Intro Electro Flashcards
conduction flows in ____, convection flows in ____
conductors
fluids or gases
Current recorded as
I, amperes
Postive ions =
are attracted to ____ which are
cations, cathode, negative
Negative ions =
attracted to__, which are
anions, anode, positive
T/F current flows pos to neg
no both directions
coulomb
charge carried by ampere for one second
basic unit of measured charge
ampere or amp
rate of flow of current
measures current intensity
volt
energy difference between two physical points
inert needed to move a coulomb between 2 points
Resistance measured in
ohms
Ohms Law
voltage related to resistance and current
Voltage = current x resistance
Watt
rate of converting energy (power)
Is skin homogenous
no
Why dry epidermis impede electric current
Ohmic resistance
capacitive reactance
inductive reactance
Skin resistance depends on
dry or wet
warm or cold
pulse duration
current intensity
impedance
resistance
Impedance inc or dec electrode off the skin
increase
in practice do we use constant voltage or current
voltage
Biological effects of applied electrical charges
Electrochemical (new compounds)
electrophysical (stimulate)
electrothermal (heat)
cellular signalling (cell behaviour)
biolelectricity
all living cells generate it
membranes have voltage gradients
essential for healing
4 applications of therapeutic modalities
pain
performance (facilitate or inhibit)
inflammation/healing
flexibility ROM
three ways tissue damage from current happens
chemical burns
prolonged mm contraction (heart)
high density cause tissue heating
macroshock
current through skin
1mA for 1 sec
microshock
current through heart
how many mA may be fatal
100
how many uamps may cause ventricular fibrillation
20
variable that determines severity of shock
current
how to prevent tissue heating
size of electrodes
contact
current intensity Low as effectively possible
5 contraindications for estim
electric devices preg infection seizures cardiac disorders
can you give equipment to patients
only if the manual says you can
4 components of device safety
equipment meets standards
3 pin plug used
inspect cord and test it
Screen for risks
strength duration curve
technique to identify state of injury or mm/nerve
SD testing
gets minimal palpable contraction
indications for SD use
monitor lesion progress
establish pulse duration for treatment
establish integrity of tendon when pt can’t contract
Three concepts for nerve depolarization
intensity
pulse duration
rise time
rheobase
minimum current intensity for perceptible contraction
chronoaxie
minimum duration of impulse to produce response
small or large diameter depolarize first
L
what is stimulated first from skin
AB (sensory) Aa (Motor) Ao (pain)
Inactive Red Anode
area near membrane becomes positive
harder to depolarize
Active Black cathode
area near membrane more negative
easier to depolarize the nerve
normal or denervated mm require longer duration to demoralize
denervated
factors affecting outcome of SD curve
skin tissue position of electrode pressure humidity oedema
advantages of SD testing
monitor progress
non-invasiev
simple
high inter rater reliability
disadvantages of SD testing
poor repeatibilty
unable to localize nerve trunk
less valuable for large mm
curve of partially denervated mm’s
location of kink not signification
left to kink = innervated, right denervated fibres
curve change 6 wk before clinical changes
no recovery by 5 months, poor prognosis
