Lecture 1 Flashcards
Understanding the Introduction to EMG...The mechanics and terminology. (125 cards)
1
Q
Another name for DC would be
A
Galvanic/Monophasic and has polarity
2
Q
Biphasic has
A
Two phases Generally AC
3
Q
Monophasic has
A
One Phase Generally DC
4
Q
What type of currents are out there?
A
Continuous Direct(Galvanic/DC) continuous monophasic Continuous Alternating Current (AC) Pulsed Current (AC or DC)
5
Q
What is an electrode?
A
A medium used to apply or record electrical current
6
Q
Early Electrodes
A
were conductive metal covered with a sponge or felt. These were good conductors but not able to conform well to the body. Still used for probes where conformity does not matter
7
Q
Carbon empregnated silicon rubber electrodes
A
these are flexible they can be trimmed to a specific size they have a low resistance (typically <100 ohms) they are highly conductive, they can be used many times, however their conductivity does decrease over time. They require a medium to transmit current (gel is the most common) With a sponge or paper towel they dry out (30 min max)
8
Q
What type of electrodes should be used for treatment of 30 minutes or longer
A
Synthetic Gels
9
Q
Cleaning
A
All electrodes as well as the skin should be cleaned prior to use to remove dirt, oils, dead skin, and to increase comfort of treatment
10
Q
Disposable Electrodes+++
A
Some need to be hydrated with ultrasound gel
Last from 5-10 uses
May be more comfortable if gel is added.
11
Q
Other types of electrodes
A
- Percutaneous (needle)
2. Surgically implanted (pain, epilepsy, bladder, Parkinson’s, etc.
12
Q
Electrode placement and size effect
A
1. Pathway of current flow (PLACEMENT) 2. Concentration of current in tissue (SIZE) 3. Ability to discriminate between the three excitatory responses (size/placement) --Sensory --Motor --Noxious
13
Q
Current density and resistance
A
Increase as electrode size decreases
14
Q
Electrodes that are too large
A
may stimulate unwanted muscle groups
15
Q
The further apart they are
A
The deeper that the penetrate…on back feel in stomach
16
Q
Electrode too small
A
may miss motor point
Keep electrodes at least quarter size with medium frequency (russian and interferential) currents to prevent burns.
17
Q
Electrodes should:
A
- Promote low skin electrode impedance
- Conduct current uniformly
- Maintain uniform contact with the skin
- Allow desired movement of the body part
- Avoid skin irritation (cautious of latex allergies but typically do not bother them-Pads)
18
Q
The coloring of electrodes
A
May not represent polarity–when does it represent polarity…If it is DC the coloring does mean something….AC does not have polarity…DC does have polarity.
19
Q
Current will follow
A
the path of least resistance
20
Q
Types of electrodes
A
conductive metal covered with a sponge or felt.
carbon-impregnanted silicon rubber electrodes.
disposable gel electrodes.
21
Q
Electrode spacing and depth of penetration
A
The closer the electrodes are together the more superficial the current is.
The further the electrode spacing is apart the deeper the current is.
22
Q
Current
A
The flow of charged particles The movement of electrically charged Measured in Amperes(mA) Will change depending upon the resistance. I=V/R
23
Q
Average(total) current
A
• Absolute value of current per unit time
(amount of current averaged over 1
second)
• Associated with strength of contraction
and strength of sensation
• Much more important than peak current
• Measured in micro or milliamperes
• Proportional to the amount of heat
production in the tissue
24
Q
Voltage
A
a potential—but nothing being delivered
circuit is not connected
25
Amperage
Work being delivered circuit is connected
26
The most commonly used current in treatment is
Pulsed AC
27
The current that comes out of the wall is
AC continuous
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The current is the
Flow of charged particles--there is no current without a completed circuit
29
Voltage
is potential and always there
30
Current is measured in
mA milliamps
31
Current is
I=v/r the number on the machine during treatment for current is irrelevant
32
The higher the current
the more you will feel...the average current is different than the peak current. also measured in mA. Proportional to the amount of heat production in the tissue
33
Polyphasic
many phases...
