1. Low Frequency and Medium Frequency Currents
Foundations in
Electro 2
Low Frequency and Medium Frequency Currents

2. OBJECTIVES
Review on the difference between high, medium, and low medium frequency currents and their therapeutic/clinical implications

3. OBJECTIVES
Be familiar with terms used in electrotherapy current modulations particularly with WAVEFORM, (electric) PULSE, FREQUENCY, CURRENT INTENSITY, PULSE DURATION

4. OBJECTIVES
Enumerate the characteristics of the three types of low/medium frequency currents
Formulate guidelines in the selection and/or prescription of the most appropriate (low/medium frequency current) electrical modality

5. OBJECTIVES
Describe the basic design features of electrical stimulators
Be familiar with the clinical importance of the design features of electrical stimulators

6. OBJECTIVES
Identify the common controls present on electrical stimulator units
Be familiar with the parameters regulated by each control present on the electrical stimulator units

7. A review on the differences…
High Frequency Currents
Medium Frequency Currents
Low Frequency Currents

8. HIGH FREQUENCY CURRENTS
Frequency is >6000 Hz
Short wavelengths (<10 mm)
Effects occur only at superficial structures
General effect = HEATING
Sample modalities:
US, MWD, SWD, IRR, UVR, LASER

9. MEDIUM and LOW FREQUENCY CURRENTS
Frequency ranges from 1 to 6000 Hz
Longer wavelengths (>10 mm)
Effects occur at deeper structures
General effects:
MFC: blocks pain
LFC: nerve stimulation

10. MEDIUM and LOW FREQUENCY CURRENTS
Sample modalities:
Electrical stimulators, Diadynamics, Biofeedback, Iontophoresis, TENS, IT

11. Definition of some relevant terms…
ELECTRIC PULSE
PULSE DURATION
CURRENT INTENSITY
WAVEFORM
FREQUENCY

12. ELECTRIC PULSE A unit of stimulating current
Otherwise known as a PHASE (current phase)

13. ELECTRIC PULSE
Can be more fully described according to DURATION (pulse duration expressed in seconds), INTENSITY (current intensity expressed in amperes or volts), and SHAPE (waveform)

14. PULSE DURATION
Amount of time needed for the rise and fall pattern to occur at a given pulse
Expressed in SECONDS (millisecond=ms)

15. CURRENT INTENSITY Rate of flow of electrons
Usually expressed in AMPERES (milliamperes = mA)

16. WAVEFORM Describes the rise-and-fall pattern of a pulse
The shape of the waveform reflects the time required for the current to reach the maximum intensity

17. WAVEFORM
Waveforms with sudden rise in intensity are suitable for innervated muscle
Waveforms with slowly rising intensity are best suited for denervated muscle

18. FREQUENCY Rate of change of an electrical pulse
Expressed in HERTZ (Hz)

19. Therapeutic/Clinical Uses…
MEDIUM and LOW FREQUENCY CURRENTS

20. MEDIUM and LOW FREQUENCY CURRENTS
Assists in functional training
Assists in muscle force generation and contraction
Decreases unwanted muscle activity
Increases rate of healing of open wounds and soft tissues

21. MEDIUM and LOW FREQUENCY CURRENTS
Helps maintain muscle integrity after surgery
Modulates and/or decreases pain
Decreases or eliminates soft tissue swelling, inflammation, or restriction

22. TYPES OF MEDIUM-LOW FREQUENCY CURRENTS
Direct Currents
Alternating Currents
Pulsed Currents

23. Noted Characteristics…
QUANTITATIVE:
Frequency (Hz)
Pulse duration

24. Noted Characteristics…
QUALITATIVE:
Number of PHASES
Shape and symmetry of WAVEFORMS
Other qualitative characteristics

25. Direct Current
Refers to a current passing continuously in the same direction (unidirectional current)

26. Direct Current (cont.)
Synonyms:
Constant Current
Galvanic Current / Galvanism
Galvanic stimulation is useful only for stimulating denervated muscles

27. Direct Current (cont.)
Interrupted Direct Current (IDC) is used to stimulate innervated muscles
Direct current is also used in IONTOPHORESIS

28. Direct Current (cont.)
2 Types of IDC:
Long Duration IDC
> 1 ms
For sensory and motor nerve stimulation (denervated)

29. Direct Current (cont.)
Short duration IDC (Faradic-Type)
< 1 ms
For pain control and nerve stimulation (innervated)

30. Direct Current (cont.)
Physiological effects:
Sensory stimulation
Hyperemia
Electrotonus
Relief of pain
Acceleration of healing
Tissue destruction

