Electrotherapy Overview

1. Electrotherapy Overview Farley Brown Product Manager. Recovery Sciences/Chattanooga Line

2. Electrotherapy objectives • Introduction (historical) • Indications / Contraindications • Physiological response to current • Electrodes • Waveforms • Pain Management • Muscle strengthening (NMES) • Conclusion

3. Introduction • Cavemen rub amber fur and utilize charges. • •46 AD torpedo fish to treat Gout and Headaches. • •Late 1700’s- • Galvani stimulates frog muscle with electrical • charge of metal. • •Current practices?

4. Indications for Electrotherapy • Relatively short list of indications provides multiple dynamic treatment opportunities • –Pain control • –Enhance muscle recruitment • –Retard muscle atrophy • –Muscle strengthening • –Stimulate motor(re)learning • –Edema management • –Transdermal drug delivery

5. Contraindications for Electrotherapy • *Cardiac pacemaker • Cardioverter defibrillator • Over the carotid sinus/anterior transcervical area • Over heart transthoracic area • Over the abdominal, lowback and pelvic area during pregnancy • Areas of venous or arterial thrombosis • Thrombophlebitis • Neoplasm • Superficial metal (e.g. staples, pins, external fixators) • Patients prone to seizures • Transcerebral stimulation • Pain of unknown etiology

6. Concepts to understand • Electrical circuits involve 3 basic components : • Voltage • Current • Resistance

7. Ohm’s law • Current flow (intensity/amplitude) changes with changing resistance • Ohm’s law (I=V/R) governs relationship between intensity and resistance • Clinical implications

8. Current Flow • The rate of current flow depends on two factors; the force (voltage) driving the electrons and the amount of resistance offered by the conducting pathway defined as lead wires, electrodes and skin. V Ohm’s Law: Current (I) = Voltage Resistance R I Mains power or Batteries

9. Current • Flow of charged particles between electrodes • Current flow is measured in milli-Amperes (mA) • Neurons in path of current depolarize when critical threshold is reached

10. Current intensity ( increasing amplitude) • Increase the depth of penetration • Increase the number of neuroreceptors & depolarize both superficial and deep. • Amplitude should be adjusted to produce a desired physiologic response. • Physiologic response is the key, do not focus on the number of milliamps…………. • PATIENT TOLERANCE!!

11. Polarity • Difference in electrical charge between two sides of a membrane • Nerve cell: • Positiveoutside • Negativeinside

12. Depolarization • Polarity reverses temporarily • Positive inside • Negative outside

13. Action potential • Depolarization travels towards muscle and/or spine • Results in • Contraction • Sensation

14. Positive Vasoconstrictor Icing effects Greater analgesic effects than negative or alternating Indications Nerve root irritation Swelling Acute Trigger points Negative Vasodilator Heating effects Softens tissue such as scars, fibrotic tissue Enhances circulation Indications Adhesions Scars, Fibrotic tissue Chronic irritations Parenthesis Physiological response to current

15. CC or CV • Constant Current mode (CC) • Machine keeps intensity constant by changing voltage to compensate for changing resistance • Very constant stimulation. • Possible discomfort with small electrode. • Constant Voltage mode (CV) • Machine keeps voltage constant regardless of changing resistance. • Intensity level (and therapeutic effect) will fluctuate. • Ideal for dynamic, high intensity applications since risk of discomfort is low.

16. Review of Electrotherapy Currents

17. Pulsed Current • Pulsed current is an isolated unit of uni- or bi-directional movement of charged particles that periodically ceases for a finite period of time. • Pulsed current waveforms • Highvolt (monophasic) • Biphasic • VMS™ • Microcurrent

18. Alternating Current • Historically referred to as “Faradic Current” involves the continuous or uninterrupted bi-directional flow of charged particles. • AC Waveforms • Interferential • Premodulated • Russian

19. Direct Current (DC) • Direct Current: Historically refered to as “Galvanic Current” involves the continuous or uninterrupted flow of charged particles. • Clinical applications • Iontophoresis • Stimulating denervated muscle + 0 - Direct Current

20. Electrodes-

21. Electrode issues • Common reason that clinicians & patients get a negative impression of electrotherapy. • Considerations: • The correct size electrode for the job! • Identifying when the electrode is spent! • Firm fixation. • Keeping a complete inventory.

22. Electrode issues • Do’s & Don’t’s….. • –Have low impedance. • –Conduct current uniformly. • –Maintain uniform & constant contact. • –Not restrict movement. • –Not irritate skin.

23. Electrode skin interface • The skin is a resistor to the flow of current • Good skin preparation is important; always clean skin to remove dirt, oils, and dead skin • To lower impedance clean the skin (alcohol or soap) • Proper electrodes and conductive medium are essential !

24. Electrode Spacing issues • Electrodes should be placed so the flow of current can reach the target tissue. • The farther apart the deeper the penetration. • Placed too close the potential exists for greater concentration. • Superficially this can result in discomfort.

25. Choosing the appropriate electrodes Small electrode Large electrode Large electrode (ex: 4 x 5 inches) Decreases current density. Recruits more motor units More comfortable. Better for targeting larger areas. • (ex: 2 x 2 inches) • Increases current density • Recruits fewer motor units. • More “uncomfortable” • Better for targeting small areas.

26. Waveforms • Interferential • Premodulated • Russian • Biphasic • “VMS” • High Volt Pulsed current • Microcurrent • Direct current

27. Which waveform do I choose? • Concept: “the waveform is not the treatment” • We use waveforms to deliver a specific electrotherapy intervention (e.g. sensory level electro-analgesia) • Always choose treatment first then choose suitable waveform.