34
Average (total) current
50% duty cycle...delivering current 50% of the time. Both Russian and interferential current possess an interrupted sine wave (polyphasic) with a typical carrier frequency if 2500 Hz is greater and a 50% duty cycle, Due to the high total current, small electrodes(under a quarter size) should not be used.
35
Interferential Current
The most common current we will use
36
Continuous Direct Current (Galvanic) (DC)
Only used for iontophoreisis
continuous unidirectional flow of charged particles
Used in PT/OT practice only for iontophoresis
Has a polarity
37
Continuous Alternating Current (AC)
Uninterrupted bi-directional flow of charged particles
THe current periodically changes direction
Two current reversals make up one cycle-the number of cycles or oscillations per second is called the frequency and is called/ measured in Hz
Used to power many appliances
Not used in CLINICAL PRACTICE
No polarity effect
38
Pulsed Current
Unidirectional (DC) or Bidirectional (AC) flow of charged particles that periodically cease for a finite time period before the next event.
39
Cathode
the electrode that is negative with respect to the other electrode
negative pole of the circuit
if current is biphasic, there is no polarity
attracts cations
in a car battery the black terminal
40
Anode
The electrode that is positive with respect to the other electrode
positive pole of circuit
if current is biphasic, there is no polarity
attracts anions(-)
In a car battery the red terminal
41
Physiological Responses to continuous Direct Current
vasomotor responses occur to maintain normal tissue pH and chemical balance
--increase in blood flow
--increase in metabolic rate
the changes do not happen with most current types due to long interpulse intervals and low average current, the body has adequate time to restore homeostasis
42
Average Total Current
In pulsed current, the peak may be much higher than the average due to long interpulse intervals
How many pulses/seconds would occur in this example?
43
Phase Charge/pulse Charge
The whole area under the curve
represent the phase duration, amplitude, and waveform
Phase duration X Amplitude=microcoulombs
the quantity of electrons affecting the medium with each phase of each pulse
Total pulse charge is the summation of all phase charged contained in the pulse
Measured in Microcoulombs
44
Phase Charge Safety Limits
```
Maximal phase charge (per phase)
(for phase duration up to 300 usec)
15-20 ucoul:weak stimulator
20-25 ucoul: moderate
30-45 ucoul: strong
```
45
Amplitude (current, Intensity, output, mA, volts, magnitude)
Peak amplitude-the maximum current value reached in a monophasic pulse or for any single phase of biphasic pulse
Associated with depth of penetration
46
Frequency
The number of pulses per unit time
The rate of oscillation or alternation in cycles per second
Expressed as pulses/sec PPS or Hertz (Hz)
Often labeled as rate pulse rate or pulses/sec or frequency on stimulators
Fused or Tetanic contraction around 15-20 HZ
47
Waveforms
the shape of a visual representation of pulsed current on a current/time plot or voltage/time plot
Can be symmetrical, asymmetrical, balanced, unbalanced, biphasic, monophasic, polyphasic, eyc
48
Pulse
An isolated electrical event separated by a finite time from the next event.
49
Pulse Width (duration)
the duration of a pulse, usually measured in the microseconds
the elapsed time between the beginning and the end of all phases
50
Phase
Unidirectional current flow on a current/time plot
51
Phase duration(phase width)
The elapsed time between the beginning and the end of a single phase from current deviation from the baseline and return to the baseline
52
Interpulse Interval
The time between two successive pulses
| Usually in microseconds
53
Biphasic how many phases equal a pulse
2 phases=1 pulse
Biphasic duration 200 phase duration =400 pulse duration
Most machines use pulse duration
54
In monophasic how many phases equal a pulse
in monophasic a phase is equal to a pulse
55
Monophasic Current
Pulse that deviated from the baseline in only one direction
In a monophasic waveform the pulse and phase are the same thing
In a monophasic waveform the pulse and the phase duration are equal
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Biphasic Current
Pulse the deviates from the baseline first in one direction and then in the opposite direction. The phases may be symmetrical or asymmetrical. If they are asymmetrical they still may be balanced.
