L9: Introduction to Electrical stimulation Flashcards
1
Q
Our body is an ______ circuit
A
electrical
2
Q
Nerves conduct _____.
A
electricity
3
Q
Nerves depolarise by generating an _______.”All or none” threshold in order to send a _______.
A
action potential; signal (motor or sensory)
4
Q
Electrical stimulation devices operate by ______ nerves from externally placed electrodes
A
depolarising
5
Q
What are the 2 therapeutic uses of electrical stimulation?
A
- Pain relief
- Motor stimulation
6
Q
What is the pain inhibitory system?
A
7
Q
What is segmental inhibition (pain gate theory)?
A
- A beta (β) fibrestimulation
- high frequency, intensity just to sensory threshold
8
Q
What is descending inhibition (endogenous analgesia)?
A
- Stimulation of A delta (δ)fibres activates interneuronesin posterior horn ⇒encephalin release -endorphin type effect on C fibres
- Via higher centres(encephalin + mid brain serotonin)
- low frequency, intensity to 2-3 x sensory threshold
9
Q
What is the purpose of the descending inhibition (endogenous analgesia)?
A
- Apply slightly painful stimulus
- After 20mins –> can have pain relief for 2 hrs
10
Q
What are 5 things that sensory response to low frequency stimulation depend on?
A
- Intensity
- Duration
- Frequency
- Shape of stimulus
- Polarity
11
Q
Higher intensity equal higher _____.
A
current
12
Q
Chronic injuries require _____ (longer/shorter) electrical stimulation.
A
longer
13
Q
Acute injuries require _____ (longer/shorter) electrical stimulation.
A
shorter
14
Q
A lower frequency goes _____ (shallower/deeper).
A
shallowed
15
Q
A higher frequency goes _____ (shallower/deeper).
A
deeper
16
Q
How to apply therapeutic electrical currents?
A
Usually involves a stimulator leads and electrodes
17
Q
In order to depolarise nerves we can _______ various characteristics (parameters) of the electrical current to overcome skin impedance and affect different types of nerves
A
manipulate
18
Q
What are 5 basic characteristic of therapeutic electric current which can be manipulated to produce desired effect?
A
- Frequency (Hz)-no. pulses or bursts /sec
- Amplitude (mA) –intensity of current –total no. nerve fibres recruited
- Pulse duration (ms)
- Pulse interval (ms)
- Pulse shape
19
Q
Most clinical effects of electrical currents are the result of ______ stimulating an action potential (nerve impulse) in sensory and/or motor nerves
A
current
20
Q
Nerves have resting membrane potential of _____ mV
A
-70
21
Q
Stimulus must be more than mV (ie. down to -55mV) to overcome threshold. Remember its an ‘_______’ phenomena
A
15; all or none
22
Q
Increasing current amplitude or pulse duration does not make _____ greater
A
AP
23
Q
What are 2 factors that ease with which nerve membrane?
A
- Strength (amplitude) of the stimulus
- Duration for which it is applied
24
Q
What are 3 different nerves?
A
- Sensory
- Motor
- ‘Nociceptors’
25
Each nerve is shown by \_\_\_\_\_\_curve
strength duration
26
What is a rheobase?
Minimum nerve impulse required to elicit a response from a tissue
27
What is a chronaxie?
minimum time must flow at twice the rheobaseto produce a threshold response
28
Rheobase determined by \_\_\_\_\_, ______ and proximity to stimulus
size; myelination
29
What are 2 advantages of rheobase?
1. Short pulse duration, high intensity, therefore recruit more nerves (motor stimulation)
2. Longer pulse duration, low intensity
30
What are A-beta cells?
Mechanoreceptors
31
What are C fibres?
Don’t transmit very quickly --\> take a while
32
What are strength duration curve?
33
What are 4 things that the strength duration curve tells you?
