Electrical Stimulation Flashcards
ES: General Characteristics Nerve/Muscle Cells
Duration of 1 ms is enough to depolarize a nerve cell, too short to stimulate a muscle cell 10 ms with high intensities needed for denervated muscle Rate of rise must be rapid enough to prevent accomodation (square wave = instantaneous rise)
ES: Rheobase
Intensity of the current (have a long duration) required to produce a minimum muscle contraction
ES: Chronaxie
Pulse duration of stimulus at twice rheobase intensity.
Chronaxie of a denervated muscle is greater than 1 ms
ES: Motor Point
Area of greatest excitability on skin Small currenct generates a muscle response
- innervated muscle located at/near where motor nerve enters muscle, usually over belly
- denervated muscle - located over muscle distally towards insertion
ES: Types of MS Contraction
Low freq pulse (1-10/sec) produces brief twitch with each stim
Increasing number of stim progressively fuses twitches to tetanic contraction
Asynchronous/worm-like (vermicular) muscle response is noted in denervated muscle
ES: Amperage
Rate of flow of electrons
ES: Voltage
Force driving electrons
ES: Ohm’s Law
Current is directly proportional to voltage and inversely proportional to resistance.
ES: Monophasic Waveform
Direct/galvanic Unidirectional flow Has either positive or negative charge
ES: Biphasic Waveform
Alternating current Bidirectional flow Half cycle above baseline, half below Two phases = one cycle Zero net charge if symmetrical
ES: Polyphasic Waveform
Russian current or interferential current Biphasic current modified to produce three or more phases in a single pulse
ES: Surge Mode
Gradual increase in decrease in intensity over finite period of time
ES: Ramped Mode
Gradual rise in intensity with maintenence of intensity at a selected lever for a given period of time. Then gradual or abrupt decline.
ES: Indications
- Pain modulation
- Decrease muscle spasm
- Increase/Maintain ROM
- Muscle re-education
- Disuse atrophy
- Soft tissue repair
- Edema Reduction
- Spasticity
- Denervated muscle
ES: Contraindications
- Anywhere in body w/ demand type pacemaker
- Unstable arrhythmia
- Suspected epilepsy or seizure disorder
- Over area of carotid sinus
- Thrombosis
- Eyes
- Thoracic region
- Phrenic nerve
- Urinary bladder stimulators
- Abdomen Low back during pregnancy
- Transcerebrally or thoracic
- Active bleeding or infection
- Superficial metal implants
- Pharyngeal or laryngeal ms
- Motor level stim should not be applied in conditions that prohibit motion.
ES: Precautions
- Cardiac dx
- Impaired mentation
- Areas of impaired sensation
- Malignant tumors
- skin irritation
- open wound
- Iontophoresis after other agent
- Hyper or hypotension
- Excessive adipose tissue/edema
- Bleeding disorders
- Menstruating uterus
- Pregnancy: during labor or delivery
ES: Electrodes
- Two required - one active (stimulating), one dispersive
- Active placed on motor point
- Dispersive placed on treatment site or at a remote site
- Current density is relative to electrode size (small size, high density, strong stim)
- Electrode size should be relative to size of treatment site
ES: Electrode Placement
- Unipolar/monopolar:
- Single or bifurcated active electrodes placed over treatment area.
- Usually larger size dispersive electrode placed ipsilaterally away from treatment area.
- Bipolar:
- Equal sized active and dispersive electrodes in same treatment area.
- Space between A and D electrodes should be at least the diameter of the active electrode and as far as practically possible.
- Greater space = less current density in intervening tissue - less risk of burns and skin irritation.
ES: Ms Strength/spasm/edema (ms pump)
- Slowly increase intensity until muscle response observed 10-25 contractions may be sufficient depending on goal
- Muscle re-education sessions may last 10-30 mins
- Interrupted/ramped allows muscles to recover Ratio of 1:3 or more minimizes fatigue
- Use continuous to enduce fatigue for spasm
ES: Methods to decrease muscle spasm
- Muscle fatigue - tetanic contraction
- Muscle pump - interraupted/surge modulation, increase circulation
- Muscle pump and heat - Combination of elec stim and US to increase tissue temp and produce muscle pump at same time
ES: Methods to increase ROM
mechanical stretching - used when muscle strength in deficient of dysfunction (e.g. spasticity) prevents adequate joint movement
ES: Wound Healing - Pulsed Currents
Interrupted modulations Improved circulation (muscle pump) - improved tissue nutrition and waste metabolism
ES: Wound Healing - Monophasic
- Low volt continuous, high volt pulsed Low amp for 30-60 mins
- -Restores electrical charges at wound -
- Disruption of bacerial DNA, RNA synthesis, cell transport
- Increased ATP concentration, amino acid uptake, protein and DNA synthesis
- Inflammation -
- Macrophages (+ve), mast cells (-ve), neutrophils (+ve/-ve)
- Proliferation
- Fibroblasts (+ve) Wound contraction - Alternating (+ve/-ve)
- Epithelialization - Epithelial cells (+ve)
ES: Edema Reduction
- Muscle pump - increase lymph and venous flow
- Electrical field phenomenon - Effect of electrical charge in interstitial proteins increase lymph and venous flow.
ES: Spasticity
Fatigue of agonist Reciprocal inhibition - stimulate antagonist, inhibit agonist
ES: Stimulate Denervated Ms
- Controversal Goal is to decrease effects of disuse and shorten recovery time
- May be deleterious to denervated muscle by:
- Interfering with regeneration of NMJ and subsequent reinnervation
- Traumatizing hypersensitive denervated muscle
- Financial cost and prolonged treatment time required until reinnervation are additional factors to consider.