31. Alternating Current
Defined as continuous or uninterrupted bidirectional flow of charged particles

32. Alternating Current (cont.)
2 Types:
Sinusoidal Current
Evenly alternating sine wave currents of 50 Hz
For pain relief, edema, and improvement of circulation

33. Alternating Current (cont.)
Diadynamic Current
Rectified monophasic sinusoidal current
For pain relief, tissue healing, muscle re-education and improvement of circulation

34. Pulsed Current
Defined as the uni- or bi-directional flow of charged particles that periodically ceases for a finite period of time

35. Pulsed Current (cont.)
Types:
Symmetrical Biphasic
Balanced Asymmetrical Biphasic
Unbalanced Asymmetrical Biphasic
Monophasic

37. GUIDELINES…
Selecting, Prescribing, or Purchasing the MOST APPROPRIATE Electromodality

38. GUIDELINES… Determine your treatment goals
Note for the presence of contraindications
Determine the usual conditions of or problems presented by patients of the facility/area

39. GUIDELINES…
Consider the market availability of the modality and its cost
Consider the requirements for maintenance of the modality

40. BASIC DESIGN FEATURES and CONTROLS…
Electrical Stimulators

41. BASIC DESIGN FEATURES
Path from power source to the unit (plugs and cables)
Control knobs and/or buttons
Electrodes (with cables)
Alternative power source
Safety features

42. BASIC DESIGN FEATURES Controls or adjustment knobs/buttons for:
Frequency
Intensity
Mode (continuous or pulsed)
Pulse Duration and Intervals
Treatment Duration

43. Basic Electrode Systems
Malleable metal electrodes
Electrodes that conform to the body surfaces
Water Bath

44. Malleable Metal Electrodes
Made of tinplate or aluminum with pad of lint, cotton gauze or sponge at the end
Pad/gauze/sponge is wet with water before being applied to skin
Electrodes kept in place with bandages / straps

45. Malleable Metal Electrodes (cont.)
If unequal in size, the smaller electrode is active & most effects will occur here; the other electrode is the indifferent or dispersive electrode

46. Electrodes that Conforms to the Body Surface
Made of carbon-impregnated silicone rubber
Used with sponge pads or thin layer of conducting gel
Kept in place with strap or adhesive tape

47. Electrodes that Conforms to the Body Surface
Less efficient in passing current than metal electrodes
Has lower impedance than polymer electrodes

48. Water Bath
Used for hand, forearm, foot and leg which is placed between the electrodes
Provides a large area for the indifferent electrode & for applying muscle stimulating currents
Current density depends on location of electrodes

50. Methods of Electrode Placement
UNIPOLAR
BIPOLAR
QUARDRIPOLAR

51. Unipolar Motor Point Stimulation
One small active electrode & one large dispersive electrode
Site of stimulation: motor point for stronger response

52. Unipolar Motor Point Stimulation
Same amount of current passes thru each electrode
Smaller sized electrode has higher current density (stronger effect)

54. Unipolar Motor Point Stimulation (cont.)
Used for innervated and denervated muscles
Indications:
Peripheral nerve injuries
Tendon transplants

55. Unipolar Motor Point Stimulation (cont.)
Contraindications:
Cases wherein active motion is prohibited
Patients with pacemakers
Directly over superficial metal implants

56. Unipolar Motor Point Stimulation (cont.)
Contraindications:
Active bleeding over treatment site
Malignancies over treatment site

57. Unipolar Motor Point Stimulation (cont.)
Precautions:
Sensory loss over treatment site
Open wounds
Extreme edema

58. Bipolar Motor Point Stimulation
Equally sized electrodes
Effect of stimulation is dependent on electrode placement
Current density is equal in both electrodes
Effective for stimulating muscle groups or very large muscles

60. Bipolar Motor Point Stimulation (cont.)
Used for innervated and denervated muscles
Indications:
Peripheral nerve injuries
Inhibition of muscle activity due to joint pain and effusion

61. Bipolar Motor Point Stimulation (cont.)
Indications (cont.):
UMN lesions to decrease spasticity & facilitate active contraction
Disuse atrophy
Immobilization
Orthopedic & neurological cases with LOM

