Electrical Agents Flashcards
Resting membrane potential - cell membrane is more permeable to
potassium compared to sodium and negatively charged proteins (anions)
Electrical potential is generated across the cell membrane due to
higher concentration of K and anions on the inside relative to concentration of Na on outside
Resting membrane potential is maintained by
active Na/K pump that takes in K and extrudes Na
Action potential - a stimulus causes the cell membrane to become
more permeable to Na ions
An action potential is generated when
the influx of Na causes a reduction in resting membrane potential which occurs slowly at first
this reduction in membrane potential is called depolarization
During depolarization, transmembrane potential is where
can be as high as+35 mV
a positive charge is generated inside the cell and a negative charge outside the cell is produced
Repolarization - what happens
K channels are fully open at about the time that the Na are closed and K rushes out of the cell making the membrane potential more negative
Hyperpolarization - what happens
K channels stay open long enough to repolarize the membrane
Strength-duration curve: Rheobase
the intensity of the current with a long duration stimulus required to produce a minimum muscle contraction
Strength duration curve: Chronaxie
the pulse duration of the stimulus at twice the rheobase intensity
Motor point
An area of greatest excitability on the skin surface in which a small amount of current generates a muscle response
In an innervated muscle, the motor point is located
at or near where the motor nerve enters the muscle, usually over the mm belly
In denervated muscle, the motor point is located
over the muscle distally toward the insertion
The current has what relationship with voltage
directly related
The current has what relationship with resistance
inverse relationship
Inverse of resistance is called
conductance
Monophasic wave forms
Direct or galvanic
A unidirectional flow of charged particles
Current flow in one direction for a finite period
All either above or below baseline
Biphasic wave forms
alternating current
a bidirectional flow of charged particles
1/2 the cycle above baseline, 1/2 below
Polyphasic wave forms
biphasic current modified to produce three or more phases in a single pulse
medium freq and can be Russian or IFC
Current modulation - Surge mode
a gradual increase and decrease in the current intensity over a finite period of time
Current modulation - Ramped mode
a time period with a gradual rise of the current intensity which is maintained at a selected level for a given period or time followed by a gradual or abrupt decline in intensity
Contraindications to Estim
Anywhere that pt has pacemaker or electronic device
Over or in area of carotid sinus, thromb, eyes, thoracic area, phrenic, low back with preg
Presence of active bleeding or infection
Superficial metal implants
Pharyngeal/Laryngeal mm
Guidelines - Electrode size
Two leads are required to complete the current circuit
One active and one inactive (or dispersive)
Guidelines - current density
relative to electrode size
A given current intensity passing through the smaller active electrode produces high current density and thus a strong stimulus while same current is perceived as less intensive under a larger dispersive electrode
Active electrode is usually placed over
the treatment site - motor point
Unipolar/Monopolar placement
one electrode or multiple bifurcated active electrodes placed over a treatment area
Bipolar placement
Equal sized active and dispersive electrodes on same mm group or in same tx area
Space between active and dispersive should be
at least the diameter of the active electrode
Ionto - what is it
application of a continuous direct current to transport medicinal agents through the skin or mucous membranes for therapeutic purposes
Ionto - polar effects - positive ions move toward
negative pole (cathode) where a secondary alkaline reaction (NaOH) occurs
Ionto - polar effects - negative ions move toward
the positive pole (anode) where an acid is produced (HCl)
Ionto - the number of ions transferred through the skin is directly related to the
duration of treatment
current density
concentration of ions in the solution
Characteristics of ionto
direct current
max intensity of 4-5 mA
TENS is what
designed to provide afferent stimulation for pain management
TENS - physiological effects
pain modulation through activation of central inhibiiton of pain transmission
Large diameter A beta fibers activate inhibitory interneurons producing inhibiiton of smaller A delta and C fibers (pain fibers)
TENS - characteristics - wave form
typically asymmetrical biphasic with a zero net direct current component
Current can be continuous, pulsatile, or burst
conventional high rate TENS - amplitude -
comfortable tingling sensation, paresthesia, no mm response
gate theory
conventional high rate TENS - pulse rate
50-80 pps
conventional high rate TENS - pulse duration
50-100 usec
conventional high rate TENS - mode
continuous
High voltage pulsed galvanic stimulation is what
high voltage pulsed current - typically monophasic, twin peaked pulses of short duration
ES characteristics of HVPC - wave form
paired monophasic, with instantaneous rise and exponential fall of current
ES characteristics of HVPC - current
continuous, surged, or interrupted pulsatile current
ES HPVC - procedure of how it works
Intact skin surface is neg with respect to deeper epidermal layers
Injruy to skin develops pos potentials initially and neg potentials with healing process
Absent or insufficient pos potentials retard tissue regeneration
Addition of pos potentials may accelerate or promote healing
HPVC - wound healing parameters
Amplictude - analgesic Pulse rate - 50-200 pps Pulse duration - 20-100 usec Mode - continuous Tx time - 20-60 min
Medium frequency current ES is what
freq in range of 2000-5000 pps that are modulated to produce physiologically applied freq
Russian and IFC
Russian current description
a 2500 Hz which is interrupted for 10 ms at 10 ms intervals, producing 50 10 ms bursts per second
ES characteristics with Russian - wave form
wave form is polyphasic, sinusoidal
Russian - parameters
Amplitude - mm contraction
Pulse rate 50-70
Pulse duration 150-200 or 50% duty cycle
Mode - interrupted, ramp 1-5 sec, duty cycle 1:5
Russian - mm spasm protocol
1:1 ratio
IFC - description
characterized by crossing of two sinusoidal waves with similar amplitudes but different carrier freq that interfere with one another to generate an amplitude modulated beat freq
IFC - constructive interference
two waves are in phase, the sum of superimposed wave is large
IFC - destructive interference
the sum of the two waves is zero when the waves are 180 degrees out of phase
IFC - beat freq
resultant freq produced b the two freq going in and out of phase
Can be constant (both freq are fixed) or can be variable (where one is fixed and other varies in freq)
Functional ES
encompasses wide rage of stimulator units and techniques for disuse atrophy, impaired ROM, mm spasm, mm re ed, and spasticity management
FES also called NMES
ES characteristics of FES - wave form
asymmetrical biphasic square
current is iterrupted pulsatile current
FES - parameters if using for shoulder subluxation after CVA
Amp: tetanic mm conraction
Pulse rate - 12 to 25 pps
Tx time - 15 to 30 m
On/off ratio of 1:3
EMG biofeedback
electronic instrument used to measure motor unit action potentials generated by active mm
signals are detected, amplified, and converted into audiovisual signals that are used to reinforce voluntary control