1. 1st response usually sensory
2. Larger fibre, more easily stimulated
* sensory (Aα)and motor (Aβ)
3. short duration pulses-sensory and motor thresholds can be exceeded without reaching pain tolerance limit
4. Sensory stimulation for pain control and no motor response, need shorter duration pulse
* Have a lot of leeway with short duration pulses because can turn up intensity quite high before causing pain
34
What are 3 characteristics of refractory period?
1. Once nerve has depolarized, it cannot send another signal until after refractory period
2. So to increase the signal, need to recruit more nerves instead of stimulating the same one again
3. In practice this means as you turn up the intensity/amplitude you recruit more nerves so can have a greater effect
35
What are 4 characteristics of intensity?
1. Due to all or none phenomenon, no matter what the current intensity, the same nerve impulse is triggered
2. If turn up the intensity of current …..
3. Patient will feel increased sensory effects or stronger muscle contraction
4. Due to larger number of nerve fibres being stimulated not the increase in current or a greater effect on the nerve
36
What are 3 characteristics of accommodation?
1. Ability of the nerve or muscle to adapt to slowly increasing current intensities
2. Muscle -low accommodation
3. Nerve-high accommodation –do not respond to long slow rising pulses
* Respond to short or long pulses with sharp leading edge
37
What are 4 types of electrical current used in electrotherapy?
1. Direct Currents (DC)
2. Alternating Currents (AC)
3. Continuous
4. Pulsed
5. Pulsed Currents
38
What is frequency?
number of pulses per second (pps) (Hertz) (1 sec=1000ms)
Nb. 1 ms= 1000 microseconds (μs)
39
What is amplitude?
Intensity= no. of nerves recruited
40
What are 3 characteristics of pulse duration, pulse interval?
1. Pulse and phase characteristics
2. Pulse rate
3. Duty cycle (on-off time for a pulsed current)
41
What are 4 characteristics of pulse shape?
1. Rectangular
2. Triangular
3. Saw tooth
4. Sinusoidal
42
What are 5 shapes of pulse?
1. Phase
* Monophasic / Biphasic
2. Waveform
* Symmetrical / Asymmetrical
3. Ramping
4. Pulsed current
5. Balanced/unbalanced
43
What are 2 characteristics of monophasic waveform?
1. Current moves in one direction, dangers of charge building up on electrodes which can cause skin irritation/burns and deterioration of electrodes
2. More excitation possible under –veactive electrode
44
What are 2 characteristics of biphasic waveform?
1. Current moves in both directions, so no charge accumulation
2. Lose some of advantages of excitation
* Compromise –asymmetrical current (small ms)
45
What are effects of different waveforms?
1. Monophasic
2. Biphasic
46
What are 3 different types of wave?
1. Ramping –relates to intensity (important in motor stimulation)
* More gradual to mimic normal
2. Modulation
* Can vary (increase and decrease)
3. Sweep Eg. Interferential
47
What are 3 types of electrical current?
1. Direct current (DC)
2. Alternating current (AC)
3. Pulsed currents (AC or DC)
* Low frequency ( \< 1,000 Hz)
* Medium frequency ( 1,000-10,000 Hz)
* High Frequency (\> 10 000 Hz)
48
The higher the frequency --\> ____ (more/less) able to penetrate the body (\_\_\_\_\_\_\_\_ (deeper/shallower))
more; deeper
49
Be aware there are variations as to how currents are described which can lead to confusion eg • Pulse duration for \_\_\_\_\_\_is in μs, for HVS • Frequency can be measured in _____ or pps
TENs; Hz
50
1 second = ______ milliseconds (ms)
1000
51
1 ms= _____ microseconds (μs)
1000
52
What are 2 different naming systems for defining ES currents?
1. Descriptive
2. Named system
53
What are 3 descriptive currents?
1. Direct current
2. Alternating current
3. Pulsed current
* Low (\< 1,000 Hz)
* Medium (1,000-10,000Hz)
* High (\>10,000Hz)
54
What are 5 descriptive currents?
