General Principles For Application Of Electrophysical Agents Flashcards
What is an electric current
The flow of electrons from an electron source to the wires and electrodes used to deliver it to the tissues
When does the electric current flow?
If there is a (potential) difference in the distribution of electrons between the two poles of electrical circuit
(Electromotive force)
Components of a circuit
Electro therapeutic device
Wires
Electrodes
Medium
Conductor
What is conductance
Ability to transmit charged particles
Electrons can move if there is a easy pathway which is the ____________________.
Conductor
Examples of conductors :
Carbon
Copper
Aluminium
Gold
(Metals)
What is a conductor
Material permits free movements of electrons
What is a capacitor
The ability to store charges
What is the most important capacitor in our body
Cell Membrane
What is a resistor
Materials resist the flow and have no free ions/electrons
(Materials that offer resistance to the electron flow)
What is resistance ?
Ability of a resistor to oppose the current flow
What is impedance
The opposition of our biological tissues to the flow of an electrical current
Both resistance and electrical impedance are measured in what unit?
Ohms (Ξ©)
Components of the device
Generator
Oscillator
Transformer
Rectifier
Filter
Regulator
Amplifier
Types of devices based on power sources
Small portable devices (battery)
Large clinical devices (electric current circuit)
Types of current
Direct current
Alternating current
Pulsatile current
What is direct current
Continuous unidirectional flow of charged particles for 1 second or longer
The direction of the flow is determined by what ?
Polarity
Another name for direct current
Galvanic current
Direct current is good for the treatment of what kind of muscles ?
Denervated muscles
Iontophoresis is an example of which type of current
Direct current
What is another name for alternating current
Faradic current
What kind of muscle is alternating current used for
Innervated AND denervated
What is alternating current
Continuous bidirectional flow of charged particles for 1 second or longer relative to the baseline (zero)
What is pulsatile current
Noncontinuous interrupted periodic flow of direct current OR alternating current
What direction does a pulsatile current flow in?
Can be UNIDIRECTIONAL (monophasic) or BIDIRECTIONAL (biphasic)
What are some current waveform shapes?
What can we conclude from current wave forms?
Waveform shapes:
- sinusoidal
- rectangular
- square
- spiked
Current waveform is a graphic presentation of:
- shape
- direction
- amplitude
- duration
- pulse frequency
What shape is this waveform ?
Sinusoidal
What shape is this waveform?
Rectangular
What shape is this waveform?
Spiked (twin-spiked)
What is meant by monophasic current ?
A pulse or cycle that moves in only ONE direction from the zero baseline to return to it after a finite time
(Unidirectional)
What is meant by biphasic current ?
A pulse or cycle that moves in ONE DIRECTION and then in the OPPOSITE DIRECTION from the zero baseline to return to that baseline after a finite time .
(Bidirectional)
Biphasic current may be ______________________ or _____________________.
Symmetrical
Asymmetrical
What is meant by SYMMETRICAL biphasic current
A pulse or cycle with the positive phase geometrically IDENTICAL to the negative phase.
What is meant by ASYMMETRICAL biphasic current
A pulse or cycle with the positive phase geometrically DIFFERENT to the negative phase.
Asymmetrical biphasic currents can be either _________________ or __________________.
Balanced
Unbalanced
What is meant by BALANCED asymmetrical biphasic current
Biphasic pulse or cycle with EQUAL charges in each phase
What is meant by UNBALANCED asymmetrical biphasic current
Biphasic pulse or cycle with UNEQUAL charges in each phase
What is a pulse ?
Is it monophasic or biphasic ?
What is another word for pulse ?
A current flow in each direction of the phases for a determined period of time
Can be either monophasic or biphasic
Cycle
What is a phase
The period of time, collapsing from the beginning to the end of one phase, usually expressed in microseconds or milliseconds
Pulse duration (width) vs Phase duration (width)
Pulse duration:
-period of time from the beginning to the end of TWO phases within a pulse or cycle
- INCLUDING interphase duration (time between 2 phases)
- expressed in microseconds or milliseconds
Phase duration:
- period of time from the beginning to the end of ONE phase
- Expressed in microseconds are milliseconds.
Highlight the pulse duration in this image
Highlight the phase duration in this image
Phase duration A is separate from Phase duration B
Highlight the interphase (intrapulse) duration in this image
NOTE:
- Inter = between
- Intra = within
Highlight the interpulse duration in this image
Interpulse interval VS Interphase interval
Interpulse interval :
- Time between two successive pulses/cycles
- Expressed in microseconds or milliseconds.
Interphase duration:
- Time when the current is not flowing between two phases of a pulse
- Expressed in microseconds or milliseconds.
