L12: Electrical Stimulation 2 Flashcards
1
Q
What are the 4 uses of EPAs?
A
- Reduce pain
- Reduce swelling
- Stimulate healing
- Re‐educate muscles
2
Q
EPAs must be used in with other ______.
A
treatment
3
Q
What are the 2 main effects of a pulsed current?
A
- Stimulation of excitable tissue
- sensory nerves
- motor nerves
- pain nerves (nociceptors)
- muscle tissue directly (when no nerve supply)
- Stimulation of non excitable tissue
- Local tissue effects
4
Q
What are 4 things that the strength duration curve tell you?
A
- 1st response usually sensory
- Larger fibre, more easily stimulated
- sensory (Aα) and motor (Aβ)
- short duration pulses‐sensory and motor thresholds can be exceeded without reaching pain tolerance limit
- The smaller the pulse width –> achieve pain relief
- 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
5
Q
To stimulate motor nerves, need a pulse duration greater than _____.
A
0.01ms
6
Q
What is the problem with pulse durations greater than 0.01?
A
will activate pain nerves and be uncomfortable for patients
7
Q
Need a sharp rising pulse to avoid ______.
A
accommodation
8
Q
What is the frequency for tetanic contractions?
A
Frequencies 30‐50 Hz for tetanic contraction
9
Q
What are 5 effects of ES on muscle strengthening in normal muscles from ES?
A
- ES not better than a voluntary contraction‐ not sequential fibre activation
- ES causes average gain in strength of 20‐25% over 1 month (normal muscle)
- Particularly at high rather than low intensity
- but must have high intensity and high frequency (every day) –> for strength (eg. abs)
- Most helpful when have weak muscles –> still have to have high frequency and higher frequency
- Some cross transfer effect
- Efficacy shown in both older and younger age groups
10
Q
What are 3 effects of ES on muscle strengthening in weakened muscles from ES?
A
- Much clearer and significant gains
- EG. ES at 30Hz applied to quadriceps of immobilised knees for 1 hour each day for 6 weeks have been shown to reduce muscle atrophy as determined by the cross sectional area of the quads.
- Reduce muscle atrophy • Found in several knee studies
- Needs to be applied at maximum tolerable level
- Effect thought to be due to maintenance of protein synthesis rather than preventing protein breakdown
11
Q
What are fast twitch fibres?
A
induce a quick amount of activity
12
Q
What are slow twitch fibres?
A
more endurance
13
Q
What occurs to muscle fibre type during atrophy?
A
Conversion of slow twitch to fast twitch
- Try to avoid this conversion
14
Q
What are the 5 changes in muscle fibre plasticity following ES?
A
Changes in muscle fibre plasticity not very effective but is a better outcome than doing nothing
- Muscle hypertrophies not very effective but is a better outcome than doing nothing
- Fibre type conversion in response to frequency of simulation
- Low frequency (< 10 Hz) best for slow twitch. It can be used to prevent slow twitch fibres transforming to fast twitch (an undesirable process which is part of muscle atrophy)
- High frequency (>30 Hz) best for fast twitch fibres.
- Strengthening and DOMS
- Blood flow increases
- Long term changes in vascularisation at a capillary level
- Increased muscle metabolism inflammation and swelling inflammation and swelling
15
Q
What are 6 clinical applications of motor stimulation?
A
- Strengthening normal but weak muscle •
- Strengthening post surgery and prevention of, or recovery from, disuse atrophy (eg. OA or TKR) can help to reactivate muscles
- Inhibition of voluntary control e.g. post TKR
- Reeducation of muscle control
- Poor muscle control e.g. pelvic floor muscles
- Recovering peripheral nerve lesion
- Maintaining or increasing joint ROM
- Increasing muscle endurance
- Change muscle structure and function
- Muscle or motor nerve transplant
16
Q
What are 3 types of motor stimulation?
A
- Functional electrical stimulation (FES)
- Uses ES to produce a functional movement or series of movements
- Neuromuscular nerve stimulation (NMES)
- High voltage galvanic stimulation (HGVS/HVS)
17
Q
What are the 4 parameters for innervated muscle in ES?
A
- 30‐50 Hz for tetany
- Pulse duration ~ 0.1 ms
- Ramped to achieve on off contractions
- Intensity to motor contraction
18
Q
What are 5 characteristics of the electrical stimulation of de-nerve muscle?
A
- Maintain de‐nervated muscle in healthy state
- Muscles are much less excitable than nerves
- Greater intensity and longer PD uncomfortable if they have sensation
- 100‐500 ms, Frequency 0.5‐1 HZ, slow rising pulse shape) needed
- Less accommodation – slow rising pulse shape
- Great advantage to used for SCI –> reactivate muscles
19
Q
What are the 6 parameters for improving muscle strength when using ES?
