The use of electric current in physical therapy

What is the measure of charge?

(Q) or Coulomb (C)

What is voltage? What is voltage measured in?

(V) Potential difference 1J/1C

Where does AC current come from? Where does DC current come from?

AC from electric power plant DC from battery device

At least how many electrodes are needed on skin to create potential difference? What creates biologic response?

At least 2 electrodes needed to create potential difference Shifting of cations/anions in the tissue. Felt through depolarization of the cell

What is current? What are formulas for current? What is current measured in? What is current measured in in biologic systems Current depends on

I I = deltaQ/deltaT or I = V/R Amperes (A), 1A = 1C/sec millamps (mA) or microamps (uA) Current depends on voltage. Have to have voltage to create current.

What changes in a constant current device? What changes in a constant voltage device? Why is a constant current device better? How does electrotherapy change blood flow?

In a constant current device, resistance/impedance and voltage changes In a constant voltage device, resistance/impedance and current changes Because current is what the person is feeling. --Fluids are a good conductor of current. Certain amount of moisture on electrode. The skin / electrode could get drier and cause more resistance. --As muscles contract, blood flow increases which will lead to a decrease in blood flow

What are clinical applications of ES? What is their function?

NMES: neuromuscular electrical stimulation -- stimulate motor neuron to contract muscle FES: Functional electrical stimulation -- helps overcome paralysis EMS: electrical muscular stimulation -- stimulate the muscle directly TENS: transcutaneous electrical nervous stimulation -- pain control ESTR: electrical stimulation for tissue repair

What is DC current? What is time frame of DC? What source gives a direct current? When is DC used in physical therapy

Unidirectional flow of electrons, lasts greater than a second Battery Iontophoresis (deliver medicinal ions through the skin) and wound healing

Describe positive and negative on a waveform What are is area under a curve on a waveform?

Up on a waveform is negative Down on a waveform is positive Tell how much charge a patient will receive; the larger the area, the greater the charge

Charge of cation cathode Chare of anion anode What is force between two charges? Do opposite charges attract or repel Do like charges repel or attract?

cation (+), cathode (-) anion (-), anode (+) Coulomb's Law F = k(Q1xQ2)/r^2 Opposite charges attract Like charges repel one another

What are electrodes? What are requirments of electrodes (3) What are electrodes coated with? What are two types of electrodes

electrodes are sites of conversion from electron flow to ion flow 1. Must be good conductors 2. Must conform to surface of skin 3. Must be secured to skin transcutaneous and percutaneous

Components of iontophoresis machine (5)

signal generator power supply transformers, rectifiers, regulators (converts AC or DC into clinically useful current) Oscillator circuits (operator controls) Potentiometer (variable resister) controls output

Electrothermal effects of estim *Movement of electrons through a conductor causes... Vibration + friction = What is Joule's Law? Order electrothermal heating effects from smallest to largest: DC, PC, AC Does heat produce therapeutic heat?

... microvibration of molecules/atoms =heat H = 0.24 I^2Rt DC>AC>PC

What is 1 Coulomb equal to? What are biologic systems measured in? What is polarity

1 electrons = 6.28 x 10^18 microCoulomb = 10^-6 polarity is (+) or (-)

Name the effects of 1 mA 16 mA 50 mA 100 mA to 3 mA 6 A

1 mA: threshold for tingling sensation 16 mA: cannot release grip on electrical conductor due to muscle 50 mA: pain, possible fainting 100 mA to 3 A: ventricular fibrillation may occur 6A: sustained myocardial contraction, temporary paralysis, burns

What are keys to good conduction? (3)

1. clean and hydrated skin 2. clean and properly prepared electrodes 3. prevention of skin irritation

What are the 2 types of electrical stimulation devices?

1. electric-line (clinical) 2. Battery-operated (portable)

What are physiologic responses to electrical stimulation (3)

1. electrothermal effects 2. electrochemical effects 3. electrophysical effects

How to prevent injury from electricity:

3-prong plug, GFCI, annual safety inspections by biomedical technician

What is balanced PC wave? What is unbalanced PC wave? When is balanced PC wave used? When is unbalanced PC wave used?

