OBJECTIVES
Review on the difference between high, medium, and low medium frequency currents and their therapeutic/clinical implications
OBJECTIVES
Be familiar with terms used in electrotherapy current modulations particularly with WAVEFORM, (electric) PULSE, FREQUENCY, CURRENT INTENSITY, PULSE DURATION
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
OBJECTIVES
Describe the basic design features of electrical stimulators
Be familiar with the clinical importance of the design features of electrical stimulators
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
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
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 painLFC: nerve stimulation
MEDIUM and LOW FREQUENCY CURRENTS
Sample modalities:Electrical stimulators, Diadynamics, Biofeedback, Iontophoresis, TENS, IT
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)
PULSE DURATION
Amount of time needed for the rise and fall pattern to occur at a given pulse
Expressed in SECONDS (millisecond=ms)
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
WAVEFORM
Waveforms with sudden rise in intensity are suitable for innervated muscle
Waveforms with slowly rising intensity are best suited for denervated muscle
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
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
Noted Characteristics…
QUALITATIVE:Number of PHASESShape and symmetry of WAVEFORMS
Other qualitative characteristics
Direct Current
Refers to a current passing continuously in the same direction (unidirectional current)
Direct Current (cont.)
Synonyms:Constant CurrentGalvanic Current / Galvanism
Galvanic stimulation is useful only for stimulating denervated muscles
Direct Current (cont.)
Interrupted Direct Current (IDC) is used to stimulate innervated muscles
Direct current is also used in IONTOPHORESIS
Direct Current (cont.)
2 Types of IDC:1. Long Duration IDC
> 1 ms For sensory and motor nerve
stimulation (denervated)
Direct Current (cont.)
2. Short duration IDC (Faradic-Type)
< 1 ms For pain control and nerve
stimulation (innervated)
Direct Current (cont.)
Physiological effects: Sensory stimulation Hyperemia Electrotonus Relief of pain Acceleration of healing Tissue destruction
Alternating Current (cont.)
2 Types:1. Sinusoidal Current
Evenly alternating sine wave currents of 50 Hz
For pain relief, edema, and improvement of circulation
Alternating Current (cont.)
2. Diadynamic Current Rectified monophasic
sinusoidal current For pain relief, tissue healing,
muscle re-education and improvement of circulation
Pulsed Current
Defined as the uni- or bi-directional flow of charged particles that periodically ceases for a finite period of time
Pulsed Current (cont.)
Types:1. Symmetrical Biphasic2. Balanced Asymmetrical
Biphasic3. Unbalanced Asymmetrical
Biphasic4. Monophasic
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
GUIDELINES…
Consider the market availability of the modality and its cost
Consider the requirements for maintenance of the modality
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
BASIC DESIGN FEATURES
Controls or adjustment knobs/buttons for:Frequency IntensityMode (continuous or pulsed)Pulse Duration and IntervalsTreatment Duration
Basic Electrode Systems
1. Malleable metal electrodes2. Electrodes that conform to
the body surfaces3. Water Bath
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
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
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
Electrodes that Conforms to the Body Surface
Less efficient in passing current than metal electrodes
Has lower impedance than polymer electrodes
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
Unipolar Motor Point Stimulation
One small active electrode & one large dispersive electrode
Site of stimulation: motor point for stronger response
Unipolar Motor Point Stimulation
Same amount of current passes thru each electrode
Smaller sized electrode has higher current density (stronger effect)
Unipolar Motor Point Stimulation (cont.)
Used for innervated and denervated muscles
Indications:Peripheral nerve injuriesTendon transplants
Unipolar Motor Point Stimulation (cont.)
Contraindications:Cases wherein active motion is prohibited
Patients with pacemakersDirectly over superficial metal implants
Unipolar Motor Point Stimulation (cont.)
Contraindications:Active bleeding over treatment site
Malignancies over treatment site
Unipolar Motor Point Stimulation (cont.)
Precautions:Sensory loss over treatment site
Open woundsExtreme edema
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
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
Bipolar Motor Point Stimulation (cont.)
Indications (cont.):UMN lesions to decrease spasticity & facilitate active contraction
Disuse atrophy ImmobilizationOrthopedic & neurological cases with LOM
Bipolar Motor Point Stimulation (cont.)
Contraindications & Precautions:Same as Unipolar application
Quadripolar Motor Point Stimulation
Electrodes from two or more circuits positioned so that currents geometrically intersect
Used for Interferential Stimulation Technique (MFC)
Quadripolar Motor Point Stimulation (cont.)
Indications:Pain & muscle spasmEdemaHematomaChronic ligamentous lesionsUrinary stress incontinence
Quadripolar Motor Point Stimulation (cont.)
Contraindications & Precautions:Same as Unipolar application
Importance of Stimulation Parameters
The effect of electrical stimulation on the tissue will depend on the rate of change of the electrical pulse:
1. No change / Slow change in electric pulse IONTOPHORESIS /
DIRECT CURRENT
Importance of Stimulation Parameters (cont.)
2. Very fast change of rate HIGH FREQUENCY
CURRENTS3. Rate of change between nos.
1 & 2 LOW & MEDIUM
FREQUENCY CURRENTS
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
Importance of Stimulation Parameters (cont.)
A single pulse is described by their:
1. Duration Seconds / Milliseconds /
Microseconds2. Intensity
Milliamps / Volts 3. Shape
Illustrates the change of intensity with time
Importance of Stimulation Parameters (cont.)
The relationship between time and current intensity is the rate of change in current
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
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 skinInter-electrode distance
Current Flow in the Tissues (cont.)
This electrical resistance can be reduced by:Washing & wetting the surfaceWarming the skin
Skin Irritation as an Adverse Response
Skin irritation may be caused by:Electrical reactionElectrochemical responseAllergic response to electrodes, gel, or tape
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
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
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
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
Contraindications (cont.)
Current is not evenly phasic, leading to possible skin damage or irritation, especially if there is loss of sensation
Principles of Application Conduct general safety checks
with respect to the equipment Check the patient for
contraindications Explain the treatment fully
to the patient
Principles of Application (cont.)
Collect the necessary equipmentES, electrodes, wiringSoap & water for cleaning the skin
Contact gel / sponge, tape / straps / Velcro
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
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
Principles of Application (cont.)
Always turn all intensity dials to zero before beginning the treatment
Place the electrodes as appropriate for the treatment
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
Principles of Application (cont.)
Terminate the treatment; check the skin condition
Keep a full record of the treatment