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What type of current is used in HVPC?
Monophasic twin-peak current.
What is the pulse duration of HVPC?
100 microseconds or less.
What is the driving voltage for HVPC?
Greater than 150 volts.
What is considered low volt in comparison to HVPC?
Anything less than 150 volts
What is the benefit of the high peak current in HVPC?
It allows for deeper penetration.
Why is the average current lower in HVPC despite the high peak current?
Because it is a pulsed current with interpulse intervals.
What is the charge of a healthy epidermis?
-23.4 mV (negative charge).
What is the charge of the dermis compared to the epidermis?
The dermis is electropositive (positive charge).
What does the difference in charge between the epidermis and dermis create?
A natural monophasic electric current that stimulates wound healing.
How does an exogenous current applied to a wound surface affect healing?
It is believed to further enhance wound healing processes.
What is cellular electrotaxis, and how does it relate to wound healing?
Cellular electrotaxis is the movement of cells (e.g., macrophages, neutrophils, fibroblasts) toward the wound, which may promote healing.
What cells are involved in cellular electrotaxis during wound healing?
Macrophages, neutrophils, and fibroblasts.
How does electrical stimulation (ES) affect ATP and DNA production?
ES activates the production of ATP and DNA.
What effect does electrical stimulation (ES) have on fibroblasts?
It makes fibroblasts generate more collagen.
How does electrical stimulation (ES) impact blood flow and capillary density?
It increases blood flow and capillary density.
What is the duration of the double-peaked impulses in HVPC?
5-200 microseconds (μs).
What is the peak-current amplitude of HVPC?
2-2.5 amperes (A).
What is the voltage range of HVPC?
Up to 500 volts (V).
What is the frequency range of HVPC pulses?
1-125 pulses per second.
What does HVPC activate in the body?
The "skin battery" and cellular galvanotaxis.
What is the effect of HVPC on blood flow and capillary density?
It improves blood flow and capillary density.
What is the intrapulse interval in HVPC?
The space between the two twin peaks of the current.
Can the intrapulse interval be adjusted on most HVPC units?
Yes, it can be varied
What is the total duration of the two twin peaks in HVPC?
100 microseconds or less.
How does widening the intrapulse interval affect the sensation of HVPC?
It makes the sensation more comfortable because the current is on for a shorter time within the 100-microsecond window.
What happens if the intrapulse interval is shortened?
The current is on for a longer time within the 100-microsecond window, which may increase discomfort.
Why does widening the intrapulse interval decrease the time the current is on?
Because the two twin peaks are spread farther apart, reducing the overlap of current flow within the 100-microsecond duration.
Why can't HVPC be used to stimulate denervated muscle?
The pulse duration of 100 microseconds or less is too short, and the current is not continuous.
Why is HVPC not suitable for iontophoresis?
The pulse duration of 100 microseconds or less is too short, and the current is not continuous.
Why is it difficult to stimulate larger muscle groups comfortably with HVPC?
The pulse duration is too short to recruit them, requiring higher (and often uncomfortable) intensity settings.
What type of stimulator is more efficient at muscle stimulation than HVPC?
NMES stimulators with a wider pulse duration (around 300 microseconds).
What controls do HVPC units typically have?
Variable frequency controls and variable intensity controls.
What physiological responses can you potentially achieve with HVPC?
Sensory, motor, and noxious responses.
Uses of HVPC (9)
•pain reduction
•maintain or increase joint mobility
•hinder disuse muscle atrophy
•increase local blood circulation (via muscle pump or polarity effects)
•relax muscle spasms
•prevent venous thrombosis immediately post-op
•wound healing
•edema reduction (via muscle pump or polarity)
•muscle re-education/strengthening
What type of fibers carry most pain signals according to the Gate Control Theory?
Small, unmyelinated C fibers
Where do C fibers synapse to transmit pain impulses?
In the spinal cord.
How do C fibers conduct pain impulses compared to other fibers?
They conduct pain impulses slowly.
What type of fibers can be stimulated to block pain impulses according to the Gate Control Theory?
Faster, larger diameter, myelinated A fibers.
What methods can stimulate A fibers to block pain impulses?
Pressure, vibration, rubbing, scratching, electrical stimulation, heat, or cold.
Where in the spinal cord do specialized T-cells block pain impulses?
In the substantia gelatinosa.
What type of stimulation is associated with the Gate Control Theory?
Conventional (high-rate) stimulation.
What additional effect does conventional stimulation have at the site of stimulation?
It causes enkephalin release.
What type of fibers does high-frequency sensory-level TENS stimulate?
Peripheral sensory Aβ fibers.
What is the purpose of stimulating Aβ fibers in TENS?
To "close the gate" and block pain signals according to the Gate Control Theory.
What is another name for high-frequency sensory-level TENS?
Conventional TENS or sensory-level TENS.
How is the intensity set for conventional TENS?
At a level that causes a tingling sensation without muscle contraction
How long does pain relief typically last with conventional TENS?
Only while the stimulation is being applied.
What is the frequency range for conventional/high-rate TENS?
50-120 pulses per second (pps)
What is the pulse duration range for conventional/high-rate TENS?
40-125 microseconds (μs).
Can the pulse duration be adjusted on an HVPC unit?
No, it is set at about 100 microseconds or less and cannot be adjusted.
What intensity level is used for conventional/high-rate TENS?
Sensory level only (tingling sensation without muscle contraction).
Is conventional/high-rate TENS delivered continuously or pulsed?
Continuously.