Balanced: area in one part of pulse equal to another area; negativity balanced by positivity (eg. C = D) Unbalanced: one area has larger pulse than another (eg. C does not equal D) Balanced for ms contraction and pain control Unbalanced used for wound healing

What is alternating current? What is time frame of AC? Where is AC found in homes? What is shape of AC current?

Bidirectional flow of electrons less than a second electrical outlets (120 V, 60 Hz) sinusoidal or irregular shape

What unit that Russian current is measured in? What unit is interferential current measured in?

Burst Beat

What is charge density? A small electrode will have greater or lesser charge density? A large electrode will have greater or lesser charge density? Will patients feel more comfortable with a small or larger electrode?

C/cm2 Small electrode will have a higher charge density Large electrode will have a small charge density Larger electrode (patient feels more with small electrode)

Electrochemical effects of estim Name the chemical reactions that take place at the cathode and anode How does body respond to electrochemical effects? Which type of current is most likely to cause skin irritation? How to prevent this?

Cathode: 2 NA + water --> 2NaOH +H2 (alkaline) Anode: 2Cl2 + 2H2O --> 4H2Cl + O2 (acid) Normal response: increased blood flow to maintain pH DC most likely to cause irritation Low intensity DC

What is a material that current readily flow through? Give an example What is a material that current does not readily flow through? Give an example

Conductor Metal Insulator Rubber or plastic

What is relationship between electron size and density of current? What happens if electrode not in complete contact with skin? What will happen when electrodes are faced further apart?

Current inversely proportional to electrode/skin contact area Density of charge will be very high Current will go deeper and cause muscle contraction

Precautions and contraindications for electrical stimulation

Current passing through the heart Cardiac pacemakers Implanted stimulators Current passing through the carotid sinuses in the neck High or low blood pressure Peripheral vascular disease Thrombophlebitis Pregnancy Current passing through the pharyngeal area Sensory deficits Acute trauma / inflammation History of seizures Immature or confused patients Obesity Osteoporosis Cancer Performance of electrotherapy treatments in close proximity to patients receiving diathermy

What is pulsed current? What are types of pulsed currents?

Current that flow less than a second Monophasic or biphasic Symmetrical or asymmetrical Balanced or unbalanced

Electrophysical effects of estim What is movement of ions called? Where does excitory response occur? Where does non-excitory response occur?

Electrokinetic effect Nerves, muscles Cell processes, microcirculation

What is a train of pulses? What is a ramp up, ramp down of pulses What will patient feel with train of pulses?

Equal in frequency, amplitude, duration Increase in intensity, decrease in intensity Buzz, buzz, buzz, buzz

Is interferential used to pain control or muscle strengthening Is Russian used for pain control or strengthening? What is most commonly used electrotherapy in PT

Interferential is used for pain control Russian is used for strengthening Pulsed current

Is there current or voltage in a parked car? What does turning the key of the car do? Is current or voltage moving? Where does current come from in line driven devices?

No current. Yes for voltage (potential difference due to battery) Turning key allows potential of difference of battery to flow through the car Current is moving. Voltage is not moving Power plant

What is resistance? What is resistance measured in? What is 1 Ohm equal to What is Ohm's law? What is relationship between current and voltage? What is relationship between current and resistance? Where is the greatest resistance in a patient? What must a therapist do prior to electrotherapy What are 3 properties of conductance? What is capacitance?

R Ohms 1 Ohm = 1A to flow at 1 V I = V/R Current and voltage is directly proportional Current and voltage are indirectly proportional Stratum corneum (dead layer of skin, top layer of skin, above epidermis) PT's clean the skin of lotions or dirt Capacitance, biologic capacitor, impedance (Z) The ability to store charge; couple of insulators with a charge in between

What is another name for time-modulated AC? What is another name for amplitude-modulated AC?

Russian or burst interferential