Therapeutic Electric Current 2024 PDF

PT PAP 101 Application of Direct and Alternative current in Physiotherapy December 25, 2024 www.gmu.ac.ae COLLEGE OF ALLIED HEALTH Objectives On completion of this unit, the student will be abl...

PT PAP 101 Application of Direct and Alternative current in Physiotherapy December 25, 2024 www.gmu.ac.ae COLLEGE OF ALLIED HEALTH Objectives On completion of this unit, the student will be able to: Know to differentiate between direct and alternative current Know electric conduction properties of human body Correlate Ohm’s law in therapeutic current Know the ways to reduce skin resistance Therapeutic benefit of direct and alternative current Classification of electric currents  Concept of electrotherapy application Every living cell has a membrane potential (of about -70mV), with the inside of the cell being negative relative to its external surface. The cell membrane potential is strongly linked to the cell membrane transport mechanisms in that much of the material that passes across the membrane is ionic (charged particles), thus if the movement of charged particles changes, then it will influence the membrane potential. Conversely, if the membrane potential changes, it will influence the movement of ions. Different cells and tissues respond preferentially to different types of energy and at different ‘doses’ should be no surprise.  Electrotherapy application principle Firstly, one can deliver sufficient energy to overcome the energy of the membrane and thereby force it to change behaviour. Secondly, one can deliver much smaller energy levels, and instead of forcing the membrane to change behaviour, it can be ‘tickled’. Low energy membrane tickling produces membrane excitement, and membrane excitement in turn produces cellular excitement These processes are fundamental for the generation of graded and action potentials, sequence of changes in the voltage across a membrane  Sinusoidal current It is an alternating current with a frequency of 50 cycles per second (Hz) and a pulse duration of 10 ms It is called sinusoidal because the shape of the wave is sine wave ( S-shaped)  Effect of Sinusoidal current It is similar in its effects in almost every respect to the faradic current. However, it differs from the faradic current in that: 1. It has a more marked stimulation of sensory nerve endings in the skin → a more marked improvement of circulation both locally and generally. 2. Also, it is a more painful, because the time of stimulation is longer. Therapeutic effect of Direct Current Sensory changes mild tingling or prickling sensation which may merge into a mild irritation or itching sensation localized erythema (with prolonged stimulation) relief of pain Acceleration of healing Stimulate denervated nerve Tissue destruction – at higher current densities  Ohm’s law Current in any circuit is directly proportional to the Voltage and inversely to the resistance; thus, the intensity to be used also depends on the resistance encountered resistance here is from the epidermis. The larger the cross- sectional area the lesser the resistance.  Alternating Current It is a Bidirectional flow of electrons No true positive and negative poles Examples  Interferential stimulation  Premodulated currents Pain relief Neuromuscular stimulation.  Practical tips to decrease skin Resistance Decrease distance between electrodes (length) Increase the size of electrodes (cross section area) Minimize air-electrode interface Use electrodes jelly or moisten the electrodes Pre-warming the skin by moisten heat (i.e. hot packs)  Conductor Conductor is a substance that can transport electrical charge (orcurrent) from one point to another.  Higher conductance materials  Silver, Copper,  Electrolyte solutions  Blood cell: highest ionic & H20  Inner layer of the skin  Nerves  Muscle fibers  Cell membrane  Low conductance materials  Air, Wood, Glass, Rubber  Bone  Cartilage  Tendons  Ligaments  Outer layer of Skin has keratinizedepithelium (little H20) acts as insulator  Spinal pain modulation > 60-120Hz < 20Hz Individual twitch Supra-spinal pain modulation ≤ 20Hz  High Frequency Current [HFC] Mechanism of the HF currents action is based on transformation of the absorbed electric energy into heat Q according to Joule’s law: Q = U.I.t where U is voltage, t is the time of current I passage. This mechanism of heat production depends on the way of HF currents application.  Mechanism of Heat Production using HFC Capacitors are devices which are used to store electrical energy in a circuit. The energy supplied to the capacitor is stored in the form of an electric field which is created between the plates of a capacitor. When the voltage is applied across a capacitor, a certain amount of charge accumulates on the plates. Induction field: The strength of a magnetic field is determined by the amount of current flowing through the conductor which produced the magnetic field. The larger the current, the stronger the magnetic field. Eddy currents are currents that circulate in conductors like swirling eddies in a stream (a whirlpool). They are generated by changing magnetic fields and flow in closed loops perpendicular to the magnetic field plane to produce in heat in tissue or metal  Summary Low frequency currents are used for stimulation of muscles and nerves. Medium frequency currents are used for re-education of deeply situated muscles, pain relief and for drainage of edema. [A pulse fre 100hz, duration range of 100–200 µs may activate large-diameter fibers] High frequency currents are used for the production of deep heat inside the tissues.