What polarity is used for acute pain in conventional TENS?
Positive (+).
What polarity is used for chronic pain in conventional TENS?
Negative (-).
What is the intrapulse interval for conventional TENS?
255.
How long can conventional TENS be used in a single session?
Up to 24 hours, though clinic treatments are typically 30 minutes
What is the recommended home use protocol for portable TENS units?
Use for 30 minutes. If pain relief occurs, turn it off. If no relief, leave it on until relief occurs. Repeat as needed when pain returns.
What are the Pros of Conventional/high rate simulation? (4)
1. Quick onset of pain relief (usually within 5-10 minutes)
2. Perceived as comfortable by the patient
3. Can be used in acute and chronic conditions because there is no muscle contraction
4. Can treat for long periods of time
What are the cons of Conventional/high rate stimulation? (2)
1. Short carry-over of pain relief once the unit is turned off because the gate is open once the unit is off and enkephalins have a very short half-life
2.Accommodation is common with continuous stimulation
What are endorphins?
Substances released from the pituitary that act as the body's own opiate-like analgesics.
What triggers the release of endorphins?
Muscle contraction.
How do endorphins provide pain relief?
They act as natural opiate-like substances, producing an analgesic effect.
How does the response of endorphins differ from that of enkephalins?
Endorphins produce a systemic response, while enkephalins produce only a local response.
What is required for endorphin-mediated pain relief?
muscle contraction
What is the frequency range for low-rate TENS?
2-10 pulses per second (pps). However 1-10 will get you there.
Is the pulse duration adjustable on an HVPC unit for low-rate stimulation?
No, it is fixed.
What is the pulse duration range for low-rate TENS on portable units?
200-500 microseconds (μs)
What intensity level is used for low-rate TENS?
Strong enough to produce a muscle contraction.
What polarity is used for acute pain in low-rate TENS?
Positive (+).
What polarity is used for chronic pain in low-rate TENS?
Negative (-).
What is the intrapulse interval for low-rate TENS?
5
What is the maximum treatment time for low-rate TENS?
Up to 60 minutes per session.
How many times per day can low-rate TENS be used?
3-5 times per day.
Why is a resting period required between low-rate TENS treatments?
To prevent muscle fatigue and soreness.
Pros of low rate stimulation (2)
1.•Long lasting analgesia from endorphin release because endorphins have a long half-life of about 4 hours
2.•Accommodation is not common because there is a mm contraction
Cons of low rate stimulation (5)
1. Sometimes the muscle contraction is perceived as uncomfortable or annoying to patients
2. Muscle contraction may be contraindicated in some acute cases, such as over a fracture, sprain, or strain
3. Motor response may limit patient's functional activities
4. Motor response may produce mm soreness and/or fatigue
5. Onset of analgesia is delayed 20-30 minutes
Where should electrodes be placed for pain relief?
In the dermatome where the pain is located.
What is one common placement for electrodes?
On or around the site of pain.
Where can electrodes be placed to target motor points?
Over motor points.
What are acupuncture or trigger points, and why are they used for electrode placement?
They are areas of low resistance to stimulation and can be targeted for pain relief.
Where should electrodes be placed to target spinal nerves?
Over spinal nerves corresponding to the dermatome where the pain is located.
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Can HVPC be used for muscle strengthening and re-education?
Yes, but it may require high intensity, which can be uncomfortable for the patient.
Why might HVPC be less efficient for stimulating larger muscle groups?
The pulse duration of 100 microseconds or less is too short for efficient stimulation of larger muscles.
What is a potential drawback of using HVPC for muscle strengthening?
The intensity may need to be turned up to an uncomfortable level to achieve a good muscle contraction.
What is the goal of muscle re-education with HVPC?
To help patients regain the ability to contract muscles that have "forgotten" how to contract due to disuse or injury.
What are some reasons a patient might need muscle re-education?
Immobilization after surgery (e.g., TKA, meniscus repair, ACL repair), CVA, head injury, or other conditions where the muscle is not regularly contracting.
Why might a muscle "forget" how to contract?
The connection between the brain and the muscle is disrupted, even though the muscle itself has the ability to contract.
What types of surgeries might require muscle re-education post-immobilization?
Surgeries like TKA, meniscus repair or removal, ACL repair, or any reconstruction surgery involving immobilization.
How does HVPC assist in muscle re-education?
It helps stimulate the muscle to contract, re-establishing the connection between the brain and the muscle.
What intensity is used for muscle re-education with HVPC?
Strong enough to elicit a good muscle contraction.
What frequency is used for muscle re-education to prevent muscle fatigue?
20-30 pulses per second (pps)
What is the pulse duration for muscle re-education with HVPC?
100 microseconds (μs), as it is fixed in the HVPC machine.
What would be a more efficient pulse duration for muscle contractions if it could be varied?
300 microseconds (μs).
What is the intrapulse interval for muscle re-education?
5
What is the recommended ramp time for muscle re-education, and why
Approximately 2 seconds, as it closely correlates to a normal muscle contraction.
What polarity is used for muscle re-education, and why?
Negative (-), as it helps depolarize the nerve and muscle more efficiently and increases blood flow to deliver more oxygen.
What is the recommended on/off time ratio for muscle re-education?
1:3 ratio (e.g., 4 seconds on, 12 seconds off).
What is the typical treatment time for muscle re-education?
10-30 minutes, depending on the patient's fatigue level.
How often is muscle re-education typically performed?
Once or twice daily (qd to bid), 1-5 times weekly.
