EXAM 2: Week 1 Flashcards
4 Principles of Electricity
- Two charges (positive proton, negative electron)
- Like charges repel while opposites attract
- Charge is neither created nor destroyed
- Charge can be transferred from one object to another
Polarity
Refers to the charge on an object
- cathode: negatively charged pole
- anode: positively charged pole
Voltage
Force of attraction or repulsion created by an electrical field, represents potential energy
Greater force = _______ potential energy
Greater
Charges in the body
Na+
K+
Cl-
Electrochemical gradient with potential energy charges inside and out of cell
Greater Na+ outside cell
Greater Cl- inside cell
List conductors and insulators in the body
- Conductors: water/fluids, nerve, muscle tissue
- Insulators: fat
Current
Movement of ions/electrons in response to voltage force
Ohms Law
I=V/R
Current = voltage/resistance
Ohm = standard of resistance
More resistance to current, the less current there will be
Capacitance
When current is flowing in an insulated area with high resistance, current will slow and charge will start to store in that area
When current flow STOPS, stored energy will flow back through the conductors
Impedance
Resistance to the flow of alternating current (gels and adhesive conductive agents help decrease impedance)
Types of Electrical Current
- direct current
- alternating current
- pulsed current
Waveforms axis
X- time or duration
Y- amplitude or intensity
Types of direct current
- direct
- interrupted
- reversed
-interrupted/reversed
What is the most common use of direct current
Iontophoresis
Alternating current
- uninterrupted bidirectional flow of electrons, must change direction at least once per second
If it does not, it is direct
Pulsed Current
Unidirectional OR bidirectional flow of electrons that periodically ceases for a short time period, the interphase/inter pulse interval, before the next event of pulse
Burst (in PC)
2+ pulses separated from the next series of pulses
Pulsed Current On Time
Duration that a series of pulses or bursts is delivered
Duty Cycle of pulsed current
On time/ total time (x 100)
Any 1: 4 RATIO WILL BE 20% DUTY
Amplitude Modulation
Gradually/progressively increase current amplitude
Phase Charge vs Pulse Charge
Phase charge: charge within one phase of a pulse
Pulse charge: charge within a single pulse
Effects of electrical current
- electrochemical effects
- electro thermal effects
- electrophysical effects
Electrochemical effects of electrical current in body tissues
AAA- anode attracts acid —> skin hardens
CAB- cathode attracts base —> skin softens
Electro thermal effects of electrical current in body tissues
- as particles flow through a conductor, friction occurs as they meet resistance and produce kinetic energy which produces heat
Skin resists transcutaneous delivery of current making heat at the electrode site a concern
How do you reduce friction
reduce friction by shaving, removing oils, removing lotions
True or False: Nerves are depolarized first, then muscles
TRUE
Levels of response to E-Stim
Sensory: perception of pins and needles; simulation of A-B sensory fibers in the superficial dermis
Motor: increased stimulus causes A-alpha motor neuron to depolarize and elicit a motor response
Noxious: further increase in intensity or duration beyond that capable of eliciting sensory or motor response stimulates pain receptors (USED FOR THERAPEUTIC PURPOSE)
Strength Duration Curve (order of depolarization)
Sensory, motor, a delta sharp pain, c dull pain, denervated muscles
Russian current (burst modulation)
Variation of AC used for strengthening muscles
High volt pulsed current (HVPC)
Continuous, reciprocating, or surge; monophonic
Used for pain modulation, tissue repair, wound healing
Interferential current (IFC)
Quadripolar or bipolar set ups
Used for pain modulation
Clinical devices vs battery powered devices
Clinical - line powered, limited portability
Battery - needs batteries, portable, pt can take to do at home
Modulator circut
Takes original current source and changes it into the desired output current
Constant voltage
- voltage force driving the current stays constant and current intensities change
- current increases/decreases based on resistance of the skin
(Sweat decreases resistance and thus current will increase)
Constant Current
Maintains constant flow of current by modulating voltage
May be a better choice for tx as intensity is maintained closer to the level required for therapeutic purposes
Types of electrodes
- disposable - many shapes and sizes, reusable for multiple applications (18-20 applications)
- flexible - carbonized silicon rubber, reusable, pliable with good conductivity
- metal - wet sponge btw metal and tissue, great conductor, lack flexibility
Electrode size determined by
Goal of tx
Size of tx
Smaller electrode, higher the density will be under it
Smaller electrode, ________ density will be under it
Higher current density
- high levels of simulation with small electrode may cause BURNING
- appropriate for smaller muscles and tx areas
Large electrodes = ________ current density
Smaller current density = more comfortable
E stim uses
Activate skeletal muscle performance and strength
Decrease pain
Increase blood flow
Decrease or control edema
Facilitate tissue healing
Contraindications for ESTIM
- over pace makers
- over pregnant women
- carotid bodies
- phrenic nerve or urinary bladder stimulators
- peripheral vascular disease
- eyes or gonads
- areas of hemorrhage
- areas of active osteomyelitis
Iontophoresis
- delivery of medications across skin to target tissue through ESTIM
Iontophoresis Uses (DC)
Soft tissue inflammatory conditions
Neuralgia
Edema
Ischemic skin ulcers
Plantar warts gouty arthritis
Calcification tendinitis
Scar tissue
Electromigration physiology of Iontophoresis
Using estim to move charge ions into the target tissue
Like charges repel, opposites attract
Electroporation physiology of Iontophoresis
Increase in porosity of superficial skin in response to ES allows meds to enter target tissue more easily
Electroosmotic flow
- when positive and negative electrodes applied to skin , ions of + charge in the extracellular fluid attracted to the cathode & ions of - charge attracted to the anode
- creates bulk movement of solute in response to the electrical field and helps move ions into the tissue
*human skin contains net negative charge, the direction of electroosmotic flow is from the anode to the cathode
Dexmethazone charge
A NEGATIVE MEDICATION
Current density formula
Current amplitude / conductive surface of electrode
Iontophoretic equation
Dosage = current x duration
Typical iontophoresis dosage
20-80mA (current) min
- require 5-20 min duration with peak amp of 4 (pts may report burning, itching, or stinging/tingling)