1. Galvanic (DC)
2. Russian (Alternating)
3. IFT (Crosses over --\> Cancels it out --\> small and low frequency (oscillates))
4. TENS, Faradic, FES, HVS
5. SWD, Microwave
55
What are 2 main effects of a pulsed current?
1. Stimulation of excitable tissue
* sensory nerves
* motor nerves
* pain nerves
* muscle tissue directly (when no nerve supply)
2. Stimulation of non excitable tissue
* Local tissue effects
56
What are 4 characteristics of stimulation of excitable tissue?
1. sensory nerves
2. motor nerves
3. pain nerves
4. muscle tissue directly (when no nerve supply)
57
What is a characteristics of stimulation of non excitable tissue?
Local tissue effects
58
What are 3 effects of electrical stimulation of sensory/pain nerves?
1. Increasing afferent input at spinal cord level or to supraspinallevels
2. Main reasons for using sensory stimulation:
1. to alter pain perception or
2. to alter cortical activity
3. Mainly used for pain relief but can be used to reduce spasticity (increased tone in neurological conditions)
59
What are 2 main reasons for using sensory stimulation?
1. to alter pain perception or
2. to alter cortical activity
60
What are 3 characteristics of transcutaneous electrical nerve stimulation (TENS)?
1. Small portable battery operated units
2. Can also be found on larger machines
* Short pulses (microseconds) –e.g. 50-400 μs
* Medium frequency 2-200 Hz
3. Motor and sensory nerves
61
TENS is a ________ or _______ pulse shape.
Biphasic symmetrical or asymmetrical pulse shape
62
What are 2 types of pain relief for TENS?
1. Using pain gating
2. endogenous analgesia
63
What does TENS look like?
Pain modulator that is mobile --\> can use to be more active Uses microsecs
64
With a longer pulses is ____ (faster/slower) rate.
slower
65
What are 3 modes of TENS?
1. Conventional TENS=pain gating
2. Acupuncture type = endogenous analgesia
3. Burst type= probably uses both systems (pain gating and endogenous analgesia)
66
What is conventional TENS used for?
Pain gating
67
What is an accupunture type of TENS?
endogenous analgesia
Not as comfortable but more effective for pain relief
68
What is a burst type of TENS?
probably uses both systems (pain gating and endogenous analgesia)
69
What are 8 current parameters for conventional TENS?
**EXAM QUESTION**
1. Short pulse duration -50μs
2. Frequency -40-200Hz (most often 100 or 150Hz)
3. High frequency/low intensity
4. Stimulates Aβfibres –fast onset pain relief
5. Not painful and does not cause muscle contraction
6. Duration 30-60 mins
7. Can also be used continuously
8. Pain relief only while on and for short time afterwards
70
What are 7 current parameters for acupuncture TENS?
**EXAM QUESTION**
1. Pulse width 200μs
2. 2Hz
3. Low frequency/high intensity
4. Stimulates Aδor C fibres
5. Applied acupuncture or motor points
6. Latent effect, lasts several hours
7. Need to apply for 20-30mins to gain effect
71
What are 4 current parameters for burst TENS?
**EXAM QUESTION**
1. series of pulses repeated 1-5 times/sec
2. each burst contains a number of pulses at the conventional TENS frequency 4-150Hz
3. delivered at higher frequency
4. ?combines the effects of conventional and acupuncture
72
What are 2 other parameters of TENS?
1. Brief intense
* Long pulse width –high intensity
* Apply for 15 mins
2. Modulated
* Some units have modulation facility
* Allows pulse width, frequency and/or intensity to be varied
* Prevents accommodation of nerve when used over a long time
73
What are 3 characteristics of brief intensity for TENS?
1. Chronic use
2. Long pulse width –high intensity
3. Apply for 15 mins
74
What are 3 characteristics of modulated TENS?
1. Some units have modulation facility
2. Allows pulse width, frequency and/or intensity to be varied
3. Prevents accommodation of nerve when used over a long time
75
What are 6 characteristics of the position of electrodes in TENS?
