Electro Physical Agents, Part 2, 2022 PDF

Electro Physical Agents, Part 2, 2022 Table of contents No Topics Page 1. Introduction to Electrophysical agents 2 2. Basic Principles of Ele...

Electro Physical Agents, Part 2, 2022 Table of contents No Topics Page 1. Introduction to Electrophysical agents 2 2. Basic Principles of Electrical Stimulation 3 3. Pain Management 7 4. Neuromuscular Electrical Stimulation 34 5. Transcutaneous Electrical Nerve Stimulation (TENS) 47 6. Iontophoresis & interrupted direct current 56 7. High voltage pulsed current & Microcurrent therapy 67 8. Diadynamic Current 76 9. Functional electrical stimulation (FES) 81 10. Medium frequency Currents (Interferential current) 92 11. Medium frequency Currents (Russian, Aussie ) 99 12. Rebox current 103 Basic Science Department, Faculty of Physical therapy, SVU Page 1  Electro Physical Agents, Part 2, 2022 Introduction to Electrophysical agents In physical therapy practice, different terms were used to describe the methods or modalities used for patient management. Therapeutic modalities and physical agents are commonly used to describe a wide range of treatments and interventions that provide a variety of therapeutic benefits. The term physical agents represent the use of physical energies such as thermal, mechanical, electromagnetic, or light but it doesn’t declare the purpose of their usage. The term therapeutic modalities, however, is more appropriately indicates the ability of these interventions to provide therapeutic benefits. A very critical issue when using electrophysical agents and other therapeutic modalities is to identify and establish agreement for: - Optimal doses - Treatment procedure. This is the same when a physician or pharmacists are dealing with drug prescriptions or surgical interventions. In 2014, the American Physical Therapy Association (APTA) started recommending use of the term “biophysical agents” or Electrophysical Agents (EPA) instead of electrotherapy to collectively refer to physical agents and modalities used in physical therapy. Here, in this part we summarized the basic principles of electrical stimulation and types of therapeutic currents used in physical therapy. We dedicate this work to all the colleagues and students with whom we have worked and from whom we have learned so much. Basic Science Department, Faculty of Physical therapy, SVU Page 2  Electro Physical Agents, Part 2, 2022 Basic Principles of Electrical Stimulation: Electricity is a result of the continuous movement of free charged particles (electrons) in a circuit. The unit of electric current (I) is Ampere and measured by ammeter Types of electricity 1. Static electricity: When the charges on a body do not flow 2. Current electricity: Electric current is produced when there is a flow of charged particles in a conductor. Current will flow under two conditions: (1) When there is a source of energy creating a difference in electrical potential (2) When there is a conducting pathway between the two potentials. Great references are present in the library of faculty of physical therapy, SVU Calling for you. Basic Science Department, Faculty of Physical therapy, SVU Page 3  Electro Physical Agents, Part 2, 2022 Electricity is the force created by an imbalance in the number of electrons at two points Negative pole an area of high electron concentration (Cathode) Positive pole and area of low electron concentration (Anode) Electricity is most often described by its strength (charge), rate of flow (current), driving force (voltage), and opposition (resistance/impedance). Types of electric currents: 1. Direct current (DC): is uninterrupted and unidirectional flow of charged particles with duration of at least 1 second. Because one electrode is always positive and one is always negative, there is an accumulation of charge. This accumulation of charge is called chemical or polarity effect. USES: Iontophoresis 2. Alternating current (AC): is an interrupted and bidirectional flow of charged particles changing direction at least once a second. USES: Interferential current 3. Pulsed or pulsatile current can take on the directionality characteristics of AC or DC current. It is the unidirectional (like DC) or bidirectional (like AC) flow of charged particles periodically ceasing for less than 1 second (milliseconds or microseconds) before the next electrical event. USES Russain, interrupted DC, faradic, burst TENS Charge is the basic property of electromagnetic force and by which living cells communicate with one another. Measured in coulombs (C) Four basic properties of electrical charge explain how charge is used for therapeutic purposes: 1. There are two types of charge—positive and negative. Basic Science Department, Faculty of Physical therapy, SVU Page 4  Electro Physical Agents, Part 2, 2022 2. Like charges repel while opposites attract. 3. Charge is neither created nor destroyed. 