Physiological and therapeutic uses of low frequency(F/G) currents

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Physiological and therapeutic uses of low frequency(F/G) currents

  1. 1. A.THANGAMANI RAMALINGAM PT, MSc (PSY), MIAP
  2. 2.  420B.C-hippocrates-in torpaedo fish  46A.D-scribonius largus-gout/headache  1700-luigi galvani & alessantro volta  1745-leyden jar for ES  1831-michael faraday  1850s-duchene-motor points(father of ES)  1909-rheo/chron-louis  1916-SD curve-Adrian  FES-1961-liberson  1962-HVPC-robert becker
  3. 3. Types of electrical stimulators Constant current stimulator Constant voltage stimulator  Less areamore currentburn  Less arealess currentsafety
  4. 4.  Transformers  Rectifiers  Filters  Regulators are used for pulse generation in circuits
  5. 5.  Cellular level  Tissue level  Segmental level  Systemic level
  6. 6.  Excitation of nerve cells  Changes in cell membrane permeability  Protein synthesis  Stimulation of fibrobloast, osteoblast  Modification of microcirculation
  7. 7.  Skeletal muscle contraction  Smooth muscle contraction  Tissue regeneration
  8. 8.  Modification of joint mobility  Muscle pumping action to change circulation and lymphatic activity  Alteration of the microvascular system not associated with muscle pumping  Increased movement of charged proteins into the lymphatic channels
  9. 9.  Transcutaneous electrical stimulation cannot directly stimulate lymph smooth muscle, or the autonomic nervous system without also stimulating a motor nerve
  10. 10.  Analgesic effects as endongenous 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 pain stimuli
  11. 11.  Electro chemical effect 2cl2 +H20 4HCl+O2 - under anode- coagulation/sclerosis 2Na +2H202NaoH +H2 -under cathode – sclerolytic/haemorrhage  Electro thermal effect- H α I2 R t  Electro physiological effect – RMPAPconduction
  12. 12.  Control acute & chronic pain  Reduce edema  Reduce & or inhibit muscle spasm  Reduce joint contractures  Minimize atrophy  Facilitate tissue healing  Facilitate muscle reeducation  Facilitate fracture healing  Strengthen muscle
  13. 13.  AC/DC  Short duration pulse  <1sec or micro sec  DC  Long duration pulse  >1sec  elicits a muscle contraction from de - nervated muscle, but the phase duration is so long that C fibers are also stimulated
  14. 14.  Two phases  PD: 1 ms  No polarity needed  Surged  Mild prickling sensation Freq:50 Hz PD: 1 ms
  15. 15.  Faradic is high frequency current(50-100Hz), where as galvanic is low frequency  single phase  PD: >1 ms  polarity needed  galvanic give stabing type of sensation
  16. 16.  Metal electrode  Rubber/silicon  Water bath  Adhesive  Needle  Probe electrode  Pad electrode
  17. 17. Unipolar method Bipolar method  Stabile  Labile  Nerve conduction method  Group stimulation method
  18. 18.  Current Density- - Refers To The Volume Of Current In The Tissues  Highest At Surface And Diminishes In Deeper Tissue
  19. 19.  Change The Spacing Of Electrodes  Moving Further Apart Increases Current Density In Deeper Tissues  Current density for any electrode/skin contact area should not exceed 2 mA rms/cm’
  20. 20.  washing the surface to remove some of the keratin and sebum and leaving the skin wet.  Warming the skin  If the adhesion of the electrode to the skin surface alters, or the pressure of sponge or pad decreases, this can lead to a higher resistance
  21. 21.  Sensory nerves: Marked prickling sensation longer duration  Motor nerves: Tetanizes, with a sequence of contraction followed by relaxation  NO chemical effects  Swelling: Absorption of exudate  Circulation: Superficial vasodilation via axon reflex (capillary vasodilation) hyperaemia
  22. 22.  Give as a group activity  Facilitate muscle contraction  Re-educate muscle action  Train new muscle action  Exercise for paralyzed muscles  Hypertrophy  Increase strength  Improve circulation  Prevent and loosen adhesions
  23. 23. For every substance, small doses stimulate, moderate doses inhibit, large doses kill.
