Diadynamic Currents in Electrotherapy

Study Notes

Diadynamic Currents

Diadynamic currents are a variation of sinusoidal current, being monophasic sinusoidal with a duration of 10 ms.
They are half or full wave rectified sinusoidal currents.

Half Wave Rectification

Half wave rectification removes half of the sinusoidal oscillation, resulting in a series of pulses.
The current is no longer AC, but a series of pulses.

Full Wave Rectification

Full wave rectification involves reversing the polarity of one phase of sinusoidal AC current, resulting in current flowing in the same direction with each pulse.

Diadynamic Current Production

Diadynamic current is produced by rectifying mains frequency AC, which is sinusoidal and has a frequency of 50Hz in most countries.
The sine waves have a period or cycle duration of 1/50s, resulting in each pulse being 1/100s or 10ms.
The 'diadynamic' pulses are a series of 10ms half sine wave-shaped pulses with 10ms pulse intervals, resulting in a frequency of 50Hz.
Full wave diadynamic current is a continuous series of 10ms sinusoidal pulses, resulting in a frequency of 100Hz.

Characteristics and Effects

S-D graphs indicate that this type of current is likely to be quite uncomfortable, with a minimal increase in intensity changing the stimulation from being sensory to causing pain.
The high duty cycle (50% and 100%) of these long duration monophasic pulses will result in electrochemical changes and consequent irritation of the skin under and adjacent to the electrodes.
Sinusoid-like impulse currents have inhibitory or facilitation effects, depending on the frequency, intensity, and other parameters.
The current with a frequency of 100 Hz has a predominantly inhibitory effect, while the current with a frequency of 50 Hz acts rather dynamogenically, causing excitation, facilitation, and supporting muscle tone.

Types of Diadynamic Current

There are two main types of diadynamic currents, characterized by the different types of waveforms produced by the device.
Half-wave rectification (single phase or monophase fixe (MF)) produces a monophasic pulsed current with a pulse duration equal to the interpulse interval and a frequency equal to that of the original AC.
Full-wave rectification (double phase or diphase fixe (DF)) produces a monophasic pulsed current with no interpulse interval at twice the original AC frequency.

Classic Current Types

There are five classic current types: MF (monophase Fixe), DF (diphase Fixe), CP (Courtes Periodes), LP (Longues Periodes), and RS (Syncopal ryhthm).
MF: Half wave rectified alternating current with a frequency of 50 Hz, causing a strong vibration sensation, and used in treatment of pain without muscle spasm.
DF: Full wave rectified alternating current with a frequency of 100 Hz, causing a tickling sensation and muscle contraction, and used for initial treatment and has an analgesic effect.
CP: Rapid alternation between one second of MF current and one second of DF current, used to prevent accommodation and has an analgesic effect.
LP: Slow alternation between six seconds of MF current and six seconds of DF current, used to prevent accommodation and has an analgesic effect.
RS: Comprises one-second phase of MF current, followed by a one-second rest phase, used for muscle stimulation and testing excitability of the nerve.

Physiological Effects

Relief of pain due to direct and indirect mechanisms.
Direct mechanism: Stimulation of sensory nerves leading to pain relief through stimulation of pain gate mechanism.
Indirect mechanism: Improvement of circulation, reduction of inflammation, and release of endorphins.

Description

Test your knowledge of diadynamic currents, a variation of sinusoidal current used in electrotherapy. Learn about half wave and full wave rectification, and how they affect the current. Ideal for students and professionals in the field of physical therapy and rehabilitation.