Medium Frequency Currents IFT it is the medium frequency current in interferential therapy.It is used for significant physiological effects of medium frequency.
PROPERTIES
- Frequency ranges from 1 kHz to 100 kHz
- Longer wavelengths (>10 mm)
- Effects occur at deeper structures
- General effects:
◦MFC: blocks pain
◦LFC: nerve stimulation
- Sample modalities:
◦Electrical stimulators, Didynamics, Biofeedback,
Iontophoresis, TENS, IT
ELECTRIC PULSE
A unit of stimulating current
Otherwise known as a PHASE (current phase)
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)
CURRENT INTENSITY
- Rate of flow of electrons
- Usually expressed in AMPERES (milliamperes = mA)
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
- Waveforms with sudden rise in intensity are suitable for innervated muscle
- Waveforms with slowly rising intensity are best suited for denervated muscle
FREQUENCY
- Rate of change of an electrical pulse
- Expressed in HERTZ (Hz)
Therapeutic/Clinical Uses…
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
Helps maintain muscle integrity after surgery
Modulates and/or decreases pain
Decreases or eliminates soft tissue swelling,
inflammation, or restriction
TYPES OF MEDIUM-LOW FREQUENCY CURRENTS
1)Direct Currents
2)Alternating Currents
3)Pulsed Currents
Noted Characteristics…
QUANTITATIVE:
◦ Frequency (Hz)
◦ Pulse duration
QUALITATIVE:
◦ Number of PHASES
◦ Shape and symmetry of WAVEFORMS
Direct Current
Refers to a current passing continuously in the same direction (unidirectional current)
Direct Current (cont.)
Synonyms:
◦ Constant Current
◦ Galvanic Current / Galvanism
Galvanic stimulation is useful only for stimulating
denervated muscles
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)
2.Short duration IDC (Faradic-Type)
◦< 1 ms
◦For pain control and nerve stimulation (innervated)
Alternating Current
Defined as continuous or uninterrupted bidirectional flow of charged particles
Alternating Current (cont.)
2 Types:
1.Sinusoidal Current
◦Evenly alternating sine wave currents of 50 Hz
◦For pain relief, edema, and improvement of circulation
2.Didynamic 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
INTERFERENTIAL THERAPY (IFT)
Medium Frequency Currents
- Medium frequency currents are the currents which has a frequency falling between the range of 1000 to 10000Hz(1 kilohertz to 100 kilohertz)
- Used therapeutically due to their advantage over the low frequency current
- greater penetration,
- higher tolerance and
III. comfort
INTERFERENTIAL CURRENT
It is the application of alternating medium frequency currents to produce a low frequency effect for therapeutic purpose.
Low frequency stimulators have the problem of skin resistance and produce skin irritation(pain).
High frequency will not stimulate nerve because their pulse duration is less than 0.01msec., having thermal effect.
To overcome the skin resistance, two medium frequency currents are interfered to produce a low frequency effect.
PRINCIPLES OF IFT
Z= 1/2FC
Where Z – Impedance (Ohms)
F – Frequency (Hz)
C – Capacity of the skin (microfarads)
So the skin resistance reduces with increase in frequency.
PRINCIPLES OF IFT
PHYSIOLOGICAL EFFECT
The physiological effect on the tissues depends upon:
Frequency
Use of constant/swing frequency
Intensity of the current
Accuracy of electrode placement
Location of lesion
Tissue type and underlying pathology.
THERAPEUTIC EFFECTS
1)Effect on pain:
- “Analgesic effect of IC”
- Pain relief due to the following reasons:
- Effect on the pain gate (90-100Hz)
- Increased circulation (0-100Hz, 90-100Hz)
- Physiological block of nerve conduction (above 40 Hz).
Motor stimulation effect on weak nerve:
- Innervated muscles are stimulated
- Both skeletal and smooth muscles are stimulated, which is not possible with faradic currents.
- Very little sensory stimulation
- Helpful to stimulate deep muscles (pelvic muscles), rhythmic contraction.
2)Effect of edema:
◦Absorption of exudation is possible when using 1- 10 rhythmic and 1- 100 rhythmic.
◦Causing pumping action on the muscles
◦Increased blood supply
◦Removal of exudates, swelling and edema.
3)Effect on muscle spasm:
- Causes muscle relaxation by
- Increased vaso dilation
- Removal of pain stimuli
- Breaks the pain – spasm cycle.
4)Sympathetic dysfunction:
- Reflex sympathetic dystrophy,
- Shoulder hand syndrome,
- Neuralgia,
- Migraine of sympathetic cause and
- atrophy.
