Exam 3 (Ch: 11 Flashcards
What is a positive electrode?
Anode
What is a negative electrode?
Cathode
Charge equation?
Q= I*t Q= Coulombs I= Current t= time
Which type of current is a series of pulses where charged particles move in only one direction?
Monophasic current
What type of current is a series of pulses where charged particles move in one direction and then the opposite direction?
Biphasic current
This type of current is bidirectional and has no net charge?
Alternating current
With an alternating current, describe the relationship b/t frequency and duration?
Frequency INCREASES the cycle duration DECREASES and
Frequency DECREASES the cycle duration INCREASES
This type of current is a continuous unidirectional flow of charged particles?
Direct current (DC)
This type of current is an interrupted flow of charged particles whereby the current flows in a series of pulses separated by periods when no current flows?
Pulsatile current
Describe on/ off time?
On time is the time during which a train of pulses occur
Off time is the time between trains of pulses where no current flows
What is the goal of on and off times?
To produce muscle contractions
What happens to a muscle during on time?
It contracts
What happens to a muscle during off time?
It relaxes
Why is off time required?
To reduce muscle fatigue
What is rise time?
The time is takes for the current to increase from zero to its peak during one phase
What is decay time?
The time is takes for the current to decrease from its peak level to zero during one phase
What is ramp up time?
The amount of time it takes for the current to amplitude to increase from zero during the off time to its max amplitude during the on time
What is ramp down time?
The time it takes for the current amplitude to decrease from its maximum amplitude during the on time to zero during the off time
What are ramps used for?
To improve patient comfort when e-stim is used to produce muscle contraction.
Allows for patient to become accustomed to the stimulation.
Ramp up/ down time in relation to ON/OFF time
Ramp up time is included in the ON TIME
Ramp down time is included in the OFF TIME
What is the time in between individual pulses?
Interpulse interval
What is the time in between phases of a pulse?
Intrapluse interval
What is Ohm’s law?
V = I*R
V- voltage
I- intensity
R- resistance
What is voltage?
The force or pressure of electricity
What is resistance?
Opposition of a material to the flow of electrical current
What can cause resistance during e-stim?
Hair, skin, amount of fat in an area
What is the amount of current per unit area?
Current density
What is impedance?
Frequency dependent opposition to current flow
In biological systems, it describes the ratio of voltage to current more accurately than resistance b/c it includes effects of capacitance and resistance
How is impedance noted & measured?
Noted by Z
Measured in Ohms
What is the delivery of ions through an electrical current for therapeutic purposes?
Iontophoresis
What is functional electrical stimulation (FES)?
Application of an electrical current to produce muscle contractions during a functional activity
What are examples of Functional Electrical Stimulation?
E-stim of dorsiflexion during the swing phase of gait
E-stim of wrist & finger flexion during grasp activities
What is neuromuscular electrical stimulation?
E-stim to motor nerves to produces contractions of the muscles they innervate
What is the place in a muscle where e-stim will produce the greatest contraction w/ the least amount of electricity?
Motor point
Where are motor points usually found?
Over the middle of the muscle belly
What are the uses of e-stim?
Pain Muscle strengthening Decreasing edema Wound care to promote epithelialization Functional E-stim Biofeedback for sensory input EMG
Interferential current (IFC)
Produced by two medium frequency (1000- 10,000 Hz) sinusoidal ACs of slightly different frequencies.
Delivered through 2 sets of electrodes through separate channels in the same stimulator
Electrodes are configured on the skin so that the two ACs intersect
Stimulates larger area than Premod, at a lower amplitude
Premodulated current (Premod)
Produced by an AC w/ medium frequency (1000- 10,000) Hz
Sequentially increasing and decreasing current amplitude
Single circuit w/ 2 electrodes
Same waveform as IFC