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150 Cards in this Set
- Front
- Back
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potential difference |
difference between high potential and low potential must exist if you want movement of electrons |
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electrical potential |
electrical force that is capable of propelling ions from higher to lower energy levels |
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electrical current |
net movement of electrons |
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amperes |
rate of electron flow |
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electromotive force |
volt must be applied to produce flow of electrons difference in electron population between two points |
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voltage |
force resulting from an accumulation of electrons at one point in an electrical circuit, corresponding to deficit of electrons at another point movement of electrons from high to low concentrationac |
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conductors |
material that permits free movement of electrons |
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conductance |
ease with which the current flows along a conducting medium measured in siemens metals, electrolyte solutions |
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insulators |
materials that resist current flow contain fewer free electrons air, wood, glass skin |
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resistance |
opposition to electron flow in a conducting material electrical impedence ohms higher with DC than biphasic current
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ohm's law |
current flow = voltage/resistance |
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electrical power |
watt = volts * amperes rate at which electrical power is being used |
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three types of current |
biphasic or alternating current monophasic or direct current pulsatile PC |
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monophasic or DC |
uninterrupted, unidirectional flow of electrons toward positive pole flow direction can be reversed phase duration >1 sec used for denervated muscle, iontophoresis polarity only important here biochemical effects under cathode - soften tissues, alkaline reaction, more effective than anode biochemical effects under anode - acidic reaction |
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biphasic or AC |
continuous flow bidirectional reversing polarity repeatedly for pain control and muscle contraction increasing frequency decreases phase/pulse width |
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pulsatile PC |
usually 3 or more pulses grouped together uni (if < 1 sec) - polarity matters but not as many biochemical effects as DC bi directional (VMS - biphasic) (Russian - polyphasic) interrupted for short periods of time and repeat themselves at regular intervals IFC and Russian |
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TENS |
transcutaneous electrical nerve stimulators stimulates peripheral nerves |
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NMES EMS |
neuromuscular electrical stimulator electrical muscle stimulator electrical current stimulates muscle directly denervated muscle |
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series circuit |
only one path for current to get from one terminal to another amperes of an electrical current flowing through is exactly the same at any point in the circuit Rt = R1 + R2 + ... Vt = V1 + V2 + ... |
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parallel circuit |
two or more routes exist for current to pass between two terminals Vt = V1 = V2 each resistance added decreases total resistance 1/Rt = 1/R1 + 1/R2 + ... adding alternative pathway improves current flow |
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electrical circuit in human tissue |
combination of series and parallel circuit electrodes on skin = series (go through skin and fat) parallel circuit where current can travel through either bone, muscle, blood, or nerves to get to muscle usually current will choose tissue with highest water content - blood |
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muscle is composed of ___% water and conducts current in which direction |
75% longitudinal |
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which conducts current better, muscle or tendon? |
muscle tendon is more dense, has little water, poor conductor |
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fat contains ___% water and is therefore a _____ conductor |
14% poor |
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peripheral nerve conductivity is about ___ times that of muscle |
6 |
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bone contains ___% water |
5 extremely dense poorest biologic conductor |
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waveform |
graphic representation of shape, direction, amplitude, duration, pulse frequency sinusoidal, rectangular, square, spiked |
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pulse |
individual waveform may contain one or more phases |
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pulse/phase duration in DC |
length of time that current is flowing pulse = monophasic cycle = biphasic |
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AC waveform |
waveform has two separate phases during each cycle |
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PC waveform |
electrical current is conducted as a series of short pulses of short duration monophasic or biphasic interphase interval - between phases pulse duration - sum of all phases and interphases interpulse interval - between pulses, period of time where current is not flowing |
