Electrotherapy Flashcards
What is charge?
The mechanism through which a living cell communicates with another cell.
There are four properties of electric charge. Name them.
- There is + and - charge
- Like charges repel while opposites attract
- Charge is neither created or destroyed
- Charge can be transferred from one object to another
Explain polarity.
Electrons flow from negative to positive poles.
What surrounds charged particles?
An electric force field.
Define voltage.
An electromotive force or potential difference expressed in volts.
True or False
Conductors store electricity.
False.
Conductors allow for the free movement of the electrons and transfer of charge.
What is an insulator?
Insulators impede the movement of electrons and the transfer of charge.
What does resistance denote about a charge?
Normally, it denotes the direction. Resistance is whether something will slow down the current or not.
True or False
Capacitance is the storage of particles.
True
What is impedence?
How much resistance it takes to get through the material. Skin will have a certain amount of impedance, and muscle will have a different amount of impedence.
If the voltage stays the same but the impedance changes, what will happen to the current?
The current will become more or less intense.
Which is safer, constant current or constant voltage?
Constant current is safer than constant voltage.
What are the three types of current and waveforms?
- AC
- DC
- Pulsed
What defines direct current?
Continuous stream of charged particles flowing in 1 direction for at least 1 second.
What is direct current used for?
Iontophoresis, wound care, and stimulating contractions in denervated muscle
Is direct current comfortable?
No
What charge does the anode hold?
Positive.
The cathode is negative.
Describe interrupted DC current.
On for one second. Off for a bit. Then on for another second.
Describe reversed DC current.
Flows negative to positive for a second. Then positive to negative for a second.
What kind of current flows from negative to positive for one second, stops for a bit, and then flows positive to negative for a second?
Interrupted reversed DC current
Continuous, sinusoidal, bidirectional flow of charged particles are characteristics of which type of current?
Alternating current (AC)
Clinically, what is AC used for?
Pain control and muscle contraction. It normally feels better than direct current.
True or False
Frequency = rate at which AC switches direction (Hz)
True!
What are two examples of AC?
Russian current and IFC.
What are the characteristics of pulsed current?
- Interrupted flow of charged particles
- Current flows in a series of pulses separated by periods where no current flows
What does the carrier frequency have to do with?
It has to do with the underlying wave form of the bursts in pulsed current.
The time in between the pulses in PC is…
The interburst interval
What is a burst?
A group of little pulses
Five little pulses together would make up what?
The burst frequency
In PC what would a square, rectangle, or triangle denote?
It would show how fast the burst goes up in amplitude.
True or False
In monophasic PC, a phase does not equal a pulse.
False
In monophasic, a phase equals a pulse.
What is the difference between monophasic PC and biphasic PC?
Monophasic flows in one direction. Biphasic flows in both directions and is the most common.
What makes up a pulse in biphasic PC?
There is a positive phase and a negative phase, and those added together make up the pulse.
Why does the phase duration in PC have to be under 1 second?
If it was one second or more, it would be DC.
What is the intra-pulse interval?
It is the time between the positive phase and negative phase of a biphasic pulse.
Which types of current can be modulated?
Any of them. AC, DC, or PC
What is modulation?
It is a process where one or more characteristics of a wave are changed.
What is the difference between regular and irregular modulation?
Regular modulation repeats the same pattern. Irregular modulation is harder for the patient to get used to and stop feeling it.
What are aspects you can modulate in a current?
- Amplitude
- Frequency
- Pulse/phase duration
If you have the amplitude varying, you don’t want to turn the machine up when the amplitude is at its low point. Turn it up when it is at the high point, or it might be too high at the top.
True or False
Symmetrical currents are also balanced.
True!
Define symmetrical current.
The positive phase looks exactly like the negative phase.
What is more likely with an unbalanced wave?
Skin irritation is more likely.
Define asymmetrical current.
In asymmetrical current, the pulses do not look the same.
What is a balanced current?
The amount of positive phase charge = the amount of negative phase charge
Explain the electrochemical effects of electrotherapy.
