Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Stimulus (physiology) wikipedia , lookup
Embodied language processing wikipedia , lookup
Neuroregeneration wikipedia , lookup
Transcranial direct-current stimulation wikipedia , lookup
Synaptogenesis wikipedia , lookup
End-plate potential wikipedia , lookup
Muscle memory wikipedia , lookup
Proprioception wikipedia , lookup
Neurostimulation wikipedia , lookup
Electromyography wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Neuromuscular Electrical Stimulation (NMES) Mohammed TA, Omar, Ph.D. PT Rehabilitation Health Sciences Neuromuscular Electrical Stimulation (NMES) Neuromuscular electrical nerve stimulation (NMES) is electrical Stimulation of The Excitable Tissue (Nerve & Muscle) Using Surface Electrodes to Induce Muscle Contraction Aiming for. Muscle re-education Prevention/Retardation of disuse atrophy Muscle strength and /or endurance Reduce edema (Muscle pump contraction) What is the Motor Point? A point on the skin where an electrical stimulus will cause the maximum contraction of an underlying muscle. Area of greatest excitability on the surface of the skin overlying superficial muscles that can produce maximum contraction with minimum amount of current intensity. The point where the motor nerve enters the muscle and it lies at muscles belly between the proximal one third & distal 2/3 of muscle belly or fleshy part of the muscle fibers. What is the Motor Point? To trace motor point 1. Interrupted direct current at 1ms (1000µs) for innervated muscle 2. Interrupted direct current at 100ms for denervated muscle Position of the MP of quadriceps and gastrocnemii Chart for Motor Point Clinical practice ES parameters F(1-2Hz) Intensity (start 1mA) Pulse duration 100-200µseconds Pen electrodes (active) Dispersive electrode Alcohol swap (cotton) and markers A, B, C, D, http://www.youtube.com/watch?v= ltQTB5ekhf4 What is the Motor Unit? Motor unit MU is a single motor neuron (alpha motor neuron from anterior horn cell and all the muscle fibers it stimulate (AHC+α motor neuron+ muscles fibers) Each motor unit supplies from 4-100 muscles fibers. Dependent on movement precisions Motor neuron determines fiber type . Motor unit classification Muscle fiber classification Slow Type I [SO] slow oxidative vascular ++ fatigue resistant (red fibres – old term) Fast fatigue resistance Type IIa [FOG] Fast Oxidative Glycolytic Intermediate; some oxidative metabolism therefore some fatigue resistanc. Fast fatigue ype IIb [FG] Fast Glycolytic least oxidative; least fatigue resistance highest, fastest force production What is the Motor Unit? What is the Motor Unit? Sensory and motor nerve impulse propagation Sensory Motor Orthodromic propagation is propagation of nerve is a propagation of nerve impulse toward the sensory impulse periphery toward cortex. neuromuscular junction Antidromic Propagation is propagation of nerve is a propagation of nerve impulse toward the periphery impulse proximally toward the (sensory receptors on the CNS. skin). Long pulse duration Short pulse duration ≥ 10ms (comfortable stabbing sensation) ≤ 1ms (mild/moderate prickling sensation). Strength Duration Curve (SDC) The SD curve is a graph representation of a quantitieves non liner relationship between intensity and duration of current to determine whether a muscle is innervated, or denervated. It depends on; Numbers of motor units recruitment Intensity of current. Frequency Placement of electrodes. Strength Duration Curve (SD) Rheobase is a minimal intensity of stimulus amplitude (strength) required to elicit a minimal visually perceptible muscle contraction (for 1000ms impulse). Normal values of Rheobase are (2-18mA, 5- 35volts) Chronaxie is a minimal pulse duration required to produce a minimal perceptible response in a muscle, at twice the intensity of rheobase. Chronaxie of innervated muscles is less than 1ms (range 0.05-0.5ms). Chronaxie of fully denervated muscle may be 30 to 50 ms Denervated Muscles; Muscles that have loss nerve supply. Deneravtion