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amplitude |
current intensity highest point of phase voltage not the same thing as the total amount of current being delivered to tissues
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how can total current being delivered to tissues be increased |
increase pulse duration increase pulse frequency |
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pulse charge |
amount of electricity being delivered to patient during each pulse monophasic - phase charge = pulse charge and always > 0 biphasic - pulse charge = sum of phase charges and zero if symmetrical |
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duration |
length of time current is flowing in one cycle |
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pulse period |
pulse duration + interpulse interval |
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pulse |
rise and fall in amplitude increase frequency, increase speed of amplitude change |
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muscle responds with individual twitch contractions to pulse rates of less than ____. beyond this muscle responds with ____. |
50pps tetanic contraction |
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types of current modulation |
continuous burst beat ramping |
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burst modulation |
PC or biphasic current flows for short duration and then turned off for short time in a repetitive cycle no muscle contraction during interburst cycle |
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beat modulation IFC pre-modulated interferential |
two interfering biphasic current waveforms with differing frequencies delivered to two separate pairs of electrodes through separate channels within the same generator electrodes set up in criss cross fashion so circuits interfere beat frequency = difference in frequency between two biphasic current frequencies |
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ramping |
current amplitude will increase to preset maximum and then decrease intensity ramp up usually 1/3 of on time |
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motor nerves are not stimulated by a steady flow of _______ |
DC nerve will not depolarize again until change in current intensity occurs |
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which produces higher tension - tetanic contraction or twitch |
tetanic (influenced by frequency) |
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increasing intensity causes current do reach _____ into tissue |
deeper |
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difference between high volt and low volt currents |
high volt reaches deeper tissues in body |
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negative electrode positive electrode |
cathode - distal - muscle contraction anode - proximal mimics body natural movement of ions |
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effects of polarity |
1. chemical effects (long duration only): pH change under electrode, reflex vasodilation, and ability to facilitate movement of ions 2. ease of excitation 3. direction of current flow |
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why does the cathode produce a muscle contraction more easily than the anode |
greater facility for membrane depolarization at negative pole versus positive pole positive pole would require larger intensity - more discomfort for patient |
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if the electrodes are spaced closely together, the area of highest current density is relatively ________. if the electrodes are are spaced farther apart, the current density will be higher in _____ tissues. |
superficial deeper (including muscle and nerve) |
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the current density ______ as the electrode size decreases |
increases |
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one of the biggest causes of poor results from electrical therapy is _______ |
electrode misplacement |
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electrode placement |
1. on or around a painful area 2. over specific dermatomes, myotomes, or sclerotomes that correspond to painful area 3. close to spinal cord segment that innervates painful area 4. over sites where the peripheral nerve becomes superficial and can be stimulated easily 5. over superficial vascular structures 6. over trigger points 7. over motor points of muscle or muscle belly 8. crossing patterns used for IFC and premod. signals from each set add together at some point in the body and intensity accumulates |
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bipolar |
uses electrodes of same size in same general treatment area current density under each electrode is the same physiologic effects under each electrode is the same |
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monopolar |
uses one or more small active electrodes over a treatment area and a large dispersive electrode placed somewehre else on teh body higher current density under small electrode physiologic response under small electrode |
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quadripolar |
uses two sets of bipolar electrodes, each of which comes form a completely separate channel on electrical stimulator |
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if you place equal size electrodes close together on a body part with thick fat layers, will the current reach the nerve? |
no |
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if you place electrodes very close together, where will you produce a high density current? |
superficially |