4. Charge can be transferred from one object to another. Charge is also described by its polarity, where polarity referring to the net charge of an object (negative or positive). 1. The pole or electrode with net negativity is termed the cathode 2. The pole or electrode with net positivity is the anode. Types of current A, Direct, B, alternating and C, pulsed. Direct Current Direct current is the continuous unidirectional flow of ions or electrons for at least 1 second1 Basic Science Department, Faculty of Physical therapy, SVU Page 5  Electro Physical Agents, Part 2, 2022 Iontophoresis uses direct current to move ions. Negatively charged ions placed under the cathode will be “pushed” or repelled into the tissue. Direct current (DC) comes in many forms, conventional DC (top) being the most common Alternating Current In contrast to DC, alternating current (AC) is the uninterrupted bidirectional flow of ions or electrons and must change direction at least one time per second. The rate at which AC switches direction is termed frequency and is described with the international unit hertz (Hz) or in the unit cycles per second. Alternating current (AC) as a sinusoidal waveform Basic Science Department, Faculty of Physical therapy, SVU Page 6  Electro Physical Agents, Part 2, 2022 Mono- and biphasic current. For monophasic pulses, phase and pulse are synonymous. Biphasic pulses have phases that deviate from the isoelectric line in different directions. (A represents the interpulse interval.) Describing Pulsed Current: The Bottom Line When describing pulsed current, three basic characteristics need to be specified: The waveform type and shape (e.g., symmetrical biphasic square) The pulse frequency (e.g., 50 Hz) The pulse duration (e.g., 400 sec) Amplitude and time (duration) characteristics of pulsed current Basic Science Department, Faculty of Physical therapy, SVU Page 7  Electro Physical Agents, Part 2, 2022 Voltage The force of attraction or repulsion created by an electric field represents potential energy. The greater the force is, the greater the potential energy. This force is termed voltage and represents the driving force that moves electrons. The unit of electrical force is the volt (or millivolt). Conductors and Insulators Materials in which ions or electrons move freely are termed conductors. Metals and water are examples of conductors. In the human body, tissues such as muscle, nerve, and bodily fluid serve as conductors. In part, this reflects the high water content and presence of ions in these tissues. Basic Science Department, Faculty of Physical therapy, SVU Page 8  Electro Physical Agents, Part 2, 2022 Materials in which charged particles are not free to move or do not move easily are termed insulators. Rubber and plastic are typical materials considered to be insulators. Classification of waveforms and key parameters Ohm’s Law: Resistance, Capacitance, and Impedance Current is the free or unresisted flow of ions or electrons in a conductor in response to an applied voltage. The magnitude of current flow is directly proportional to the voltage force and quantity of charge moving. Resistance is opposition to the flow of current and comes in many forms in the body. Basic Science Department, Faculty of Physical therapy, SVU Page 9  Electro Physical Agents, Part 2, 2022 The relationship between resistance and the flow of current is given in Ohm’s law: I = V/R, where current (I in amperes) is directly proportional to the voltage force (V) pushing the current and inversely proportional to resistance (R) to the voltage force.2 The standard international unit of resistance is the ohm. From a more clinical view, Ohm’s law means that the more resistance to the flow of current, the lesser the current that flows in the tissue. Ohm’s Law Factors affecting resistance: 1. Material composition. High water content decreases impedance and improves conductance. Bone, fat, tendons, and fascia are also poor conductors with low water contents of 20% to 30%. The intracellular components of nerve and muscle have high water contents of 70% to 75%, but their membranes have a high capacitive reactance that opposes charge movement. 2. Length (greater length yields greater resistance) 3. Cross sectional area of the path. The greater cross sectional area of the path, the less resistance to current flow. 4. Temperature. Skin resistance is inversely proportional to its temperature. Heat increases moisture and surface salt content, which promotes conductivity. 