DPT 752

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DPT 752
2011-06-11 14:33:18
Physical Agents part

Second half info on electrical current
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  1. receptor proteins
    binding sites for neurotransmitters and neuromodulators
  2. channel proteins
    with certian conditions a pore is formed through the membrane to facilitate the movement of ions
  3. transport proteins
    bind and transfer substances through the membrane
  4. Resting state of the excitable cell membranes
    • readily permeable to potassium
    • slightly permeable to sodium
    • impermeable to a number of large negatively charged proteins and phosphates (anions)
  5. In the resting state
    • atp used to actively transport sodium and potassium across the membrane
    • sodium-potassium pump moves sodium ions out of the cell while moving potassium ions in
  6. Outside the cell
    Na+ is higher
  7. Inside the cell
    • K+ is higher
    • anions are higher
    • more negative than outside creating -60 to -90 mV charge
  8. threshold
    critical voltage level that triggers sodium and potassium channels to open
  9. Sodium Channels
    open rapidly
  10. Potassium channels
    open slowly
  11. Absolute refractory period
    while the nerve is depolarized, no additional APs can be created. (regardless of the intensity of the stimulus)
  12. Relative refractory period
    brief period of membrane hyperpolarization during which a greater stimulus than usual is required to produce another AP
  13. Accommodation
    situation in which if the stimulus is low enough the nerve cell will adapt to the stimulus and not fire.
  14. AP direction
    current causes AP direction to depolarize in both directions but the effect will only be felt on the end with the NT release.
  15. Electrical Current
    • flow of charged particles
    • noted as (I)
    • measured in Amperes (A)
  16. Charge
    • either +/-
    • noted as (Q)
    • measured in Coulombs (C)
  17. Polarity
    • property of having two oppositely charged conductors
    • + anode
    • - cathode
    • current flows from -to +
  18. Voltage
    • force capable of moving charge
    • aka the potential difference
    • noted as (V)
    • measured in volts (V)
  19. Resistance
    • property of a conductor to resist flow of current
    • noted as (R)
    • measured in Ohms (omega)
  20. Ohm's law
  21. Impedance
    • frequency-dependent opposition to current
    • noted as Z
    • measured in Ohms (omega)
    • in biological systems we can say it is a ratio of potential flow to actual flow
  22. E-stim Waveforms
    • direct current (DC)
    • alternating current (AC)
    • pulsed current or pulsatile current
    • interferential current
    • premodulated current
    • Russian protocol
  23. Direct Current (DC) - uses
    • iontophoresis
    • stimulating denervated muscle
    • facilitate wound healing
  24. Alternating Current (AC)
    • bi-directional flow of current
    • no pulse charge left in tissue
    • inverse relationship between cycle duration and frequency
  25. Pulsed Current
    • current delivered discontinuously
    • uni- or bi-directional
    • monophasic (like DC)
    • biphasic (like AC)
  26. Biphasic pulsed current
    • symmetric
    • asymmetric balanced
    • -charge of the phases are equal and opposite leaving zero net charge
    • asymmetric unbalanced
    • - charges are not equal leaving a net charge of some kind
  27. Interferential Current
    • two sine waves are overlapped causing a pulse or beat in the stimulus
    • slower of the two frequencies is called the carrier frequency
  28. Premodulated Current
    • waveform produced by one channel
    • same as if you were doing IF
    • continuous sine wave with medium frequency
    • uses sequentially increasing and decreasing amplitudes
  29. Russian protocol
    • 2500 Hz carrier frequency AC sine wave modulated to 50 bps
    • burst is a polyphasic waveform delivered for 10 ms followed by an interburst interval of 50 ms
  30. Time Dependent Parameters
    • Frequency
    • Pulse Duration/Phase Duration
    • Interpulse Interval
    • Interphase/Intrapulse Interval
    • Rise/Decay Time
    • On/Off Time
    • Duty Cycle
    • Ramp Up/Down Time
  31. Frequency
    • Cycles or pulses per second
    • noted in (Hz)
  32. Pulse duration/phase duration
    • beginning of first phase to the end of the last phase of a pulse
    • expressed in micro or milli- seconds
  33. Interpulse interval
    time between pulses
  34. Interphase interval
    time between phases of a pulse
  35. Rise/Decay time
    time it takes to increase from zero to peak or peak to zero during any one phase
  36. On/Off time
    • time during which a train of pulses occurs then the time between the trains of pulses
    • expressed often as a ratio
  37. Duty Cycle
    ratio of the on time to the total cycle time
  38. Ramp Up/Down Time
    • time it takes to increase from min to max amplitude and decrease from max to min amplitude
    • helps with tolerating treatment better
    • sometimes called "soft start"
  39. Other Current Parameters
    • Amplitude
    • Modulation
    • Frequency Modulation
    • Amplitude Modulation
    • Phase Duration Modulation
    • Burst Mode
  40. Amplitude
    • magnitude of current or voltage
    • not intensity
  41. Modulation
    Varying one or more of the stimulation patterns
  42. Frequency Modulation
    • variation in the number of pulses or cycles per second
    • aka - sweep
  43. Amplitude Modulation
    • variation in peak current amplitude
    • aka - scan
  44. Phase or Pulse Duration Modulation
    variation in pulse or phase duration
  45. Burst Mode
    series of pulses delivered in a package as a single pulse
  46. Rheobase
    minimum amplitude needed with a very long duration pulse to depolarize the cell.
  47. Chronaxie
    minimum duration pulse required to produce an AP at twice the rheobase
  48. Inducing current in excitable tissue
    • depends on inherent excitability
    • relative location with respect to the electrode the closer the better
  49. Sensory-level stimulation
    • low amplitudes
    • higher amplitudes = deeper sensations
  50. Adaptation
    • gradual diminution in the ability to sense the stimulation
    • occurs in sensory-level stimulation at frequencies >15pps for long periods of time
  51. Motor-level stimulation
    • normal voluntary contraction recruits the smalles motor units first.
    • e-stim recruits all at once
    • after motor threshold is reached, small increases in ampitude cause large increases in force of contraction
    • can be used to help strength gains and function
    • need long duration pulse to get denervated muscle >10ms
  52. Noxious-level Stimulation
    • high intensity that triggers A-delta and C fibers
    • level may vary in each patient
  53. Ionic effects of current
    • DC pulsed monophaisc and unbalanced biphasic waveforms leave a net charge in the tissue
    • cathode attracts positive ions
    • anode attracts negative ions
    • used in iontophoresis
  54. e-stim for pain
    • duration = 50-80 microseconds
    • frequency = 100-150 pps (high rate) 2-10 pps (low rate)
    • burst mode uses same theory as low rate TENS
    • Subsensory-level stimulation has little evidence
    • Electrode placement over the site of injury
  55. E-stim for pain: Contraindications
    • over or near medical stimulators
    • confused or uncooperative patients
    • damaged skin or subcutaneous tissues
    • skin with impaired sensation
    • malignancies
    • arterial or venous thrombus
    • anterior neck
    • carotid sinus
    • laryngeal or pharyngeal muscles
    • phrenic or vagus nerve
  56. E-stim for pain: precautions
    • pregnant women
    • across the head or through the chest
    • heart disease
    • HTN, Hypotension
    • diagnosed or suspected epilepsy
    • keep out of reach of children
    • while operating machinery or vehicles
  57. E-stim for muscle contraction: innervated muscle discomfort
    • subjects coping style
    • whether the stimulus causes a muscle contraction
    • whether the subject is judging intensity or unpleasantness of the stimulation