28. Interferential Current • Marketing made IFC very popular in Europe since 50’ies, in USA since 80’s. • High carrier frequency allows deeper and more comfortable penetration. • Low modulation frequency produces low frequency effect in targeted tissue.

29. Interferential Quad-Polar • Alternating Current • Amplitude modulated medium-frequency current (2,000-5,000 Hz) • Uses two channels of differing carrier frequencies to create a “beat” frequency within the tissues. • Scan -amplitude modulation • Sweep -frequency modulation

30. Interferential waveform

31. Interferencial clinical benefits • •Comfortable • •Targeting hard to reach tissues (e.g.-subscapularis) • •Indication: Pain modulation • –Acute pain • –Chronic pain • Acute or chronic pain

32. PremodulatedCurrent Beat Frequency: 100 Hz Premodulated Current – is simply taking two alternating medium frequency currents mixed within the electronics of the unit and delivered through two electrodes. Beat Frequency: 100 Hz

33. Premodulated clinical benefits • Comfortable • Simple two electrode setup • Easily applied to small joints of the upper extremity • Indication: Pain Modulation • Acute Pain • Chronic pain • Muscle Contraction

34. Russian Stimulation • Compared to other waveforms. • Tissue reacts to each burst as if it were a single pulse. • Muscle strengthening effects not better than pulsed current. • Stimulation not more comfortable, actually less comfortable at high intensities. • Literature support. • Muscle strengthening: Yes • Pain inhibition: good case report literature.

35. Biphasic. • Most frequently used waveform • When used for pain inhibition: TENS (Transcutaneous Electrical Nerve Stimulation) • When used for muscle strengthening: NMES (Neuromuscular Electrical Nerve Stimulation) • Versatility depends on pulse characteristics.

36. Biphasic current • Two phases per pulse • Symmetrical or asymmetrical • Balanced or unbalanced • Frequency 0-250Hz • Can be bursted • Different on:off ratios

37. Biphasic current-most versatile • Suitable for high intensity and/or long term applications • Abundance of equipment available • Literature support • Edema management: Yes • Stimulation of circulation: Yes • Muscle strengthening: Yes • Pain control: Yes

38. VMS™ “Excellent Versatility” • VMS™ a trademarked name of the Chattanooga Group • Variable Muscle Stimulation • Symmetrical Biphasic Square Waveforms with a 100 mSec interphase interval

39. High Volt • Monophasic, twin-peak • Pulsed: 1-200 pps • Pulse duration: 100μs • Voltage: 150-500V • Wound healing • Retardation of inflammation • Muscle strengthening • Pain control

40. Low Voltage • So, What is a Low Voltage Waveform?? • Short answer = any Waveform that is not high volt • “Low Volt” uses longer pulse durations, hence require less peak voltage (↓ 150 V)1 • Example: Biphasic current

41. Direct Current • First accounts of medical use of electrical currents go back hundreds of years. • Unidirectional nature provides electromotive force that can move electrically charged particles. • Primary use is iontophoresis. • Has polarizing effect on tissue….Skin damage may result if not dosed properly.

42. Direct current • Intensity very low • Cathode: negative • Anode: positive • Monophasic • Continuous or pulsed (interrupted)

43. Direct current • Iontophoresis: • Active electrode of same polarity as medications. • Dispersive electrode proximal to it and larger. • EMS (deinnervated muscle): • Equal size electrodes on either side of muscle belly. • Polarizing effect under electrodes.

44. Pain and types of : • Nociceptive – dull ache or pressure caused by injury or disease outside the nervous system (cancer or arthritis) • Neuropathic – burning or stabbing damage to nerve tissue (pinched nerve). • “Pain is the last thing to show but the first thing to go”!

45. The Mechanisms of pain There are 4 key steps in the transmission of pain: • Receptors stimulated and pain signals generated ,local release of Substance P, histamin and prostaglandins • Processing in the dorsal horn “computer” • Further processing in the Thalamus • Reaching primary sensory cortex – pain is perceived

46. Pain is conducted by two sensory nerve fibres: Aβ: Thick,myelinated fibers that produce fast sharp impulses. C-fibres: Thin unmyelinated fibers that produce dull, longer lasting impulses. PAIN!

47. Release of endogene opoid substances – β endorphins Stimulating the motor nerves (Aα) creates a muscular response (twitch). Activated with endorphinic or acupuncture-like stimulation at a low frequency (2-4 Hz).. Inhibited transmission of the nociceptive message By stimulating the thick myelinated sensory nervous fibres (Aβ), there is a release of opoid neuropeptides (dynorphin,enkephaline) at a segmental level. Pain relief systems ENDORPHINE RELEASE Low & Slow 2-4Hz High & fast 80-100Hz GATE CONTROL EFFECT

48. Gate Theory-Classic TENS • Melzak and Wall 1965 • Substantia Gelatinosa and T-cell (dorsal horn of SC) control nerve impulses to the brain. Only allow one impulse through at a time; like a gate. • A-delta afferents “fast pain” 4-30 m/s • C-fibers “slow pain” 0.5 -2 m/s • A-beta afferents “pleasant/fast” 36-72 m/s

49. Muscle Strengthening (NMES) • Two broad approaches using electrotherapy • Strengthening of static, postural strength • Slow twitch fibers • Enhance endurance • Improve joint stability • Strengthening of explosive strength • Fast twitch fibers • Increase speed of contraction • Increase bulk strength

50. Fiber types Type I (slow twitch) Type II (fast twitch