5. Impedance changes in the presence of injury and disease. It increases with edema, ischemia, atherosclerosis, scarring, and denervation. It decreases in open wounds and abrasions. Basic Science Department, Faculty of Physical therapy, SVU Page 10  Electro Physical Agents, Part 2, 2022 Wave Form: It is a spatial drawing depicting the shape of the pulse, reflecting amplitude (strength) and duration (length of time) of the pulse. The symmetrical biphasic waveform is cited as most comfortable waveform. Asymmetrical balanced biphasic may be a better choice with small muscles. Monophasic and symmetrical biphasic waveforms were found to generate muscle contractions with greater torque than polyphasic waveforms and they were also less fatiguing. Different wave form shapes Basic Science Department, Faculty of Physical therapy, SVU Page 11  Electro Physical Agents, Part 2, 2022 Amplitude: It is the magnitude or intensity of the stimulus and it is one factor determining strength of stimulation High Volt: greater than 100-150 V but Low Volt: less than 100-150 V Peak amplitude is associated with depth of current penetration. Higher peak amplitudes penetrate deeper into tissue. N.B. Peak amplitude is measured in current (milliamperes or microamperes) or voltage (volts) A. Peak amplitude and B. peak to peak amplitude C, Rise time and D, decay time Basic Science Department, Faculty of Physical therapy, SVU Page 12  Electro Physical Agents, Part 2, 2022 Phase / pulse duration: Phase charge Phase charge is the amount of electrical energy delivered to the tissue with each phase of each pulse which can be measured in micro coulombs per second (μC/sec). Phase charge and pulse charge Interpulse interval: Period of time without current flow between two successive pulses Basic Science Department, Faculty of Physical therapy, SVU Page 13  Electro Physical Agents, Part 2, 2022 Interpulse interval and interburst interval Types of currents according to number of phases Total current: Peak amplitude, pulse frequency, and phase duration are all directly proportional to total current. Basic Science Department, Faculty of Physical therapy, SVU Page 14  Electro Physical Agents, Part 2, 2022 Different current parameters Frequency: number of pulses /second and measured by HZ Frequency Total current and its relation to current parameters Basic Science Department, Faculty of Physical therapy, SVU Page 15  Electro Physical Agents, Part 2, 2022 The strength duration curve (SDC), Membrane excitability: There are three criteria for depolarization: the stimulus must be strong enough (amplitude), long enough (duration), and fast enough (rise time). If the duration of the stimulus that is applied is infinitely long, which is defined as 300 milliseconds, the minimum current amplitude that will produce excitation is called Rheobase. If the rheobase intensity is doubled, the amount of time (pulse duration) that current must flow to achieve excitation is called Chronaxie. If one gradually decreases the stimulus duration below 300 milliseconds and records the minimum intensity of stimulation required to generate a threshold response, a curve can be plotted representing the tissue’s excitability, which is the strength duration curve (SDC) Chronaxie and Rheobase Basic Science Department, Faculty of Physical therapy, SVU Page 16  Electro Physical Agents, Part 2, 2022 Strength-duration curve: Points A and B represent two combinations of stimulus amplitude and duration capable of eliciting a motor response. The stimulus point C is incapable of eliciting a response, as the pulse duration is too short despite the greater intensity Levels of response to electrical stimulation Subsensory No nerve fiber activation No sensory awareness Sensory Non noxious paresthesias Tingling, prickling, or pins and needles Cutaneous A-beta nerve fiber activation Motor Strong paresthesias Muscle contraction A-alpha nerve fiber activation Noxious Strong, uncomfortable paresthesias Strong muscle contraction Sharp or burning pain sensation A-delta and C fiber activation Accommodation: There are conditions under which a nerve cell will not generate an action potential even in the presence of what would normally be considered a threshold stimulus. These conditions include subthreshold depolarization of the nerve prior to delivery of a threshold stimulus or presenting the nerve with a stimulus that has a slowly rising intensity (slow rise time). These Basic Science Department, Faculty of Physical therapy, SVU Page 17  Electro Physical Agents, Part 2, 2022 situations raise the threshold of the nerve cell so that it now takes a supra- threshold (extremely high) stimulus to elicit an action potential. This property is called accommodation, which is unique to nerve cells. The ability of muscle cells to accommodate is minimal. In addition to meeting certain minimal excitation requirements of the nerve, the current must reach its maximum intensity rapidly in order to avoid the effects of accommodation; otherwise, the stimulus will be ineffective in generating an action potential. Levels of stimulations Current Modulation: Modulation is alteration in the current parameters in order to reduce or minimize accommodation. 1. Amplitude modulations: Variations in the peak amplitude of a series of pulses. 