06-04: Electricity Flashcards
0
Q
Electrons
A
Negatively charged particles
1
Q
Ions
A
Negatively and positively charged particles
2
Q
Electrical current
A
Net movement of electrons
3
Q
Ampere
A
Unit of measure = rate of electric current flow
4
Q
Coulomb
A
Number of electrons that move
5
Q
Volt
A
- Electromotive force applied to cause the flow of electrons
- Electrons only move if there is a difference in concentration/charge causing an electrical potential difference
6
Q
Conductance
A
Ease with which current flows
7
Q
Insulators
A
Materials that resist current flow
8
Q
Resistance
A
Electrical impedance
9
Q
Ohm
A
Opposition to electron flow in a material
10
Q
Watt
A
Measure of electrical power
11
Q
Cathode
A
- Negative electrode
- Greater number of electrons
- Attracts positive ions
12
Q
Anode
A
- Positive electrode
- Attracts negative ions
- Lower number of electrons
13
Q
Direct current (DC)
A
- Galvanic current
- Uninterrupted, unidirectional flow of electrons towards positive pole
- PTA may change direction of polarity which changes direction of current flow
14
Q
Alternating current (AC)
A
- Continuous flow
- Bi-directional
- Constantly changing direction
- Reversing of polarity
15
Q
Pulsatile current
A
- Contains 3 or more pulses grouped together
- May be unidirectional or bidirectional
- Groups interrupted for periods of time.
17
Q
TENS
A
- Transcutaneous Electric Nerve Stimulation
- Refers to a group of E-Stim modalities
- Sometimes refer to specific type of pain relief E-Stim
18
Q
Electrodes
A
- Placed on the skin to deliver electricity
- Self-adhesive
- Keep electrodes specific to one pt
- Carbon: Need moist surface or ultrasound gel to adhere to skin
19
Q
Waveform
A
Graphic picture of an electric current
20
Q
Waveform properties
A
- Shape
- Direction
- Amplitude
- Duration
- Frequency
21
Q
Wave Shapes
A
- Sinusoidal
- Square
- Triangle
- Sawtooth
- Biphasic, Monophasic, and Pulsatile may take on any waveform shape
22
Q
Pulse vs. Phase
A
- Pulse = one waveform
- Phase = part of the wave that rises above or below baseline
- Monophasic = Waveforms with one pulse and one phase in the same direction, DC
- Biphasic = Waveforms with two separate phases during each cycle (current reverses direction once during a cycle; symmetrical or asymmetrical)
- Cycle = One waveform above and below baseline (refers to biphasic)
- Pulse duration = length of time one waveform lasts
- Interpulse interval = Short time between phases with no current flowing (seen in pulsatile current)
23
Q
Biphasic vs. Monophasic
A
- Monophasic: Causes chemical change if pulse duration is longer than 1 min
- Most machines do not permit adjustment of the duration of current, so no chemical effect unless Rx more than 1 hr
- Don’t usually do elective Rx for more than 30 min.
24
Q
Intensity
A
- Increasing intensity drives electrical current into deep tissue
- More fibers are stimulated
25
Q
Hi-Volt Stimulators
A
- Deeper penetration into tissue
- Desirable for stimulating deep muscle tissue
- Usually pre-set pulse duration
26
Q
Lo-Volt Stimulators
A
- More superficial stimulation
- Usually adjustable pulse duration
27
Q
Characteristics of Pulse
A
- Phase Duration
- Pulse Amplitude
- Rate of Rise
- Rate of Decay
- Pulse Frequency
28
Q
Phase Duration
A
- Length of time the pulse lasts (monophasic)
- Length of time current flows in one cycle (biphasic)
29
Q
Pulse Duration
A
- Length of time current flows in one cycle
- Duration determines quantity of nerve fibers stimulated if intensity the same
- Increase duration = more nerve fibers stimulated (current available for longer period of time)
30
Q
Pulse Amplitude
A
- Height of the phase, with maximum amplitude being tip of each phase
- Higher the peak, higher the intensity
- Measures in amperes (amps), microamperes or milliamperes (milliamps)
- Same as voltage and current intensity
- Peak amplitude not same as total amount of current administered
31
Q
Rate of Rise
A
How quickly the pulse reaches max amplitude in each phase
32
Q
Rate of Decay
A
Time required for the pulse amplitude to return to 0 volts
33
Q
Accomodation
A
- Current constantly bombards nerve fiber, nerve fiber becomes unexcitable at that intensity (gets used to it, needs more intensity to escalate to level)
- Faster rate of rise, less likely nerve will accommodate = greater ability to excite tissue
34
Q
Pulse Frequency
A
- Number of pulses or cycles per second
- Each pulse = rise and fall in amplitude
- Frequency increases = amplitude tends to increase and decrease more rapidly (rise and decay)
- Muscle responds to frequencies of less than 50pps with twitch contractions; >50pps, a tetanic contraction occurs (muscle contracts and holds)
- Controls amount of fiber shortening and of recovery
35
Q
Higher Frequency
A
More muscle contraction
36
Q
Lower Frequency
A
Less muscle contraction, produces muscle pumping for edema control
37
Q
Tetany
A