ranges from complete denervation (CD) to partial deneravation (PD). Complete denervation (CD), all motor unit loses all innervation Partial denervation (PD) some of motor unit in the muscles lose its innervation Results in Atrophy or Wasting Muscle atrophy is a reduction in size of muscles (disease/ disuse). Muscle wasting is the unintentional loss of 5–10% of muscle mass. Normal Innervation: All nerve fibers supplying the muscle are intact Stimulation of Denervated Muscles Physiological & chemical characteristics of denervated muscles Long Duration Interrupted direct current (LIDC) Current parameters and specifications Effect of ES on denervated muscles Physiological &chemical Characteristics of Denervated Muscles Decrease size, and diameter of muscles fibers (atrophy) Decrease amount of tension generated Increase time required for contraction Loss of voluntary contraction and reflex activities Degenerative changes progress until muscle is reinnervated by axons regenerating across site of lesion (2-6months) If reinnervation does not occur within 2 years fibrous connective tissue replaces contractile elements and recovery of muscle function is not possible EFFECTS of DENERVATION in SKELETAL MUSCLES 1. Paralysis (immediately): 2. Fasiculation (immediately): spontaneous firing of the injured axon, causing twitching of motor units. 3. Fibrillation (days) : spontaneous twitching of individual muscle fibers due changes in muscle excitability (e.g., Na channels) 4. Muscle atrophy (>1 week): 5. Receptiveness to innervation: allows reinnervation of the muscle by motor axons Long Duration Interrupted Direct Current Unidirectional, characteristic; Pulse duration Long pulse duration (100ms-600ms) 100-300ms PD ≥ 300ms CD interrupted direct Inter-Pulse Interval 3-5times of pulse duration. current with following Frequency Depends on pulse duration e.g. If Pulse duration = 100ms Frequency of 30 Hz Waveforms shape: Saw-tooth, Triangular, & Trapezoid Stimulating Denervated Muscle First 2 weeks. ◦ Use asymmetric, biphasic waveform and pulse duration < 1 ms After 2-3 weeks, ◦ Interrupted DC square wave with long pulse duration > 10 ms, ◦ AC sine wave with frequency < 10 Hz Inter-Pause interval 3 to 5 times longer (about 3-6 seconds) than stimulus duration to minimize fatigue. Use monopolar or bipolar electrode setup with small diameter active electrode placed over most electrically active point. Stimulation using 3 sets of 5 -20 repetitions, 3/ per week Effects of LIDC Neuropraxia Compression on nerve 100ms, rectangular Axonotmesis partial denervation 100-600ms, triangular, trapezoidal Neurotmesis Complete denervation 100-2000ms triangular, saw-tooth Effect of ES on Denervated Muscles Retardiation of denervated atrophy Utilization of substrates Prevent venous & lymphatic stasis Working hypertophy Maintenance of muscle extensibility NMES- Faradic Current Faradic Current Stimulation Faradism is unevenly alternating current with each cycle consisting of two unequal phases, with frequency 1-150Hz. B-Negative: Low intensity long duration A-Positive: High intensity short duration A B Faradic Current Stimulation Faradic current is a short-duration interrupted Surged direct current with a pulse duration of 0.1 to 1ms, and frequency of 30 -100Hz Frequency: Therapeutic frequency (0.5, 1.5, 10, 50, 75, 100 Hz)In order to achieve a constant contraction, the stimulus must be applied at rate of 3060stimuli per seconds. Waveforms Rectangular shaped pulse more comfortable than triangular pulse for normal muscle contraction. If disuse atrophy waveform can be used. triangular Pulse duration (0.02-1ms) Therapeutic selection 0.02, 0.05, 0.1 & 1ms. PD=0.1ms , frequency of 70Hz, & Skin resistance = 50Ώ, PD=1ms with frequency of 50Hz, and skin resistance = 1000Ώ Polarity : Active electrodes usually the cathode (-) Physiological Effects of Faradic Stimulation Sensory nerves Mild prickling due to stimulation of sensory nerve . Mild erythema due to local reflex vasodilatation of superficial blood vessels, which