A
- Regularly 1‐2 times a day
- Freq of 35 – 50 Hz (PD best 100 ‐300 μs / 0.1‐0.3ms)
- Up to an hour a session
- Max intensity
- 6 weeks or more
- Low intensity rehab unit (eg. nursing home) - this wouldn’t be effective as it needs to be done so frequently
20
Q
What are the 3 characteristics of the effects on cutaneous blood flow?
A
- vasodilation in area
- due to sensory nerve stimulation activating the axon reflex and release of histamine‐like substances
- Stimulation of autonomic nerves
21
Q
What is the effect on reduction in oedema
A
Muscle pumping action
22
Q
What are the 3 proposed effects of the reduction in oedema?
A
- Displacement of ‐ve charged plasma proteins in interstitial fluid.
- Increased mobility of albumin should accelerate normal capillary lymphatic uptake
- Decreases permeability of capillaries
23
Q
What are the 3 characteristics of altering th eionic
A
- Growth and activity altered by monophasic pulses
- Tissue healing accelerated
- Use in wound healing eg. pressure sores, monophasic currents
24
Q
Electrical charged ______ can be drawn through the skin - using +ve and -ve charges
A
drugs
25
What are 5 contraindications for ES?
1. General rule: Wherever strong muscle contraction contraindicated
2. Over carotid sinus
3. Trans‐thoracic applications
4. To the pelvic region during pregnancy
5. Over an in‐built stimulator eg. pacemakers
26
What are the 7 precautions/dangers of ES?
1. Circulatory insufficiency
2. Risk of dissemination
3. Exacerbation of existing conditions malignant cells
4. Unable to communicate if its too painful --\> can cause further injuries
5. Reduced sharp/blunt sensation
1. take care with Low and Medium Frequency‐
2. CI if using DC or long monophasic IDC pulses
6. Broken skin
7. Self adhesive electrodes
* interrupted direct current --\> use HBS - need be careful -\> possible chemical burns --\> there can be a built up of chemicals under the electrodes
27
What are 8 general points to consider with electrical stimulation?
1. What machine?
2. What type of electrodes?
3. Size of electrodes?
4. Need for couplant?
* gel or water (in hospital- won't have adhesive pads)
5. Check electrodes and leads
6. Always turn machine on before applying to patient and detach patient from machine before switching off in case of a power surge don't want the current to jump and cause pain/shock for the patient
7. Motor stimulation or pain relief
8. Optimum patient position for effect
28
What are 6 principles of ES Application?
1. Electrodes ‐ carbon rubber or metal
2. Skin resistance
3. Coupling to skin ‐ water, wet pad/sponge
4. Polarity
5. Current density
6. Skin impedance
29
What are 2 types of electrodes?
1. Polymer based electrodes
2. Reuseable adhesive electrodes
30
What are 2 characteristics of Polymer based electrodes?
1. carbon‐impregnated silicone rubber
2. used with wet sponge pads
31
What is a characteristic of
Gel based adhesive
32
What are 5 characteristics for carbon electrodes?
1. Need wet pad or gel between electrode and skin
2. Need to ensure that electrode is not cracked check wires as well
3. May use adhesive pad with these electrodes
4. Use if get skin irritation with adhesive pad
5. Lower cost Environmentally friendly
33
What are 7 characteristics for adhesive electrodes?
1. Stainless steel knitted mesh fabric
2. Good gel system – good adherence
3. Even distribution of ES
4. Irritation of skin is common
5. Expensive – $8‐12 for 4 pack
6. Patient may be asked to buy own
7. Need replacing when dry
34
What are the 3 things that the electrode size depends on?
1. Depends on body part
2. Depends on aim of treatment
3. Generally larger better- less likely to cause skin damage
35
Total current at each electrode is the same but _____ ie. current/unit area will be different
current density
36
If using 2 electrodes of different sides current density will be _____ (greater/lesser) under smaller electrode
greater
37
What is the larger electrode called?
‘dispersive’ or ‘indifferent’
38
What are 3 characteristics of the larger electrode (dispersive or indifferent)?
1. Positioned so not directly over excitable tissue will react straight away (muscle bulk)
2. Usually proximal
3. Larger so more nerve fibres stimulated
39
What is the smaller electrode called?
Active
40
What are 3 characteristics of the smaller electrode (active)?
1. usually –ve electrode
2. positioned over motor point
3. current density higher more likely to get
41
What is the motor point?
point on skin that allows a contraction to occur using the least energy (usually located close to where the motor nerve enters the muscle).
42
What are 5 characteristics of uni-polar application?
