Part 3: The Evidence

As with all bioinstrumentation, a foundation of knowledge of the literature is needed before applying these methods to patients. The validity of Interferential Therapy (IFT) as a form of treatment for Urinary Stress Incontinence (USI) was found by critically reviewing 5 studies, the fifth of which will be discussed in a later post.

1.    Electrode Placement Methods = Dumoulin et al. (Part 1) ^[1]

This study compared two IFT electrode placement methods to maximally stimulate the PFM. Both methods involve a posterior electrode above the anus; Laycock and Green^[3] then suggest an anterior electrode on the clitoral region and Dumoulin^[2] suggest the anterior electrode should be above the pubic symphysis. A diagram of these configurations can be seen below. Bipolar electrode placement was used as it was shown to be equally effective, and because of its ease of application.

A 2-group crossover design was used, involving 10 continent women randomly assigned to 2 study groups, each receiving both treatments in random order. The force of PFM contraction was measured using a vaginal pressure probe attached to a manometer, seen in the figure below. No difference in pressure was found between the two methods of electrode placement; however, the Dumoulin method required less current amplitude to achieve the same pressure and was better tolerated by the subjects. The study concluded that greater pressures could be more comfortably reached using the Dumoulin method.

The advantage of this trial was that it was randomized. The disadvantages were that it involved only a small and specific sample population of women who did not suffer from incontinence and it tested the bipolar electrode pattern rather than the conventional quadripolar pattern. It’s important to note that this study was to develop treatment guidelines for the following study on postpartum women.

2. Postpartum Women = Dumoulin et al. (Part 2) ^[2]

This trial examined 8 postpartum women who’d suffered from USI for over 3 months after delivery. Treatment included pelvic floor reeducation for 9 half hour sessions combining IFT and pelvic-floor muscle (PFM) exercises. 5 subjects became continent and conditions improved for the other 3. After the intervention the PFM strength was greater and the volume of urine loss and frequency of incontinence were lower after the intervention. A 1-year follow-up survey found these results to remain consistent.

The advantage of this trial was that it involved a significant intervention time. The disadvantages were that it used only a small and specific sample population of women and it mixed 2 modes of treatment rather than determining the most effective.

3. Elderly Overactive Bladder Incontinence = Oh-oka ^[4]

The focus of this study was the ability of IFT to inhibit detruser muscle contraction. This muscle is responsible for activating the urge to empty one’s bladder. Therefore an overactivity of this muscle results in a form of incontinence known as overactive bladder (OAB).

80 elderly patients between the ages of 69 to 78 years with OAB incontinence were given 3 months of IFT. The frequency of incontinence and volume of urine loss were reduced and improvements were seen in the quality of life questionnaires related to a greater average time spent outdoors. These effects were seen after an average of 8 sessions and the improvements were found to last 3 months post-intervention.

The advantages of this trial were that it examined a large sample population over a relatively long time and conducted a follow-up study to determine the longevity of the treatment effects. The disadvantage was that it focused on overactive bladder incontinence that is relevant to, but not exactly USI.

4. Comparing Different USI Severity = Turkan et al. ^[5]

This study examined the effectiveness of IFT with Kegel exercises in treating patients with different intensities of USI. 48 patients were assigned to 3 study groups according to the severity of their USI and were given 15 sessions over 5 weeks. The results showed that the number of pads used per day, voiding frequency and leakage decreased while the PFM strength and QoL increased. 88% of the mild USI group and 18% of the moderate group were cured of their condition while none of the severe group showed a cured effect, indicating that IFT treatment is better suited to mild and moderate than severe USI.

The advantage of this trial was that it used a relatively large sample population. The disadvantage was that it combined IFT with Kegel exercises rather than focusing primarily on IFT, or comparing the two treatments.

References

1.     Dumoulin, C., Seaborne, D. E., Quirion-DeGirardi, C. & Sullivan S. J. (1995). Pelvic-floor rehabilitation, part 1: comparison of two surface electrode placements during stimulation of the pelvic-floor musculature in women who are continent using bipolar interferential currents. Journal of the American Physical Therapy Association, 75(12), 35-42.

2.     Dumoulin, C., Seaborne, D. E., Quirion-DeGirardi, C. & Sullivan S. J. (1995). Pelvic-floor rehabilitation, part 2: pelvic-floor reeducation with interferential currents and exercise in the treament of genuine stress incontinence in postpartum women – a cohort study. Journal of the American Physical Therapy Association, 75(12), 44-49.

3.     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.

4.     Oh-oka, H. (2008). Efficacy of interferential low frequency therapy for elderly wet overactive bladder patients. Department of Urology Kobe Medical Center Japan, 24(2), 178-181.

5.     Turkan, A., Inci, Y. & Demirturk, F. (2005). The short-term effects of physical therapy in different intensities of urodynamic stress incontinence. Gynecologic and Obstetric Investigation, 59(1), 43-48.