PTA 130 Electric Currents

Direct Current

one direction of charged particles

uses: inotophoresis, stimulating contractions of deinnervated nerves

Alternating Current

continuous (no breaks in line)

bidirectional (up & down)

uses: pain control, muscle contraction

Pulsed Current

interruption of a flow of charged particles; series of pulses & series of no current flow

2 types: monophasic & biphasic

uses: pain control, tissue healing, muscle contraction

Monophasic Pulsed Current

uses: any but most commonly promotes tissue healing & manage acute edema

high volt pulsed current (HVPC) aka pulsed galvanic current

Biphasic Pulsed Current

uses: most common in electrotherapy, produce muscle contraction, control pain

types: symmetrical, asymmetrical, unbalanced asymmetrical

Interferential Current

2 medium frequency current each slightly different

2 pair of electrodes, 2 separate channels, 2 AC intersect interference

thought to be more comfortable & to penetrate better

Current interference

if currents in the same phase → produces higher amplitude

if currents in opposite phase → produces lower amplitude

Premodulated Current

1x AC medium frequency current → increasing & decreasing current amplitude, 1x current, 2x electrodes

positives: same effect as IFC, easier to set up

negatives: not as beneficial or comfortable, smaller area, decreased efectiveness

Russian Protocol

strength

medium frequency AC, 2500 Hz 10ms burst (50 bursts/sec), 10 ms interval btwn bursts

Pulse Duration

how long each pulse lasts

short: pain control

long: muscle contraction

Phase duration

duration of one phase of a pulse, can have 2 phases in a pulse

Interpulse interval

amount of time btwn pulses

Basic terminology

frequency: # of waves per sec

Hertz: 1 cycle per sec

amplitude: magnitude of current flow, strength, intensity, in Amps or Volts

On time vs Off time

On: time current is on

Off: time current is off

Ramp up vs Ramp down

time for current amplitude to:

up: go from zero to max amp it is set to

down: max amp it is set for to zero

ie. it takes 3 secs to get from 0 → 2 amps

Action Potential

depolarizing nerve membranes

electrical current cause depolarization of nerve membranes → increase in AP

Absolute Refractory Period

when depolarized-nerve cant be further excited no matter how high the stimulus is

Relative Refractory Period

after depolarization before nerve returns to resting potential, there is a brief period of membrane potential hyperpolarization

this means a greater stimulus can creater another AP

Nerves requirements to produce AP

sensory: lower amp, shorter pulse duration

motor: higher amp, longer pulse duration

c fiber pain: even higher amp, even longer pulse duration

Contraindications & Precautions

contras: demand cardiac pacemaker, unstable arrhythmia, over carotid sinus, DVT, pregnancy

pre: cardiac disease, impaired sensation, impaired mentation, malignancy, skin irritation/open wound

Galvanotaxis

directional movement of cells due to an electrical field

specific cells: neutrophils, macrophages, lymphocytes, fibroblast

cells carry a charge

How does galvanotaxis work

normal cells → have electrical charge across them bc of sodium/potassium pump

injured cell, ruptured membrane → charged ions leak out of the cells, center of wound is no charged (skin battery)

activates healing

Cells attracted to anode (+)

negatively charged; promote healing of inflamed or infected tissues

macrophages, epidermal cells, inactive neutrophils

Cells attracted to cathode

positively charged; promote healing of wound w/o inflammation

lymphocytes, platelets, mast cells, keratinocytes, fibroblasts, activated neutrophils

More effects of E-stim

promote epidermal cell & lymphocyte migration, proliferation, & function by increasing vascular endothelial growth factor (VEGF)

Enhanced circulation

during or after stimulation due to angiogenesis via vascular endothelial growth factor

Medicare & Medicaid Approval

used for wounds, chronic stage ¾ pressure ulcers, arterial, diabetic, venosus statis

only those that havent seen improvements in 30 days

Edema control

(+): can splint the area to prevent movement

(-): increased pain, decreased function, prolonged recovery

DO NOT USE to treat systemic edema

Iontophoresis

use of EC to promote transdermal drug penetration

avoid side effects of:

nasal → low concentration drugs only, uncomfortable

oral: gastrointestinal distress, incomplete absorption

parenteral routes: injection, infusion, risk of infection site

How Iontophoresis works

low amp DC to facilitate transdermal drug delivery

fixed charge of electrodes pushes charged ion of drug through skin, can also increase permeability of the outmost layer of skin