Exam 2 Study Guide Flashcards
Pulse Period
amount of time from the start of one pulse to the start of the next pulse
Pulse Duration
contributes to the comfort of the stimulation, the amount of chemical changes that occurs in the tissues, and nerve discrimination. 50 to 100 us is typically used for sensory stim, 200 to 300 is used for motor stim
interpulse interval
time between the end of one pulse and the start of the next pulse, allows for mechanical changes in the tissues, such as when eliciting muscle contractions
Constant Current Stimulators
the advantage is to ensure a consistent physiological response during the treatment, the negative is potential pain when the voltage increases to overcome resistance.
Constant Voltage Stimulators
This unit is advantageous in preventing discomfort with changes in resistance, but quality of response can be decreased with these automatic resistance changes
What is the advantage of pulsed biphasic current? How can a physical therapist manipulate duration and frequency to treat a variety of ailments?
This is alternating current with Interrupted flow of charged particles where the current flows in a series of pulses separated by periods where no current flows. Used for pain control, tissue healing, muscle contraction and is the waveform most often used for electrical stimulation
What is interferential current? How is IFC set up differently than pulsed biphasic?
Interference of 2 medium frequency alternating currents of different frequencies, delivered on separate channels/electrodes (placement of electrodes matter)
Benefit: the different waveforms reduce impedence allowing for a deeper sensory experience, great for joint pain (“bracket the joint”)
What is modulation? Why would a therapist consider using modulation?
Irregular patterns of stimulation to minimize the accommodation effects of regular patterned stimulation. It is useful for patients who use TENS for multiple hours in the day.
Describe how iontophoresis works
Iontophoresis is the use of DC current for transdermal drug delivery for musculoskeletal inflammation. Polarity of medication is matched to the polarity of the electrode. Medication is pushed into the stratum corneum over a targeted anatomical structure (dexamethasone)
How is iontophoresis different than phonophoresis?
Phonophoresis is the use of sound energy, it also transports whole molecules into the skin while iontophoresis transports ions into the skin
Impedance
The resistance of the tissue to the passage of electrical current.
Electrical Current (negative and positive electrodes)
Negative electrode: Cathode (black cat) high electron concentration, active electrode and attracts positive ions. Alkaline reaction
Positive electrode: Anode low electron concentration, thus will attract negative ions. Acidic reaction
ONLY USE THESE TERMS WITH MONOPHASIC CURRENT
Circuit Types
Series Circuit: one pathway is available for travel (this is how current enters the body)
Parallel Circuit: two or more routes exist for the current to pass between the two terminals (this is how current moves in the body)
Human Tissue: Conductor or Non-Conductor
Skin: offers the chief resistance to current flow and is considered an insulator. The greater the impedance of the skin, the higher the voltage of the electrical current must be to stimulate the underlying nerve and muscle.
Blood (best conductor), muscle (good conductor), tendons (poor conductors), fat (poor conductor), bone (poorest conductor)
Effects of Electrical Stimulation
Electrical currents exert physiological effects by depolarizing the nerve membranes resulting in production of an action potential. Electrical currents reverse the electrical gradient of the nerve to create a depolarization.
Amplitude
Increasing amplitude provides current to deeper tissues. Lower settings = sensory stimulation, higher settings = motor level stimulation, also termed intensity. Amplitude and pulse duration have the most impact on how a patient feels and responds to electrical currents.
Pulse Duration/Width
Short duration with low intensity depolarizes sensory nerves
longer pulse durations are required to stimulate motor nerves.
very long pulse duration with high intensity is needed to stimulate denervated muscle.
interpulse interval
Increasing the pulse frequency decreases the interpulse interval and vice-versa
Pulse Frequency/Pulse Rate
E-Stim = more fatiguing, preferential to type II muscle fibers
Contributes to the type of contraction.
1-10 pps = twitch contraction
>30 pps = tetanic contraction
30-70 pps = non-fatiguing tetanic contraction
100-1000 pps = fatiguing tetanic contraction
Monophasic/Direct Current (DC)
Flow of electrons is unidirectional, polarity is constant. The placement of the cathode and anode electrodes matter, want to create chemical changes by building polarity.
Alternating Current (AC) or Pulsed Biphasic Current
The placement of the cathode and anode does not matter, bidirectional flow of electrons marked by periods of noncurrent flow. Jack of all trades, 3 types of biphasic currents: Symmetrical (most common), balanced asymmetrical or unbalance asymmetrical is not commonly used.
Strength Duration Curve
Represents the minimum combination of current strength (amplitude) and pulse duration (msec) needed to depolarize motor nerves.
A-beta nerves, motor nerves, a-delta nerves, C fiber/ dull pain nerves, denervated muscle
Lower amplitudes and shorter pulse durations (<80 us)
depolarize sensory nerves
Higher amplitude and longer pulse durations (150-300 us)
depolarize motor nerves
What is a motor point?
Area of greatest excitability on the skin surface at which a small amount of electrical current generates a strong muscle contraction.
How can you find motor points?
Locate motor points by trial and error
Innervated muscles – where motor nerve enters the muscle, over the belly.
Denervated muscles – over the muscle distally toward the insertion
Accommodation
Process by which a nerve gradually becomes less responsive to stimulation.
Electrode size has effect on current density…
Small size = high density, low current spread (better for small muscles)
Large size = less density, increased spread (better for large muscles)
Electrode placement has effect on current density
Spacing between electrodes affects the depth and course of currents, close spacing results in superficial application, far apart spacing results in deeper application, minimum 1 inch apart.
Quadrapolar Technique
Four electrodes of equal size, requires two channels or leads, currents intersect with each other, most popular use is with interferential stimulation.
Bipolar Technique
Electrodes from leads are of equal size, resulting in nearly equal current density under them, sensory and motor applications.
Monopolar Technique
Electrodes of unequal size, creating active and dispersive electrode (larger) applied to remote location. Active electrode applied to treatment area, dispersive electrode applied to remote location, iontophoresis is the primary example.
Indications for TENS
Pain relief
Indications for Monophasic
Reduce edema, wound healing, improve circulation, administer medication, stimulation of denervated muscle, fracture healing.
Indications for NMES
Reduce edema, decrease atrophy, increase strength and endurance, muscular reeducation, improve circulation.
Indications for FES
Decrease atrophy, increase endurance, muscle reeducation.
Indications for Micro current
Fracture Healing
Low-Rate TENS
low frequencies (2-10pps) and long durations combined with high intensities, produce brief sharp pain resulting in release of endogenous opioids. Recommended when a longer duration of pain control is required (hours)
High Rate TENS
Recommended when sensation, but not muscle contraction will be tolerated. Example is after a recent injury where inflammation is present or over tissues that may be damaged by muscle contraction
High Rate E-Stim pulse frequency
100-150 pps