57
Polyphasic (IFC0(russian
a type of AC current in which more than 3 phases occur before the current returns to baseline
Most common applications are interferential current (IFC) and Russian
58
High Voltage Pulsed DC Current (monophasic current)
Jack of all trades master of none
Twin Spike
Twin Peak
Can be used for strengthening...would not be 1st choice
good for small muscles and edema control...pain control and wound healing
low average current (also accounts for the off time)
high peak current
59
Rise Time
The time from the leading edge of the phase to increase in amplitude from the zero current baseline to peak amplitude of on phase
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Decay time
The time from the peak amplitude to return to the baseline (zero current) again in 1 phase only
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Rise and Decay Time
Time within each little phase when the pulse goes up and down with each individual pulse
62
Ramp
Ramp up time Usually more important for comfort.
from zero to its maximum amplitude during the on-time (usually in seconds)
Ramp down time
time it takes for the current amplitude to go from its maximum to zero (usually in seconds)
TO mimic recruitment and INCREASE COMFORT
63
Strength-Duration Curves
The S-D curve shows the relationship between the intensity of the stimulus and the amount of time for which it is applied to produce a contraction of the muscle or nerve depolarization. As a diagnostic tool, the curve can show the integrity of the nerve-muscle complex and the degree of denervation or reinnervation
64
Ramp
Some units have ramp built in
Common built in ramps are approximately a 2:1 ratio
ex...2 seconds up 1 second down or
3seconds up 1.5seconds down
If the unit or current is for strengthening it will have a ramp whether you see and adjust it or not
65
Rheobase (SD)
Magnitude--the magnitude of current (intensity) just sufficient to cause excitation of a tissue with a very long pulse duration (infinite) mA
66
Chronaxie (SD)
TIME--the minimal pulse duration required for threshold activation at twice rheobase intensity /microsec or millisec
67
Denervated Muscle SD curve
will shift up and to the right
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Recruitment 1'
| Pulse Duration
An increase in pulse duration will increase recruitment of motor units at the same depth but of smaller diameter
Increasing pulse duration too much (greater than 800 usec will stimulate fibers we may not want to (small diameter painful fibers)
69
Recruitment 2
| Amplitude
A stimulus at just above threshold from excitation will excite the closest and largest diameter fibers. Increasing the current amplitude (c) will excite smaller fibers that are close to the electrode as well as larger fibers further away
70
AC current
Interpulse and Interphase intervals are two different things
71
DC current
Interpulse and Interphase intervals are the same thing
72
Fused or Tetanic Contraction
continuous, fluid happens at 15-20Hz
73
Amplitude affects recruitment
by getting more fibers further from the pad
74
Small diameter fibers carry pain so we need to keep the pulse duration
below 800 usec to avoid the pain fibers
75
General Pulse Duration for strengthening
200-600 mA
76
As the pulse rate goes up we increase recruitment and
Decrease the amount of Amplitude/current (amperage mA) needed to initiate a contraction
77
At some point no matter how high you turn it
you will reach a maximum recruitment level strength and contraction (at this point you will only increase pain)
78
Increasing frequency
fires the existing motor units at a faster rate
79
Optimal frequency will get
the optimal physiological response while minimizing fatigue
80
Effect of fatigue on frequency
minimizing the frequency needed for tetanic contraction minimizes the fatigue
81
For Quads
Frequency at 50 is standard
82
Current density is greatest
directly under the electrodes and decreases with distance.
83
The higher the frequency
the higher the fatigue (given a continual contraction rate)
84
Bone and Fat have greater resistance than muscle
which also decreases current density in deeper tissues.