Extracellular fluid is mostly salf water. Na is positive, and Cl is negative. Na will go toward the cathode which is negative. Cl will go toward the anode which is positive. Water tends to move towards the Na which reduces the protein density in that tissue. This softens the tissues at the cathode. The opposite happens at the anode, so the tissues harden at the anode because the water is being pulled towards the cathode.
The pH at the cathode increases, and the pH at the anode decreases.
Explain the electrothermal effects of electrotherapy.
Some energy will be lost in the form of heat, so you get some thermal effects. The amount depends on the voltage. If you are doing it with heat or over an area that is calloused, you can get a larger build up of heat because there is more resistance.
Explain the electrophysical effects of electrotherapy.
The electrophysical effects are due to changes in the permeability of the cell.
What needs to be high enough to depolarize the cell and elicit an action potential?
Must have sufficient strength (current amplitude) and duration (pulse duration).
What order are the nerves stimulated in?
- A beta sensory
- Motor
- A delta sharp pain
- C dull pain
- Denervated muscle
How many mA do you need to stimulate A beta sensory nerves?
It needs to be turned to at least 20 mA
How many mA do you need to stimulate motor neurons?
At least 30 mA
How many mA do you need to stimulate A delta sharp pain?
At least 40 mA
How many mA do you need to stimulate C dull pain nerves?
At least 50 mA
How many mA do you need to stimulate denervated muscle?
At least 60 mA
Why are A beta fibers stimulated before motor fibers even though they are smaller and slower?
They are typically closer to the skin and easier to stimulate
What are two factors that contribute to which nerves are stimulated first?
- Nerve size - fibers that have greater diameters and lower resistance will depolarize first
- Location of the electrodes - the closer to the nerve you are, the easier it is to get it to fire
Clinically, how could you use stim and still teach someone the correct order of nerve recruitment?
You can have them think about contracting or have them actually move the muscle and contract with the stim on. Then they are getting the recruitment from largest to smallest and smallest to largest.
What are the levels of response for stim?
- Sensory - pins and needles or buzzing
- Motor - need to see a twitch
- Noxious - if you keep turning it up, you will get a noxious stimulus and activate C fibers
What are the parameters for Russian stim?
10 msec on (interburst) 10 msec off (interval) with the carrier frequency at 2500 Hz.
Run this for 10 sec on and 50 sec off for 10 reps.
What was Russian stim developed for?
It is a specific type of current that stimulates muscle contraction. It was developed in the Soviet Union to try and improve performance.
What would you tell a patient they will feel when they do Russian stim?
Tingling and buzzing, a twitch, and then a good contraction.
What are the parameters for “Aussie” current?
- Carrier freq: 1000 Hz
- 4 msec bursts
- 10 sec on and 50 sec off
What is “Aussie” current used for?
- Stimulates muscle contraction
- Greater torque production
- Decreased muscle fatigue
What are the parameters for high-volt pulsed current?
- Peak voltage 150-500v
- 50-100 microsec pulse duration
- Carrier freq: 1-120Hz
What modes can you put high-volt pulsed current on?
- Continuous mode
- Reciprocating mode: 2 on top, 2 on bottom
- Surge mode
What is high-volt pulsed current used for?
It stimulates both motor and sensory, so it is used for pain control. It is not used as much anymore.
What are the parameters for IFC?
The carrier frequencies for the two currents need to be at least 100 Hz different.
Explain the characteristics of IFC?
IFC is two intersecting medium frequency AC with slightly different frequencies. This produces an interferential current between two crossed pairs of electrodes. You want the two currents to intersect right over the painful spot. The different frequencies results in bursts because sometimes they amplify each other and sometimes they cancel each other out.
What does a vector scan in IFC do?
It modifies the amplitude. It can change the speed at which the beats come.
What does a sweep do in IFC?
It changes the beat frequency.
What does a swing do in IFC?
It alters the timing of the sweep pattern.
In what scenario would you use IFC?
It works well for pain control and is used fairly frequently.
What is premodulated IFC?
The currents are crossed in the machine instead of the body. It has sequentially increasing and decreasing current amplitude.
What are some characteristics of premodulated IFC?
- AC
- Medium frequency
- Single circuit and 2 electrodes
- Same waveform as the current that results from IFC
True or False
Premodulated IFC has the same theoretical advantages as IFC.
False. It does not have the same results or theoretical advantages.
