LOW FREQUENCY CURRENT IN ELECTROTHERAPY

Electrotherapy

Definition: Application of electrical stimulation transmitted via electrodes for therapeutic physiological reactions in the body.

Effects of Electrotherapy

  • Stimulates nerve and/or muscle, leading to:

    • Pain relief and relaxation of spasms.

    • Increased local circulation.

    • Muscle contraction (preventing disuse atrophy and facilitating re-education).

Key Terminology

  • Electrical current: Net movement of electrons due to a potential difference.

  • Ampere: Unit of electrical current measurement.

  • Watts (W): Units of electrical power, calculated as Watts (W)=volts×amperes\text{Watts (W)} = \text{volts} \times \text{amperes}.

  • Cathode: The negative pole/electrode.

  • Anode: The positive pole/electrode.

  • Iontophoresis: Transfer of ions through the skin using constant Direct Current (DC).

Low Frequency Currents

Definition: Currents with a frequency range of 1-2000 Hz, capable of stimulating both sensory and motor nerves.

Types of Low Frequency Currents:

  1. Interrupted direct current (IDC)

  2. Sinusoidal current

  3. Faradic current

  4. Diadynamic current

Direct Current (DC) & Iontophoresis
Direct Current (DC)

  • Flows in one direction (unidirectional flow), also known as 'Galvanic' current.

  • Physiological Effects:

    • Cathode (negative): Alkaline reaction, marked hyperemia, higher risk of chemical burns.

    • Anode (positive): Weak acidic reaction.

    • Galvanism Effects: Hyperaemia (counter-irritant pain relief) and Sedation (low dosage, long duration).

Iontophoresis

  • Definition: Transfer of ionic drugs into the body using constant DC (Positive ions at anode; negative ions at cathode).

  • Indications (Examples): Pain relief, resolving Adhesions, reducing Calcium Deposits (Acetic acid), treating Idiopathic Hyperhidrosis.

  • Contra-indications: Open skin, infection, loss of sensation, circulatory disturbances, bony area.

  • Dangers: Shock, Chemical burns.

Interrupted Direct Current (IDC)

  • Flows intermittently in the same direction.

  • Surged IDC: Gradual increase and decrease in peak current intensity.

  • Long Duration Modular Pulsed Current (100-2000 ms pulse duration, 5-10 Hz):

    • Physiological Effect: Effective in stimulating denervated or partially denervated muscles.

    • Contra-indications: Oedema, active tuberculosis/cancer, cardiac pacemaker, thrombosis, superficial metal.

Sinusoidal Current

  • Evenly alternating low frequency current (typically 50 Hz, 10 ms pulse duration). Results in no net ion transfer.

  • Physiological Effects: Surged AC provokes muscle contractions. Unsurged A/C aids fluid absorption/vasodilation. Low risk of burns.

  • Indications: Pain, Pain & Swelling (via circulatory muscle pumping).

Diadynamic Currents

  • A variation of sinusoidal currents.

  • Types include: Fixed Diphase (DF), Fixed Monophase (MF), Short Periods (CP), Long Periods (LP), and Syncopal Rhythm (RS).

  • Physiological Effects: Primarily effective for pain relief (masking, elevating threshold), promoting Hyperaemia, and stimulating muscles (CP and LP).

  • Indications: Pain and oedema related to soft tissue injuries, joint disorders, and peripheral nerve disorders.

Faradic Current/Faradism

  • Faradic Current: Uneven alternating current (1 ms pulse duration, 50 Hz) that stimulates nerve fibers.

  • Faradic-Type Currents (Short Duration IDC): Surged currents (0.02-1 ms, 50-70 Hz) targeting muscles with intact nerve supply.

  • Physiological Effects: Stimulates nerves, resulting in a rapid, tetanic-like muscle contraction.

  • Indications: Facilitates muscle contraction inhibited by pain and muscle spasm, provided the nerve supply is intact.

  • Contra-indications: Skin lesions, infections, thrombosis, cardiac pacemaker, superficial metal.