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E-Stim for pain modulation Flashcards

1
Q

Levels of physiologic response

A
  • Cellular
  • Tissue
  • Segmental
  • Systemic
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2
Q

Cellular level response

A
  • Excitation of excitable cell membranes
  • *Nerve
  • *Muscle
  • changes in cell membrane permeability
  • Protein synthesis
  • Stimulation in fibroblast, osteoblast
  • Modification of microcirculation
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3
Q

Tissue level response

A

Requires multiple cellular events

  • skeletal muscle contraction
  • smooth muscle contraction
  • tissue regeneration
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4
Q

Segmental level response

A

Regional effect of cellular and tissue levels

  • modification of joint mobility
  • Modification of muscle contractility
  • muscle pumping action to change circulation and lymphatic drainage
  • an alteration of microvasculature not associated with muscle pumping
  • increased movement of charged proteins into lymphatics resulting in fluid moving centrally
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5
Q

Systemic effects

A
  • Analgesic effects as endogenous pain suppressors are released and act at different levels to control pain
  • Analgesic effects from the stimulation of certain neurotransmitters to control neural activity in the presence of painful stimuli
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6
Q

Effects of electrical stimulation

A
  • Nerve depolarization
  • Muscle depolarization
  • ionic effects
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7
Q

Membrane structure

A
  • Phospholipid bilayer
  • Receptor proteins: binding site for NTs and neuromodulators
  • Channel proteins: form pores through the membrane for ion flow (Na+, K+, Ca+)
  • Transport proteins: bind and transport substances through the membrane
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8
Q

Membrane permeability

A
  • Easily permeable to K+
  • slightly permeable to Na+
  • Impermeable to large, negatively charged proteins and phosphates (anions)
  • large number of anions trapped inside the cell
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9
Q

Active transport across membrane

A
  • Na+/K+ pump
  • uses ATP for energy
  • moves Na+ out and K+ into the cell
  • Can move against EFM that tends to oppose their movement
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10
Q

Non-uniform distribution of ions

A
  • Na+ higher in fluid surrounding cell
  • K+ and anions higher inside cell
  • resultant electrical potential difference
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11
Q

Resting membrane potential

A
  • 90 mV for muscle
  • 70 mV for peripheral nerve
  • maintained via protein pump
  • -3 Na+ out 2 K+ in leads to (-) resting potential
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12
Q

Nerve depolarization: Action potential

A
  • Resting membrane potential
    • -70 mV for peripheral nerve
  • When stimulus sufficient in amplitude and duration, Na+ channels open rapidly and K+ channels open slowly
  • Allows for influx of Na+ rapidly while outflow of K+ is slower
  • Net result is change in membrane potential to +30 mV
  • when Vm reaches +30-+35 mV, permeability to Na+ decreases and Na+ channels close and K+ channels rapidly open increasing K+ permeability
  • K+ ions flow out of cell returning resting potential to -70 mV (repolarization)
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13
Q

Absolute refractory period

A

time after depolarization when nerve cell cannot be further excited

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14
Q

Speed of conduction

A
  • Depends upon diameter of nerve fiber and myelination of nerve fiber
  • large nerve fiber diamter= faster AP travels
    • A-Alpha motor nerves- 60-120 m/sec
    • A-gamma and A-delta: 12-30 m/sec
  • myelinated nerves=faster AP travels
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15
Q

Nodes of Ranvier

A

gaps in myelin sheath

-AP jumps from node to node in process called saltatory conduction

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16
Q

Peripheral nerve: motor

A
  • cell body: ventral horn or brainstem motor nuclei

- Axon: terminate on muscle ( A-alpha, A-gamma)

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17
Q

Peripheral nerve: sensory

A
  • Cell body: dorsal root ganglia or cranial nerve sensory nuclei
  • Axon: 50% end as free nerve endings, 50% as specialized sensory receptors
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18
Q

Peripheral nerve: composition

A
  • Axons of sensory, motor, and autonomic fibers
  • Schwann cells
    • produce myelin
    • insulate fibers from each other
  • CT
    • epineurium
    • perineurium
    • ednoneurium
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19
Q

Strength duration curve

A

graphic representation of minimum combo of current strength (amplitude) and pulse duration (frequency) needed to depolarize that nerve

  • lower current amplitudes and shorter pulse durations depolarize sensory nerves (A-beta, A-delta)
  • higher current amps and longer pulse durations depolarize motor nerves (A-alpha, A-gamma)
  • higher yet current amps and longer pulse durations depolarize pain transmitting C fibers
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20
Q

Strength duration curve: sub threshold

A

-Amplitude and duration below curve for particular nerve

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21
Q

Strength duration curve: threshold stimulation

A

amplitude and duration of curve

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22
Q

Strength duration curve: suprathreshold

A
  • amplitude and duration above curve
23
Q

True or false: peripheral nerve membrane is more excitable than muscle membrane

24
Q

Rheobase

A

minimum current amplitude with a very long pulse duration required to produce an AP
- current amplitude dependent