  24. 24.  Recruitment order small->large  Fibre type slow->fast twitch  Central fatigue  Fatigue resistant motor units first  More force-more fatigue  Opp  Opp  Peripheral fatigue  Opp  high/low-no difference
  25. 25. Muscle Re-Education  Muscular inhibition after surgery or injury is primary indication  Patient feels the muscle contract, sees the muscle contract, and can attempt to duplicate this muscular response  Current intensity must be adequate for muscle contraction but comfortable  Pulse duration must be set as close as possible to the duration needed for chronaxie of the tissue to be stimulated  Pulses per second should be high enough to give a tetanic contraction (20 to 40 pps)  Interrupted or surged current must be used  High-voltage pulsed or medium- frequency alternating current may be most effective  On time should be 1 to 2 seconds  Off time should be 4 to 10 seconds  Total treatment time should be about 15 minutes, repeated several times daily  Next, patient should alternate voluntary muscle contractions with current-induced contractions
  26. 26. Muscle Pump Contractions  Used to duplicate the regular muscle contractions that help stimulate circulation by pumping fluid and blood through venous and lymphatic channels back to the heart  Can help in reestablishing proper circulatory pattern while keeping injured part protected  Current intensity must be high enough to provide a strong, comfortable muscle contraction  Pulse duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated if not preset  Pulses per second should be at beginning of tetany range (20 pps).  Interrupted or surged current must be used  On time should be 5 to 10 seconds.  Off time should be 5 to 10 seconds.  The part to be treated should be elevated  Total treatment time should be 20 to 30 minutesrepeated two to five times daily
  27. 27. Retardation of Atrophy  Electrical stimulation reproduces physical and chemical events associated with normal voluntary muscle contraction and helps to maintain normal muscle function  Current intensity should be as high as can be tolerated  Contraction should be capable of moving the limb through the antigravity range or of achieving 25% or more of the normal maximum voluntary isometric contraction (MVIC) torque for the muscle  Patient can be instructed to work with electrically induced contraction, but voluntary effort is not necessary  Total treatment time should be 15 to 20 minutes, or enough time to allow a minimum of 10 contractions  Treatment can be repeated two times daily  duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated  Pulses per second should be in the tetany range (20 to 85 pps)  Interrupted or surge type current should be used  Medium-frequency alternating current stimulator is the machine of choice  On time should be between 6 and 15 seconds  Off time should be at least one minute preferably two minutes.  Muscle should be given some resistance, either gravity or external resistance provided by the addition of weights or by fixing the joint so that the contraction becomes isometric
  28. 28. Muscle Strengthening  Current intensity should make muscle develop 60% of torque developed in a maximum voluntary isometric contraction (MVIC)  Pulse duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated  Muscle is given an isometric contraction torque equal to or greater than 25% of the MVIC torque  Patient instructed to work with the electrically induced contraction, but voluntary effort is not necessary  Total treatment should mimick normal active resistive training protocols of 3 sets of 10 contractions  Pulses per second should be in the tetany range (20 –85 pps)  Surged or interrupted current with a gradual ramp to peak intensity most effective  On time should be 10-15 seconds  Off time should be 50 seconds to 2 minutes  Medium-frequency alternating current stimulator is machine of choice
  29. 29. Increasing Range of Motion  Electrically stimulating a muscle contraction pulls joint through limited range  Continued contraction of muscle group over extended time appears to make contracted joint and muscle tissue modify and lengthen  Pulses per second should be at the beginning of the tetany range (20 to 30 pps)  Interrupted or surged current should be used  On time should be between 15 and 20 secs  Off time should be equal to or greater than on time, fatigue is a big consideration  High-voltage pulsed or medium- frequency alternating current stimulators are suggested  Current intensity must be of sufficient intensity and duration to make muscle contract strongly enough to move the body part through antigravity range  Pulse duration should be set as close as possible to the duration needed for chronaxie of the motor nerve to be stimulated  Stimulated muscle group should be antagonistic to joint contracture and patient should be positioned so joint will be moved to the limits of available range  Patient is passive in treatment and does not work with electrical contraction  Total treatment time should be 90 minutes daily broken into 3 x 30-minute treatments