1. Over site of pain Try not to cross the spine
2. Same dermatome/myotome
3. Trigger or acupuncture points
4. Along length of peripheral nerve
5. Over spinal nerve roots
6. 1 or 2 channels 4 electrodes for a larger area
76
What is the range of the pulse width for TENS?
30 –260 μs
77
What is the range of the pulse rate for TENS?
2 –150 pps
78
What are 3 modes of TENS?
1. Conventional
2. Modulated
3. Burst
79
What is the range of the pulse width for TENS for acute pain?
Narrow pulse width (60-100 μs)
80
What is the range of the pulse width for TENS for chronic pain?
Wide pulse width (150-200 μs)
81
What is the range of the pulse rate for TENS for acute pain?
High pulse rate (80-200 pps)
82
What is the range of the pulse rate for TENS for chronic pain?
Low pulse rate (1-5 pps)
83
What is the intensity for TENS for acute pain?
Pleasant tingling
Comfortable but patient is aware
84
What is the intensity for TENS for chronic pain?
To tolerance
Uncomfortable but tolerable
85
Where can you change the intensity controls
top: dial for each channel
86
What are 7 clinical applications of TENS?
1. Musculoskeletal pain
* Low back and neck pain
* Knee and shoulder pain
2. Primary dysmenorrhea
3. Chronic pain
* Helps to take less pain killers (reduce medication intake)
4. Intractable angina
5. During painful procedures or postoperative pain
6. During labour (but unable to be submerged in water eg. water birth)
7. Help with period pain
87
When is interferential therapy (IFT) over TENS?
For more deeper structures
88
In IFT, as increase frequency ______ (increase/decrease) depolarisation of nerves (easier to get APs)
increase
89
In IFT, higher frequency currents overcome skin resistance ____ (more/less) easily, but require very high current intensities to stimulate nerve.
more
90
Why is IFT better for deeper structures?
* Need to cross the electrodes
* Cancel each other out
* Small current that goes deep (eg. ACL or hip structures)
91
What are 2 aims of ITF?
1. To produce low frequency effects at sufficient intensity at depth, most patients experience considerable discomfort in the superficial tissues (ie. the skin)
2. Resistance (impedance) of skin is inversely proportional to the frequency of the stimulation
92
What are 2 characteristics of skin impedance for IFT?
1. Skin impedance at 50 Hz is 3200Ωwhilst at 4000Hz it is reduced to approximately 40Ω
2. Higher frequencies require less electrical energy to reach the deeper tissues and giving rise to less discomfort
93
What are 4 characteristics of "true" IFT?
1. Two out of phase medium frequency currents of slightly differing frequencies that interfere with each other
* 4000-4250 Hz
2. Where 2 currents intersect , a new resultant current is formed. Resultant amplitude is the sum of the 2 original currents
3. Where a peak and a trough coincide they augment each other , but
4. where a peak meets a trough they cancel each other out
94
What are 5 characteristics of amplitude modulation?
1. This resultant current varies in amplitude
2. The frequency by which the new current varies is called the beat frequency
3. The beat frequency is equal to the difference between two original frequencies
4. So example, if current A is 4000Hz and current B is 4100Hz, the resultant beat frequency is 100Hz
* Low frequency but high amplitude
5. It is this modulation pulse deep in the tissues that triggers the nerve impulse (AP)
95
What is the beat frequency?
The frequency by which the new current varies
96
What does the beat frequency equal to?
the difference between two original frequencies
97
The ______ which is deep in the tissues that triggers the nerve impulse (AP)
modulation pulse
98
What are 3 characteristics of the frequency of IFT?
1. Most IF machines allow a constant beat frequency 10, 50, 100Hz
2. Usually use a sweep mode between pre-set frequencies over a specifed time eg0-150Hz, 80-120Hz, 0-100Hz
3. Sweeping is helpful for swelling and to limit nerve accommodation (larger sweep for swelling)
99
What is sweeping important for?