What are the proposed advantages of IFC?
- Freq exceeding 1 KHz are hypothesized to more easily penetrate the skin due to decreased skin impedance
- Amplitude of the 2 currents summate in deeper tissues-passing the more superficial nerves
- Beat frequency of the interference is similar to other waveforms used to stimulate muscle and for pain modulation
- Only used for pain
What are the advantages and disadvantages of small electrodes?
- They are high density
- Specific but uncomfortable
- Don’t use for large muscles
What are the advantages and disadvantages of large electrodes?
- They are low density
- Less specific
- More comfortable
True or False
The current goes deeper if the electrodes are closer together
False!
The current goes deeper if you place the electrodes further apart.
Where is ideal electrode placement if you are trying to get a muscle contraction?
It is best to put it over the motor point which is usually in the proximal 1/3 of the muscle. The other electrode must be on the muscle belly not the tendon.
What are the parameters for NMES (Neuromuscular electrical stimulation)?
Indication: Muscle strengthening
Waveform: biphasic PC of burst-modulated AC (Russian or Aussie)
Pulse Frequency: 50-80 pps or bursts per second
Pulse Duration: 200-800 microsec
Amplitude: as high as tolerated with a goal of reaching more than 60-70% maximal voluntary contraction (MVC)
Duration: 10-20 strong contractions
What are the parameters for FES (Functional Electrical Stimulation)?
Indication: muscle contraction for functional use
Waveform: biphasic PC or burst modulated AC (Russian or Aussie)
Pulse Frequency: 20-60 pps or bursts per sec
Pulse Duration: 200-800 microsec
Amplitude: to level commensurate with functional activity
Duration: task specific
How might you need to adjust amplitude to the task?
You might need a higher amplitude to lift the shoulder than to grip with the hand.
How does TENS help modulate pain at the sensory level?
Conventional or high-frequency TENS stimulate A-beta fibers which activates the gate theory of pain modulation.
How does TENS help modulate pain at the motor level?
Descending methods of pain modulation - release of endogenous opioids (refer to gate theory)
What is brief intense TENS?
Combo of high and low frequency TENS for modulating pain
What is hyperstimulation TENS?
It uses a noxious stimuli to modulate pain.
What are the parameters for TENS high-frequency stim?
Waveform: mono- or biphasic PC
Pulse frequency: at least 50 pps, typically 80-110 pps
Pulse Duration: 50-100 micro sec
Amplitude: mA to maximum comfortable perception (or parasthesia). No or barely visible motor activity
Duration: 20-30 min (longer if used during activity)
What are the parameters for TENS low-frequency?
Waveform: mono- or biphasic PC
Pulse Frequency: short - less than 10 pps
Pulse Duration: high - greater than 150 microsec
Amplitude: mA to visible strong muscle twitches
Duration: 20-45 min
What are the parameters for brief intense stimulation TENS?
Waveform: mono- or biphasic PC
Pulse Frequency: high - approximately 100 pps
Pulse Duration: high - greater than 150 microsec
Amplitude: mA to visible strong muscle twitches
Duration: less than 15 min
What are the parameters for hyperstimulation TENS?
Waveform: DC or monophasic
Pulse Frequency: high - 100 pps
low - 1-5 pps
Pulse Duration: long - greater than 250 microsec up to 1 sec
Amplitude: mA to highest tolerated painful stimulus
Duration: 30-60 sec to each area
Which type of TENs is used for more acute pain?
High-frequency because there is not a lot of muscle activation.
Which types of TENS are more for chronic pain?
Low-frequency and brief intense stimulation.
Don’t put these on a motor point on their back and let them drive with it. They will have muscle spasms, and it will not be good for driving.
What should a patient feel with TENS?
Strong but comfortable tingling and buzzing sensation.
What kind of current does iontophoresis use?
Low-amplitude DC (only flows in one direction)
How deep does the drug go with iontophoresis?
The depth of drug delivery is unknown (3-20mm)
How is the amount of electricity described?
As mA-min (40-80 mA-min)
How does iontophoresis work?
Via electrochemistry, electroosmosis, and passive diffusion.
If you have a negatively charged drug, you put it on the negatively charged cathode and the electrical current will draw the drug through.