  30. 30. Reducing Edema  Sensory level direct current used as a driving force to make charged plasma protein ions in interstitial spaces move in the direction of oppositely charged electrode  Distal electrode should be negative  Treatment should begin immediately after injury  Thirty minute treatment showed good control of volume for 4 to 5 hours  High voltage pulsed generators are effective, low voltage generators are not effective  Current intensity should be (30V-50V) or 10% less than needed to produce a visible muscle contraction  Preset short duration interrupted DC currents with high pulse frequencies (120 pps) on high voltage equipment are effective
  31. 31. Stimulating Denervated Muscle  Purpose for electrically stimulating denervated muscle is to help minimize the extent of atrophy while the nerve is regenerating  Degenerative changes progress until muscle is reinnervated by axons regenerating across site of lesion  If reinnervation does not occur within 2 years fibrous connective tissue replaces contractile elements and recovery of muscle function is not possible  Length of pulse should be as short as possible but long enough to elicit a contraction  Current waveform should have pulse duration = or > than chronaxie of denervated muscle  Amplitude of current along with pulse duration must be sufficient to stimulate a denervated muscle with a prolonged chronaxie while producing a moderately strong contraction of muscle fibers  Muscle fibers experience a decrease in size, diameter and weight of the individual muscle fibers  There is a decrease in amount of tension which can be generated and an increase in the time required for contraction  A current with an asymmetric, biphasic (faradic)waveform pulse duration < 1 ms may be used during the first 2 weeks  After 2 weeks, either an interrupted DC square wave or a progressive DC exponential wave with long pulse duration > 10 ms, or a AC sine wave with frequency < 10 Hz will produce a twitch contraction  Pause between stimuli should be 4 to 5 times longer (about 3-6 seconds) than stimulus duration to minimize fatigue  Either a monopolar or bipolar electrode setup can be used with small diameter active electrode placed over most electrically active point  Stimulation should begin immediately using 3 sets of 5 -20 repetitions 3 x per day
  32. 32. Basic Model of Electrotherapy
  33. 33. Denervated muscle stimulation  ES may disrupt regenerating NMJ  Trauma of the muscle  Time consuming  Three stimulation sessions/day three to five sets of 5-20 isometric contractions  5s –rest period/contraction  1m-rest period /set  pW >than chronoxie
  34. 34. Muscle Contractions 1 pps = twitch 10 pps = summation 25-30 pps = tetanus (most fibers will reach tetany by 50 pps) 50-100 micro sec –sensory stimulation 200-300 micro sec –motor stimulation
  35. 35. Frequency selection:  100Hz - pain relief  50-60 Hz = muscle contraction  1-50 Hz = increased circulation  The higher the frequency (Hz) the more quickly the muscle will fatigue  1-4 Hz-beta endorphin  40-100Hz-enkepalin,serotonin
  36. 36. Electrocution and dangers  Electric and earth shock  ELCB  BF/CF areas  Guidelines by Robertson et al(2001)  AC is more dangerous than DC(P=V*I)  The strongest stimulation is where the current exits the body
  37. 37. Unexpected effects of ES Over and above the normal physiological and psychological limits  Skin  Eyes  General symptoms  Cardio-resp  Neurological  Attitude  musculoskeletal
  38. 38. Risk Management  Risk grading-0,(1,2),3  Safety& maintenance( quality assurance)  Infection  Aversion  Children (guidelines)
  39. 39. Contraindication Other Low Frequency (e.g. muscule stim, diadynamics etc) Pregnancy (local) CI** SEE NOTE Local Circulatory Insufficiency PRECAUTION Pregnancy (general) Epilepsy CI NECK Malignancy LOCAL CI Devitalised Tissues PRECAUTION Specialised Tissues EYE, TESTIS Active Epiphysis LOCAL CI Active Implants (incl Pacemakers) CI TESTS Tissue Bleeding CI Thermal Skin Test Metal Implant Sharp/Blunt Skin Tests YES
  40. 40. Polarity With Continuous DC Current  Important Consideration When Using Iontophoresis  Positive Pole  Attracts - Ions  Acidic Reaction  Hardening of Tissues  Decreased Nerve Irritability  Negative Pole • Attracts + Ions • Alkaline Reaction • Softening of Tissues • Increased Nerve Irritability
  41. 41. Motor points

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