Foundations Of Electrical Stimulation PDF

# FOUNDATIONS OF ELECTRICAL STIMULATION Electrical stimulation uses dates back to ancient Egyptian times when electric eels were used to treat painful spines and limbs. - Application of electrical stimulation to elicit or facilitate some desired therapeutic response. - **Electrical Stimulation** -...

# FOUNDATIONS OF ELECTRICAL STIMULATION Electrical stimulation uses dates back to ancient Egyptian times when electric eels were used to treat painful spines and limbs. - Application of electrical stimulation to elicit or facilitate some desired therapeutic response. - **Electrical Stimulation** - the stimulation of tissue for therapeutic purposes. - These tissues may be excitable or non-excitable tissues. ## Current classification There are three basic used in commercial therapeutic electrical stimulation units: direct current, alternating current, and pulsed current. ### 1-Direct Current (**DC**) (formerly known as **Galvanic**) - Continuous unidirectional flow of charged particles with a duration of at least 1 second. - One electrode is always the anode (+) and one is always the cathode (-) for the entire event. - There is a build-up of charge since it is moving in one direction causing a strong chemical effect on the tissue under the electrode. - Most used for wound healing and with iontophoresis. - Iontophoresis and microcurrent are clinical examples of direct current interventions. **Note**: Monophasic also refers to direct current, but it is interrupted and not continuous (i.e., pulsed), so the chemical effect is minimal ### 2-Alternating Current (**AC**) - **Biphasic** - Uninterrupted, bidirectional flow of ions. - Electrodes continuously alternate their polarity each cycle, therefore no build-up of charge under the electrodes. - Types of modulated AC current used on biological tissue. - **Burst-modulated** - known as "**Russian**" current. - **Amplitude-modulated** is known as **interferential** current. ### 3-Pulsed Current (pulsed - AC and DC) - The flow of charged particles stops periodically before the next event. - Monophasic pulses do not alternate; pulsed monophasic (travels in one direction) current allows for a charge to accumulate in biological tissue. ## Electrical Stimulation Parameters Electrical stimulation (ES) refers to the use of electrical currents to elicit a physiological response in tissues, primarily for therapeutic or research purposes. Various parameters need to be considered for effective electrical stimulation, including: ### Phase Duration A phase is the period when electrical current flows in one direction. The phase duration is how long a phase lasts and is usually measured in microseconds (10^-6 seconds). - For monophasic currents, pulse duration and phase duration are synonymous (only 1 phase). - Biphasic pulses have two phase durations. - The phase duration determines which nerve type is affected. ### Pulse Duration A pulse is the period when electrical current flows in any direction. A pulse may be made up of one or more phases. The pulse duration is how long each pulse lasts and is the time from the beginning of the first phase of the pulse to the end of the last phase of the pulse. The pulse duration is sometimes called the **pulse width**. - Pulse duration is usually measured in microseconds (10^-6 seconds) - **Interpulse interval** is the amount of time between pulses; The time between the end of one pulse and the start of the next pulse. - Increasing the pulse frequency decreases the interpulse interval and vice-versa. - **Intrapulse intervals** are brief interruptions of current flow. - Are always shorter than the interpulse interval. - They allow for physiologic adaptations to the current and/or to decrease the total charge delivered by the pulse. - **Amplitude** is the magnitude of the current flow and is often also called the strength or intensity. - Amplitude can be measured in amperes or volts. - **N.B.:** Electrical stimulation should be adjusted according to the patient's response, not an absolute number. - It needs to be adjusted to a level that produces the desired response without causing discomfort. - **Frequency** is the number of electrical pulses delivered to the body in one second. "Pulse frequency or pulse rate" - Also called pulses per second (pps), Hertz (Hz) with AC - Higher frequencies cause higher levels of muscle fatigue due to less time between pulses. - **FYI** - Frequency - the rate at which the current switches direction - Biphasic pulsed currents are the most used waveform in electrotherapy. This type of current can be used to produce muscle contractions or to control pain. - Pulse duration is how long a pulse lasts. - Frequency is the number of **pulses/second**. - Amplitude is the magnitude of the current flow. - These parameters can be adjusted based on the specific therapeutic goals, patient tolerance, and the type of tissue being stimulated. - Proper parameter selection is crucial for maximizing the efficacy and minimizing the side effects of electrical stimulation therapy. ## Types of Electrical Stimulation according to the therapeutic use: ### 1. Neuromuscular Electrical Stimulation (NMES): The use of pulsed electrical currents applied to skeletal muscles with the objective to elicit contraction caused by the electrical depolarization of intramuscular nerve branches. - Electrical stimuli are delivered using surface electrodes that are positioned over muscle bellies. - The main purpose of NMES is to preserve and recover muscle function in patients and to improve muscle strength in healthy individuals. ### 2. Functional Electrical Stimulation (FES): The application of NMES for enhancing the control of movement and posture. It focuses on the enhancement of impaired motor functions, such as hand grasping, and locomotion, using complex transcutaneous and percutaneous electrical muscle stimulation systems. - FES is a technology one can use to artificially generate body movements in individuals who have paralyzed muscles due to injury to the central nervous system. - The main purpose of FES is to enable motor function by replacing, or assisting, a patient's voluntary ability to execute or control the impaired functions. - For FES to be effective, it must produce a contraction of sufficient force to carry out the desired activity, it must not be painful, and it must be controlled and repeatable. To do this, at a minimum, the lower motor neuron, the neuromuscular junction, and the muscle must be intact, and the delivery method must be acceptable to the user. - FES may be delivered with transcutaneous electrodes, similar to NMES. For patients with stroke and footdrop, FES can initiate ankle dorsiflexion during the swing phase of gait to assist with walking, substituting for an ankle-foot orthosis (AFO). ### 3. Electrical muscle stimulation (EMS) The application of electrical current for denervated skeletal muscles.