Electrotherapy Lec 1 PDF

ELECTROTHERAP Y BS 221 Presented by: Amal Abdelbaky Lecturer of physical therapy Basic science department Aims of electric stimulation Create muscle Stimulate sensory nerves Create an electrical field in contraction through to control pain biological tissues...

ELECTROTHERAP Y BS 221 Presented by: Amal Abdelbaky Lecturer of physical therapy Basic science department Aims of electric stimulation Create muscle Stimulate sensory nerves Create an electrical field in contraction through to control pain biological tissues to nerve or muscle stimulate or alter the healing process Definition of electric stimulation (ES)  Electric stimulation is the application of therapeutic electrical currents to stimulate excitable tissues to produce a physiological reaction leading to therapeutic effects. BASIC PHYSICS OF ELECTROTHERAPY  All matter is composed of atoms that contain positively and negatively charged particles called ions  The net movement of electrons is referred to as an electrical current.  These charged particles possess electrical energy and thus have the ability to move about, They tend to move from an area of higher concentration toward an area of lower concentration  An electrical force is capable of propelling these particles from higher to lower energy levels, thus establishing electrical potentials  Electrical potentials Think of a battery!! One terminal has a higher electric potential than the other. When you connect a wire between them, charges flow from the higher potential to the lower potential, creating an electric current. Current flows under 2 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  BASIC PHYSICS OF ELECTROTHERA PY  Electricity is the result of the movement of electrons  The net movement of electrons is referred to as an electrical current.  Current is the flow of electric charge.  In electric circuits, this charge is often carried by moving electrons in a wire. BASIC PHYSICS OF ELECTROTHERAPY  Materials that offer little opposition to current flow are good conductors  Metals ( copper, gold, silver, aluminum) are good conductors of electricity, as are electrolyte solutions because both are composed of large numbers of free electrons  Materials that resist current flow are called insulators which contain relatively fewer free electrons and thus offer greater resistance to electron flow such as Air, wood, and glass  BASIC PHYSICS OF ELECTROTHERAPY  Electrical Current Measured by:  ampere (A) : is defined as the movement of 6.25 x 1018 electrons per second  milliampere (mA) : 1\1000 amp  Microampere (µA): 1\1000,000 amp Basic physics of electrotherapy Ohm’s law: The relationship between current , voltage , and resistance is defined by Ohm’s law Current intensity = force /resistance Amp(I) = Volt (V) /ohm(R) Basic physics of electrotherapy  Current flow is directly proportional to voltage.  Current flow is inversely proportional to the resistance  The magnitude of current therefore increases when voltage increases or resistance decreases. Current intensity(magnitude) = force (volt) /resistance Factors affecting resistance 1. Material composition 2. Temperature 3. Impedance change in the presence of injury and disease. Factors affecting resistance Material composition 1. High water content decreases impedance and improves conductance 2. Bone, fat, tendons, and fascia are also poor conductors with low water contents of 20% to 30%. 3. The intracellular components of nerve and muscle have high water contents of 70% to 75%. Factors affecting resistance Temperature 1. Skin resistance is inversely proportional to its temperature 2. Heat increases moisture and surface salt content, which promotes conductivity. The presence of injury Resistance decreases in open wounds and abrasions.  Minimizing Impedance is important for all applications of electrical stimulation to increase patient comfort. Minimizing Impedance through: 1. Cleaning the skin surface with alcohol before electrode application …this will remove dirt and body oils 2. Removing excess body hair (shaving) 3. Warming the region to be stimulated before electrical stimulation All currents have parameters in the vertical y-axis and horizontal x- axis  Horizontal axis X is used to describe and quantify time or duration characteristics of current (milli sec- micro sec)  Vertical axis Y is used to describe or quantify the magnitude or intensity  Intensity: ( milli ampere – micro ampere)  Duration: (milli second- microsecond)  Isoelectric zero is the demarcation between positive and negative where there is no net charge. It can also sometimes be referred to as baseline. WAVEFORM Waveform is a visual representation of pulse. The shape of the pulse …reflecting amplitude (strength) and duration (length of time) Wave form parameters: Direction Frequenc Shape Duration Intensity y Direction or type of current:  Direction Direct current Alternating Current Positive or negative polarity Positive and negative polarity Monopolar\ monodirectional Multidirectional DC and Skin Irritation: AC and Skin Irritation: Electrolysis: DC can cause electrolysis, a process Rapid Direction Change: AC constantly where electrical current breaks down water changes direction, preventing the buildup of molecules into hydrogen and oxygen gases. This charge at any one point. This rapid change can lead to skin irritation, redness, and even burns. minimizes the risk of electrolysis and Chemical Reactions: DC can also induce chemical chemical reactions. reactions in the skin, leading to the formation of acidic Reduced Skin Impedance: AC can more or alkaline substances that can irritate the skin easily penetrate the skin due to its alternating nature, reducing the electrical resistance (impedance) of the skin. This can lead to a more efficient stimulation of tissues without causing excessive skin irritation. Current Classification Three basic waveforms are used in therapeutic electrical stimulation units: direct current, alternating current, and pulsed current.  Direct Current (DC) (Iontophoresis) Unidirectional monophasic flow of charged particles One electrode is always the anode (+) and one is always the cathode (-), so there is a build-up of charge (accumulation) since it is moving in one direction causing a strong chemical effect on the tissue under the electrode Ex: Iontophoresis: DC is delivered continuously to promote the absorption of the medication through the skin (anti- inflammatory ionized solution)  Alternating Current (AC) Russian current and interferential current  Bidirectional biphasic flow of charged particles changing direction.  Electrodes continuously change polarity each cycle, there is no build-up of charge under the electrodes  Often used in interferential or Russian currents  Pulsed Current (pulsed) pulsatile high-voltage pulsed current (HVPC)  Can be unidirectional (like DC) or bidirectional (like AC)  Flow of charged particles stops periodically for less than 1 second before the next pulse  Rectangular Triangular Shape: Sinusoidal Spike wave saw tooth Shape: Rectangular or square wave Shape: Sinusoidal Shape: Triangular Shape : Twin Spike wave high voltage pulsed current Shape: Sawtooth Pulse classification Pulses are classified by the number of phases they have. For example, there are monophasic, biphasic, and polyphasic waveforms Biphasic waveform can be subdivided into 2 types: Symmetrical biphasic : The phases are identical. the chemicals formed in one phase are neutralized by the reversal of current in the second phase.  Asymmetrical biphasic: the 2 phases are not identical. The asymmetrical biphasic pulse can be subdivided into  balanced…the charge of one phase is electrically equal to the charge of the other phase (zero net charge)  Unbalanced: the electrical charge of one phase is unequal to the electrical charge of the other phase (net charge across the baseline with some residual charge in the tissues)  Polyphasic waveforms have multiple phases occurring above and below the baseline. Polyphasic means the pulse is composed of 3 or more phases. Example: interferential and Russian stimulators  The term BURST is also the same as train or envelope. It is a group of two or more successive pulses or cycles separated by a time interval during which no electrical activity occurs. The polarity of waveforms  Biphasic symmetrical waveform has the same shape and size for each phase in both directions.,  Biphasic asymmetrical waveform has different shapes for each phase.  Balanced, the net charge in each direction is equal.  Unbalanced, there is a greater net charge in one phase than in the other. Polarity changes Wave form: balanced or unbalanced Asymmetrical biphasic pulsed currents Different current waveforms Pulse Amplitude The amplitude of each pulse reflects the intensity of the current, represented by the tip or highest point of each phase. ( strength of current) Peak amplitude is determined by measuring the maximal distance to which the wave rises above or below the baseline peak to peak amplitude it is the maximum current or voltage amplitude over the 2 phases of a biphasic pulse. Amplitude is measured in amperes, milliamps (mA) or microamps (µA). Intensity Amplitude (sometimes referred to as intensity) refers to the strength of the stimulation delivered, measured in milliamps (mA).  The amplitude needs to be high enough to evoke the desired effect while remaining comfortable.  Effect of Intensity: sensational level 3.Motor Level: 1.Subsensory level: Stimulation to the motor 2. Sensory level: Aß 4.Noxious Level: Adelta Biostimulation or fibers.. Alpha motor stimulation and c fibers Mitochondrial stimulation fibers ( neuromuscular electrical stimulation) No nerve fiber activation stimulates only sensory An intensity that An intensity that No sensory awareness nerves. produces a visible stimulates pain fibers. This level is found by contraction without Strong uncomfortable increasing the output to causing pain. sensation cell membrane stimulation the point at which a Sharp and burning pain slight muscle twitch is sensation. Ex:Microcurrent seen and then decreasing the output intensity by approximately 10%. The patient feels a tingling, prickling ,pins and needles.  