How does iontophoresis affect pH?
- Electrodes repel hydrolyzed ions of the same charge
- Build up ions on the skin can cause irritation or burns
- Use a buffered electrode
Why can pH changes at the electrode be a problem?
- Can alter the transfer of medication
- Alters the degree of ionization of organic compounds present in solution
- Decreases effectiveness of drug
Does the cathode or the anode repel negative ions?
The cathode repels negative ions, and the anode repels positive ions.
True or False
In iontophoresis, increasing concentration of drugs administered does not increase drugs delivered.
True!
What is the limiting factor for drug delivered during iontophoresis?
It is limited by number of pathways.
Ion transport is limited to medications/ionic solutions that have what?
- Ions must be charges
- Relatively small ions because they have to get through the skin
- Must be in a solution - no creams or suspensions
- Ions must be effective in a small target area - needs to be like a tendon or a part of a tendon
Current = ?
voltage/resistance
How long can you leave a patch on?
It can be on for 12-14 hours.
More dosage with a patch = ?
More drug
What amplitude does a patch deliver?
80-100mA-min
What are competing ions?
- Any ion present in the electrode or solution that has the same charge as the therapeutic ion
- “Compete” with preferred ions to be delivered through the skin
- Smaller ions generally more mobile
- They decrease the efficiency of the drug delivering
- Buffered electrodes eliminate competing ions
What would you start the amplitude at for iontophoresis?
Start at 40mA for the dose, and then turn the current up if they can tolerate it.
What is electroporation?
- Opening of pores, sweat glands, cell membranes in skin through the application of voltage
- Happens with DC
- Takes 3-5 min for the drug to actually start going through the skin
How long does iontophoresis normally take with a machine?
About 10 minutes, so for the first 5 minutes, they weren’t actually getting any drug in. They started creating patches that you could put on and send out.
Which drugs have a positive polarity?
- Copper
- Hyaluronidase
- Lidocaine
- Magnesium
- Zinc
Which drugs have a negative polarity?
- Acetate
- Chloride
- Dexamethasone phosphate
- Iodine
- Salicylate
- Tap water
Indication for acetate
Calcium deposits
Indication for chloride
Sclerotic
Indication for copper
Fungal infection
Indication for dexamethasone phosphate
Inflammation
Indication for hyaluronidase
Edema reduction
Indication for iodine
Scar
Indication for lidocaine
Local anesthetic
Indication for magnesium
Muscle relaxant, vasodilator
Indication for salicylate
Inflammation, plantar warts
Indication for tap water
Hyperhidrosis
Indication for zinc
Dermal ulcers, wounds
Describe a normal response to iontophoresis.
- Skin under both electrodes will be pink
- Should fade within a couple of hours
- Sweat retention vesicles may form - will reabsorb if left alone, but do not do DC current over the vesicles
What are the precautions for ES?
- without intact sensation
- unable to communicate
- compromised mental ability or lack of cognition
- with cardiac dysfunction
- over neoplasms
Where should you not place electrodes?
- Compromised skin (except in wound care)
- Tissues vulnerable to hemorrhage or hematoma
- Cervical or craniofacial regions in pts who have a Hx of CVA or seizures
- Do not use ES devices within 5 yards of diathermy units or other electromagnetic devices
What are the contraindications for ES?
- pacemakers, impantable defibrillators, or unstable arrhythmia
- phrenic nerve, eyes, gonads, or urinary bladder stimulators
- placement of electrodes over carotid sinus
- areas where venous or arterial thrombosis or thrombophlebitis or DVT is present
- pregnancy - over abdomen or low back
- do not use stimulated muscle contraction when muscle contractions may disrupt healing
- transcervical (anterior) or transthoracic
- uncontrolled seizures
- over intercostal muscles
- areas of active osteomyelitis
- areas of hemorrhage
What are the contraindications for ionto?
- Do not apply after any intervention that alters skin permeability
- decreased sensation
- sensitivity to drug administered
- sensitivity to DC
What do you need to add to documentation for ES?
- Waveform
- Waveform parameters
- Electrode type, shape, size, placement, and integrity of skin before and after
- Pt position
- Dosage
- Treatment duration