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if you place the electrodes farther apart, where will you produce a high density current? |
deeper |
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the lower the ratio of on time to off time, the _____ total current the patient will receive |
lower on/off time = duty cycle |
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effects of electrical current passing through the various tissues of the body |
thermal - causes a rise in temperature in conducting tissues, higher resistance will increase temperature more. minimal thermal effects chemical physiologic - migration of ions from DC |
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perceived excitatory effects |
electrical sensation muscle contraction electrical pain |
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what can you change to get more nerve cells to fire |
increase current increase duration |
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rheobase |
specific intensity of current necessary to cause an observable tissue response |
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chronaxie |
specific duration required for a current of twice the intensity of rheobase to produce tissue excitation |
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electrical current required to reach threshold for depolarization (lowest to highest) |
a beta (tingling sensation) motor neurons (muscle contraction) a delta (pain) c fibers (pain) |
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how does estim cause contraction in denervated muscle and why do you use it |
normally, muscle contracts in response to depolarization of motor nerve. in denervated muscle, current causes muscle membrane to depolarize prevent atrophy, limit edema and venous stasis, delay muscle fiber fibrosis and degeneration |
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indications for estim |
modulating acute, postacute, chronic pain muscle re-ed retarding atrophy muscle strengthening increase ROM decrease edema decrease muscle spasm decrease muscle guarding stimulate healing process wound, fracture, tendon, ligament healing stimulate nerve regeneration stimulate pns function change membrane permeability synthesize proteins stimulate fibroblasts and osteoblasts regenerate tissue increase circulation through muscle pumping |
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contraindications for estim |
pacemakers, arhythmias, over carotid sinus site of infection malignancies pregnancy exposed metal impants known area of thrombosis decreased sensationst musculoskeletal problems where muscle contraction would exacerbate the condition |
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purpose of using high volt currents |
high volt - twin-peaked pulsed waveform that has long interpulse interval elicit muscle contraction (most common) pain control reducing edema |
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minimize fatigue |
low frequency high intensity |
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how do you find the motor point of a muscle |
move the probe around the muscle until you see the largest contraction for that intensity |
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how does estim retard atrophy? |
electrical stimulation reproduces physical and chemical events associated with normal voluntary muscle contraction and helps to maintain normal muscle function |
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how does estim increase ROM? |
pulls joint through the limited range continued contraction of muscle group over extended time modifies and lengthens muscle works in patients with hemiplegia, no evidence for contracted joints from athletic or surgical injuries |
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gate control theory |
sensory cutaneous stimulation to peripheral sensory a beta fibers closes the gate to painful afferent impulses being trasmitted tos pinal cord on a delta and c fibers blocks pain at spinal cord level as long as stimuli is applied, perception of pain is diminished sensory level tingling sensation a beta fibers stimulates substantia gelatinosa in dorsal horn of spinal cord to inhibit C and D fibers in T cell |
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descending pain control theory |
electrical stimulation of a delta and c fibers stimulates midbrain, pons, and medulla causing release of enkephalin through descending neurons blocks pain at spinal cord level cognitive input from cortex motor level muscle contraction higher centers of CNS can effect gate at dorsal horn of spinal cord release serotonin opiates at the spinal cord to inhibit T cell |
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endogenous opiate pain control theory |
electrical stimulation of sensory nerves stimulates the release of beta-endorphin and dynorphin from pituitary gland and hypothalamus into CSF noxious electrical current large dispersive pad and small pad on motor unit beta endorphin and dynorphins delayed effect from low frequency, high intensity |
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greater duration (pulse width) _____ patient discomfort |
increases |
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russian current |
two basic waveforms: sine wave and a square wave cycle with fixed intrapulse interval sine wave - burst mode that has 50% on/off time 50 bursts per second with interburst interval of 10 milliseconds reduces total current but allows patient to tolerate greater current intensity used for strengthening gradually increasing the numbers of bursts interrupts the mechanical relaxation cycle of the muscle and causes more shortening to take place
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higher frequency currents _____ resistance to teh current flow |
