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Physical Agents > E-Stim for pain modulation > Flashcards

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

A

true

24
Q

Rheobase

A

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

25
Q

Chronaxie

A
  • The minimum duration it takes to stimulate that tissue at twice the rheobase amplitude
  • time/duration dependent
26
Q

Strength duration curve: all or none response

A

once threshold is achieved, nerve fiber fires

27
Q

Strength duration curve: accommodation

A

if stimulus is too slow, nerve can adjust threshold level

28
Q

Strength duration curve: propagation

A
  • 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
Q

Pain modulation: intensity

A

intensity controls peripheral nerve axon recruitment

30
Q

Threshold level stimulation

A
  • a current applied @ an intensity and duration just strong enough to reach threshold will excite only large superficial fibers in mixed nerve
31
Q

Increased current intensity

A
  • 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
Q

Transcutaneous Electrical Nerve Stimulation: Pain modulation

A
  • 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
Q

How do you control for adaptation

A
  • modulate rate

- modulate width

34
Q

Pain modulation: low rate or acupuncture like TENS

A
  • 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
Q

Pain modulation: noxious-intensity TENS

A
  • 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
Q

Pain modulation: burst mode TENS

A
  • 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
Q

TENS parameters: conventional high rate TENS

A
  • 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
Q

TENS parameters: acupuncture like low rate TENS

A
  • pulse frequency: 2-10 pps
  • pulse duration: 100-200 us
  • amplitude: to visible contraction
  • modulation: NONE
  • tx time: 20-30 mins
  • Endorphin release
39
Q

TENS parameters: Burst mode TENS

A
  • 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
Q

High frequency TENS studies

A
  • decrease in VAS for pain when compared to SHAM

- higher % improvement vs SHAM at 4 and 8 weeks (greatest at 4 weeks)

41
Q

Low frequency TENS studies

A
  • LF TENS had better short term response to pain relief vs SHAM
  • LF TENS decreased VAS more than SHAM
42
Q

TENS and chronic pain study

A
  • 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
Q

TENS and acute pain study

A

-HF TENS had decrease usage of meds but no difference in length of stay

44
Q

Dose response and TENS studies

A
  • 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
Q

Interferential current: physiological effects

A
  • Depolarize peripheral motor and sensory nerve
46
Q

Interferential current: therapeutic effects

A
  • Increase pain threshold
  • muscle contraction
  • muscle pumping
47
Q

Interferential current: peripheral nerve depolarization leads to..

A
  • 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
Q

Interferential current: therapeutic purposes

A
  • 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
Q

Interferential current: indications

A
  • pain of known origin

- possibly for muscle exercise to increase blood flow, muscle relaxation, and edema reduction

50
Q

High volt pulsed current

A
  • Twin-peaked, monophasic, pulsed current
  • driven by characteristically high EMF (current) from 150-500 volts
    • 150= high volt stimulator
51
Q

HVPC: twin peak monophasic pulse

A
  • pair of monophasic spike like waveforms
  • almost instantaneous rise followed by exponential decline
  • pulse duration- short
    • 100-200 usec
52
Q

HVPC: biophysical characteristics

A
  • 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
Q

HVPC: therapeutic purposes

A
  • 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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