Where is the interphase (intrapulse) interval in this image
There is none (no space between the phases)
Describe the interpulse and interphase durations in alternating current
Alternating current DOES NOT have interphase NOR interpulse duration
Length of time a cycle lasts is called CYCLE DURATION
What does a direct current DC not have?
No phases
No pulses
No cycles
What is current amplitude
What is the unit for current amplitude
The magnitude of current to the isoelectric (zero) baseline
Unit: amperes
What is the peak amplitude
Maximum amplitude which is the highest point of each phase
What is pulse charge
What is the unit of pulse charge
The total amount of electricity being delivered to the patient during each phase
Unit: Coulombs or micro-coulombs
NOTE: you can calculate the pulse charge from the graph by adding (phase charge A + phase charge B = pulse charge)
What is frequency (rate)
Unit of frequency
The number of times per seconds that a pulse, cycle, bursts, or beat will repeat itself
Unit: Hertz (Hz)
(Or pulse/sec, burst/sec, cycle/sec etc)
Relationship between frequency and cycle duration in alternating current AC
Inversely proportional
Relationship between frequency and pulse duration in pulsatile current PC
NOT RELATED
Change in frequency will NOT affect pulse duration
Describe the Types of current frequencies and provide examples if possible
Low frequency current (1 - 2000 Hz)
- meets 3200 Ξ© skin resistance at 50 Hz
- examples: Diadynamic (DD) and ES (i think she means electrical stimulation?)
Medium frequency ( 2000 - 10,000 Hz)
- meets little skin resistance
- stimulates sensory and motor fibers
- examples: IF and TENS
High frequency (10,000 Hz and above)
- has NO effect on sensory and motor fibers (because its too fast so it just passes them)
What is meant by current modulation
Automatic variations in amplitude, pulse or cycle duration, or frequency of current during a series of pulses or cycles.
What is meant by ON time and OFF time
ON-TIME: period when current is being delivered (seconds)
OFF-TIME: period when NO current is being delivered (seconds)
(Related to current modulation)
What is meant by RAMP UP and RAMP DOWN
RAMP-UP: increase in amplitude β¬οΈ
RAMP-DOWN: decrease in amplitude β¬οΈ
(related to current modulation)
To conduct electrical current to the patientβs body , what do we need?
- Different types, shapes, and sizes of electrodes
- Conductive substance (ex: gel, water, soaked sponge)
- Wires attach the electrodes to the treatment device
What type of tissue are considered the best conductors of electricity ?
Order them from strongest to weakest .
Tissue with high water content which have high ion content are considered best conductors of electricity
Blood (best conductor) > Muscle 75% > Fat 14% > Bone 5%
Why do we prepare the skin before treatment? How do we prepare it ?
Skin offers primary resistance to current flow and is considered as an insulator .
To overcome it we have to prepare the skin by:
- clean the skin (from oil etc)
- clip hair if necessary
- appropriate coupling medium
- adequate contact
What to consider when setting up electrodes
Electrode size
Number electrodes
Position of electrodes
Distance between electrodes
Orientation of electrodes
Electrodes polarity
Purpose of different sizes of electrodes
Small electrode for small areas
Large electrode for large areas
Pointer electrode for facial muscles (ex: Bellβs palsy, facial palsy or paralysis)
Uneven sizes ( smaller electrode gives more current)
Dispersive electrode remote from treatment area
Current density is higher under which size of electrode
Small electrodes have higher current density
What is A and B
A is Rise Time
B is Decay Time
What determines the number of electrodes required
Size of treatment area
(Can use multiple channels to add electrodes)
Different positions of electrodes
Monopolar
Bipolar
Quadrapolar
Etc.
(Placed on motor point or dispersive)
Purpose for different distances between electrodes
Close together = Superficial and more current density in the skin
Further apart - Deep
Orientation of electrodes
Parallel to the direction of muscle fibers
Along nerve trunk and on motor points
Electrode polarity
Cathode (NEGATIVE) electrode : has great level of electrons
Anode (POSITIVE) electrode
(Important for Diadynamic)
Basic physiology of nerve excitation
Resting membrane potential is between -60 mV and -90 mV (no action potential )
Stimulus
Action potential = depolarization
Repolarization back to resting membrane potential
Order of nerve recruitment depends on :
Type of nerve fibers
( sensory > motor / myelinated > unmyelinated)
Size/length of nerve fibers
(Short > long)
Diameter of nerve fibers
(Small > large)
Location of nerve fiber with respect to electrode
( superficial > deep)
Superficial nerves are _______________ nerves
SENSORY
First muscle fibers to be stimulated are :
Large fast twitch muscle fibers > Small slow twitch muscle fibers
Effects of electrical current on stimulated tissue ( 3 types of neurophysiological responses)
- Sensation (sensory)
- Skeletal muscle contractions (motor)
- Pain (noxious level)
(IN THAT SPECIFIC ORDER)