    greater force = greater discomfort
  58. E-stim to improve extremity function with stroke, SCI, or CP
    • pulse duration 200-300 microseconds
    • frequency 30 pps
    • on:off time 1:2
    • 20 min 5-6 days a week for 4 weeks
  59. E-stim for dorsiflexors
    • triggered by swing phase foot switch
    • pusle duration 300 microseconds
    • 40 pps
  60. E-stim for denervated muscles
    • longer pulse duration more than 10 ms
    • DC current is applied for a number of seconds
    • denervation is not improved by e-stim
  61. Patient positioning
    • dictated by:
    • -patient comfort and modesty
    • -area to be treated
    • -goals of the treatment
    • -deviced used
  62. Electrode placement: general
    • smooth against the skin
    • not over bony prominance
    • closer together more superficially the stimulus
    • for larger muscle groups use distal and proximal attachment
    • for single muscles attach pad to motor point (belly)
    • For pain pads should be at least an inch apart
    • For muscle contraction pads should be 2 inches apart
  63. electrode placement for pain
    • use inferential current
    • place over trigger point or accupuncture point
    • place pads proximal to area if point cannot be accessed directly
  64. Pad placement for edema
    • negative pole over area of inflammation and the dispersement electrode more proximal
    • for edema d/t lack of motion stimulate muscles around the deep veins
  65. Parameter Selection: pulse duration
    • muscle contraction: 150-350 microsecond
    • biphasic conventional TENS: 50-80 microsecons
    • low rate TENS: 100-200 microseconds
    • interferential curreent pulse durations: inversely proportional to carrier frequency
  66. Parameter selection: Frequency
    • determines response or muscle contraction
    • low frequency: less than 30 pps, motor nerves, separate twitch contraction
    • smooth tetanic contraction:35-50 pps, greater muscle strengthening but more rapid fatigue
    • Pain control: HR TENS 100-150 pps LR TENS less than 10pps
    • Edema control: 120 pps
  67. Parameter Selection: on/off time
    • pain control, wound care, acute edema, iontophoresis: continuous
    • muscle contractions: 1:5 ratio moving to 1:4 or 1:3
    • spasm relief or pump out edema: 1:1 2-5 seconds
  68. Parameter Selection: Ramp time
    • 1-4 seconds
    • may not need it for functional activity because you need stimulation immediately
  69. Parameter selection: Current amplitude
    • for strengthening: 50% of max voluntary control
    • for muscle reeducation: use sensory-level stimulation moving to contraction-level
    • for spasms: sufficient to produce a visible contraction
    • for pain control: HR TENS comfortable as possible LR and Burst TENS visible contraction
    • Edema: comfortable sensory level
  70. Parameter Selection: Treatment time
    • Muscle strength: 10-20 contractions or 10-20 minutes multiple times a day
    • muscle reeducation: no more than 20 min a session
    • pain control: HR TENS all day LR TENS 20-30 min every 2 hrs
    • edema: 30 minutes can be used more than once a day
  71. Documentation for E-stim
    • Area of body
    • Treatment duration
    • Patient position
    • Electrode placement
    • Treatment parameters
    • Response to treatment
  72. Iontophoresis: Drug Delivery
    • Electromigration
    • Electroporation
    • Electro-osmosis
  73. Acetic Acid
    • Calcific tendonitis
    • myositis ossificans

