Table 1.
Characteristics of Pulse and Current Parameters, Electrode Application, and Treatment Position
| Characteristic | Recommendation | Important Considerations |
|---|---|---|
| Pulse and current parameters | ||
| Pulse waveform | Biphasic waveform | Sensory level transcutaneous electrical nerve stimulation (TENS) is applied by biphasic or monophasic waveforms or bursts in different shapes.27 |
| Pulse frequency (Hz) | 50 to 120 Hz (100 Hz is most common) | High-frequency (HF) sensory-level TENS stimulation frequencies are broadly classified as HF (>50 Hz), low frequency (LF) (1 Hz to 4 Hz), or burst (bursts of HF stimulation applied at a much lower frequency).23 HF TENS - patient experiences an intense, comfortable, nonpainful paresthesia. LF TENS - experienced as an intense, painful pulsating sensation often accompanied by muscle twitching. Most patients typically find higher frequencies more comfortable.23 |
| Phase duration (µs) | 100 µsec24,26 | Most frequent setting in previous studies on patients affected by primary dysmenorrhea (PD) was 100 µsec.3,6–10,17–20,24,26 |
| Current amplitudes | The highest tolerable intensity with continuous adjustment of the current amplitude so that an intense sensation is felt throughout the entire treatment process. Maintaining the same level of sensation by continually increasing the current amplitude. |
Dose-response effect: higher intensities (strong, nonpainful, at sensory threshold) produce greater and longer-lasting decreases in pain and nociceptive response, whereas TENS delivered at or below the sensory threshold (or placebo) was ineffective.24,25 LF TENS applied typically at higher intensities.22 Continuous increase throughout TENS produced greater analgesia compared to the case at which the intensity was maintained at the initial level.26 Higher currents activate deeper tissue afferents allowing greater analgesia, in addition to the activation of more sensory afferents.34 |
| TENS treatment dosage: Duration, number of treatments and frequency | Using the device whenever severe pain is felt | A consistent clinical dosage of TENS is lacking.26 |
| Habituation/repeated use | Use a fixed high frequency, increase the current intensity continually up to the instance at which anintense, maximum tolerated sensation is felt. | Rational: decrease in habituation effect. Repeated application of the same dose (frequency, intensity, duration) of TENS daily over a period of five days results in analgesic tolerance in healthy women.16 Resolve the conflict between the cumulative effects and tolerance may be in the mode of application. It is suggested that for chronic pain, a cumulative effect is achieved if the intensity is increased during treatment until the patient describes the sensation as “intense, but comfortable.” Patients likely become more comfortable with TENS over time, and are able to tolerate higher intensities.39 Animal studies show that increasing the intensity by 10% on a daily basis, delays the onset of analgesic tolerance. |
| Electrode application and treatment position | ||
| Skin preparation | Ensure intact skin area. Cleanse skin prior to application. |
Skin breakdown will result in extreme discomfort.27 Cleansing reduces skin impedance.27 |
| Type of electrodes | Self-adhesive. Dual-channel devices using four large-sized electrodes corresponding to the painful area(s). |
Self-adhesive electrodes are easy to apply and less cumbersome but are costlier as they are disposable.27 Other types require conductive material at the electrode–skin interphase (eg, gel, water-saturated material) and additional use of Velcro belts, or tight-fitting clothing to hold the electrode in place. Advantages include the facts that they are not disposable and can be used in several patients. Few studies investigated the effects of different types of electrodes on the analgesic effect of TENS.25,26 However, no prior study provided a clear answer as to which of the two types is better. Accordingly, each woman will require her own electrode set. |
| Size and location of electrodes | Adjust specifically to each woman according to thetypical area of her pain. Education and training should emphasize the fact that the electrode should not be fixed to the same point and should be adjusted to the actual area of pain experienced in each menstrual cycle. |
The choice of electrode size and location depends on the TENS type (HF versus LF), the size of the painful area and the pathophysiology of the condition.26 Focus on HF TENS and apply TENS over nonacupuncture points. The electrode placement is based on the rationale that the HF TENS operates via a segmental mechanism, and the pain pattern usually covers a large area and more than one location (eg, lower back and upper leg). Two suggested options includetheapplication of the electrodes over the thoracic spine in areas related to the spinal nerve roots that receive nociceptive information from the uterus. Alternatively, place them on dermatomes corresponding to the referred uterine pain (on the lower pelvis, medially, at the suprapubic region in the lower abdominal quadrants).23 |
| Position | Use TENS during an activity that is typically interrupted by PD pain. | Rational: previous studies indicated that TENS is more effective for reducing pain during movement compared to resting conditions.39 Given thatup to 20% of women may have severe painsthatinterfere with daily activities, it is suggested that they use the dynamic mode. The TENS apparatusis small and lightweight and can be attached to clothing. |
| Treatment setting | Self-use of TENS at home in accordance with the appearance of PD symptoms. | Major advantages of TENS equipment include the facts that they are practical, relatively inexpensive, and easy to use. TENS machines are portable, battery-operated devices.9 Home use of the TENS was evaluated in four studies during menstrual cycles.6,17,8,10 However, no study compared the effectiveness of TENS between clinical and home settings. It is impractical and time-consuming to use TENS for PD in a clinical setting and an unnecessary utilization of healthcare services, as the symptoms appears for a limited time period (hours to days) every month in young women. The therapist should be aware that some patients are not suitable for HF TENS, as they cannot tolerate higher intensities.6,19 |
| Adverse effect | A safe treatment modality. | Pay attention to the skin status and increased menstrual flow. Caution should be exercised to ensure that TENS is used correctly by the patient. Only two studies reported adverse effects associated with treatment.18,10 Dawood et al18 reported that 4/32 women using HF TENS experienced muscle vibrations, tightness, and headaches, as well as slight redness or burning of the skin after use. Wang et al10 reported that 1/13 women experienced increased menstrual flow during TENS stimulation. The clinical importance of these minor yet adverse effects is unclear.18 Nevertheless, TENS has fewer side effects than pharmacological agents do. |
Abbreviations: TENS, Transcutaneous electrical nerve stimulation; PD, primary dysmenorrhea; HF, high frequency; LF, low frequency.