Electrotherapy Basics Quiz

Electrotherapy II - 1st Lecture

• The lecture covers an introduction to electrical stimulation and electrical currents.
• The instructor is Dr. Ahmed aboulfotouh.

Objectives

• Define electrical stimulation and electric current.
• Differentiate between alternating, direct, and pulsed currents.
• Categorize various waveforms and pulse characteristics.
• Identify the different parameters of electrical stimulation.

Introduction

• Electrical stimulation (ES) is the application of electrical currents to elicit or facilitate a therapeutic response.
• Common uses of ES include activating skeletal muscles for strengthening or improving movement, decreasing pain, and facilitating tissue healing.
• These effects are based on stimulating tissues using applied electric currents.

Electrical Stimulation: How?

• Electrical stimulation can be delivered by implanted or external stimulators using electrodes.
• In physiotherapy, external stimulators, using external, surface, or transcutaneous electrodes, are commonly used to deliver electrical currents.

Basics of Electricity

• Discussing electrotherapy applications without understanding fundamental electricity is like playing a game without knowing the rules.
• Functional electrotherapy understanding must begin with the basics.

Electrical Current

• Electrical current is the movement of ions or electrons in a conductor in response to a voltage force.
• The flow of current is directly proportional to the voltage.
• The standard unit for current is the ampere (amp or A); however, milliamperes (mA) and microamperes are often used in therapeutic applications.

Types of Currents and Waveforms

• Main types of electrical currents are direct current (DC), alternating current (AC), and pulsed current (PC).
• In electrotherapy, pulsed current is the most common type.
• This classification considers the flow as: Direct (DC); Alternating (AC); and Pulsed (PC).

The Waveform

• A waveform is a visual representation of current characteristics, showing shape, magnitude, and duration.
• All currents have parameters in the vertical (y-axis) and horizontal (x-axis) directions.
• Horizontal axis parameters describe and quantify duration (milli- or microseconds); vertical axis parameters describe and quantify magnitude/intensity (milli- or microamps or milli- or microvolts).

Waveforms (Examples)

• Examples of waveforms include square, rectangular, and triangular waveforms.

1- Direct Current (DC)

• DC is a continuous, unidirectional flow of ions or electrons for at least 1 second.
• By convention, upward deviations from the isoelectric baseline indicate positive current flow and vice versa.
• Common clinical uses of DC include iontophoresis and wound care.
• DC is also known as galvanic current.

Forms of DC

• Variations of DC exist, but variations must remain unidirectional and uninterrupted for a period of time.
• Common forms of DC include interrupted DC, reversed DC, and interrupted reversed DC.

2- Alternating Current (AC)

• AC is an uninterrupted, bidirectional flow of ions or electrons that changes direction at least once per second.
• The frequency of the direction changes is measured in hertz (Hz), or cycles per second.
• AC is the most common electricity type in homes.

3- Pulsed Current (PC)

• PC (or pulsatile current) is the unidirectional or bidirectional flow of ions or electrons that periodically ceases for a set period before the next electrical event.
• A pulse is an isolated electrical event separated from the next by an interpulse interval.

Shapes of Pulse

• Pulses can be square, rectangular, or triangular in shape.

Electrical Current Parameters

• Current characteristics are described by: waveform, pulse and phase, pulse duration, amplitude, and frequency.

Wave Forms

• Various waveform types exist (sine, rectangular (square), spike, combined, and twin-spiked).

Pulse and Phase

• Pulsed current flows in a series of pulses separated by interpulse intervals.
• A pulse is an isolated electrical event.
• Current flow during a pulse can be monophasic (single direction) or biphasic (back and forth).

Monophasic or Biphasic

• Monophasic pulses deviate from the isoelectric line in a single direction.
• Biphasic pulses deviate in both directions.

Difference between Monophasic and Biphasic

• Monophasic current effects primarily occur with continuous stimulation over a period of time.
• Biphasic current does not usually lead to polarity effects.

Pulse Duration & Phase Duration

• Pulse duration is the total time for a pulse, including the interphase interval.
• Phase duration is the time from the beginning to the end of a single phase.
• The interphase interval is between phases within a pulse, while the interpulse interval is between successive pulses.
• Duration is commonly measured in milliseconds (msec) or microseconds (µsec).

Phase and Pulse Charge

• Phase charge is the charge within a phase of a pulse, while pulse charge is the cumulative charge in a single pulse.
• In monophasic pulses, phase charge and pulse charge are the same.
• The total charge greatly affects the electrophysiological effects.

Symmetrical & Asymmetrical Waveforms

• Symmetrical waveforms have identical characteristics in both phases, while asymmetrical waveforms have different characteristics in each phase.

Balanced & Unbalanced

• Balanced biphasic (symmetrical) waveforms have equal charge in each phase. Unequal charge signals unbalanced waveforms.

Amplitude

• Amplitude measures the magnitude of current or voltage concerning the isoelectric or baseline, typically reported in milliamperes (mA) or microamperes (µA).
• Peak amplitude refers to the highest voltage during any phase of either a monophasic or biphasic waveform.

Frequency

• Frequency is the number of pulses per second.
• Measured in hertz (Hz), it describes the rate at which an alternating current (AC) switches its direction. Pulses per second also describe frequency in pulsed current.
• Inverse relationship exists between frequency and pulse duration.

Frequency (Types)

• Low frequency currents stimulate nerves (1-1000 Hz).
• Medium frequency currents stimulate nerves after modulation (1 kHz range).
• High-frequency currents have no effect on nerves (above 1 MHz).

Burst

• A burst is a series of consecutive pulses separated by an interburst interval.
• Burst frequency refers to the frequency at which bursts are generated.
• The underlying waveform frequency within a burst is the carrier frequency.