62. Bipolar Motor Point Stimulation (cont.)
Contraindications & Precautions:
Same as Unipolar application

63. Quadripolar Motor Point Stimulation
Electrodes from two or more circuits positioned so that currents geometrically intersect
Used for Interferential Stimulation Technique (MFC)

65. Quadripolar Motor Point Stimulation (cont.)
Indications:
Pain & muscle spasm
Edema
Hematoma
Chronic ligamentous lesions
Urinary stress incontinence

66. Quadripolar Motor Point Stimulation (cont.)
Contraindications & Precautions:
Same as Unipolar application

67. Break? or
Break?

68. Importance of Stimulation Parameters
The effect of electrical stimulation on the tissue will depend on the rate of change of the electrical pulse:
No change / Slow change in electric pulse
IONTOPHORESIS / DIRECT CURRENT

69. Importance of Stimulation Parameters (cont.)
Very fast change of rate
HIGH FREQUENCY CURRENTS
Rate of change between nos. 1 & 2
LOW & MEDIUM FREQUENCY CURRENTS

70. Importance of Stimulation Parameters (cont.)
The current intensity determines the extent of physiological changes
When stimulating a muscle at a constant frequency the only way to increase the force produced is to recruit more motor units by increasing the intensity of stimulation

71. Importance of Stimulation Parameters (cont.)
A single pulse is described by their:
Duration
Seconds / Milliseconds / Microseconds
Intensity
Milliamps / Volts
Shape
Illustrates the change of intensity with time

72. Importance of Stimulation Parameters (cont.)
The relationship between time and current intensity is the rate of change in current

73. Current used in Galvanic current and Iontophoresis

74. Current used for Nerve Stimulation

75. Current used for producing Single Nerve Impulse

76. Current used for TENS & Faradic Stimulators

77. Surged current producing Muscle Contraction

78. Current Flow in the Tissues
The quantity of current that flows in the tissues and the path it follows will depend on the impedance of that pathway
Generally, watery tissue such as blood, muscle and nerve has low ohmic resistance

79. Current Flow in the Tissues (cont.)
Bone and fat has higher ohmic resistance
The epidermis has the highest ohmic resistance, which is determined by:
Thickness & nature of skin
Inter-electrode distance

80. Current Flow in the Tissues (cont.)
This electrical resistance can be reduced by:
Washing & wetting the surface
Warming the skin

81. Skin Irritation as an Adverse Response
Skin irritation may be caused by:
Electrical reaction
Electrochemical response
Allergic response to electrodes, gel, or tape

82. Skin Irritation as an Adverse Response (cont.)
Skin irritation may be caused by:
Mechanical irritation caused by shearing forces between adhesive substances and the skin

83. Hazards in Electrotherapy
Chemical damage due to inadequate skin protection when direct or interrupted current is used
Disruption of stimulating devices due to proximity of diathermy output
Skin irritation
Electric shock

84. Contraindications to Electrical Stimulation
Strong muscle contraction might cause joint/muscle damage; detachment of thrombus; spread of infection; and hemorrhage
Stimulation of autonomic nerves might cause altered cardiac rhythm or other autonomic effects

85. Contraindications (cont.)
Currents might be unduly localized due to open wounds or skin lesions
Currents might provoke undesirable metabolic activity in neoplasms or in healed tuberculous infections

86. Contraindications (cont.)
Current is not evenly phasic, leading to possible skin damage or irritation, especially if there is loss of sensation

87. Principles of Application
Conduct general safety checks with respect to the equipment
Check the patient for contraindications
Explain the treatment fully to the patient

88. Principles of Application (cont.)
Collect the necessary equipment
ES, electrodes, wiring
Soap & water for cleaning the skin
Contact gel / sponge, tape / straps / Velcro

89. Principles of Application (cont.)
Position the patient in the comfortable position
The skin should be uncovered & examined for any contraindications to treatment
Test the equipment as appropriate; demonstrate the technique to the patient

90. Principles of Application (cont.)
Wash the skin over the region of electrode contact. Soaking the skin for 3-4 min either in a bath or with a warm, damp pad may reduce skin resistance
Select appropriate treatment parameters

91. Principles of Application (cont.)
Always turn all intensity dials to zero before beginning the treatment
Place the electrodes as appropriate for the treatment

92. Principles of Application (cont.)
Increase intensity until desired result is produced
Never lift the active electrode from the skin or replace it without turning the intensity to zero

93. Principles of Application (cont.)
Terminate the treatment; check the skin condition
Keep a full record of the treatment

94. THANK YOU!