EEI 10/10a Stim I Flashcards
(30 cards)
define electricity
a form of energy and it can produce significant effects on biological tissues
Electric Charge
- fundamental physical property
- operationally defined
- can never see a charge, but can see through experiementation how it is manifested
Uses of electrical stimulation
- Neuromuscular dysfunction (NMES/FES)
- Pain (TENS)
- Wound/Tissue Healing (HVPC)
- Delivery of Pharma Agents (Iontophoresis)
- Electric Muscle Stim (EMS)
- Edema Management
- Evaluate nerve and muscle injury (NCV)
Types of electrical currents
- Direct Current
- Alternating Current
- Pulsatile Current
Usage of electrical current
- Sensory
- Motor
- Noxious
Direct Current
uninterrupted flow of charged particles
continuous flow from negative to positive
Alternating Current
Positive to negative repetitively, no breaks in between waves
Pulsatile current
space between pulses
monophasic or biphasic
Charge
- Q (coulombs - C)
- 1 coulomb is 6.24 x 10^18 electrons
- clinically, metals carry charge
- provide a charge and it changes the polarity of muscles to transmit the current
Current
- I (amperes - A - milliamps 10^-3)
- movement of charged particles through a conductor in respones to an applied electric field
- flows in path of least resistance
Current flowing through an incision
leads to electrical burn because flows through path of least resistance
current flow between two electrodes that are close to each other
Burn
Current flow with dry skin or dry electrodes
less water content
more resistance, may have to jack up stim, but would be dangerous to pt if there are any abrupt changes
current flow with lotion of or oily skin
less water content
more resistance
Voltage
- V (V - Volts)
- amount of flow able to be stimulated
- potential difference or electromotive force that makes charged particles move
- typically in milli and micro
Resistance
- R (Ohms)
- DC Current
- Opposition to Current
- dependent on length and cross sectional area
- resistors in series = skin and fat
- resistors in parallel = nerve, muscle, and bone
Impedence
-Z (ohms)
Capacitance
C (Farads)
You are working with a patient and using NMES to strengthen their quadriceps in the early post-operative period after ACL reconstruction. You are at 100V, but the measured electrode/tissue impedance using 2.75x5 inch electrodes is 4.467 kΩ. What is the actual current that is reaching the peripheral nerves that innervate the quadriceps?
V = IR -> I = V/R = 20mA
what happens if there is a drop in impedance with a constant voltage device?
there is a change in resistance, the current jumps and increases
what happens if there is a drop in impedence with a constant current device
there is a change in the resistance, thus the voltage drops significantly
instances when resistance may change?
- abrasion
- sweat
- dry skin
- oily skin
iontophoresis
direct current stim
- dexamethazone has negative polarity and is put under a negative electrode
- the molecules get pushed to the other side
- poor evidence
normal use of stim
sensory, but used for both motor and noxious as well
