High Volt Flashcards
Overview-High voltage pulsed current
- Typically uses a twin-peaked monophasic waveform
- UNBALANCED
- Results in polarity
- Short pulses reduce polar effects on skin (educate patient that if it gets uncomfortable to speak up)
Do short pulse durations, high voltage
When turning up the amplitude, what are you changing?
The current.
HVPC
General electrical stimulations contraindications
- Pregnancy
- Cancer
- DVT
- etc.
HVPC Clinical indications
- Muscle contraction
- Pain relief (provides sensory and pain options)
- Acute edema
- Wound healing
Acute edema treatment with HVPC
HVPC shown to delay or prevent onset of acute edema
Acute edema physiology
Tissue Injury –>
chemical and electric signals->
enhanced vessel permeability –>
proteins accumulate (pull water with it) –>
fluid follows = local tissue edema
Ex: Ankle Sprain
HVPC Acute edema prevention/reduction theory
Current theory suggests an effect on vascular smooth muscle (permeability), exact mechanism not clear
Acute edema Clinical Bottom Line
HVPC delays or prevents onset of edema, but does not reduce existing edema
Acute edema clinical procedures
- Application within first 24 hours (sooner the better)
- High frequency (120 pps)
- Intensity: 10% < visible motor stimulation (See muscle twitch then back it down a little)
- Short pulse duration (~60 µs (microseconds - pulse duration), often not programmable)
- Cathode placed distally on extremity (near ankle/injury)
- Treatment time approx. 30 min, combine w/ PRICE principles (Multiple 30 minutes sessions are good, give an hour off)
Waveform itself is different and has an effect on edema compared to tens
Chronic Wounds Types (4)
- Pressure necrosis
- Diabetic neuropathy
- Venous insufficiency
- Arterial insufficiency
Chronic Wound physiology
- Epidermal and some Epithelial cells carry (-) charge
- Wound bed carries (+) charge
– Creates a natural voltage
– Thought to assist in migration of skin cells across granulation tissue (red wound bed)
Chronic Wound healing
HVPC may augment (increase) skin migration
HVPC attracts other cells as well (galvanotaxis or electrotaxis)
Enhancement of natural electric signals, triggering of chemical signal pathways
Anode attracts:
- Macrophages
- Neutrophiles
- Vascular fibroblasts (new blood vessels) and smooth muscle cells
- Some endothelial cells for angiogenesis (cover skin)
- ?? Some epidermal and some epithelial cells
Cathode attracts:
- Fibroblasts
- Keratinocytes
- Microvascular endothelial cells
- Some Epithelial cells
These cover over the wound bed
HVPC Stimulation in wound healing has been shown to:
Increase angiogenesis
Improve collagen synthesis
Release of other growth factors
Anode vs Cathode Over Wound
Anode over wounds:
* Autolysis (clean up garbage over wound)
* Angiogenesis
* Now shown to improve re-epithelialization and epidermal resurfacing too
Cathode over wounds:
* Enhance proliferative phase of wound healing (fill in with granulation and connective tissue)
* Fills in granulation tissue and re-epithelialization
Anything yellow, black, green need to get rid of that over wound
Garbage - Anode; Hole - Cathode
Extra contraindications for wound healing with HVPC
- Local skin cancer
- Local osteomyelitis (infection of bone)
- Silver or iodine ions in wound bed (Must be cleaned out before applying)
Chronic Wound Care - Clinical Procedures
- Usually implemented when other measures have failed
- Irrigate wound with saline
- Fill dead space with moist gauze (saline or hydrogel to moisten)
- Foil or electrode over gauze
- Other electrode over skin nearby (Is VERY large so it has very little effect there and goes to concentrate over the other electrode on gauze)
- HVPC, 100 pps, sensory level (50-150 V), short pulse duration (usually not programmable)
- ~60 min, 5-7 days/week
- Polarity in wound based on needs (?)
Long term treatment
Direct technique - HVPC Chronic Wound
Active electrode in wound bed, dispersive away from wound
Straddle
- Neurogenic skin - No intact peripheral N. (SCI)
- Neuropathic skin - Nerves intact but dull sensation (DM)
- Both electrodes have same polarity (use cable splitter), dispersive(s) placed away
- Amplitude to just visible muscle contraction
Can turn up intensity to see muscle twitch then back off. This is a unique setup of 3 electrodes.
HVPC wound healing outcomes
- Increased capillary density 43.5% (Junger et al. 1997)
- Antibacterial effects (Laatsch et al. 1995)
- Improved healing rate 144% (Gardner and Frantz, 1999)
- Best evidence to support using cathode solely. Anode and Cathode together is better than nothing.
Electrophysiologic testing
- Motor Nerve Conduction Velocity (NCV)
- Sensory NCV
- Reflexes
- Needle EMG
- Sensory evoked potentials (SEPs)
MNCV - m wave
M-Wave (orthodromic conduction, motor down) - How fast you can conduct a nerve (From stimulus up the nerve down to monitoring device)
- Compression neuropathies:
– Prolonged distal latency
– Velocity normal proximal to injury, but slowed across lesion
– Wave amplitude may be diminished
– Wave duration may be prolonged - Systemic neuropathy
– Latency time and velocity may be slowed or normal
– Wave amplitude diminished, duration prolonged
– Diabetes Mellitus, Muscular Dystrophy Disorders
Past shoulder to fingers
MNCV - f wave
- F wave (antidromic conduction, motor up, motor down)
- Used to evaluate proximal nerve segments
- Latency time only useful metric
- Normal ranges have been established
Shoulder and Neck
SNCV
- Similar to MNCV (only a single phase wave)
- Can be ortho- or antidromic
- Latency, velocity, amplitude, wave duration all affected by neuropathy
- Compression or systemic disease affecting myelin will show sensory signs first
H Reflex
(sensory up [tibial nerve], motor down/muscle monitoring [soleus])
Used to test integrity of S1 nerve root (essentially tests monosynaptic stretch reflex) - Most commonly effected
Commonly compromised with disc lesions
NCV Studies
- Part of comprehensive exam
- ??? Sensitivity because partial nerve involvement is possible (the test might only stimulate the healthy part)
EMG
- Examines integrity of efferent pathways from SC to muscle, and muscle fibers
- Useful for radiculopathies, muscle disease
- Monitor, not stim
- Insertional activity
- Rest
- Voluntary contraction
Insertional activity - EMG
Normal activity with needle insertion/movement lasting 50-230 ms
Activity shorter or longer is abnormal
Rest/Spontaneous activity - EMG
- Normal muscle = no activity at rest
- Certain types of activity can be diagnostic:
– Positive Sharp waves (PSWs) – indicates denervation (Peripheral N injury)
– Fibrillation potentials – random activity, single fiber - denervation (Not intact nerve)
– Myotonic discharges – characteristic run of discharges indicative of specific neuromuscular pathology
– Fasiculation potential – multi-fiber random activity, normal or abnormal, must be correlated with other signs (Random eye twitch)
Voluntary muscle contraction
- Small to large (light to strong contraction)
- Shape, amplitude, duration, sound
- Ability to achieve full, smooth muscle contraction
Sensory Evoked Potentials
Monitoring electrical activity of the brain in the sensory cortex.