2. Pulse or phase duration modulations: Regular changes in the time over which each pulse in a series acts. 3. Frequency modulations: consist of cyclic variations in the number of pulses applied per unit time. 4. Surged (ramped) modulations: are characterized by an increase (ramp up) or decrease (ramp down) of pulse amplitude, pulse duration, or both over time. Basic Science Department, Faculty of Physical therapy, SVU Page 18  Electro Physical Agents, Part 2, 2022 Types of current modulation Burst modulation: The generation of two or more consecutive pulses separated from the next series of consecutive pulses is termed a burst, and the time between bursts is the interburst interval. The frequency at which bursts are generated is the burst frequency, while the frequency of the underlying AC waveform in the burst is termed the carrier frequency. Burst modulation Basic Science Department, Faculty of Physical therapy, SVU Page 19  Electro Physical Agents, Part 2, 2022 Ramp time Techniques of application / Configuration of Electrodes /Types of electrodes: Metal Plate Electrodes Carbon - Impregnated Rubber Electrodes Self-Adhering or Single use Electrodes Special Electrodes Techniques of application: 1. Monopolar - single electrode from one channel- Active electrode placed directly over target tissue, often smaller in size; greatest perception will be over target tissue the use of two electrodes; (1) an active electrode placed where the treatment effect occurs. (2) A dispersive electrode used to complete the circuit and placed at distant location. The size of the dispersive electrode is larger than that of the active electrode. The high current density focuses the electrical current under the smaller active electrode and because of the relatively low current density under the dispersive electrode little or no stimulation should occur under the dispersive electrode. This technique is usually used for motor point stimulation. 2. Bipolar - two electrodes from one channel, usually equal size and shape. Both electrodes are located in the target treatment area Basic Science Department, Faculty of Physical therapy, SVU Page 20  Electro Physical Agents, Part 2, 2022 Because the 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 group or at the origin and insertion of the same muscle. 3. Quadripolar - electrodes from 2 or more channels, each lead with 2 electrodes. it may be considered the concurrent application of two bipolar circuits. The current from each of the two channels may intersect and intensify and localize the treatment effects as is found with interferential stimulation. Other quadripolar configurations include parallel placements as in TENS or agonist-antagonist placements used in NMES. The volume of current in the tissues, It depends on: 1. The space between 2 electrodes. 2. The size of electrodes. Effect of electric current on different tissues: Electricity has an effect on each cell and tissue that it passes through direct and indirect effects. Direct effects: occur along lines of current flow and under electrodes. Indirect effects: occur remote to the area of current flow and are usually the result of stimulating a natural physiologic event to occur. Tissues are classified as being either excitable or non-excitable. Excitable tissues are directly influenced by the current, while non-excitable tissues do Basic Science Department, Faculty of Physical therapy, SVU Page 21  Electro Physical Agents, Part 2, 2022 not respond directly to current flow but may be influenced by the electrical fields caused by the current. Excitable Tissues Response to Electrical Current: Excitable tissues include nerves (sensory, motor, and autonomic) and muscles. Stimulation of sensory nerve result in perception of the stimulated sensation and used for modulation of pain. Stimulation of motor nerves supplying the muscle result in muscle contraction (stimulation of innervated muscle) Stimulation of autonomic nerves result in alteration of blood flow and circulation Stimulation of muscle directly (stimulation of denervated muscle) results in muscle contraction. N.B: It is a common misconception that electrical stimulation to contract muscle works by directly stimulating the muscle fibers. This is not accurate, assuming the muscle maintains normal innervations. The nerve, with an RMP of –70 mV, will depolarize before the muscle cell with an RMP of –90 mV. Activation of innervated skeletal muscle occurs by first depolarizing the nerve and then propagating the stimulus along the motor axon, across the neuromuscular junction, and the across the sarcolemma. Non-excitable Tissue and Cells Response to Electrical Current: Improvement of cell function. Stimulation of extra-cellular protein synthesis. Increase release of cellular secretions. Gap junctions unit neighboring cells. Allow direct communication between adjacent cells (forms electrical circuit) Cells connected by gap junctions can act together when one cell receives an extra-cellular message. Basic Science