1. Uneven sized electrodes
* doesn't mean one electrode = still 2 electrodes just uneven sized
2. single active (smaller) electrode over motor point or pain area
3. second larger dispersive (indifferent) electrode elsewhere
4. Used for motor stimulation of innervated muscles
5. Can be used for pain relief/sensory stimulation
43
What are 2 characteristics of bi-polar application?
1. Electrodes even sized
2. De‐nervated muscle and sensory stimulation (pain relief)
44
What are 2 other methods for ES?
1. Foot bath
2. Point electrode
used to try and find motor points
45
What are 3 processes in the skin examination?
1. Check for areas of low resistance e.g. cuts, abrasions ‐ cover with petroleum jelly & cotton wool
2. Check for areas of high resistance e.g. warts or scars, avoid stimulation near these
3. Remove any oils/lotions/grease from skin
46
What are 3 processes in the skin preparation?
1. Reduce resistance of skin with alcowipe to remove keratin and sebum
2. Leave skin damp
3. Warm skin washing skin with warm water --\> reduce resistance make sure to give warnings before turning on the machine
47
What are the 4 safety considerations with ES?
1. Direct or monophasic currents ‐ chemical burn
2. Watch for signs of redness, itchiness
3. Currents of sufficient intensity ‐ can lead to heat – can cause burn (tissue damage)
4. Care with muscle contractions
48
What are 6 characteristics of pulsed current for motor stimulation?
1. Small sharp‐rising pulse shape (\<0.1ms)
* Could use HVG, TENS, faradic
2. Frequency 30‐50Hz
3. Unipolar technique
* Active negative electrode over motor point
* Dispersive large current elsewhere
4. Intensity – until you get a motor response (ask when they feel something)
5. Electrode position‐ unipolar if no response while getting uncomfortable, turn it down and move it
6. Ramp
49
What are 6 characteristics of pulsed current for denervated muscle stimulation?
1. Bipolar technique
2. Electrodes either end of muscle belly
3. Slow rising pulse shape
4. Long PD (100 – 500 ms)
5. Frequency 0.5 – 1 Hz
6. Intensity – until get a muscle contraction • Ramp ‐ NO
50
What are 8 characteristics of High voltage galvanic stimulation (HGVS)?
1. Also known as high voltage pulsed current (HVPS), high voltage stimulation (HVS)
2. Low frequency monophasic current (DC)
3. Used for motor or sensory stimulation
4. Good for pain free sensory stimulation and a comfortable way (even with high intensity) of producing muscle contraction
5. Wound healing
6. High voltage output (up to 500 volts)
* Characteristic twin spike pulse waveform
7. Frequency of the double pulse can be varied between 1‐100 Hz.
8. Duration of two pulses is usually fixed, each lasts for only a few ms (0.1‐0.2 ms)
* with such short peaks, very high voltages are needed to provide enough currents to stimulate the nerve fibres
51
HGVS uses Low frequency _____ (mono/biphasic) current (DC)
monophasic
52
HGVS is used for ____ or ____ stimulation.
motor; sensory
53
What is HGVS used for?
Good for pain free sensory stimulation and a comfortable (even with high intensity) way of producing muscle contraction
54
What kind of waveform is HGVS?
Characteristic twin spike pulse waveform
55
In HGVS, duration of ____ pulses is usually fixed, each lasts for only a few ms (0.1‐0.2 ms)
two
56
What are 3 reasons why HVGS should be chosen?
1. High voltage currents theoretically encounter less tissue impedance
2. Potentially should produce most comfortable muscle contraction because using very short duration pulses
3. Short pulse duration less likely to stimulate pain nerves more comfortable
57
How does HVGS work?
58
What are 5 machine specifications for HVGS?
1. May be one or two options for pulse shape
2. Frequency between 0‐100 Hz.
3. Will be able to select the polarity of the active electrode (red‐ multifunction units, blue or red older machines)
4. Will have a ramp or surge setting
5. May have a burst setting
59
What is polarity?
Current flows in body negatively charged ions move from negative electrode (cathode) to positive (anode), positive ions move to negative electrode
60
When does polarity tend to build up?
Tend to get a build up of ions under electrodes due to change in pH of skin and couplant ‐worse under cathode (alkaline)
61
What are 3 scenarios of current were polarity occurs faster?
1. direct or pulses are longer duration monophasic
2. If pulses are long duration but high intensity biphasic unbalanced
3. Less likely to build up if low intensity, short pulses and longer time in between (pulse interval)
62
What are 4 characteristics of HVGS on the multi-function machines?
1. Choose negative polarity when doing muscle stimulation: ‐ve electrode = active
2. Cycle time is based on exercise parameters you want to use ie:
* Strength (shorter ‘on’ time)
* Endurance (longer ‘on’ time, shorter ‘rest’ time)
3. Repetitions need to be less than for voluntary muscle exercise
4. Risk of DOMS
63
Do you want a shorter or longer "on" time as a progression for HVGS?
