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About Waveforms

Parts of a Waveform

A waveform is the visual shape of a pulsed electrical current. It includes the following components:

Phase Duration: The time elapsed from the beginning to the termination of one phase of a pulse. Measured in microseconds (µsec.)

Pulse Duration: (Pulse Width) The time elapsed from the beginning to the end of all phases plus the interphase interval within one pulse. Measured in microseconds (µsec.)

Interphase Interval: (Intrapulse Interval) The time between two successive components of pulse when no electrical activity occurs. Measured in microseconds (µsec.)

Interpulse Interval: The time between two successive pulses.

Pulse Rate: The number of pulses per measure of time (one second). Also referred to as frequency. Measured in hertz (Hz).

Symmetrical Biphasic	Asymmetrical Biphasic

Most TENS units utilize an asymmetrical biphasic waveform. With biphasic waveforms there is not the problem of producing a net skin charge which could lead to possible burns.

Asymmetrical biphasic waveforms have two phases, an active phase and a balancing (usually passive) phase. In the active phase the positive going current travels through the positive electrode into the tissue, and during the balancing phase the current returns out the negative electrode. A mirror image of the waveform at the positive electrode occurs at the negative electrode.

Neurons depolarize more readily to negative current.

NERVE CELLS ARE POLARIZED; INSIDE IS NEGATIVE AND OUTSIDE IS POSITIVE.

Types of Waveforms

Type	Clinical Uses	Waveform
Monophasic Waveforms
Direct Current 4(DC) or Galvanic	Iontophoresis, wound healing, denervated tissue
Pulsed Galvanic or Interrupted DC	Edema reduction, wound healing, innervated muscle contraction
Biphasic Waveforms
Symmetrical AC	Pain suppression, innervated muscle contraction
Asymmetrical AC	Pain suppression, innervated muscle contraction
Triphasic Waveforms
Unbalanced Triphasic	Edema reduction, pain suppression