reduce |
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interferential currents IFC |
electric field is created that resembles a four-petaled flower, with the center of the flower located where the two currents cross and the petals falling between the electrical current force lines maximum interference effect takes place nera the center, with teh field gradually decreasing in strength as it moves toward the poitns of the petal numbness under electrode frequency 1 = 4080, frequency 2 = 4000, output = 80 |
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premodulated IFC |
both frequencies = 4000, but each generator has bursts and overall syncs them in same polarity and same time no numbness larger treatment area than IFC |
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low-volt currents |
medical galvanism iontophoresis |
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therapeutic benefits of electricity |
modulation of pain muscle re-education and strengthening edema reduction muscle spasm reduction limiting atrophy wound care and tissue healing healing bone |
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capacitance |
ability of a tissue to store a charge the higher the capacitance, the longer before you see a response from the tissue greater intensity of stim needed nerve has less capacitance than muscle |
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ohm's law |
V=IR |
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constant current |
increase resistance, increase voltage maintain therapeutic effects consistent level of stimulation but potential for burn |
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constant voltage |
increase resistance, decrease current reduces risk of adverse effects to patient pt may experience rapid surge of current |
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pulse duration |
beginning to end of all phases, includes interphase interval |
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pulse period |
beginning to end of all phases, includes interphase interval AND interpulse interval |
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pulse rate |
number of pulses per second frequency rate cycles per second bursts per second beats per second pulses per second |
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accommodation |
patient's perception of stimulus changes over time nerve fibers become less responsive to stimulus increase threshold modulation can reduce this |
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modulations |
amplitude (scan) duration frequency (sweep) ramping duty cycle |
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ramping |
surging time it takes for repetitive pulses to reach maximum amplitude useful for muscle re-ed because it simulates normal contraction |
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strength-duration curve |
plots minimal intensity needed to evoke response at specific stimulus durations rheobase - intensity chronaxie - duration |
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order of stimulation in strength duration curve |
a beta motor neurons a delta c fibers denervated fibers |
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interferential current |
amplitude modulated AC or medium frequency beat AC 2 channels, each sinusoidal, symmetrical alternating currents with different frequencies beat frequency is lower than individual channels' frequency channels crossed and combined to peak amplitude is higher at the area where the channels cross - stim greatest here, less stim under electrodes
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russian current |
time modulated AC or medium frequency burst AC |
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high volt |
monophasic pulsed current |
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motor point |
specific location on the skin which requires lowest intensity of estim to excite muscle below |
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trigger point |
hyperirritable focus in fascia or muscle which is tender or painful to compression and may refer pain |
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acupuncture point |
tender site utilized for pain management and originally associated to traditional chinese medicine |
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comon uses for sensory or motor level TENS for pain control |
pain of musculoskeletal origin neuropathic pain pain from cancer post-operative pain acute and chronic pain |
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sensory level TENS |
biphasic, monophasic, ifc no muscle contraction low duration < 100 high frequency 80-150 continuous or modulated gate theory put pads in location or in dermatome 30 minutes |
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motor level TENS |
biphasic or monophasic muscle contraction low frequency < 10 high duration > 200 30-60 sec bursts for 20-45 minutes put pads over acupuncture, trigger points, and remote sites goal - stimulate motor fibers delayed onset of pain relief but longer lasting |
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noxious level TENS |
brief intense TENS/hyperstimulation analgesia biphasic or monophasic (point stimulators, up to 8 points for 30 seconds, needs large dispersive pad) high duration > 200 high frequency 100 30 sec to 1 minute, no more than 15 minutes longer pain relief - opiates pads over pain, trigger points, remote site, acupuncture points |
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best settings for patient comfort |
high frequency, low duration |
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burst mode TENS |
high frequency bursts delivered at a low frequency |