- Rapid, intense and involuntary muscle fiber contractions which can cause spasms or cramping
- Therapeutically used to fatigue muscles, reduce spasm
- Occurs at pulse frequencies >50pps
38
Q
Modulation
A
Changes made to current amplitude, duration, frequency
39
Q
Continuous current
A
- Amplitude constant for several seconds/minutes
- Associated with long pulse duration, monophasic (always uniform direction)
- DC
- Ex: iontophoresis, medical galvanism
- If amplitude produces contraction, only occurs when current flow turned on or off
40
Q
Burst modulation
A
- Pulsatile or AC
- Current on for short duration, then turned off for short time in repetitive cycles
- Pulsatile: Sets of pulses combined into “bursts”; interruptions called “interburst intervals”
41
Q
Beat modulation
A
- 2 different waveforms with different frequencies delivered through 2 separate electrodes through 2 separate channels - they interfere with each other
- Total of 4 electrodes in criss-cross pattern
- Ex: Interferential treatment
42
Q
Ramping modulation
A
- Ramp-up and ramp-down intensity
- Current amplitude increases gradually to preset maximum (or ramp down gradually)
- Ramp-up is 1/3 of the on time
- Increases comfort as it modulates “surge” of current
43
Q
Polarity
A
- AC: Electrodes change polarity with each current cycle
- DC: PTA designates one electrode as positive and one as negative by connecting wirt
- General placement: Active, cathode (-) is distal, Anode (+) is proximal
44
Q
Series Circuit
A
- One pathway for current to get from one terminal to another (Ex: Christmas lights)
- Loss of voltage as current flows through path
45
Q
Parallel Circuit
A
- 2 or more paths exist for current to get from one terminal to another
- Current chooses pathway of least resistance
- Voltage is same at beginning as at the end
46
Q
E-Stim process in human body
A
- E-Stim modalities use combo of series/parallel circuits
- Electrodes on skin stimulate muscle contraction
- Series: Current passes through skin and fat
- Parallel: Current passes through bone, connective tissue, blood, muscle; Can pass through several different pathways to reach muscle
47
Q
Best tissue conductors
A
- Nerve
- Blood (2nd best)
- Muscle
- Tissues with high water content
48
Q
Best tissue resistors
A
- Bone
- Skin (2nd best - resists DC more than AC)
- Tendon
- Fat
49
Q
E-Stim Safety
A
- Generates heat in tissue
- Causes chemical (ion) changes in tissues which can be acidic
- 2 pronged devices are not grounded (use 3-pronged devices)
- If not grounded, or cord is cut, unit can become charged and shock a person
- Do not pull on cord to remove plug
- Use in dry environment because water conducts
- Burns on skin
50
Q
Therapeutic effects of E-Stim
A
- Relaxation of muscle spasm
- Muscle strengthening
- Improve ROM
- Facilitate wound healing
- Decrease edema
- Eliminate disuse atrophy
- Muscle re-education
- Increase local circulation
- Facilitate bone repair
51
Q
Indications for E-Stim
A
- Muscle spasm
- Muscle weakness
- Pain management
- Decreased ROM
- Idiopathic scoliosis
- Fracture
- Joint effusion
- Facial neuropathy (including Bell’s Palsy)
- Muscle atrophy
- Open wound/ulcer
- Labor and delivery
- Stress incontinence
- Shoulder subluxation
52
Q
Contraindication for E-Stim
A
- Cardiac pacemaker
- Cardiac arrhythmia
- Bladder stimulator
- Over carotid sinus
- Seizure disorder
- Phlebitis
- Malignancy
- Over pregnant uterus
- Osteomyelitis
53
Q
Monopolar electrode configuration
A
- Active (stimulating) electrode over target area
- Dispersive (2nd) electrode placed away from target area (usually larger than active electrode)
- DC
- Wounds, iontophoresis, edema
54
Q
Bipolar electrode configuration
A
- 2 active electrodes placed over target area (1 channel)
- Electrodes the same size, do not intersect
- Muscle weakness, NM facilitation, spasms, ROM, Russian, NMES
- AC
55
Q
Quadripolar electrode configuration
A
- 2 electrodes each from 2 separate stimulating circuits (2 channels
- Positioned so individual currents intersect with each other
- Interferential Current (IFC)
56
Q
Small electrodes
A
- Increase density size
- Increased resistance to electrical current
- Decrease current flow
- Concentrate electrical current
- Pt more susceptible to pain and tissue damage
57
Q
Large electrodes
A
- Decrease density size
- Decreased resistance to electrical current
- Increase current flow
58
Q
Electrode Placement
A
- Current density is greatest under the electrode
- Placement close to neural structure provides increased success with least amount of current
- 2 electrodes close together = increase current density superficially
- 2 electrodes spaced apart = increase current density in deeper tissue (nerve, muscle)
59
Q
Electrode Placement - 1 large, 1 small
A
- Greater current density under smaller electrode; larger electrode spreads current over larger area
- Small electrode concentrates current over motor point; larger electrode disperses over larger area
