Electrotherapy Lec 2 PDF

Current modulation  Modulation refers to the ability of the electrical stimulation units being able to vary one or more of the electrical parameters over time  This prevents adaptation to the current  Adaptation decreases the effectiveness of electrical stimulation  Modulation is alteratio...

Current modulation  Modulation refers to the ability of the electrical stimulation units being able to vary one or more of the electrical parameters over time  This prevents adaptation to the current  Adaptation decreases the effectiveness of electrical stimulation  Modulation is alteration in the amplitude, duration, or frequency of the current during a series of pulses or cycles Burst modulation frequency modulation  With pulsatile currents, sets of pulses are combined. These combined pulses are bursts, packets, envelopes, or pulse trains.  The interruptions between individual bursts are called interburst intervals.  The time interval over which the series of pulses or cycles is delivered is called the burst duration.  The number of bursts delivered per unit of time is called the burst frequency.  Shape of the wave can differ. Ramping Modulation Amplitude modulation  Also called surging modulation, the current amplitude will increase or ramp up gradually to maximum then decrease or ramp down to zero.  Ramp-up time is ⅓ of the on-time.  Ramping modulation is used clinically to elicit muscle contraction and is generally considered a very comfortable type of current since it allows for a gradual increase in the intensity of a muscle contraction. (WITHOUT PAIN )  (Normal motor recruitment and smoother muscle contraction) Beat modulation  Beat modulation will be produced when two interfering alternating currents with different frequencies are delivered through separate channels within the same generator to create a beat frequency equal to the difference between the two alternating current frequencies.  Deep penetration is produced  The two pairs of electrodes are set up in a crisscrossed or cloverleaf-like pattern so that the circuits interfere.  Muscle responds to low-frequency current so we use the medium frequency current to stimulate the deep muscles. Current density Current density is the amount of current per unit area cm2 or mm2 Current density is highest where electrodes contact the skin and decreases as the electricity penetrates deeper tissues Factors affecting current density Spacing of electrodes As the interelectrode distance increases the depth of penetration increases Factors affecting current density Electrode size Current density is inversely proportional to electrode size The current density in a smaller electrode will be greater than that in a larger electrode Increasing the size of electrodes decreases density and decreases impedance (more comfortable than smaller electrodes)  Physiologic responses to electrical current Electrical currents are used mainly to produce either muscle contractions or pain relief through effects on the motor and sensory nerves Clinically, therapists use electrical currents for the following reasons To create muscle contraction through nerve or muscle stimulations To help in treating pain To stimulate or alter the healing process (Bactericidal effect) To drive ions beneficial to the healing process into or through the skin Physiologic responses to electrical current As electricity moves through the body, physiological effects of electrical stimulation occur through different levels Cellular level..this can be broken down into 5 major effects : 1. Excitation of nerve cells 2. Changes in cell membrane permeability 3. Protein synthesis (collgen-elastine-enzymes…. 4. Stimulation of fibroblast, osteoblast (tissue healing) 5. Modification of microcirculation (increased) Physiologic responses to electrical current Tissue level 1. Skeletal muscle contraction 2. Smooth Muscle contraction (urinary bladder control and pelvic floor ms ) 1. Tissue regeneration. (tissue healing)  Skeletal muscle contraction Voluntary (physiological )muscle Electrically produced muscle contraction contraction Motor unit Small diameter type I slow Large diameter type II fast(Glycolytic recruitment twitch(endurance) muscle fibers and oxidative) twitch muscle fibers are are first stimulated stimulated first because the axons of their motor units are larger and more superficial and offer lower resistance to electrical stimulation. Pattern of motor Random firing is highly energy The motor units that meet stimulus unit efficient ,delay the onset of fatigue threshold fire and continue to fire until and helps maintain smooth steady the electrical stimulus stops muscle tension Direction of The action potential moves away Bidirectional propagation orthodromic action potential from the nerve cell body in an and antidromic (action potential back propagation orthodromic direction toward the cell body from the stimulus site) Physiologic responses to electrical current Segmental level 1. Modification of joint mobility. 2. Muscle pumping action …..increases circulation and lymphatic activity. 