-
receptor proteins
binding sites for neurotransmitters and neuromodulators
-
channel proteins
with certian conditions a pore is formed through the membrane to facilitate the movement of ions
-
transport proteins
bind and transfer substances through the membrane
-
Resting state of the excitable cell membranes
- readily permeable to potassium
- slightly permeable to sodium
- impermeable to a number of large negatively charged proteins and phosphates (anions)
-
In the resting state
- atp used to actively transport sodium and potassium across the membrane
- sodium-potassium pump moves sodium ions out of the cell while moving potassium ions in
-
Outside the cell
Na+ is higher
-
Inside the cell
- K+ is higher
- anions are higher
- more negative than outside creating -60 to -90 mV charge
-
threshold
critical voltage level that triggers sodium and potassium channels to open
-
Sodium Channels
open rapidly
-
Potassium channels
open slowly
-
Absolute refractory period
while the nerve is depolarized, no additional APs can be created. (regardless of the intensity of the stimulus)
-
Relative refractory period
brief period of membrane hyperpolarization during which a greater stimulus than usual is required to produce another AP
-
Accommodation
situation in which if the stimulus is low enough the nerve cell will adapt to the stimulus and not fire.
-
AP direction
current causes AP direction to depolarize in both directions but the effect will only be felt on the end with the NT release.
-
Electrical Current
- flow of charged particles
- noted as (I)
- measured in Amperes (A)
-
Charge
- either +/-
- noted as (Q)
- measured in Coulombs (C)
-
Polarity
- property of having two oppositely charged conductors
- + anode
- - cathode
- current flows from -to +
-
Voltage
- force capable of moving charge
- aka the potential difference
- noted as (V)
- measured in volts (V)
-
Resistance
- property of a conductor to resist flow of current
- noted as (R)
- measured in Ohms (omega)
-
-
Impedance
- frequency-dependent opposition to current
- noted as Z
- measured in Ohms (omega)
- in biological systems we can say it is a ratio of potential flow to actual flow
-
E-stim Waveforms
- direct current (DC)
- alternating current (AC)
- pulsed current or pulsatile current
- interferential current
- premodulated current
- Russian protocol
-
Direct Current (DC) - uses
- iontophoresis
- stimulating denervated muscle
- facilitate wound healing
-
Alternating Current (AC)
- bi-directional flow of current
- no pulse charge left in tissue
- inverse relationship between cycle duration and frequency
-
Pulsed Current
- current delivered discontinuously
- uni- or bi-directional
- monophasic (like DC)
- biphasic (like AC)
-
Biphasic pulsed current
- symmetric
- asymmetric balanced
- -charge of the phases are equal and opposite leaving zero net charge
- asymmetric unbalanced
- - charges are not equal leaving a net charge of some kind
-
Interferential Current
- two sine waves are overlapped causing a pulse or beat in the stimulus
- slower of the two frequencies is called the carrier frequency
-
Premodulated Current
- waveform produced by one channel
- same as if you were doing IF
- continuous sine wave with medium frequency
- uses sequentially increasing and decreasing amplitudes
-
Russian protocol
- 2500 Hz carrier frequency AC sine wave modulated to 50 bps
- burst is a polyphasic waveform delivered for 10 ms followed by an interburst interval of 50 ms
-
Time Dependent Parameters
- Frequency
- Pulse Duration/Phase Duration
- Interpulse Interval
- Interphase/Intrapulse Interval
- Rise/Decay Time
- On/Off Time
- Duty Cycle
- Ramp Up/Down Time
-
Frequency
- Cycles or pulses per second
- noted in (Hz)
-
Pulse duration/phase duration
- beginning of first phase to the end of the last phase of a pulse
- expressed in micro or milli- seconds
-
Interpulse interval
time between pulses
-
Interphase interval
time between phases of a pulse
-
Rise/Decay time
time it takes to increase from zero to peak or peak to zero during any one phase
-
On/Off time
- time during which a train of pulses occurs then the time between the trains of pulses
- expressed often as a ratio
-
Duty Cycle
ratio of the on time to the total cycle time
-
Ramp Up/Down Time
- time it takes to increase from min to max amplitude and decrease from max to min amplitude
- helps with tolerating treatment better
- sometimes called "soft start"
-
Other Current Parameters
- Amplitude
- Modulation
- Frequency Modulation
- Amplitude Modulation
- Phase Duration Modulation
- Burst Mode
-
Amplitude
- magnitude of current or voltage
- not intensity
-
Modulation
Varying one or more of the stimulation patterns
-
Frequency Modulation
- variation in the number of pulses or cycles per second
- aka - sweep
-
Amplitude Modulation
- variation in peak current amplitude
- aka - scan
-
Phase or Pulse Duration Modulation
variation in pulse or phase duration
-
Burst Mode
series of pulses delivered in a package as a single pulse
-
Rheobase
minimum amplitude needed with a very long duration pulse to depolarize the cell.
