H Wave Therapy
H Wave therapy has been around for a fair number of years, but does not appear to have taken off in a particularly substantial way - though there are many usear out there and some very strong advocates of this form of electrical stimulation.
The published research is not broad or deep - most was derived from work done at the University of Ulster back in the early 1990's, though there have been some other unpublished and 'pending' papers. I published a preliminary report (not experimental) back in 1994, and I will try and summarise what is known and what is thought to be the case with this intervention.
The H Wave device is still available (in the UK can be obtained from MIE and from SKF/Mobilis - links on the manufacturers page - I am not sure about the position elsewhere in the world, but I am sure to find out once I put this page up and live!!). There is what appears to be a main (USA) page - Electronic Waveform Lab.
H Wave : 3 channel device
H Wave : 2 channel device
The H Wave machine - as already suggested - is a variation of electrical stimulation. The delivered waveform is somewhat different to that of most other modalities, but many of its effects and claimed benefits are based on the same principles as that of TENS, NMES etc. Whether the 'special' nature of the waveform in fact generates an 'additional' or 'better' effects remains to be categorically established. There are also 'Vet Wave' devices which are designed for the treatment of animals - most particularly horses, but from what I can see, there is no fundamental difference in the device - only in the manual.
The waveform delivered by this device 'mimics' the H wave (a physiological recorded neuro reflex : Hoffman Reflex) and is more complex than is found with many other stimulators. It is suggested that because the stimulus shape mimics a physiological signal, it is more effective - nice idea, but not something that I can actually see any evidence for - and is also something claimed by other stimulation modalities - such as APS Therapy.
That aside, the wave is a 'double' stimulus with 2 exponentially decaying peaks with reverse polarity (Watson, 1994). The peaks are sufficiently separated to enable the absolute recovery period to have passed and therefore both components are able to initiate an action potential. If the machine is set at 2Hz stimulation, the nerve will fire at 4Hz. A representation of the wave is illustrated below
Physiological Effects :
There is still some considerable debate with regards the ACTUAL physiological effects of this mode of stimulation therapy. If you look at the various web sites where H Wave is 'listed' and advocated, you will see a range of impressive effects claimed BUT if you try and match those up with the published evidences (references at the end of the page) you will probably struggle (like I have) to rationalise the claims and the evidence.
There is no doubt that the device initiates action potentials, and it will do so in both motor and sensory nerves - fair enough - any electrical stimulation can achieve this. The question is one of is it 'better' at doing this job than other stimulation methods, and if so, which bits is it 'best' at achieving?
In terms of pain relief, the McDowell et al paper from 1999 demonstrated a significant hypoalgesic effect, but this was no different from that achieved by TENS, nor were there any significant differences between the tested H Wave frequencies. This was a lab (as opposed to a clinical) study, and mechanical pain threshold was the primary outcome. This resuly MAY not transfer directly to the clinical / real patient environment.
The 1996 study by the same group (McDowell et al 1996) considered the effect of H Wave therapy on conduction capacity in the radial nerve. The testing was again on 'normals' in the lab. H wave (at 3 different frequencies) was tested against a control condition. The stimulation (at 2, 16 or 60Hz) was applied for 3 x 5 minute periods with nerve conduction being tested before and after each. The 2Hz group showed no significant changes in nerve conduction latency. The 16Hz group did, and the 60Hz did even more so. These cahnges correlate with a rduction in nerve conduction velocity, and this MAY be a mechanism by which the stimulation is able to achieve hypoalgesic effects (though not actually proven to be the case). There were also skin temperature changes demontrated in the same experiemt, and it remain possible that the changes may be associated with sympathetic stimulation effects (see the original paper for a useful discussion).
The fact that the 2Hz stimulation had a significant effect on mechanical pain threshold (first study listed) but did not demonstrate significant peripheral nerve conduction changes would imply that there are at least 2 different mechanisms at work - one peripheral and one central. I have my own theories about what these might be, but that is not evidence - just my theories!
The Blum hypothesis paper (2004) suggests that the stimulation increased the smooth muscle activity in the lymphatic vessel walls, therefore 'milking' the lymphatic system and facilitating oedema removal and reabsorption (the paper is a bit more comprehensive than this 2 line summary!). This would be consistent with my own clinical experience of the mosality, and the experience of others which has been reported back to me.. The 2Hz stimulation appears to be most beneficial for the oedema effect, and this would be consistent with the Blum hypothesis (2004), but apart from a very limited mention of some case study evidence, there is currently not a major volume of published work to support or refute the conjecture (unless I have missed it!).
Other papers which identify effects include :
McDowell et al (1999) - skin blood perfusion
Skin blood flow was recoded using laser doppler techniques using healthy volunteers (placeo, 2Hz and 60Hz stimulation groups) with the stim applied for 20 minutes. The skin blood flow was most significantly increased with the 2Hz stimulation (compared with placebo and 60Hz stim) and an increase in skin temperature was also demonstrated. These effects were not observed with the 60Hz stimulation. This would add some weight to the Blom hypothesis, though they are not based on exactly the same physiology.