25
Chronaxie
- The minimum duration it takes to stimulate that tissue at twice the rheobase amplitude - time/duration dependent
26
Strength duration curve: all or none response
once threshold is achieved, nerve fiber fires
27
Strength duration curve: accommodation
if stimulus is too slow, nerve can adjust threshold level
28
Strength duration curve: propagation
- normal physiological stimulation- AP propagated one way only (orthodromic) - electrical stimulation: AP propagated both ways ( only those transmitted in usual way have effect) (antidromic)
29
Pain modulation: intensity
intensity controls peripheral nerve axon recruitment
30
Threshold level stimulation
- a current applied @ an intensity and duration just strong enough to reach threshold will excite only large superficial fibers in mixed nerve
31
Increased current intensity
- Increased current intensity now excites medium sized superficial fibers and deeper large sized fibers - further increasing current amp will now excite small, superficial, medium deeper and large deepest fibers
32
Transcutaneous Electrical Nerve Stimulation: Pain modulation
- Selective stimulation of A-beta fibers can block pain transmission in the spinal cord (gate control theory) - E-Stim transcutaneously (conventional) * * short pulse duration( 50-80 usec) * * pulse frequencies of 100-150 pps - Low current amp (tingling) - will block pain only while stim is on - may be used 24 hours per day
33
How do you control for adaptation
- modulate rate | - modulate width
34
Pain modulation: low rate or acupuncture like TENS
- Frequencies of 2-10 pps - longer pulse duration (100-200 usec) - higher current amplitude (visible contraction) - will control pain for 4-5 hours after a 20-30 min tx - half life of endogenous opiates is 4.5 hours - stimulates A-delta nociceptive and A-alpha fibers
35
Pain modulation: noxious-intensity TENS
- Short duration stim (<1 min) - can use low frequency (1-5 pps) - can use high frequency ( 80-110 pps) - pulse duration: up to 1 sec - amplitude: 2x motor threshold - stimulates A-delta and C fiber nociceptors as well as A-alpha and A-beta fibers - opioid-mediated and nonopioid-mediated analgesia - serotonin and noradrenaline mediated in cord - muscarinic mediated supraspinally
36
Pain modulation: burst mode TENS
- works like low frequency TENS - stim is delivered in bursts composed of a number of pulses each - stimulation delivered in bursts or packages of 10 pulses - pulse duration: 100-300 us
37
TENS parameters: conventional high rate TENS
- pulse frequency: 100-150 pps - pulse duration: 50-80 us - amplitude: to produce tingling - modulation: if available - tx time: may be worn 24 hours as needed for pain - gating at spinal cord
38
TENS parameters: acupuncture like low rate TENS
- pulse frequency: 2-10 pps - pulse duration: 100-200 us - amplitude: to visible contraction - modulation: NONE - tx time: 20-30 mins - Endorphin release
39
TENS parameters: Burst mode TENS
- pulse frequency: generally preset in unit @ 10 bursts - pulse duration: generally present and may have max of 100-300 us - amplitude: to visible contraction - modulation: not generally possible - tx time: 20-30 mins - endorphin release
40
High frequency TENS studies
- decrease in VAS for pain when compared to SHAM | - higher % improvement vs SHAM at 4 and 8 weeks (greatest at 4 weeks)
41
Low frequency TENS studies
- LF TENS had better short term response to pain relief vs SHAM - LF TENS decreased VAS more than SHAM
42
TENS and chronic pain study
- no difference with LF-TENS vs HF TENS vs SHAM TENS - likely due to multiple factors affecting chronic state of pain - led to discussion about reimbursement for TENS for chronic pain
43
TENS and acute pain study
-HF TENS had decrease usage of meds but no difference in length of stay
44
Dose response and TENS studies
- greatest relief with frequencies between 20-80 pps with sensory level TENS - modulated modes of TENS performed better vs constant frequency sensory level TENS
45
Interferential current: physiological effects
- Depolarize peripheral motor and sensory nerve
46
Interferential current: therapeutic effects
- Increase pain threshold - muscle contraction - muscle pumping
47
Interferential current: peripheral nerve depolarization leads to..
- sensory fibers gate closing * *pain management - evoked tetanic muscle contraction * * pelvic floor contraction which leads to urinary incontinence management * * muscle pumping which leads to blood flow/ edema management
48
Interferential current: therapeutic purposes
- 50-120 pps > pain management * * stimulating large diameter afferent neurons (ex A-beta fibers) - 20-50 pps > muscle contraction - 1 pps > acustim pain relief
49
Interferential current: indications
- pain of known origin | - possibly for muscle exercise to increase blood flow, muscle relaxation, and edema reduction
50
High volt pulsed current
- Twin-peaked, monophasic, pulsed current - driven by characteristically high EMF (current) from 150-500 volts * * 150= high volt stimulator
51
HVPC: twin peak monophasic pulse
- pair of monophasic spike like waveforms - almost instantaneous rise followed by exponential decline - pulse duration- short * * 100-200 usec
52
HVPC: biophysical characteristics
- HVPC pulses generally fixed by the manufacturer - some allow for adjustment of interspike interval - pulse frequency: 1-200 pps (pain of monophasic spike like waveforms) - versatility * * high volt output an monophasic pulsed waveform allows for; electic neve/muscle stim, and wound healing
53
HVPC: therapeutic purposes
- 80- 120 pps > sensory TENS pain managment * * stimulating large diameter afferent neurons * *activates spinal gate (A-beta) - 30-60 pps > muscle contraction - 2-4 pps> motor TENS pain relief * * activates endorphin descending loop ( C, a-delta fibers)

Physical Agents (21 decks)

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