Interferential Current (IFC) (WEEK 10)

Question 1

IFC: how does it work/goal

Answer 1

electrical current delivered to the surface of the skin to stimulate nerves to fire (sensory, motor, nociceptors) to manage pain control

pain control**

Question 2

IFC vs TENS: mechanism

Answer 2

IFC: transcutaneous application of two alternating media,-frequency electrical currents

TENS: one alternating current at a low frequency

Question 3

IFC carrier frequency range

Answer 3

3000-5000Hz

Question 4

IFC: Therapeutic Effects

Answer 4

main therapeutic benefit: PAIN MODULATION

pain modulation by

1. pain gate mechanism
2. DEOS
3. endogenous opioid release at the level of the spinal cord

Question 5

IFC: other therapeutic effects

Answer 5

• oedema control

- muscle retraining

Question 6

IFC vs. TENS

• frequency
• comfort
• depth

Answer 6

• frequency
  IFC: Medium
  TENS: low
• comfort
  high frequency IFC is more comfortable
• depth
  IFC penetrates deeper into tissue and therefore can stimulate deeper nerves

Question 7

IFC: depth

Answer 7

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.

Question 8

IFC: currents cancel out

Answer 8

If two oscillating currents are a half cycle out of sync then they cancel each other out completely - 100%

Question 9

IFC: currents slightly out of sync

Answer 9

When two oscillating waves are slightly out of sync (5000Hz and 5100Hz), the resulting wave pattern is a series of “BEATS”

Question 10

IFC: Beats

Answer 10

currents slightly out of sync
1. Perfect summation: every few beats circuit 1 and 2 are in sync and summate

2. Perfect cancelation: every few beats circus 1 and 2 are half cycle out of sync and cancel out
3. Partial summation or cancellation: majority of the time the beats partially summate or cancel

Question 11

Beat frequency - what is it?

Answer 11

• 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

Question 12

Beat frequency - significance

Answer 12

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

Question 13

IFC pattern

Answer 13

clover-leaf pattern of current

Question 14

True IFC: how does this work?

Answer 14

• cross-fire arrangement of 4 electrodes to create 2 separate currents
• interference of two currents occurs within the tissue
• stimulation: superficial and deeper tissue

Question 15

Pre-modulated ICF

Answer 15

• 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

Question 16

Pre-modulated ICF: stimulation location

Answer 16

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

Question 17

True vs. Pre-modulated ICF

Answer 17

• 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

Question 18

ICF vs. TENS: Beat frequency/AMF

Answer 18

when setting frequency we do not consider pulse width directly, rather we are setting the beat frequency

Question 19

Beat frequency/AMF
- sensory

• motor
• pain

Answer 19

• sensory: 50-80Hz
• motor: <10Hz
• pain: >120Hz

Question 20

Intensity:
- sensory

• motor
• pain

Answer 20

• sensory: comfortable
• motor: less comfortable
• pain: uncomfortable/painful

Question 21

Proposed mechanism

Answer 21

• sensory: pain gate
• motor: DEOS, opioid release at SC
• pain: DEOS, opioid release at SCI

Question 22

Onset/Duration of pain relief

Answer 22

• sensory: fast and short
• motor: slow and long
• pain: fast and long

Question 23

Treatment times

Answer 23

• sensory: 15-20 mins
• motor: at least 30 mins to stimulate opioid release
• pain: depends on pt tolerance (15-30 mins)

Question 24

AMF: frequency - beat relationship

Answer 24

• high beat frequency, we get shorter beats (shorter “pulse duration”)
• lower beat frequency, we get longer beats
• increase frequency, decrease pulse duration

Question 25

AMF - strength duration curves

Answer 25

lower beat frequency would move us to the right of the graph (just as longer pulse duration would)

Question 26

AMF parameter

Answer 26

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

Question 27

AMF relevance

Answer 27

- behaviour in tissue is unpredictable because perhaps - currents not crossing gat all - no AMF is being created

Question 28

True and pre-modulated ICF predicability

Answer 28

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

Question 29

Comfort (Frequency)

Answer 29

- higher AMF setting (50-100Hz) more comfortable than low frequency (1-10Hz)

Question 30

Modulation setting (sweep, modulated)

Answer 30

- decrease habituation/accomodation of the target nerve | - fluctuating AMF may reduce habituation of nerve due to repetitive stimuli

Question 31

ICF and TENS: experimental pain

Answer 31

effective in treating various forms of experimental pain - Mechanical pain - Cold pain - Heat pain - Ischaemic pain - Chemical pain

Question 32

IFC: LBP

Answer 32

- effective for pain and disability in chronic LBP

Question 33

IFC: OA

Answer 33

- reduced pain and increased function; better with exercise | - no significant additional effects over exercise alone

Question 34

Adjunct treatment (acute/chronic LBP, frozen shoulder, knee OA)

Answer 34

- more effective than control at discharge | - more effect than placebo at 3 months follow up

Question 35

IFC Alone (chronic LBP, knee OA, jaw pain)

Answer 35

not significantly better than placebo or therapies