory threshold unaffected with varying AMF
- True IFC frequencies showed similar deep stimulation
- Similar + effects on pain when applying AMF frequency on Knee OA
AMF relevance
- behaviour in tissue is unpredictable because perhaps
- currents not crossing gat all
- no AMF is being created
True and pre-modulated ICF predicability
Pre-modulated: ICF highest voltage in line with one circuit
True ICF: lowest was in the middle of the 4 electrodes, highest was recorded outside (5cm) the electrodes
Comfort (Frequency)
- higher AMF setting (50-100Hz) more comfortable than low frequency (1-10Hz)
Modulation setting (sweep, modulated)
- decrease habituation/accomodation of the target nerve
- fluctuating AMF may reduce habituation of nerve due to repetitive stimuli
ICF and TENS: experimental pain
effective in treating various forms of experimental pain
- Mechanical pain
- Cold pain
- Heat pain
- Ischaemic pain
- Chemical pain
IFC: LBP
- effective for pain and disability in chronic LBP
IFC: OA
- reduced pain and increased function; better with exercise
- no significant additional effects over exercise alone
Adjunct treatment (acute/chronic LBP, frozen shoulder, knee OA)
- more effective than control at discharge
- more effect than placebo at 3 months follow up
IFC Alone (chronic LBP, knee OA, jaw pain)
not significantly better than placebo or therapies
