Cameron Chapter 11
Electrical Current
A flow of charged particles (electrons or ions)
What is premodulated current produced with?
A single circuit and two electrodes
3 Types of Waveforms
Alternating Current (AC) Direct Current (DC) Pulsed Current (PC)
Premodulated Current
An AC current in the medium frequency range with sequentially increasing and decreasing current amplitude
Pulsed Current (PC)
An interrupted flow of charged particles where the current flows in a series of pulses separated by periods where no current flows
Why do electrical currents most often produce clinical results?
Because they stimulate action potentials in sensory and/or motor nerves
Precautions for Electrical Currents
Cardiac Disease Impaired Mentation Impaired Sensation Malignant Tumors Areas of Skin Irritation or Open Wounds
Direct Current
Continuous stream of charged particles flowing in one direction
Alternating Current (AC)
Continuous, sinusoidal, bidirectional flow of charged particles where the current is always flowing back and forth
Current Flow: DC
Current flows equally throughout the stimulation time so the only parameters are the current amplitude, also known as strength or intensity and the total treatment time
Electrodes Placed Further Apart
Current travels deeper
Electrodes Placed Close Together
Current travels more superficial
Contraindications for Electrical Currents
Demand cardiac pacemaker, implantable defibrillator or unstable arrhythmia Placement of electrodes over carotid sinus Areas where venous or arterial thrombosis or thrombophlebitis is present Pregnancy-- over or around the abdomen or low back
What type of current comes out of a battery but not battery driven electrical stimulation devices?
Direct Current (DC)
Action potential travel (faster or slower) in large diameter myelinated nerves than in small diameter or unmyelinated nerves
Faster
The most commonly encountered monophasic pulsed current is ______ also known as pulsed galvanic current
High-Volt Pulsed Current
______________ Current is thought to be more comfortable and to penetrate deeper than biphasic pulsed waveforms
Interferential
Types of AC Waveforms
Interferential Current Premodulated Current Russian Protocol
What is low-level DC used for?
Iontophoresis and for stimulating contractions in denervated muscle
Why is DC not commonly used for electrotherapy?
It is generally uncomfortable to the patient
How long do pulses need to last in order to produce contractions in denervated muscle?
Longer than 10 ms
Russian Protocol
Method developed by Yadou Kots to strengthen muscles in Russian Athletes
Does increasing the current amplitude or pulse duration make action potential larger?
No
Should electrodes be placed directly over bony prominences?
No
Ramp Down Time
Number of seconds it takes for the current amplitude to decrease from its maximum amplitude during the on time to zero during the off time
Biphasic Pulsed Current
PC that flows back and forth during a pulse
Monophasic Pulsed Current
PC that flows in only one direction during a pulse
What can AC be used for?
Pain Control and Muscle Contraction
What is PC often used for?
Pain Control, Tissue Healing or Muscle Contraction
Biphasic pulsed currents are the most commonly used waveform in electrotherapy and are mainly used to:
Produce muscle contractions or control pain
Interferential Current
Produced by the interference of two medium-frequency ACs with slightly different frequencies
Clinical Applications of Electrical Stimulation in Rehab
Producing muscle contractions for strengthening and improving endurance and motor control, controlling pain, promoting tissue healing, enhancing transdermal drug delivery and providing electromyographic feedback
Waveform of Premodulated Current
Same waveform as the current that results from the two circuits used to produce interferential current
Current Flow: AC and PC
The current flow varies over time
What is the basis for the specificity of the effect of electrical stimulation?
The interplay of amplitude and pulse duration
Ramp Up Time
The number of seconds it takes for the current amplitude to increase from 0 during the off time to its maximum amplitude during the on time
Off Time
The seconds when the current is off
On Time
The seconds when the current is on
Iontophoresis
The transcutaneous delivery of medications facilitated by an electrical current
What are monophasic pulsed currents most commonly used for?
To promote tissue healing and to manage acute edema
When does an action potential occur in a nerve?
When its threshold is reached