-
Chronaxie
minimum duration pulse required to produce an AP at twice the rheobase
-
Inducing current in excitable tissue
- depends on inherent excitability
- relative location with respect to the electrode the closer the better
-
Sensory-level stimulation
- low amplitudes
- higher amplitudes = deeper sensations
-
Adaptation
- gradual diminution in the ability to sense the stimulation
- occurs in sensory-level stimulation at frequencies >15pps for long periods of time
-
Motor-level stimulation
- normal voluntary contraction recruits the smalles motor units first.
- e-stim recruits all at once
- after motor threshold is reached, small increases in ampitude cause large increases in force of contraction
- can be used to help strength gains and function
- need long duration pulse to get denervated muscle >10ms
-
Noxious-level Stimulation
- high intensity that triggers A-delta and C fibers
- level may vary in each patient
-
Ionic effects of current
- DC pulsed monophaisc and unbalanced biphasic waveforms leave a net charge in the tissue
- cathode attracts positive ions
- anode attracts negative ions
- used in iontophoresis
-
e-stim for pain
- duration = 50-80 microseconds
- frequency = 100-150 pps (high rate) 2-10 pps (low rate)
- burst mode uses same theory as low rate TENS
- Subsensory-level stimulation has little evidence
- Electrode placement over the site of injury
-
E-stim for pain: Contraindications
- over or near medical stimulators
- confused or uncooperative patients
- damaged skin or subcutaneous tissues
- skin with impaired sensation
- malignancies
- arterial or venous thrombus
- anterior neck
- carotid sinus
- laryngeal or pharyngeal muscles
- phrenic or vagus nerve
-
E-stim for pain: precautions
- pregnant women
- across the head or through the chest
- heart disease
- HTN, Hypotension
- diagnosed or suspected epilepsy
- keep out of reach of children
- while operating machinery or vehicles
-
E-stim for muscle contraction: innervated muscle discomfort
- subjects coping style
- whether the stimulus causes a muscle contraction
- whether the subject is judging intensity or unpleasantness of the stimulation
greater force = greater discomfort
-
E-stim to improve extremity function with stroke, SCI, or CP
- pulse duration 200-300 microseconds
- frequency 30 pps
- on:off time 1:2
- 20 min 5-6 days a week for 4 weeks
-
E-stim for dorsiflexors
- triggered by swing phase foot switch
- pusle duration 300 microseconds
- 40 pps
-
E-stim for denervated muscles
- longer pulse duration more than 10 ms
- DC current is applied for a number of seconds
- denervation is not improved by e-stim
-
Patient positioning
- dictated by:
- -patient comfort and modesty
- -area to be treated
- -goals of the treatment
- -deviced used
-
Electrode placement: general
- smooth against the skin
- not over bony prominance
- closer together more superficially the stimulus
- for larger muscle groups use distal and proximal attachment
- for single muscles attach pad to motor point (belly)
- For pain pads should be at least an inch apart
- For muscle contraction pads should be 2 inches apart
-
electrode placement for pain
- use inferential current
- place over trigger point or accupuncture point
- place pads proximal to area if point cannot be accessed directly
-
Pad placement for edema
- negative pole over area of inflammation and the dispersement electrode more proximal
- for edema d/t lack of motion stimulate muscles around the deep veins
-
Parameter Selection: pulse duration
- muscle contraction: 150-350 microsecond
- biphasic conventional TENS: 50-80 microsecons