Department, Faculty of Physical therapy, SVU Page 22  Electro Physical Agents, Part 2, 2022 The tissue can be coordinated in its response by the gap junction’s internal message system. Physiological effects of electrical stimulation: Muscle contraction Pain modulation Effects on blood flow Reduction of edema Altering the ionic distribution around the cell Promotion of tissue repair General Therapeutic Uses of Electricity: Controlling acute and chronic pain Strengthening muscle Edema reduction Muscle spasm reduction Reducing joint contractures Minimizing disuse/ atrophy Facilitating tissue healing Facilitating fracture healing PRECAUTIONS  Unstable fracture  Impaired cognitive ability  Documented Patients  evidence of epilepsy, cerebral vascular accident or reversible ischemic neurologic deficit  Recent surgical procedure  Open skin Basic Science Department, Faculty of Physical therapy, SVU Page 23  Electro Physical Agents, Part 2, 2022 General Contra- Indications:  The abdominal, lumber, and pelvic region during pregnancy.  Over the carotid sinus  Over the esophagus, larynx, or pharynx  Pacemaker  Over or in proximity to cancerous lesions  Exposed metal implants or superficial metals  Arterial disease:  Deep Vein Thrombosis:  Infective conditions  The steps in the clinical decision-making process when deciding to use ES: Regardless of the purpose, when deciding to use ES, the steps in the clinical decision-making process remain the same. Questions to ask when considering use of electrotherapy include the following: 1. What is the clinical goal? 2. Is the patient appropriate for an electrotherapeutic agent? 3. Is there a type of electrotherapeutic agent that can assist in achieving this goal? If there is an identifiable goal and the answers to the latter two questions are yes, then use of electrotherapy is indicated. The clinician must then continue with the following questions: 1. Is equipment with the appropriate waveform available? 2. What are the specific parameters of the selected waveform? 3. What electrodes and electrode configuration should be used? 4. What factors would necessitate a change in the treatment plan? Documentation Tips: Appropriate documentation of the application of electrical stimulation should include the following: Waveform Basic Science Department, Faculty of Physical therapy, SVU Page 24  Electro Physical Agents, Part 2, 2022 Symmetrical biphasic square, twin-peak monophasic, Russian, interferential, etc. Waveform parameters (these will depend on the waveform used) Pulse duration and frequency, amplitude, on- and off-time, ramp-up and ramp- down, burst duration, beat frequency, sweep, scan, swing Electrode Type, shape, and size Placement location Integrity of skin before and after treatment Patient position Dosage For neuromuscular electrical stimulation (NMES): the amplitude required to achieve the desired response For iontophoresis: the product of current amplitude × treatment duration (e.g., 80 mA × min) Treatment duration Tips to Assure the Safe Application of Electrical Stimulation 1. Use the Appropriate Type of Electrodes The U.S. Food & Drug Administration (FDA) guidance document for Powered Muscle Stimulators specifies that the stimulators “should only be used with the leads and electrodes recommended for use by the manufacturer.” High- quality electrodes should be used, those provide uniform conductivity and are designed for higher current density applications among a broad patient population including aging adults. 2. Use the Appropriate Size Electrodes: Electrodes should be as large as possible for the target muscle without causing overflow to the adjacent non-targeted muscle. Using large, low-resistance, uniform conducting electrodes is the single most important contributor to comfortable stimulation and good muscle force generation. Basic Science Department, Faculty of Physical therapy, SVU Page 25  Electro Physical Agents, Part 2, 2022 3. Appropriately Inspect & Prepare the Skin Inspect the skin for breaks; do not apply electrodes over areas of damaged or open skin. Wash the skin with soap and water to hydrate and clean. Do not apply alcohol wipes as this dries skin and increases skin resistance. Use LVPC if decreased sensation and skin integrity are issues to reduce current density. 4. Use the appropriate Electrode placement technique: Electrodes should be placed at least 1 inch apart for even current distribution to prevent risk of burns at the edges of electrodes. 5. Correctly Remove and Store Electrodes Slowly peel off the electrode by folding it upon itself rather than pulling the electrode up off the skin. Store electrodes in foil pouch and make sure it is sealed and correctly labeled with appropriate patient information. Failure to seal the pouch correctly could allow the electrodes to dry out. 6. Inspect the skin for redness or burns after each treatment. Basic Science Department, Faculty of Physical therapy, SVU Page 26