Therapeutic Currents

Different Wave Forms Wave form means Graphical representation of the direction, shape, amplitude, & pulse A pulse may contain either one or two phases It rise above or goes below the base line for some specific period of time Direct current/mono phasic current Have only single phase Current flow in unidirectional Flow in same direction towards positive or negative pole Alternating current/biphasic current Have two separate phases Current flow is bi directional Wave form may be symmetrical or asymmetrical

Wave form shape Could be of any type like sine, rectangular or triangular Depends on the capabilities of the generator

` Pulse amplitude Magnitude of current The peak current is the maximum amplitude of the current Maximum amplitude of pulse can be shown by tip of highest point of each phase

` Pulse frequency Number of pulses per second As frequency of wave form is increased the amplitude tends to increase & decrease more rapidly

` Pulse duration Length of time that current is flowing in one cycle

` Current Modulation Physiologic response to various wave forms mainly depend on current modulation Modulation refers to any alteration in the magnitude or any variation in the duration of the pulses Continuous modulation amplitude of the current remains the same for several seconds or minutes Interrupted modulation current flows for some period of time called on-time & periodically turned off during off time Burst modulation occurs when pulsed current flows for a short duration & in a repetitive cycle Ramping modulation also called surging modulation current increases gradually or decreases gradually in its intensity

Surging of current The intensity of each successive pulse gradually increases Each impulse reaches to higher intensity than that of preceding one After the peak levels either falls suddenly or gradually

Classification of Currents 555 Classification of Currents On the basis of direction of flow of current Alternating current: flow in both direction Direct current: flow in one direction b. On the basis of frequency Low frequency: range of 50 to 100 Hz e.g. IDC, Faradic, galvanic, sinusoidal, TENS Medium frequency: range of 100 to 4000 e.g. interferential currents High frequency currents: frequency more than 1MHz e.g. SWD, MWD, UST c. On the basis of voltage Low voltage currents: less than100 Volt High voltage currents: greater than 100 volt d. On the basis of amperage low amperage currents: 1 to30 mAmp e.g.- high TENS high amperage currents: 500 to2000 mAmp

Interrupted Direct Currents (Galvenic Current) Interruption is the most useful modification of direct current It makes the flow of current commence & cease at regular intervals Rise & fall of intensity may be sudden- rectangular gradual-trapezoidal, triangular, saw tooth Commonly used for stimulation of denervated muscles & electro diagnosis purpose Impulse duration & frequency can be adjusted Duration of 100ms commonly used Impulse duration ranges between 0.01 to 300 msec Frequency vary as per the pulse duration & interval selected e.g- pulse duration 100msec requires frequency of 30 per min

Shape of the pulsed waves Monophasic Rectangular pulses Trapezoidal pulses Triangular pulses Saw tooth pulses Biphasic: risk of skin damage is less with balanced pulses (chemical reactions taking place are reversed) Slow rising wave forms can be used because muscle has less ability to accommodate than nerves.

Rectangular pulses have sudden rise where as others like trapezoidal, triangular & was tooth have gradual rise The impulses in which current rises gradually are often termed “selective” A contraction of denervated muscle can often produced with an intensity of current that is sufficient to stimulate motor nerves because accommodation occurs

Selection of impulses Rectangular impulse is capable of producing muscle contraction but selective impulse is always satisfactory With rectangular impulses rise is sudden where as with trapezoidal it is slow, with triangular even slower & with saw tooth still slower A low intensity & gradual rise is often best for stimulation of denervated muscle as it brings about satisfactory contraction with less sensory stimulation than with rectangular impulses Proper selection of current leads to eliminate unwanted contraction of innervated muscles present in closes proximity In long standing denervation a muscle contraction may be obtained with a slowly rising current when there no longer response to rectangular impulse

Faradic Type Currents Short duration interrupted direct current Pulse duration 0.1-1 ms Frequency 50-100 Hz Produced by induction coil known as Faradic coil Used for stimulation of innervated muscles Each cycle consists of two unequal phases Low intensity long duration currents High intensity short duration currents Faradic coils are now being replaced by electronic stimulators They almost have same physiological effect, but differs in wave form

Modified Faradic Currents Faradic current can be interrupted at regular intervals to avoid fatigue of muscles For better result in treatment faradic current is surged to produce a near normal tetanic like contraction & relaxation of muscle The apparatus should have sufficient control to surge the current In original Faradic coils current was surged by hand but in modern stimulators an electronic an electronic device is used The circuit can be modified to give surges of various durations, frequencies & wave forms Various forms of surges are trapezoidal, triangular,, saw tooth etc.

Modern Faradic current Original Faradic current Modern Faradic current

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