Focusing on Interferential

As mentioned in my earlier posts the primary aim of treatment in USI is to increase the strength of the weak PFM. An increase in PFM strength will help increase urethral closure pressure, resulting in decreased urinary incontinence.  A vital aim with all USI modalities.


Electrical stimulation therapy has been reported in literature for the use of USI treatment since the 1960’s and 70’s (Alexander & Rowan, 1970).

As I also mentioned the previous post, the two main types of electrical stimulation presently used are biofeedback and interferential current therapy.  This post aims to focus on interferential current and its specific applications towards USI treatment.

Interferential current therapy is aimed at restoring normal physiological reflexes in the abnormal nerves and muscles. Interferential current is specifically aimed at increasing urethral closure pressure by restoring the reflex activation of PFM, whilst encouraging the synchronised contraction of all the PFM and increasing their individual strength (Turkan et al. 2005). This all seems very confusing and complex but put in simple terms, interferential current will contract our pelvic floor in in the right sequence when we cannot subconsciously or even consciously do so.

As well as increasing the strength and coordination of the PFM, (Bo et al. 2007) interferential therapy can act by inhibiting detrusor muscle contraction (Yamanishi & Yasuda, 1998). The detrusor muscle instigates the urge to empty one’s bladder, and overactivity of this muscle is common in people with overactive bladder dysfunction.


Two categories of electrical stimulation explained 

Estim can be divided into 2 major categories; neurostimulation and neuromodulation.

Neural stimulation
Neural stimulation works to stimulate the efferent fibres of the pudendal nerve at S2 and S3, which innervate the PFM.  A direct response at the effector organ the PFM, results in increased neural activation, causing the PFM to contract (Scheepens, 2003). In basic terms by stimulating the nerves that send the message from the brain telling the pelvic floor to contract, we can activate and retrain the PFM to contract effectively. 

Neuromodulation

http://www.sghurol.demon.co.uk/urod/neuro.htm

Our bodies have a reflex that stops us from constantly feeling like we need to go to the toilet, when we have any fluid in out bladder. This reflex stops the detrusor muscle (the muscle that contracts over the bladder, giving us the urge to pass urine) from activating therefore removing the constant urge to go to the toilet. Neuromodulation achieves the above process by reorganisation of the nerves pathways, subsequently re-stimulating  the detrusor inhibition reflex. 

Specific parameters for interferential current

Interferential current uses 2 medium frequency currents, applied via 2 or 4 electrodes. The intersection of the two medium frequency currents, generates an interference current which has the characteristics of low frequency stimulation on the PFM (Demirturk et al. 2008).

For example:

A net current of 35 Hz will be produced when two continuous currents of 4000 to 4035 intersect. The picture below gives a  clear diagrammatical representation of the main concept of interferential.

http://www.mstrust.org.uk/professionals/information/wayahead/articles/10042006_06.jsp

One if the main benefits of interferential is that it can be applied externally with no harm to soft tissue. Both carbon silicon or suction cups electrodes can be used in interferential stimulation of the pelvic floor, which can add to ease of application.

The general settings used to stimulate the PFM using interferential are as follows:

·               Multiphasic wave

·               Phase duration- 125ms

·               Pulse rate- 1-200 pulses/sec

·               Total current- 80-90mA
                      Frequency- approx 4000 Hz (interference current 20- 50 Hz) 

Contraindications for electrical stimulation specific to the pelvic floor include:

·              Poor patient cognition

·              Pregnancy

·              Puerperium (First 24 hours after birth)

·              Atrophic vaginitis

·              Reoccurring vaginal infections

·              Recent hemorrhage

·              Malignancies

·              Adverse skin reactions under surface electrodes

General contraindications for electrical stimulation include:

·              Undiagnosed pain (unless recommended by a medical practitioner)

·              Pacemakers

·              Heart disease (unless recommended by a medical practitioner)

·              Increased cellular metabolism

·              Epilepsy (unless recommended by a medical practitioner)

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REFERENCES:

Alexander, S. & Rowan, D. (1970). Electrical control of urinary incontinence: a clinical appraisal. British Journal of Surgery. 57:766- 768.

Baessler, K., Schussler, B., Burgio, K., Moore, K., Norton, P. & Stanton, S. (2008). Pelvic Floor Re-education. Springer. London.

Bo, K., Berghams, B., Van Kampen, M. & Morkred, S. (2007). Evidence based physical therapy for pelvic floor: bridging science and clinical practise. Elsevier Limited. Philadelphia.

Demirturk, F., Turkan, A., Karakaya, I. C., Yuksel., Kirdi, N., Demirturk, F. et al. (2008). Interferential current versus biofeedback results in urinary stress incontinence. Swiss Medical Weekly. 138(21-22): 317-321.

Scheepens, W. (2003). Progress in sacral neuromodulation of lower urinary tract. Thesis. University of Maastricht. The Netherland.

Turkan, A., Inci, Y. & Fazli, D. (2005). The short-term effects of physical therapy in different intensities of urodynamic stress incontinence. Gynecol Obstet Invest. 59: 43-48.

Yamanishi, T. & Yasuda, K. (1998). Electrical stimulation of stress incontinence. International Urogynecology Journal and Pelvic Floor Dysfunction. 9: 281-290.