- (Vaso motor tone is increased due to sympathetic activity)
INDICATIONS/THERAPEUTIC USES:
Edema
Hematoma
Trigger point
Stress incontinence
Degenerative joint diseases
Muscle spasm
Venous & lymphatic drainage
Re-education of deeply situated muscles
Phantom pain
Inflammatory conditions
CONTRA INDICATION:
Arterial and venous diseases
Infective conditions
Pregnant uterus
Hemorrhage and menstruation.
Malignant tissues
Artificial pacemaker
Cardiac problems
Unreliable patient
Dermatological conditions
DANGERS
Electrical burns: due to bare metal electrodes, skin currents, increased intensity and interference by other modalities.
Hematoma
Increased pain
General malaise
Nausea
Vomiting
Dizziness and faintness
Neurological defects.
DOSIOMETRY (Dosage)
Dosage is divided into
- Low dosage- not felt by the patient
- Medium dosage – just a noticeable feel
- High dosage – experience and pleasant
- Very high dosage – strong vigorous and unpleasant.
Interferential therapy can be applied according to the following criteria:
- 10-20 minutes
- For 10 to 25 days
- once a day basis
Types of Electrodes :
Metal plate electrodes
Carbon rubber electrodes
Vacuum(suction) electrodes
- Metal plate electrodes:
Metal plate of variable size encased in a sponge/lint pad
Water socked / moistened with water before application
CONTINUATION…
- Carbon rubber electrodes:
- Variable shape (circular/ square) made of rubber
- Used with conducting gel
- Suction electrodes:
- Flexible rubber cups
- Electrode is kept at the base of cup and wire or lead is connected at narrow end.
- Tube connects to the pump of the machine
Continuation…
Generally a soaked sponge is kept just below the electrodes so as to achieve even contact to skin and hence better conduction
Advantage- of mild massage effect on the skin stimulate cutaneous sensory nerve endings causing vasodilation.
Disadvantage- can not be used if skin condition is poor (edema/ elderly patient)
TECHNIQUE OF APPLICATION
Preparation of the apparatus:
Checking the machine to ensure the knobs are at zero
Any break in the electrodes and wires
Preparation of the tray:
Pads/sponge
straps
Vaseline
Pillows and tools
Continuation…
Preparation of the patient:
- Explanation about the treatment
- Expose the part
- Check the contra indications
- Skin sensation testing for pricking using cotton and pin
- Wash the treatment part with saline to remove all grease/dirt.
TECHNIQUE OF APPLICATION
Positioning the patient
◦Comfortably with area to be treated adequately supported
Application:
◦Soak the pad/lint electrodes with 1% saline water
Methods of application:
- Quadripolar method
- Bipolar method
- Sterodynamic
- Labile method
TECHNIQUE OF APPLICATION
1.Quadripolar method:
Via 4 electrodes
- a) Static quadripolar:
The electrodes are placed diagonal to each other
The interference takes place in the middle and the clover pattern is static.
Continuation…
- b) Vector quadripolar (dynamic interference)
The electrodes are placed diagonal to each other
The interference takes place in the middle and the clover pattern rotate at angle of 45 degree.
2.Bi polar method:
- Pre modulated method
- Via using 2 electrodes
- Modulated inside the machine.
- 2 red or 2 black used.
3.Sterodynamic system:
- three pairs of electrodes are used
- Machine provides three outputs
- It reduces accommodation and provides three-
dimensional interferential field - Although, with the aid of the two-field interferential current technique, the site of stimulation can be displaced into the depth of the body and, with appropriate equipment, it is not possible to involve all areas of the body within the stimulating effect. All the areas located outside of the area demarcated, are not stimulated, unless the electrodes are repositioned. If, however, a third field is added to the two existing fields, the resulting field strength vector can “move out of” the area and pass along any spatial direction, that is, can “reach” any structure within the area to be treated (spatial stimulation = stereo stimulation.
4.Labile Method:
- Two labile electrodes are used for the treatment
purpose - Operator moves them during the treatment
Precautions:
Interferential apparatus must be kept at least 6meters distance away from shortwave diathermy apparatus
Otherwise circuit damage can occur or patient may experience a sudden surge of currents when the short wave diathermy machine is turned off
To avoid this a filter circuit can be used in interferential therapy machine
ADVANTAGE:
Does not produce any sensory and motor irritation
Metal is not contraindicated in interferential therapy
Useful in treating tissues at greater depth
Current is localized more effectively in specific areas
Assignment
Medium frequency currents
Introduction
Principles
Frequency
IFT
Introduction
Principle
Physiological effects
Therapeutic effects
Indications and contraindications
Dangers
Dosage and application
