PTA 252: Chp 13 Neuromuscular Electrical Stimulation (NMES) – Flashcards
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The introduction of electrical current across the skin is used to
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excite nerve or muscle tissue
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There are large multipurpose units & small portable units
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IFC = clinical tx TENS = home use NMES = both
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NMES is used for the purpose of improving motor performance through this (know this)
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Intact peripheral nervous system (innervated tissue)
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With high frequency IFC & TENS the nerve fibers excited are
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Sensory
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With low frequency IFC & TENS the nerve fibers excited are
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Motor = muscle
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A pt has suffered a traumatic injury including severed nerves. Which type of electrical current would be used to stimulate the denervated muscle's
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Direct current, because the nerve is no longer intact
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Neuromuscular Electrical Stimulation (NMES) is also called
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Electrical Muscle Stimulation (EMS)
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A type of electrical stimulation, Functional Electrical Stimulation (FES) is used to
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supplement or replace function: EX: drop foot (tibialis Anterior won't dorsi flex) electrodes are placed so that during ambulation swing phase the mechanism would activate dorsi flexion & release it upon heel strike
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The purpose of NMES
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to excite muscle tissue: stimulate muscles that cannot contract voluntarily
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The effects of NMES
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help strengthen weakened muscle improve recruitment of motor units during function Decrease spasticity (fatigue theory) maintain or improve mobility Improve endurance decrease edema through activation of muscle pump
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A pt is having difficulty contracting wrist extensors on command, what tx would be indicated
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NMES
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A pt has decreased peripheral circulation what tx is indicated and why
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NMES, through activation of the skeletal-muscle pump (especially important in increasing venous return to the heart, but may also play a role in arterial blood flow)
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NMES & FES can be used successfully in managing movement problems among these patients
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pt with the peripheral nervous system intact examples: cerebrovascular accident (CVA) spinal cord injury, cerebral palsy, Stroke, COPD, bell's palsy, peripheral nerve injuries, osteoarthritis, rheumatoid arthritis
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When is the use of NMES contraindicated
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areas where active motion is contraindicated (surgery, fusion or fracture) Pacemaker Cancers Metal in tx area Pregnancy Disoriented patients Active bleeding over other implanted stimulators
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Why wouldn't you use NMES on a pt during their pregnancy
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certain points on the body can star labor or cause miscarriage
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Why shouldn't NMES be used on pt's with fusion, unfixated fracture, or recently sutured nerves or tendons
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ES that imparts motion may disrupt alignment of bone fragments and healing If the joint should not be moved; the muscles that control it should not be activated
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When treating a pt with any ES it is important to do this before application of the electrodes
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skin check: make sure they have normal sensation
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Consider this precaution before using NMES
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anesthetic skin Open wounds Extreme edema Heavy scarring or thick adipose tissue (impedance) Over laryn/pharyngeal muscles or near carotid sinus chronic us of corticosteroids Uncomfortable amplitudes
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If a pt is unable to get comfortable with the amplitude of NMES, no matter how you adjust the parameters, what should you do
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reconsider the us of E-stim with this pt & consult the PT (current can cause burns to the skin)
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The specific goal of NMES is
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Muscle strengthening & increased endurance facilitate improved motor recruitment (re-education) decrease spasticity thru stimulation of spastic muscle maintain ROM decrease swelling peripheral circulation
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Why wouldn't you want to use NMES on pt with EXTREME edema
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the (very) conductive fluid prevents the current from reaching the target tissue
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Why should you avoid using NMES in areas with heavy scarring or thick adipose tissue
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These tissues are highly resistant and prevent the current form crossing the skin & the tx may be painful to the pt
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The position of the pt for a NMES tx
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resting in a neutral position the muscle can be slightly lengthened, but never shortened
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The frequency (Hz) used in NMES for muscle strengthening
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50 Hz
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The phase duration during NMES tx is
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200-300 usec (microseconds)
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Amplitude play's an important role in NMES. The intensity should be set to illicit this
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a strong muscle contraction while meeting the pt's tolerance level (stimulation should not be uncomfortable)
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Tell your pt the tx should not be painful or uncomfortable, but...
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we do need to illicit a full contraction of the muscle
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The placement of electrodes for NMES needs to be
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on the (correct) muscle motor point
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Duty cycle in NMES refers to
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hold cycle vs rest cycle active contraction vs. relaxation
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The minimum duty cycle during NMES should be
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1:5 ratio Example: 10sec on vs. 50sec off
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What is benefit of the duty cycle during NMES
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Helps avoid muscle fatigue
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To build optimal tension in the muscle being tx with NMES the hold time needs to be
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in the range of 6-10 seconds
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NMES requires tx to be measured in
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contractions (rather than tx time)
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What is the typical tx duration for NMES
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8-10 contractions (called cycles) during one tx is sufficient for strengthening
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How often should a pt receive NMES for the strengthening of muscle
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At least 3x a week for 1 month (4weeks)
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A way of progressing strength & endurance for a pt using NMES
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increase the amount of cycles of muscle contraction (10-12) reduce the duty cycle ratio (reduce rest time 1:3 or 1:4) reduce the amplitude or intensity (less motor stimulation)
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If the goals of NMES tx is endurance the frequency should be
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<40 Hz
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When choosing a duty cycle for NMES that will help build endurance consider the goal
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variable: working toward functional activity start the pt with a non-fatiguing 1:6 or 1:5 ratio working toward longer hold times & shorter rest times (1:3 or 1:2)
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The tx duration for endurance building NMES should start with
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a number of contraction the pt can tolerate without excessive fatigue, gradually increasing.
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How often should a pt be treated with endurance building NMES
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1-3x per day increase frequency as tolerated
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NMES can be used to improve peripheral circulation by activation of the skeletal-muscle pump. Only these frequency's have shown to be effective
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20-35 Hz =tetanizing frequency 3 Hz = twitch frequency
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NMES for peripheral circulation shows a strong relationship between contraction strength and blood flow increase, therefore
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pt should experience a strong but tolerable contraction (however, 10%-30% of maximal contraction is sufficient to activate the muscle pump)
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By placing the electrodes on the motor points & setting the duty cycle to a non-fatiguing level a pt can receive tx for between 10-30 minutes this often
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throughout the day or as frequently as is comfortable for the pt.