causes slight reddening of the superficial tissues. Motor nerves Faradic current stimulates the motor nerves /muscle, causes contraction of the muscles. Because the stimuli repeated 50 times (50Hz) or more, the contraction is titanic. To avoid muscle fatigue secondary to this contraction the current becomes surged Effects on motor nerve Motor-level Stimulation Comparison of Voluntary and Electrically-Induced Contractions Voluntary Electrically-induced Type I fibers recruited first Type II fibers recruited first Asynchronous Synchronous recruitment ◦ Decreases fatigue GTO protect muscles ◦ Based on PPS GTOs do not limit contraction Effects of Muscle Contraction Increased muscle metabolism. Increase oxygen demand by the muscles. Increase output of waste product & metabolites (carbon dioxide, lactic acid). Dilatation of capillaries and arterioles Increased blood flow Increase local temperature. Increase venous and lymphatic drainage Changes in muscle structure (fast twitch to slow twitch ) Increase joint range of motion. Therapeutic Uses and Indication of Faradic Current Stimulation Therapeutic Uses and Indication of Faradic Current Stimulation Facilitation of Muscle Contraction & Re-education Pain & muscle spasm, ◦ Quadriceps e.g. vastus medialis after knee injury & diseases Prolonged disuse, wasting and imbalance ◦ Intrinsic muscle of foot in case of longstanding flat foot. ◦ Abductor hallucis in hallux valgus. ◦ Scoliosis. ◦ Prolonged period of immobilization Muscle and nerve repair and transplantation. Nerve injury (----What is the degrees of nerve injury?) Pelvic floor Muscle (stress incontinence) Improve Venous and Lymphatic drainage Electrical stimulation of the muscle causes increase venous and lymphatic return, alter cell membrane permeability, these causes reduction of edema. The treatment is most effective if the current is applied by the method, termed faradism under pressure Faradism under pressure is stimulation of the muscle that generally act as the pump muscles and is combined with compression and elevation of the limb to increase venous and lymphatic drainage and hence relive edema. Retardation of muscle atrophy Maintenance of muscle tissue after injury that prevent normal muscle contraction can be achieved through using an electrical stimulated muscle contraction, which produce the physical and chemical events associated with normal voluntary muscle contraction and helps to maintain normal muscle function. Increasing Range of Motion Muscle contraction pulls the joint through limited range. The continued contraction of this muscle group over an extended time make the contracted joint and muscle tissues modify and lengthen APPLICATIONS The right quad has atrophied or wasted. Stimulation of the quad can prevent atrophy and increase strength. Placement for quad weakness/atro phy. The approximate electrode placements for foot drop. The negative is placed over the peroneal nerve. The person with foot drop is unable to dorsiflex their foot. Muscle re-education Post op ACL Problem: Quadriceps atrophy Goal: Decrease atrophy, increase strength. Waveform: Symmetric Duty cycle: 25% (4:12) Placements: Rotator cuff repair Problem: Rotator cuff atrophy, poor scapular stability Goal: Decrease/ reverse atrophy, scapular stabilizer re-ed. Waveform: Symmetric/ asymmetric Duty cycle: 25%, hand switch Placements: Isometric Abduction Scapular depression Contraindication for Faradic Current Stimulation Skin lesion & dermatological conditions such as eczema. Infection such as osetomylities. Vascular diseases such as thrombosis, & thrombophlebities. Marked loss of skin sensation (chemical burn). Unreliable patients. Superficial metal (concentration of electricity). Metal and cardiac pacemaker Over recent or non-union fractures Over potential malignancies Treatment times & frequency To be effective 2 & 3 treatments per week for the first 8-12 weeks Treatments last 15-20 minutes but no longer than 30 minutes It is better to have 3 short treatments per week than 1 long treatment