85
monopolar electrode configuration=1 pole
1 electrode is there to do the treatment and the other is there to complete the circuit
86
In monopolar configuration the nontreatment electrode is called the
disperse or non treatment electrode
87
Bifurcated monopolar electrode configuration
treatment electrode would have 2 treatment electrodes that are split
not-very common
88
DC means you have what and when is it used
positive and negative charges used on pulse most of the time
| only DC has polarity
89
Bipolar means
Both electrodes are being used for treatment and both electrodes are typically the same size....It can be monophasic or biphasic current depending on the treatment.
90
Quadripolar
Need two channels...4 electrodes in the area of treatment of similar size...used often for the treatment of pain
91
Cycle time
ON/off ratio
| Most machines call it Cycle time/ or ON/OFF
92
20 pps
Typical number for tetany--smooth contraction
93
Strengthing is typically at what level
30-50pps for strengthening with minimizing fatigue---you get a larger contraction at these currents
94
Waveform Modualtions (commonly seen with TENS and IFC units)
modulating one or multiple aspects of the waveform such as frequency, amplitude and pulse duration on a periodic basis may increase comfort and help to prevent accomodation.
95
Train
A continuous, repetitive series of pulses ata fixed frequency is called a train
96
Timing modulations-Burst
a finite series of pulses
a finite interval of alternating current delivered at a specified time interval
the time interval over which the series of pulses is delivered is called the burst duration and the time beterrn burst is called the interburst interval
97
How is a evoked contraction different from a normal contraction>
can not get fine motor task with estem
| fatigue faster with ems/nmes
98
Normal vs evoked contraction Firing Pattern
```
Normal
--asynchronous
--fine gradations of tension
Evoked(estem)
--synchronous
--maximum tension obtained at tetany
```
99
Normal vs evoked contraction --increase strength of muscle contraction
```
Normal
--increase firing rate
--increase number of motor units activated
Evoked(estem)
--increase amplitude
--increase frequency
--increase pulse duration
```
100
Normal vs, evoked contraction--Recruitment
```
Normal
--small motor units first
--innervated by small diameter nerves
Evoked(estem)
--large motor units first (mix of fast and slow twitch)
--innervated by large diameter nerves
```
101
Fatigue more quickly with
Estem over normal contraction
102
Normal vs. evoked contraction--Fatigue
```
Normal
--inability of contractile and metabolic processes of muscle fibers to continue same work
--decrease in ATP formation
Evoked(estem)
--failure in synaptic transmission
--decreased acetylcholine
```
103
Types of stimulators
```
pulsed AC and DC
Iontophoretic device
Interferential
High voltage pulsed DC
low, medium or high frequency
mocrocurrent stimulation
TENS units
Many others
```
104
TENS vs. NEMS
TENS do not have a cycle time or ON/OFF time or a RAMP
| NMES (portible muscle stimulator) have a ON/OFF TIME and a RAMP (more costly)
105
Machines can be classified by their power source
Clinical (plugged into a wall)
| Portable(battery powered)
106
Machines can be classified by their type of electrical signal applied to the patient
```
pulsed AC/DC
iontophoretic device (continuous DC)
interferential
High Voltage pulsed DC
low, medium or high frequency
microcurrent stimulation
```
107
Machines classified by frequency
```
Low Frequency 1-1000Hz
Most pulsed AC and DC units except the ones listed below (almost everything is slow)
Medium Frequency 1000-100000 Hz
Russian Stimulation (2500Hz)
Interferential (commonly 4000-5000Hz)
High Frequency 1000,000 and above
Diathermy 27 MHz (shortwave) or
4750 MHz (microwave)
```
108
Types of stimulators
Hi volt-100 V or greater
Low-volt < 100V
High Peak Current >50mA
Low peak current <50mA
109
Uninterrupted DC is used for
Iontophoresis
Average and Peak Current are the same here
there are five alternate names for Continuous DC
110
Interrupted Monophasic (DC) is used for
Denervated Muscle Stimulation if pulse width is greater than 10msec (milliseconds)
