It is probably not surprising that many students and clinicians feel intimidated or confused by clinical electrotherapy considering the many waveforms and parameters presented in Chapter 9. Waveforms vary in many ways, and these variations are even more obvious when looking at the variety of dials, buttons, switches, and lights found on electrotherapeutic devices. However, this confusion is entirely unnecessary, because a competent and clinically effective knowledge of electrotherapeutics can easily be obtained by understanding how waveforms and parameters result in the many effects produced with electrotherapy. Unfortunately, intimidation and confusion are perpetuated by commercial hype, longstanding myths, well-meaning but poorly informed clinicians, complex-appearing instrumentation, and sometimes misleading user’s manuals. This chapter is the last of Section II, “Types of Modalities”, and will present further fundamental information relevant to effective use of electrical stimulation (ES). Following this chapter, Section III will present chapters on more specific areas of ES with corresponding case studies.
INSTRUMENTATION FOR ELECTROTHERAPY
Classifying Electrotherapeutic Devices
Electrotherapeutic devices are typically known by or described by the type of current generated. For example, common clinical names used to describe devices include Russian, high-volt, microcurrent, and interferential stimulators. Sometimes, devices are classified by their power source, either line-powered or battery-powered. Line-powered devices are powered by wall current (110 volt, 60 Hz in North America) and are plugged into a traditional wall outlet for use. These devices are sometimes referred to as clinical devices because the devices tend to be large, thus limiting their portability outside the clinic. Battery-powered devices obtain their power from a variety of different battery types, with most now using rechargeable batteries. The major advantage of battery-powered devices is their portability, allowing them to be used outside the clinic and often independently by the patient at home and sometimes while the patient is engaged in activity.
Line-powered devices have traditionally been capable of delivering greater current intensities than battery-powered devices. This was particularly true with stimulators delivering large amplitude currents for muscle strengthening. For many years, evidence suggested that battery-powered stimulators used for muscle strengthening were insufficient in their ability to activate skeletal muscle compared with line-powered devices. While this is still more true than not, there is some evidence that has altered this opinion. In studies of healthy, strong adults, Laufer and colleagues1 and Lyons and associates2 reported evidence that newer battery-powered devices can stimulate skeletal muscle to levels once considered achievable only by line-powered devices.
A common misconception is that because batteries provide direct current (DC), battery-powered devices must deliver DC to the patient. This is for the most part inaccurate; the most common exception being devices used for iontophoresis. While DC is provided by a battery, electrotherapeutic devices may provide a variety of other waveforms, none or only one of which may be DC. Likewise, line-powered devices receiving alternating ...