* swelling
* to limit nerve accommodation
* (larger sweep for swelling)
100
Do you want a large or small sweep for swelling?
Large
101
What can the beat frequency for IFT be set at?
constant beat frequency can be set between 1-250Hz
102
What can the frequency modulation for IFT be set at?
can be set to sweep between for eg. 20-80Hz over 6 secs, then back 6 secs
103
What are 3 reasons for using sweeping?
1. To prevent nerve habituation/accommodation
2. Effects on cell membrane-useful for swelling due to local increased fluid flow and fluid exchange, larger sweep is better
3. Stimulation of autonomic nerve endings-may help to remove chemical irritants affecting nociceptive nerve endings –reduce tissue pressure
104
What are 9 characteristics of electrodes?
1. Carbon/rubber with damp pads or adhesive
2. Equal sized and as large as body part can accommodate
3. 4 electrodes (2 each channel)
4. Positioning relative to target tissue Make sure don’t cross heart --\> has electrical currents (eg. not front and back)
* Contra-planar (on opposite sides of a limb- Across limb )
* Co-planar (on same side e.g. for low back pain)
5. Avoid trans-thoracic applications (effects on heart)
6. As large as feasible
7. Wet pads if not adhesive
8. Wash skin to reduce impedance
9. Make sure you have full contact with skin Risk of burns if not fully contacted
105
Why can electrodes be applied with suction cups and sponges?
* Ease of application
* Need good skin condition
* Increase circulation
* Use with extreme care with haematoma or acute swelling
106
What are examples of electrode placement in the back, elbow, knee and shoulder
Channels must cross each other with target tissue in the middle
107
Channels must cross each other with target tissue in the \_\_\_\_\_\_\_.
middle
108
What are the 5 effects of frequency on sympathetic parasympathetic, motor, sensory nerve and smooth muscle
1. Sympathetic nerve 1-5Hz
2. Parasympathetic nerve 10-150Hz
3. Motor nerve 10-50Hz
4. Sensory nerve 90-100Hz
5. Smooth muscle 0-10Hz
109
What are 3 characteristics of the Pre-modulated medium frequency current (MMF)?
1. Waveform produced by one channel (2 electrodes) that is the same as the interference produced by 2 channel IFT machines
2. Interference produced in the machine
3. ‘IFT” can be applied using just 2 electrodes
* Useful for smaller parts
* Considered less effective than ‘true’ IFT because currents don’t cross deep in the target tissue
110
What are 4 main clinical applications for IFT/MMF? What another clinical application
1. Pain relief
2. Muscle stimulation
3. Increased local blood flow
4. Reduction of oedema egstress incontinence
111
Short duration in order to get patient to do ______ or so you can do some other treatment eg joint mobilisation
exercise
112
What is the general rule for clinical dosage for acute injuries?
lower intensity, short treatment time
113
What is the general rule for clinical dosage for chronic injuries?
high intensity, longer treatment time
Endogenous effects
114
What is the frequency of treatment for acute injuries?
low intensity-more regular treatment
115
What is the frequency of treatment for chronic injuries?
less frequent
116
If sweep is available, what is the clinical dosage for acute injuries?
slow rate 6/6
117
If sweep is available, what is the clinical dosage for chronic injuries?
fast rate 1/1
118
With acute injuries, they generally require _____ (higher/lower) frequency.
higher (80-150Hz)
119
With chronic injuries, they generally require _____ (higher/lower) frequency.
lower (\<10Hz)
120
What is the commonly used IFT/MMF treatment frequencies to activate pain gate mechanism (stimulation of large diameter fibres -Aβ)?
(stimulation of large diameter fibres -Aβ)
High beat frequencies, sweep between 80-200Hz ( eg80-120Hz, 100-150Hz, 100-199Hz)
121
What is the commonly used IFT/MMF treatment frequencies to activate A delta (δ) and C-fibres to release endorphins/ encephalins (Endogenous analgesia)?