The current intensity is inversely proportional to the nerve fiber diameter. The pulse duration is inversely proportional to the nerve fiber diameter Amplitude Peak amplitude is associated with the depth of the current penetration Higher peak amplitudes penetrate deeper into the tissues RATE OF RISE AND DECAY OF PULSE  The rate of rise in amplitude, or the rise time, refers to how quickly the pulse reaches its maximum amplitude in each phase.  Decay time refers to a pulse going from peak amplitude to (0) V. baseline  The rate of rise is important physiologically because of the accommodation phenomenon, in which a fiber subjected to a constant level of depolarization will become unexcitable at that same intensity or amplitude.  The faster the rate of rise, the greater the current's ability to excite nervous tissue.  Rectangular Triangular Sudden rise and sudden decay Gradual rise and Gradual decay Low duration plateau ALL or none rule Muscle need time to be stimulated Nerve is very excitable Accommodation Action Potential Membrane at rest : K+ (inside) Na+ (outside)  Action potential The Process:  Resting State: The neuron is at rest, with a negative charge inside compared to the outside. This is due to a balance of ions (sodium and potassium) on either side of the cell membrane.  Stimulus: A stimulus, such as a touch or a signal from another neuron, causes sodium channels to open. Sodium ions rush into the cell, making the inside more positive.  Depolarization: As more sodium ions enter, the membrane potential becomes more positive. If it reaches a certain threshold, an action potential is triggered.  Falling Phase: Potassium channels open, and potassium ions rush out of the cell. This helps to restore the original balance of ions and bring the membrane potential back towards negative Repolarization.  Undershoot: The membrane potential may temporarily become even more negative than the resting state, a phase known as hyperpolarization.  Refractory Period: During this period, the neuron cannot fire another action potential. Pulse Duration  Pulse duration (Pulse width) is the length of time t h e current is flowing in one cycle.  Phase duration is the length of time for a single phase to complete its rout.  Pulse duration and phase duration expressed in seconds (sec), milliseconds (ms), or microseconds (µ sec).  The current flow is off for some time (interpulse interval).  A single pulse or phase may be interrupted by an intrapulse interval.  The combined time of the pulse duration and the interpulse interval is called the pulse period. Frequency  Pulses per second (PPS) or pulse rate  The number of pulses delivered to the body in 1 sec.  The freq. is expressed in hertz (Hz).  Burst frequency is the number of bursts per sec. A-Low frequency currents  Current with frequency from 1-1000 Hz  Low-frequency currents can stimulate both sensory and motor nerves, with the best effect from 1-100 Hz  Examples: faradic current- diadynamic current, High Voltage pulsed stimulation, transcutaneous electrical nerve stimulation TENS, Microcurrent B-Medium frequency currents  Current with frequency from 1000 to 10,000 Hz  These currents can only stimulate sensory and motor nerves through current modulation  Examples: interferential – Russian current C-high frequency current Current with frequency of > 10,000Hz At this frequency, the current does not affect sensory and motor nerves….. (heat generation and electromagnetic field effects) Examples: of high-frequency currents are short-wave – microwave and ultrasound Low frequency Medium frequency High frequency Longer pulse durations, often in shorter pulse durations, typically extremely short pulse durations, the milliseconds range. This in the microseconds range. This often in the nanoseconds range. allows for stronger muscle can produce both muscular This primarily produces thermal contractions. contractions and thermal effects. effects. Higher intensity is often required Moderate intensity can be used Lower intensity is typically used to produce noticeable muscular to produce muscular contractions to produce thermal effects, as contractions. higher intensities can be uncomfortable or even damaging. Primarily stimulates motor Stimulates both motor and Primarily produces thermal nerves, leading to muscle sensory nerves, leading to effects, heating tissues and contractions. also stimulate muscle contractions and pain improving circulation. sensory nerves, causing tingling modulation. Can also produce or numbness. thermal effects, improving circulation and reducing inflammation.  Duty cycle  ON time is the time the current is delivered to the patient  OFF time is the time current flow stops  Both times are measured in seconds  If the off time is longer relative to the on time, there will be less fatigue Duty cycles play a role in neuromuscular stimulation by preventing muscle fatigue Muscular stimulation is started with a 25-duty cycle and is progressively increased as the condition improves. Duty cycle  A continuous duty cycle causes constant muscle contraction with no rest so the muscle fatigues quickly and is indicated for spasm  Interrupted duty cycle can be expressed as a percentage or ratio Duty cycle