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scan |
amplitude modulation intensity at each channel can be set to change and causes direction of vectors to shift changes the area of stimulation to encompass greater treatment area use when pain area is ill-defined |
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sweetp |
frequency modulation |
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pre-modulated IFC |
bipolar electrode placement 1 channel often used with US combo interference current produced inside machine good for sensory level but can be used for motor "trigger points" |
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high volt current |
monophasic, twin peak fixed duration < 100 high intensity voltage 100-150 polarity issues tissue healing, pain control, muscle stimulation passes through skin with less resistance, less biochemical effect, less accommodation short duration lessen chance of stimulating pain fibers (SC curve) can adjust amplitude and frequency stagnant wound care - cathode for 3-7 days inflammatory, anode for after that, reverse polarity if healing plateaus galvanotaxis - attract cells to wound site put moist gauze on wound, pad on top of gauze |
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estim + US combo |
pre mod IFC/monophasic pulsed us sound head + dispersive pad trigger point, spasm relief, relaxation |
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evidence for TENS |
acute LBP - conflicting chronic LBP - no benefit, don't use other musculoskeletal and ns disorders - no data either way |
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proposed uses and benefits of NMES |
strenghtening muscle endurance muscle re-ed override reflex inhibition improve function treat spasticity decrease spasm limit atrophy increase ROM decrease contractures muscle pumping for edema control |
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motor unit recruitment for voluntary contraction |
type 1 (slow twitch) first then type 2 (fast twitch) |
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motor unit recruitment for electrically stimulated contraction |
type 1 and type 2 simulatenous some say type 2 first |
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adaptations in healthy muscles to NMES |
to prolonged, low force = endurance changes to intermittent, high force = strength changes follows overload principle |
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factors that influence muscle contraction |
frequency duration amplitude current type/waveform technique of application |
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twitch to tetany |
summation of contractions don't get back to resting state between twitches, continue to shorten creating additional tension start in comfortable range, goal is smooth contraction frequency dependent, not intensity force-frequency relationship fatigue factors strengthening, muscle re-ed, testing for motor point location, testing integrity of nerve/tendon |
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advantages and disadvantages of altering NMES |
advantage - increase contraction by recruiting more fibers disadvantage - hurts more |
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time modulated AC - russian or mf burst |
carrier frequency 2500 hz - sine wave broken up into 10 msec bursts on and 10 msecs off delivered at 50bps high frequency and interburst intervals - less pain no evidence that russian works better than biphasic in functionality terms goal - maximum contraction |
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factors that influence force production |
frequency duration intensity electrode placement, size, contact body composition |
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reciprocal electrode placement |
biceps and triceps contracts different muscles to work on ROM |
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NMES with contraction |
patient should contract with stim and should perform isometric contraction during off cycle stim needs to be at least 50/60% of MVIC for strengthening normal muscle - this level of stim not usually tolerated so go to pt comfort less stim needed for re-ed overload muscle to maximal comfortable contraction fatigue - may help reduce spasms - stimulate antagonist for reciprocal inhibition |
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effects of NMES on strength |
russian 30-40% gains in strength and functional performance 110-130% MVIC with stimulation high frequency allowed > stim > contraction BUT no evidence though to support the claim
but, for unexercised controls effective - coma pt or couch potato
no better than voluntary exercise
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NMES after ACLR |
in combo with exercise started early post-op period better than exercise alone no difference in long term outcome but quicker recovery |
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NMES for retraining weakened muscle |
reproduces many of the physical and chemical events associated with voluntary contractions less atrophy less of a decrease in MVIC upon release from immobilization |
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NMES for muscle re-ed of innervated muscle |
arthrogenic reflex inhibition post injury tendon transfers hemiplegia combine with voluntary contraction goal is to restore voluntary contraction |
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functional electrical stimulation FES |
orthotic substitution have pt try and hold contraction gait, CVA, spinal cord injury, TBI control spasticity improve functional reach |
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NMES for denervated muscle |