- low rate TENS: 100-200 microseconds
- interferential curreent pulse durations: inversely proportional to carrier frequency
-
Parameter selection: Frequency
- determines response or muscle contraction
- low frequency: less than 30 pps, motor nerves, separate twitch contraction
- smooth tetanic contraction:35-50 pps, greater muscle strengthening but more rapid fatigue
- Pain control: HR TENS 100-150 pps LR TENS less than 10pps
- Edema control: 120 pps
-
Parameter Selection: on/off time
- pain control, wound care, acute edema, iontophoresis: continuous
- muscle contractions: 1:5 ratio moving to 1:4 or 1:3
- spasm relief or pump out edema: 1:1 2-5 seconds
-
Parameter Selection: Ramp time
- 1-4 seconds
- may not need it for functional activity because you need stimulation immediately
-
Parameter selection: Current amplitude
- for strengthening: 50% of max voluntary control
- for muscle reeducation: use sensory-level stimulation moving to contraction-level
- for spasms: sufficient to produce a visible contraction
- for pain control: HR TENS comfortable as possible LR and Burst TENS visible contraction
- Edema: comfortable sensory level
-
Parameter Selection: Treatment time
- Muscle strength: 10-20 contractions or 10-20 minutes multiple times a day
- muscle reeducation: no more than 20 min a session
- pain control: HR TENS all day LR TENS 20-30 min every 2 hrs
- edema: 30 minutes can be used more than once a day
-
Documentation for E-stim
- Area of body
- Treatment duration
- Patient position
- Electrode placement
- Treatment parameters
- Response to treatment
-
Iontophoresis: Drug Delivery
- Electromigration
- Electroporation
- Electro-osmosis
-
Acetic Acid
- Calcific tendonitis
- myositis ossificans
believed to increase solubility of calcium deposits
-
Calcium chloride
Skeletal muscle spasms
Ca stablizes excitable membranes
-
Dexamethosone
inflammation
Steroidal anti-inflammatory agent
-
Iodine
Soft-tissue adhesions
treatment not fully understood
-
Lidocaine
pain and inflammation
local anesthetic
-
magnesium sulfate
muscle spasms
decreased excitability of muscle membrane
-
Hyaluronidase
local edema (subacute and chronic)
increases permeability in connective tissue
-
Salicylates
Pain
analgesic and antiinflammatory effects
-
Zinc oxide
dermatologic disorders
general antiseptic
-
Ionto current and amplitude
-
Alternative currents ionto: AC benefits
- more predictable and less variable for getting drug into circulation
- could use it for longer periods of time becoming more effective
- less damaging to skin than equivalent application of DC
-
Alternative currents ionto: HVDC
- high volt >100 V for short time (few microseconds or milliseconds)
- not much clinical evidence
-
Current-Dosage for ionto
- mA*min
- 70-80 mA*min whenever possible to maximize effects
- low current long duration is more effective than high current low duration
-
Application principles for ionto
- low concentrations of the drug
- one drug at a time
- do not use heating agents with ionto because it will limit the localized effect of the drug
-
Procedure for application
- allergies?
- localize the electrode over the point of injur
- skin depth may contribute to effectiveness of drug
- do not use if the skin is damaged or broken
- prep skin with alcohol wipe
- connect electrodes and then ramp up the current
- upon completion ramp down the current and remove electrodes
- examine skin for signs that pt didn't tolerate treatment well
-
indictations for use of ionto
- Inflammation (Dexamethosone)
- Treat pain (Lidocaine) be cautious not to burn the pt
|
|