Thursday, 8 March 2012

Part 2: Interferential Therapy


In the treatment of Urinary Stress Incontinence (USI), Electrical Stimulation aims to improve the strength of the Pelvic Floor Muscles (PFM) to increase urethral closure pressure. This is done by stimulation of the pudendal nerves to restore reflex activation, help maintain a coordinated contraction and increase conscious awareness of the PFM [2][3]. Studies have shown that Interferential Therapy (IFT) can restore parts of the nervous system necessary for this improved muscle control [5]. IFT conventionally uses a four-pole method, where 2 pairs of electrodes are placed externally to direct current flow to the level of the PFM [4]. An advantage of IFT is its external application allowing for ease of application and patient comfort. Either suction cups or carbon silicon electrodes can be used depending on availability and preference. This form of electrotherapy has been found to produce positive results in the management of USI and is well tolerated by patients [2].

In comparison to TENS, IFT is more effective in stimulating deeper bodily structures as it utilizes a medium frequency of around 2 to 4 kHz [4]. Because the skin acts as a high pass filter, the IFT current is able to penetrate deep enough to reach the PFM, where a lower frequency would fall short. Traditional low-frequency TENS is predominantly used for superficial structures more directly; therefore, in order to stimulate the PFM intravaginal electrodes are used [4]. The invasiveness of this method is not well tolerated, resulting in a lack of compliance. An example of an intravaginal electrode is shown in the figure below [6].
This Interference Current has the therapeutic properties and sensations of low frequency stimulation. IFT traditionally uses 4 electrodes in an orthogonal pattern, but 2 electrodes in a bipolar pattern can also be used. In a bipolar system the current is ‘pre-modulated’ within the machine, instead of being generated in the body. The figure below is a diagrammatic representation of the orthogonal pattern [4].


It must be noted that electrical stimulation is not commonly used as the first approach to management of USI, but rather is used after other methods have failed. It is predominantly used for those who are initially unable to contract their PFM, but once active control is possible regular PFM exercises may be more effective [1].

References

1.     Berghmans, L. C. M., Hendriks, H. J. M., Bo, K., Hay-Smith, E. J., De Bies, R. A. & Van Waalwijk, E. S. C. (1998). Conservative treatment of stress urinary incontinence in women: A systemic review of randomized clinical trials. British Journal of Urology, 82, 181-191.
2.     Demirturk, F., Akbayrak, T., Karakaya, I. C., Yuksel, I., Kirdi, N., Demirturk, F., Kaya, S., Ergen, A., Beksac, S. (2008). Interferential current versus biofeedback results in urinary stress incontinence. Swiss Medical Weekly, 138(21-22), 317-321.
3.     Eriksen, B. C. (1990). Electrostimulation of the pelvic floor in female urinary incontinence. Acta Obstetricia et Gynecologica Scandinavica, 69, 359-360.
4.     Green, R. J. & Laycock, J. (1990). Objective methods for evaluation of interferential therapy in the treatment of incontinence. IEEE Transactions on Biomedical Engineering, 37(6), 615-623.
5.     Veale, J. L., Mark, R. F. & Rees, S. (1973). Differential sensitivity of motor and sensory fibres in human ulnar nerve. Journal of Neurology, Neurosurgery, and Psychiatry, 36, 75-86.
6.     Intravaginal Electrode [Image] (n.d.) Retrieved from http://www.healthcare4all.co.uk/images/tenscare-anal-probe.jpg 

2 comments:

  1. Thanks for fixing the image in post#1. there is a little too much redundancy in this post, meaning your peers all know about basic interferential theory. Don't stress and don't change it now. Also the phrase 'interfering with each other' is poorly put here. It sounds dodgy! better to risk plagiarism and describe the 'creation of an interferance pattern' - better still to skip over this as it was given in lectures. Preferably you would expand on the reasoning for IFT over TENS for USI not only with reference to the target muscle's depth (as you have done a little bit) but also to the pertinence (in this delicate anatomical region) of placing electrodes at some distance from the target, instead of directly over it, as one does with, say, NMES. Maybe in a subsequent post you were planning on doing so? cheers CY

    ReplyDelete
  2. Much, much better, thanks CY

    ReplyDelete