questionable/controversial may retard/delay atrophy in short term may delay fibrosis does not improve rate of regeneration or reinnervation probably does not hurt to try it though |
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NMES for nerve assessment |
neuropraxia - temporary conduction block - normal response below site of injury - limited to no response above site of injury axonal damage - denervated muscle - if complete lesion - no response above or below lesion ir partial lesion - weak response above and below |
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contraindications for NMES |
pacemakers, defibrillators, transthoracic carotid sinus/phrenic nerve pts unable to communicate or mentally immature insensibility pregnancy vascular disorders neoplasm |
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what is intophoresis |
continuous direct electrical current to drive ions into body tissue low current use of like charge to push medication through skin DC current, polarity matters non-invasive provides drug at constant rate better delivery than topical application often used for inflammatory musculoskeletal conditions used for analgesia, spasms, ischemia, calcium deposits, wound healing, scar tissue modification
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mechanism of ion flow |
neg medication on cathode cathode is active electrode - should be bigger anode is collective electrode solutions used are permeable to fat and water once the ions the pass through the skin, they combine with existing ions and free radicals to form new compounds for therapeutic effect pads up to 18 inches apart max current - 4.0 mA |
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quanityt of ions transferred into target tissue determined by |
current intensity current density (change electrode size) duration concentration of ions body tissue (skin and fat are poor conductors) |
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treatment considerations for iontophoresis |
electrodes - polarity of active electrode, spacing, size amplitude - max = 4.0mA, increase this increase propulsion of ions time - 10-20 minutes depth of penetration - 1-3mm avg, 1.5cm 12-24hr treatment medication dosage - 1-2% solution number of treatments duration of application - time inversely proportional to magnitude of current dosage = total charge delivered (usually 40mA-min) using other modalities with it - don't |
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indications for iontophoresis - limited evidence it works for anything though |
inflammation analgesia muscle spasm ischemia soft tissue calcification wounds and infection edema hyperhydrosis scar tissue and adhesions gout burns |
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contraindications |
broken or compromised skin decreased skin sensation drug sensitivity pacemaker other implanted devices in the region long term steroid use over ligaments and/or tendons |
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common negative medications and agents |
dexamethasone hydrocortisone salicylate chlorine iodine
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common medications and agents positive |
calcium magnesium lidocaine magnesium hyaluronidase mecholyl zinc |
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treatment precautions of iontophoresis |
chemical burns - pH changes at delivery electrode, most burns at cathode from accumulationof sodium hydroxide (buffered electrodes and increased electrode size can reduce this risk) heat burns - results from high resistance to current flow from poor skin contact sensitivity reaction to ions - ask pt about drug sensitivity before beginning, monitor pt skin |
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parameters for sensory TENS |
frequency 80-150 pps duration <100 clinical machine duration < 150 IFC tx time 20 minutes |
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parameters for motor TENS |
frequency <10 duration >200 clinical machine, portable unit duration <150 hvps (mpc) tx time 15-40 minutes |
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parameters for noxious TENS |
frequency 100 bps (point stimulator can be as low as 1-5 pps) duration >200 (point stimulator <150) tx time 1-15 minutes (point stimulator 30-45 sec at each point for 8-10 points) |
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parameters NMES for strengthening |
current - biphasic vms, mf burst ac, russian cycle time 6-10s on, 50s off frequency 50-80 ramp 2-5 sec duration >200 rx time 10-15 reps with max contraction, 3-5x/week used more in athletics to max strength gains |
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parameters NMES for muscle re-ed
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current - biphasic vms, mf burst, russian cycle time 1:1, 1:2 frequency 30-50 ramp 2-5 sec duration >200 rx time 15-20 min several times daily used most in rehab settings goal - voluntary contraction |
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parameters for NMES for functional estime |
current - biphasic vms, mf burst, russion cycle time - activity specific frequency 30-50 ramp short b/c used with functional activity duration >200 rx time 15-20 minutes several times daily can also be a portable unit with switches |
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parameters for EMS denervated muscle |
current dc or biphasic cycle time 5-10 sec on, 1 minute off frequency n/a or high (50-80) and low (10-25) ramp 5 sec longest duration possible rx time 10-20 contractions, 15-30 minutes 3-4x/day if using monophasic or dc current put cathode over target and use small electrode |
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HVPC can be used for muscle stim but has present short duration (usually <150) so what do you need to do to intensity |
increase it |