Try to shorter "on" time as you progression - patient has time to try and hang onto contraction
64
What is used in electromagnetic energy?
1. Shortwave diathermy (SWD)
2. Ultraviolet light
65
What are 5 characteristics of short wave diathermy?
1. High frequency (27.12 MHz)
2. AC current – electromagnetic waves
3. Thermal modality
4. Deep penetration get to deeper structures
5. Capacitive electrodes or inductothermy has plates around limb and need to wrap/coil around plates (due to high heat)
66
What are the 3 effects of SWD?
1. Thermal
2. Athermal
3. No muscle or nerve stimulation
67
What is half value depth of deep heating (thermal) in SWD?
~ 4cm
68
What are 4 athermal effects of SWD?
1. Speculative
2. Cell membrane effects‐ increased transport
3. Some evidence to suggest an alteration of cell ion binding properties which in turn , affects ATP and protein synthesis.
4. Possibly affects soft tissue healing
69
What are 4 electrical properties of the tissue that the heating produced is dependent on?
The heating produced is dependent on the electrical properties of the tissues
1. Ions
2. Water molecules
3. Uncharged atoms and molecules
4. More heating in tissues with higher water and ion content (eg muscle than fat)
70
What is the effects of heating with SWD?
Makes the ions move around/turn
71
What are 9 contraindications for SWD?
1. Pregnancy
2. Inbuilt stimulator
3. Circulatory insufficiency
4. Risk of dissemination
5. Exacerbation of existing conditions
6. Unable to communicate
7. To eyes or testes
8. Sensory loss
9. Internal or external metal in field (within 30cms of field)
* might disrupt electrical signals eg. even metal beds, jewelery ..etc
72
What are the 6 dangers of SWD?
1. Burns
2. Potential dangers of deep heating of tissues
3. Must not apply near metal
4. Concentration of electric field
5. Watches, jewellery, piercings, zips, beds
6. Wooden beds required
* Must not use near other equipment due to possible interference (eg IF)
* Could interfere with nearby hospital equipment
* Must not use on or near patients with pacemaker
73
What are the 2 standard test for SWD?
1. Thermal sensitivity
* Over area of application of electrodes/induction coil
2. Test tubes – hot/cold
74
What are the dosage of SWD dependent on?
perception of patient
75
What are the 2 types of dosage for SWD?
Continuous or pulsed
76
When is continuous dosage used for SWD?
mild comfortable warmth
77
When is pulsed dosage used for SWD?
imperceptible heating effect
78
What is the timing for SWD?
usually applied similar times as for superficial heat eg 15‐20 mins
79
What is the pulsed SWD parameters for pulse repetition rate?
15-800hz
80
What is the pulsed SWD parameters for pulse duration?
25-400us
81
What is the pulsed SWD parameters for peak power pulse (intensity)
ADD
82
What are 2 scenarios where pulsed SWD are used?
Used for **acute** conditions and **inflammation**
* Acute ankle sprain
* Acute RA
83
What are 3 typical applications of SWD?
1. Osteoarthritis hip, knee, shoulder
2. Low back or neck pain
3. Fracture healing (pulsed)
84
What is extracorporeal shock wave therapy (ESWT)?
Acoustic waves associated with sudden rise in pressure
85
ESWT is ____ (invasive/non invasive)
invasive
86
What are 4 characteristics of ESWT?
1. Characterised by high positive pressures up to 100 Mpa (over 100 times atmospheric pressure)
2. Rapid rise time (30‐120 ns) and short pulse duration (5 μs)
3. Pressure waves travel through tissues – effects occur at site where there is a change in impedance (e.g. bone‐soft tissue interface)
4. Common use to break down kidney stones
87
\_\_\_\_ is generated by hydraulic, piezo‐electric and electromagnetic devices
ESWT
88
Each ESWT generates a characteristic ____ and energy density
waveform
89
What are the 3 energy densities for low, med and high?
1. Low = \< 0.08 mJ/mm2 (not painful)
2. Med = 0.08 – 0.28 mJ/mm2
3. High = 0.28 – 0.60 mJ/mm2 (painful/needs anaesthesia)
90
What are the 2 main uses of ESWT?
1. Stimulation of bone formation or remodelling
2. Insertional tendinopathy
91
What are 3 examples of stimulation of bone formation or remodelling when using ESWT?
1. Calcaneal spurs
2. Stress fractures
3. Avascular necrosis
92
What are 2 examples of insertional tendinopathy when using ESWT?
1. Achilles tendinopathy
2. Chronic heel pain