    believed to increase solubility of calcium deposits
  74. Calcium chloride
    Skeletal muscle spasms

    Ca stablizes excitable membranes
  75. Dexamethosone

    Steroidal anti-inflammatory agent
  76. Iodine
    Soft-tissue adhesions

    treatment not fully understood
  77. Lidocaine
    pain and inflammation

    local anesthetic
  78. magnesium sulfate
    muscle spasms

    decreased excitability of muscle membrane
  79. Hyaluronidase
    local edema (subacute and chronic)

    increases permeability in connective tissue
  80. Salicylates

    analgesic and antiinflammatory effects
  81. Zinc oxide
    dermatologic disorders

    general antiseptic
  82. Ionto current and amplitude
    • DC (usually)
    • 1.0-4.0 mA
  83. Alternative currents ionto: AC benefits
    • more predictable and less variable for getting drug into circulation
    • could use it for longer periods of time becoming more effective
    • less damaging to skin than equivalent application of DC
  84. Alternative currents ionto: HVDC
    • high volt >100 V for short time (few microseconds or milliseconds)
    • not much clinical evidence
  85. Current-Dosage for ionto
    • mA*min
    • 70-80 mA*min whenever possible to maximize effects
    • low current long duration is more effective than high current low duration
  86. Application principles for ionto
    • low concentrations of the drug
    • one drug at a time
    • do not use heating agents with ionto because it will limit the localized effect of the drug
  87. Procedure for application
    • allergies?
    • localize the electrode over the point of injur
    • skin depth may contribute to effectiveness of drug
    • do not use if the skin is damaged or broken
    • prep skin with alcohol wipe
    • connect electrodes and then ramp up the current
    • upon completion ramp down the current and remove electrodes
    • examine skin for signs that pt didn't tolerate treatment well
  88. indictations for use of ionto
    • Inflammation (Dexamethosone)
    • Treat pain (Lidocaine) be cautious not to burn the pt