Indications for Use

Last blog post we discussed the parameters that are generally used for HVPC. Today, we will introduce you to the indications for HVS use.

The consensus is that HVS may be applied alone or in combination with other modalities to treat a wide range of clinical pathologies. HVS stimulates excitatory responses (Knight et al, 2007) of:

·         Sensory and motor nerves

·         Autonomic nervous system (ANS)

·         Pain fibres

The main functions of HVS are:

·         Promote wound healing

Wound healing is possibly the best indication for HVS use. HVS increases circulation and perfusion to the injured tissues, providing the damaged tissues with oxygen and nutrients. At the same time, waste and oedema are being removed, which facilitates the overall healing process and promotes wound healing. As the current flows through the body to complete the circuit between the dispersive pads, it penetrates tissues causing ionic movement within the body to attain the desired physiological effects (Belanger, 2002):

§  Increase fibroblast numbers, therefore collagen synthesis

§  Inhibit bacterial growth

§  Block SNS, therefore increasing blood supply to the tissue and healing capacity

·         Reduce edema

Edema formation is due to leakage of plasma proteins to the interstitial spaces of cells after injury, resulting in fluid accumulation in the area. HVS is thought to:

§  decrease the permeability between cells membranes and the interstitial space, especially when negatively charged electrodes are over the injury site (i.e. repels negatively charged plasma proteins)

§  produce muscle contraction which stimulates the lymphatic system and promotes the movement of fluid, hence reducing edema (Knight et al, 2007)

NMES may be a better choice for resolving edema as it can produce stronger muscle contraction and therefore increased muscle pumping action response to facilitate edema reduction (Knight et al, 2007).

There are 2 protocols that may be used to assist edema reduction (Belanger, 2002):

§  Water immersion technique: apply a negative polarity, but should be applied as soon as possible after injury

§  HVS stimulation accompanied by RICE – rest, ice, compression, elevation

·         Pain modulation

HVS modulates pain via the gating system:

§  Blocking pain nerve fibre conduction

§  Releasing endorphins

§  Reducing/blocking neuritis

However it must be noted that other estim devices, such as TENS achieve this analgesic effect more efficiently (Knight et al, 2007).

·         Muscle re-education

HVS has also been associated with muscle re-education, however this belief is controversial.

Muscle re-education may be achieved by stimulating muscle contraction via:

§  Muscle twitch – 1-10Hz pulse frequency

§  Tetany or sustained contraction – 30-80Hz pulse frequency

Those who disagree with the notion HVS can be used for muscle education have a valid theory. As we have previously mentioned, HVS uses a twin peak, pulsed, monophasic current. Due to the unique current, the peak may not be long enough in duration to depolarize muscle fibres. Which theory is right? We will let you decide, but we tend to agree with the latter – HVS is not effective for muscle re-education. There has not been any research supporting either side, it simply comes down to theroy. 

NMES is the better option for muscle stimulation as it can produce stronger muscle contraction than HVS anyways (Knight et al, 2007).

To achieve these effects, specific dosage parameters need to be set according to the desired therapeutic effects. The amplitude may range between 1-500V; however, whatever the patient perceives as most comfortable is what should be implemented. The patient should be comfortable and pain free at all times throughout treatment.

Continuous, higher frequencies of 1-200 pulses per second (Belanger, 2002) are associated with:

·         Wound Healing

Reversed electrode polarity is recommended for wound healing with a treatment time ranging from 10 minutes to 1 hour depending on available clinic time.

·         Analgesia or pain modulation

Recommended treatment time ranges from 10 minutes to 2 hours depending on available clinic time

Pulsed, lower frequencies of 30-60 pulses per second (Belanger, 2002) are associated with:

·         Muscle strengthening

o   Frequency must be high enough to produce a tetanic muscle contraction

·         Muscle spasm relaxation

o    Via muscle fatigue effects

·         Oedema

Treatment time ranges between 5 and 30 minutes, but can be gradually increased as therapeutic improvements occur with successive treatments (Belanger, 2002).

As with all physiotherapy modalities, it is important to have sound research supporting its use; after all, physiotherapy is synonymous with evidence based practice. We will present some supporting literature in our next blog post. Check back soon!

A & M 

References:

Bèlanger, A. (2002). Evidence-based guide to therapeutic physical agents. Lippincott Williams & Wilkins. Pg 109-122

Knight, K.L., & Draper, D.O. (2007) Therapeutic modalities: the art and the science. Lippincott Williams & Wilkins.

https://arizonadme.com/uploads/Instructional_Handout_Sterling_Impulse_HVG_Part_2.pdf

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