Pulsed DC
20-30 millisecond pulse duration
111
Monophasic Pulsed Twin-spike "High volt Pulsed DC" is used for
Pain Control
Edema Reduction
Tissue Healing
Muscle Stimulation (small muscles)
112
Biphasic Symmetrical "VMS" is used for
Muscle Stimulation
most muscle stimulators
low frequency
medium frequency= Russian and Interferential
113
Biphasic Asymmetrical is used for
```
Pain Control (TENS units)
Muscle Stimulation for small muscle groups
```
114
Polyphasic Symmetrical Sine Wave is used for
```
Muscle Stimulation (Russian Stimulation)
Analgesia (Interferential)
Edema reduction (Interferential)
Spasm reduction (Interferential)
all medium frequency and polyphasic 1000pulses
```
115
Low volt pulsed current stimulators-very common
```
less than 150 V
waveforms
===symmetrical biphasic square
==Asymmetrical biphasic square
=used in portable TENS and NMES devices as well as general purpose clinical stimulators. Effective waveform for pain management and muscle contractions
```
116
High Voltage Pulsed Current is used for "High Volt Pulsed DC"
1. 0-500V
2. Waveform=monophasic twin spike
3. Fixed pulse duration=100-150usec
Used for management of pain and edema, wound healing, muscle contractions of small groups
usec=microsecond
Can not change the pulse duration if It is fixed
117
Interferentail Current uses
two channels of differing carrier frequencies to create a treatment or beat frequency within the tissues
Less than 150 V, but high average current
Used for pain management, edema reduction, muscle spasm
118
Russian Current-medium frequency- interrupted sine wave
May be more or les than 150V, carrier frequency typically 2500Hz
50% duty cycle
Used for maximum motor recruitment (strengthening)
119
Microcurrent
delivers amplitudes usually less than sensory perceptions
less than 1000uA
Waveform=monophasic, pulsed at 50% duty cycle
Biphasic mode also used
Used in acute tissue trauma, facilitating healing, reduction of inflammation
120
Microcurrent
A type of current that uses a very low current (typically subsensory)
Follows the Arndt-Schultz Law
Primarily utilized for pain and for tissue healing
Use has drastically declined due to lack of evidence
121
Microcurrent (MENS) or Low Intensity Stimulators (LIS)
Intensity is limited to 1000 uamp or less (compressed to mamp)
AC and DC Units(primary DC)
Research is primary on wound healing and analgesia
Most research in pain control (DOMS) has not shown to be better than control groups
Most research in wound healing displays a lack of consensus on treatment protocols. A limited number of controlled studies have shown some evidence of accelerated healing rated compared to untreated skin ulcers. An increase in growth factor has been demonstrated which may ne the mechanism for healing.
122
When using ESTEM we depolarize
motor nerves not direct muscle tissue. It is too hard to depolarize muscle tissue
123
Definitions
ES=electrical stimulation
TS=therapeutic electrical stimulation
NMES=neuromuscular electrical stimulation
EMS=electrical muscle stimulation
FES=functional electrical stimulation
TENS=transcutaneous electrical nerve stimulation
124
Uses
NEMS=to enhance muscle performance(ROM, strength, re-ed, structural abnormality, muscle tone)
NMES=to effect function
ES=for pain control
ES=for wound healing and reduction of healing
Iontophoresis
Electrophysiologic testing
125
Contraindications
1. High intensity ES about the heart
2. Over the carotid sinus
3. In areas of neoplasm or infection may irritate the tissue
4. In individuals who cannot give clear feedback
5. About the trunk of pregnant women
6. In areas of peripheral vascular disease (PVD) or thrombophlebitis may release embolus
7. Patients with pacemakers or other implanted electrodes as it may interfere with their signal
8. Over areas of excess adipose tissue (may not got to muscle and or levels of stim needed may cause ANS response
9. In close proximity to diathermy as they may interfere with each other
10. Caution must be used when treatment is applied over anesthetic skin
11. Where active motion is contraindicated (tendon repair, fracture)
12. Seizure disorders (head/neck)
13. Over open wounds (unless treating the wound)
