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OBJECTIVES

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Following completion of this chapter, the student will be able to:

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  • Define common terminology related to electricity.

  • Differentiate between monophasic, biphasic, and pulsatile currents.

  • Differentiate between direct (DC), alternating (AC), and pulsatile (PC) currents.

  • Explain current flow through various types of biologic tissue.

  • Discriminate between series and parallel circuit arrangements.

  • Discuss the various treatment parameters including waveforms, current modulation frequency, intensity, duration, polarity, and electrode placement that must be considered with electrical stimulating currents.

  • Explain nerve, muscle, and nonexcitatory cell physiologic responses to electrical stimulation.

  • Discuss the clinical goals of using electrical stimulating currents to stimulate either motor nerves to induce muscle contraction, or sensory nerves for the purpose of modulating pain.

  • Differentiate between the various currents that can be selected on many modern generators including high volt, TENS microcurrent, Russian, interferential, premodulated interferential, low volt, and H-wave.

  • Discuss additional uses for electrical currents including bone growth stimulation, functional electrical stimulation, and transcranial electrical stimulation.

  • Be able to create a safe environment when using electrical equipment.

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Many of the modalities discussed in this book may be classified as electrical modalities. These pieces of equipment have the capabilities of taking the electrical current flowing from a wall outlet and modifying that current to produce a specific, desired physiologic effect in human biologic tissue.

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Understanding the basic principles of electricity usually is difficult even for the clinician who is accustomed to using electrical modalities on a daily basis. To understand how current flow affects biologic tissue, it is first necessary to become familiar with some of the principles and terminology that describe how electricity is produced and how it behaves in an electrical circuit.172,180,186

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COMPONENTS OF ELECTRICAL CURRENTS

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All matter is composed of atoms that contain positively and negatively charged particles called ions. These charged particles possess electrical energy and thus have the ability to move about. They tend to move from an area of higher concentration toward an area of lower concentration. An electrical force is capable of propelling these particles from higher to lower energy levels, thus establishing electrical potentials. The more ions an object has, the higher its potential electrical energy is. Particles with a positive charge tend to move toward negatively charged particles, and those that are negatively charged tend to move toward positively charged particles (Figure 5–1).1

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Figure 5–1.

The difference between high potential and low potential is potential difference. Electrons tend to flow from areas of higher concentration to areas of lower concentration. A potential difference must exist if there is to be any movement of electrons.

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Electrons are particles of matter possessing a negative charge and very small mass. The net movement of electrons is referred to as an electrical current. The ...

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