Diadynamic Currents in Electrotherapy

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.