3. Increased lymphatic contraction …..more fluid is moved centrally. Physiologic responses to electrical current Systematic effects 1. Release endogenous pain suppressors which act at different levels to control pain (indirect effect) 2. Gate control theory through stimulation of certain neurotransmitters to control neural activity in the presence of pain stimuli (direct effect)  Factors affecting the stimulation of nerves 1.The relative diameter of the nerve  The amplitude of the current is inversely proportional to the nerves diameter because the larger cross sectional area provides less capacitive membrane resistance and less current is required  Nerves with larger diameter are stimulated to threshold before nerves with smaller diameter  Sensory nerves are stimulated first followed by motor nerves and then pain fibers  The small C fibers carrying pain impulses need the greatest current Factors affecting the stimulation of nerves 2. The duration of the pulse  Short pulse duration allows the greatest range of stimulation intensity for excitation of nerves  A pulse duration of less than 1 msec will not be able to stimulate denervated muscle regardless of the current amplitude (In denervated muscle: a longer pulse duration is required to deliver a sufficient amount of electrical current to the muscle fibers and induce a contraction)  Pain fibers are stimulated with longer pulse duration and high intensity. Factors affecting the stimulation of nerves 3. The rate of rise of the pulse Rapidly rising pulses cause nerve depolarization and if the rate of rise is slow, the nerve accommodated to the stimulus Muscle fibers accommodate more slowly than nerve fibers, so gradual pulse rise may be used Factors affecting the stimulation of nerves 4. The depth of the nerves Superficial sensory nerves receive a greater amount of stimulation than deeply situated motor nerves  Indications Of Electrical Stimulation Facilitation of muscle contraction. Muscle re education. Strengthening muscles and preventing atrophy. Relief pain. Enhance wound healing. Improve circulation. Reducing edema.  General contraindications to electrical stimulation  Pacemaker or Defibrillator: Electrical stimulation can interfere with the functioning of these devices, potentially leading to serious complications  Pregnancy: The effects of electrical stimulation on a developing fetus are unknown, and it is generally avoided during pregnancy.  Active Infection: Electrical stimulation can worsen an active infection and delay healing.  Hemorrhage: Electrical stimulation can increase bleeding in areas where there is active bleeding or a risk of bleeding.  Malignancy: Electrical stimulation should be avoided in areas with known malignancy to prevent the spread of cancer cells.  Deep Vein Thrombosis (DVT): Electrical stimulation can displace blood clots, increasing the risk of pulmonary embolism.  Sensory Impairment: Individuals with sensory impairments may not be able to detect discomfort or pain from electrical stimulation, increasing the risk of tissue damage  Cognitive Impairment: Individuals with cognitive impairments may not be able to understand the instructions or cooperate with the treatment.  Metal Implants: Metal implants, such as joint replacements or pacemakers, can interfere with electrical stimulation and potentially cause discomfort or damage.  Over the eyes and the reproductive organs.  Over the anterior neck region (carotid sinus) :may result in disruption of normal respiration.  Epilepsy.  Types of electrodes 1. Metal Aluminum or foil plates enclosed within a wet sponge 2. Carbon rubber electrodes: should be enclosed in a wet sponge or use conducting gel 3. Pre gelled electrodes  Electrode Placement On or around the painful area Over specific dermatomes or myotomes that correspond to the painful area Close to the spinal cord segment that innervates a painful area Over sites where peripheral nerves that innervate the painful area become superficial and can be easily stimulated  Over superficial vascular structures Over-trigger or acupuncture point locations In a crisscross pattern surrounding the treatment area If treatment is not working, change the electrode placement  Techniques of electrode application Monopolar technique (direct) Use of the two electrodes 1.active or stimulation electrode placed over the treatment area 2.depressive or non-treatment electrode used to complete the circuit and placed at distant location The depressive electrode is larger than the active electrode The high current density focuses the electrical current under the smaller active electrode and little or no stimulation should occur under the depressive electrode Techniques of electrode application Bipolar technique Use of the two electrodes of equal size Both electrodes are placed over the treatment area Because current densities under each electrode are equal an equal amount of stimulation should occur under each electrode The electrodes should be placed over motor points within the same muscle or muscle group or may be placed at the origin and insertion of the same muscle Techniques of electrode application Quadripolar technique Use of two sets of electrodes each originating from its own channel It may be considered the concurrent application of two bipolar circuits This technique could be used in Agonist and antagonist placements as in neuromuscular stimulation (reciprocal pattern) Crossed pattern placements as in interferential current stimulation Coplanar placements for large flat area as the back