* Low frequencies, sweep between 0-25Hz (eg2-5, 10-25Hz)
* Needs to be on for at least 20 mins
122
What are the 18 steps in the procedure for applying electrical stimulation?
1. Introduce yourself, explain the treatment you propose and why you think it may be beneficial as part of the multimodal treatment
2. Gain initial consent
3. Position patient appropriately
4. Check contraindications/precautions
5. Is there any cause for extra concern?
6. Skin check
7. Test sensation
8. Clean skin
9. Turn machine on
10. Set up machine parameters (dosage)
11. Machine check on self/demonstration to patient
12. Apply electrodes to patient
13. Warnings
14. Turn up intensity slowly, ask patient when they first feel tingling
15. Turn up intensity to desired level
16. Give patient a bell
17. Check after a few minutes that feeling ok
18. At end of treatment-turn intensity to zero, remove electrodes, check skin, turn off machine
123
What are 5 contraindications of electrical stimulation?
1. Over pacemakers or inbuilt stimulator
2. Over carotid sinus (in the neck)
3. Trans-thoracic applications
4. Venous thrombosis or thrombophlebitis
5. Pregnancy-pelvic region ie. over uterus or low back (but can be used for pain relief in labour) (As the baby is already developed)
124
What are 7 precautions of electrical stimulation?
1. Metal in the area Watches, jewellery
2. Impaired sensation
3. Cognitive impairment/communication
4. Malignant tumours/risk of dissemination
5. Circulatory insufficiency
6. Skin irritation or open wounds
7. Self-adhesive electrodes Can come unstuck
125
What is important about patient positioning?
126
What are 4 characteristics to help overcome impedance in order to target desired tissues?
1. Type of current and characteristics of current
2. Need to examine skin for areas of high and low resistance
3. Skin preparation
4. Coupling
127
What is the 3 purposes of the skin examination in preparation?
1. Check for areas of low resistance e.g. cuts, abrasions –avoid positioning electrodes here and cover with petroleum jelly & cotton wool -reduces current focusing there
2. Check for areas of high resistance e.g. warts or scars-avoid positioning electrodes over these
3. Remove any grease from skin
128
What are 3 ways to lower skin resistance?
1. Reduce resistance of skin by washing to remove keratin and sebum
2. Leave skin wet
3. Warm skin
129
What are 2 features of the size and shape of electrode?
1. appropriate to body part
2. Aim to use largest electrode possible for the area
130
What are 2 features of the type of electrode?
1. Depending on machine used
2. Good quality for HVS and IFT
131
What one thing to check in the integrity of electrode?
No cracks, well adhered to body part
132
When small electrodes are close together, there is a ______ (deeper/superficial) flow of current.
superficial
133
When large electrodes are close together, there is a ______ (deeper/superficial) flow of current.
deeper
134
If using rubber electrodes need damp sponge or pads which are the ____ size as the electrode.
same
135
What are 2 characteristics of current density?
1. Total current at each electrode is the same but current density ie. current/unit area will be different
2. If using 2 electrodes of different sides current density will be greater under smaller electrode
136
What are 6 safety checks for electrical stimulation?
1. Check contraindications
2. Test patients sensation (sharp/blunt)
3. Wash skin
4. Test machine
5. Turn machine ‘on’, intensity at zero
6. Turn machine power on and off with patient not attached
137
What are 6 characteristics in patient care for ES?
1. Always give patient an explanation of what they should feel
2. Give warning
3. Supply with a bell
4. Ask (what they are feeling)
5. Look (can you see any unwanted effects egmuscle contraction)
6. Feel –after treatment for change in tissues
138
What are 6 characteristics of patient/equipment care for ES?
1. Always turn up intensity SLOWLY
2. Observe patient
3. Check for any causes of uneven resistance
4. Breaks in skin –cover with Vaseline
5. Skin condition
6. Wash off liniments, creams, oils etc