Blum et al 2009 - Range of motion effects following rotator cuff surgery
This (clinical) study looked at a real H Wave vs a Placebo H Wave treatment group post rotator cuff repair (22 patients in total). The H wave was applied for 1 hour, twice a day for 90 days. Range of motion and strength change outcomes were monitored, and whilst there were no significant strength differences between groups, there was an advantage (significant) in ROM for the H Wave group. Whilst there are some very useful review and commentary elements in this paper (which is also open access which is an advantage), there are a couple of 'issues' I have with it. The elctrode placements are described, but the frequency at which the machine was set is not - bit of a shame really - unless I missed it. The ohter issue to be aware of (it is stated in the paper) is that 2 of the authors, including the chief investigator, are paid consultants for the company making the H Wave device. Their conclusion was that this preliminary study warrants a more detailed RCT investigation - agreed - and hopefully when they do that one and publish it, they will remember to tell the rest of us what settings they used on the device!
Blum et al 2010 - venous ulcers - case series
The most recent paper that I have identified, again by Blum and associates relates to the use of H Wave therapy in 3 patients with diabetes and chronic venous ulceration. The H Wave therapy was delivered on a home treatment basis though when you read the details of the cases, there were some variations to this - some getting weekly rather than daily treatments for some of the time, some starting with clinic session and then moving to home therapy etc. Home therapy was for 1 hour a day, with one channel stimulating the quads and the other channel the gastrocs at 2Hz with the intensity set to deliver 'strong' muscle contractions.
This is an interesting study, and I am certainly not 'knocking' the results, but it is a small case series, involving 'selected' patients. The therapy each received was not identical, and, as before, there were links between the research team and the company making the device BUT that having been said, it looks like there is a potential benefit which is worth further investigation (and also comparison with non-H Wave stimulatrion of the same muscle groups of course. . . . . .)
Blum, K., et al. (2010). "Healing enhancement of chronic venous stasis ulcers utilizing H-WAVE(R) device therapy: a case series." Cases Journal 3(1): 54.
Blum, K., et al. (2008). "The H-Wave device is an effective and safe non-pharmacological analgesic for chronic pain: a meta-analysis." Adv Ther 25(7): 644-57.
Blum, K., et al. (2009). "Repetitive H-wave device stimulation and program induces significant increases in the range of motion of post operative rotator cuff reconstruction in a double-blinded randomized placebo controlled human study." BMC Musculoskelet Disord 10: 132.
Blum, K., et al. (2006). "The H-Wave small muscle fiber stimulator, a nonpharmacologic alternative for the treatment of chronic soft-tissue injury and neuropathic pain: an extended population observational study." Adv Ther 23(5): 739-49.
Blum, K., et al. (2005). "Innate properties of H-Wave device, a small fiber stimulator provides the basis for a paradigm shift of electro-therapeutic treatment of pain with increased functional restoration associated with human neuropathies by affecting tissue circulation: a hypothesis." Med Hypotheses 64(5): 1066-7.
Blum, K., et al. (2006). "H-Wave, a nonpharmacologic alternative for the treatment of patients with chronic soft tissue inflammation and neuropathic pain: a preliminary statistical outcome study." Adv Ther 23(3): 446-55.
Blum, K., et al. (2008). "The H-Wave Device Induces NODependent Augmented Microcirculation and Angiogenesis, Providing Both Analgesia and Tissue Healing in Sports Injuries." Phys Sportsmed 36(1): 103-114.
Johnson, M. I. (2001). "A critical review of the analgesic effects of TENS-like devices." Phys-Ther-Rev. 6(3): 153-73.
Johnson, M. I. (2001). "Transcutaneous electrical nerve stimulation (TENS) and TENS-like devices: do they provide pain relief?" Pain Reviews 8(3/4): 121-58.
McDowell, B., et al. (1995). "The lack of hypoalgesic efficacy of H-wave therapy on experimental ischaemic pain." Pain 61: 27-32.
McDowell, B., et al. (1996). "The effect of H-wave therapy upon conduction in the human superficial radial nerve in vivo." Experimental Physiology 81: 821-832.
McDowell, B., et al. (1996). "The effect of H wave therapy (HWT) upon mechanical pain threshold in humans." Pain Clinic 9(1): 23-30.
McDowell, B. C., et al. (1999). "Comparative analgesic effects of H-wave therapy and transcutaneous electrical nerve stimulation on pain threshold in humans." Arch Phys Med Rehabil 80(9): 1001-4.
McDowell, B. C., et al. (1999). "The effect of high- and low-frequency H-wave therapy upon skin blood perfusion: evidence of frequency-specific effects." Clin Physiol 19(6): 450-7.
Smith, T. L., et al. (2009). "H-Wave induces arteriolar vasodilation in rat striated muscle via nitric oxide-mediated mechanisms." J Orthop Res 27(9): 1248-51.
Smith, T. L., et al. (2007). "The microvascular and hemodynamic mechanisms for the therapeutic actions of H-Wave muscle stimulation." Abstract presented at: 6th Combined Meeting of the Orthopaedic Research Societies, 21 October Honolulu, Hawaii.
Watson, T. (1994). "H Wave Therapy: A Preliminary Investigation." Inter Medica 1(12): 19-24.