In general terms, combination therapy involves the simultaneous application of ultrasound with an electrical stimulation therapy.
The main advantages of such a combination are said to be in:
It would appear that by applying ultrasound to peripheral nerves their threshold of stimulation is reduced, thus making them more sensitive or excitable. It is likely that this effect is brought about by the alteration of the ion pump activity, predominantly Na+and K+, but also Ca++. By altering the transport of these ions across the cell membrane the resting potential will be altered and, in this case, it would seem that it results in a reduced threshold for depolarisation.
It is reasonable to expect that this effect occurs in other tissue (apart from nerve) although no direct evidence has been noted to date. When electrotherapy is applied simultaneously with ultrasound through the same tissues a reduced intensity is required in order to achieve the same physiological/therapeutic effects when compared with electrotherapy in isolation. This can easily be demonstrated by turning off the ultrasound component whilst continuing with the electrotherapy. The patient very soon becomes aware of a much reduced sensation/effect which can be restored by restarting the ultrasound.
In addition the simultaneous application of ultrasound with electrotherapy minimises the accommodation phenomenon normally associated with electrical stimulation of the peripheral nerves.
The combination of ultrasound with interferential therapy appears to give rise to less adverse treatment effects than are associated with the combination of ultrasound with diadynamic currents or other electrical stimulations. It has also been suggested that a greater effective treatment depth can be achieved with an ultrasound/interferential combination.
Unlike routine interferential therapy the intensity of the electrical stimulation in combination therapy may need to be REDUCED during treatment, probably due to the continued effect of the ultrasound on the nerve membrane threshold.
In summary, by combining the two treatment modalities none of the individual effects of the treatment are lost, but the benefit is that lower treatment intensities can be used to achieve the same results and there are additional benefits in terms of treatment times.
More on Tim Watson’s website www.electrotherapy.org