umh1723 2012-13 Lec02b Clasificación de las corrientes eléctricas utilizadas en Fisioterapia

Classification of Electric Currents in Electrotherapy

Overview of the Topic

• The discussion focuses on the classification of electric currents commonly used in electrotherapy.

• This presentation is part of Unit 1, Topic 2, related to the classification of electrical currents in physiotherapy.

Historical Context and Development

• A historical overview highlights how the study and application of electrical therapy have evolved over time.

• Previous sections covered significant historical milestones that contributed to the comprehensive development of therapeutic applications for electric current.

Importance in Physiotherapy

• Electric currents can complement manual therapy treatments, making them valuable resources when applied correctly in daily practice.

• The advancement in electric therapies has established them as one of the most utilized physical agents in physiotherapy today.

Classification Criteria

• The classification will be approached from multiple perspectives: polarity, alternation, phase representation, impulse form, and frequency.

• Examples of impulse succession and real electric currents used in electrotherapy will be discussed later to illustrate these classifications.

Levels of Classification

• Different levels should not be mixed; they are parallel classifications that encompass all relevant aspects for physiotherapeutic applications.

Types Based on Polarity

• Electric current can be classified as continuous or alternating based on its polarity.

Continuous vs Alternating Current

• Continuous current refers to a constant, unidirectional flow without interruption; it may or may not alternate between positive and negative phases visually represented on a graph.

• Alternating current features both positive and negative phases with a constant change in polarity during each cycle over time.

Monophase vs Biphase Current Forms

• Depending on whether the graphical representation occurs within one phase or two phases, we can categorize forms as monophase or biphase respectively.

Impulse Characteristics

Understanding Electrical Impulses in Physiotherapy

Modulation of Impulses

• The sequence of impulses can be modulated from three different perspectives, regardless of whether they are interrupted or continuous.

• Variations in impulses can occur across three parameters: intensity, duration, and frequency.

Classification by Frequency

• Frequency is defined as the number of impulses emitted per second; electrical currents used in physiotherapy are classified into low, medium, and high frequency based on this metric.

• A detailed classification chart lists all electrical currents used in physiotherapy according to their frequency levels: low, medium, and high.

Understanding Current Types

• It is crucial to memorize the nomenclature for these currents as it will aid in understanding their physical descriptions and classifications later.

• Continuous current flows in one direction only, while alternating current (AC) changes direction periodically. AC is commonly used for household appliances at 50 Hz.

Polarities and Phases

• Currents can also be classified based on polarity as either direct (monophasic) or alternating (biphasic).

• All constant polarity currents are monophasic with galvanic components that necessitate careful technique to avoid skin damage due to aggressive current use.

Characteristics of Biphasic Currents

• Alternating polarity currents are biphasic; they can be symmetrical or asymmetrical depending on the graphical representation of positive and negative phases.

• Symmetrical biphasic currents have equal positive and negative phases leading to zero net charge over time.

Effects of Asymmetry

• An example shows a non-interrupted biphasic impulse where the positive phase equals the negative phase, resulting in no galvanic component.

• In contrast, an asymmetrical waveform indicates dominance of one phase over another which leads to polar effects within the current.

Advanced Classifications

• Biphasic alternating currents may exhibit galvanic components depending on their symmetry; some cases may not present these components.

• Further distinctions include balanced versus unbalanced forms among asymmetric biphasic currents.

Classification of Electric Currents in Physiotherapy

Understanding Polar Effects and Current Types

• The resultant value of electric currents can equal zero, negating polar effects.

• Discussion on the dominance of one pole over another regarding galvanic components or polar effects; both upper and lower electric charges are equal but distributed differently.

• Electric current can be classified as bifasic or monofasic based on phase; asymmetry is present in positive and negative phases without compensation.

• Asymmetrical forms can be categorized as compensated or uncompensated, balanced or unbalanced; reiteration of bifasic and monofasic classification.

• Classification of electric currents used in physiotherapy into two major groups based on the discussed criteria.

Constant vs. Variable Currents

• The only constant current utilized in physiotherapy is direct current (galvanic); third level classification relates to current shape and intensity variation over time.

• Galvanic current is characterized by a steady flow of electrons with consistent therapeutic intensity; contrasts between constant and variable currents are established.

• Variable currents differ from constant ones, graphically represented by changing intensity over time; these are the primary forms used in physiotherapy.

Impulse Shapes and Modulation

• The shape of impulses varies depending on the type of electric current used, which will affect physiological outcomes; variable currents show graphical modifications in intensity over time.

• Emission can occur as a single isolated impulse; variations in impulse shapes will be explored further for their physiological impact.

• Modulation may involve changes to avoid accommodation, affecting how impulses are delivered—can include frequency, intensity, or duration modulation.

Types of Impulses Used

• Different types of modulation include frequency modulation, intensity modulation, and duration modulation for impulses employed during therapy sessions.

• Regardless of whether there’s a pause between impulses, they can be modulated across three potential changes—frequency, intensity, duration.

Frequency Classifications

• Common impulse shapes include rectangular, square, triangular, exponential based on darcency levels; faradic and sinusoidal forms also noted as frequently used within physiotherapy contexts.

• Gradual increases in stimulus intensity lead to progressive depolarization thresholds that result in muscle contractions—this has significant physiological implications.

• Healthy neuromuscular tissue exhibits accommodation capacity unlike pathological tissue; this distinction affects treatment approaches.

Final Classifications Based on Frequency

• Electric forms utilized in practice can be grouped into low frequency, medium frequency, and high frequency categories based on impulse characteristics.

• A visual representation outlines what constitutes low, medium, and high frequencies within therapeutic applications.

Classification of Electrical Currents in Physiotherapy

Low Frequency Currents

• There are no low-frequency currents used in physiotherapy that exceed 143 Hz, indicating a clear boundary for treatment parameters.

• All variable low-frequency currents fall within the range of 1 Hz to 1000 Hz, but practical applications do not utilize frequencies above 143 Hz.

• The classification of medium frequency shows a gap between 10,000 Hz and 100,000 Hz where no currents are available for use in physiotherapy.

High Frequency Currents

• High-frequency currents begin at 100,000 Hz; however, the lowest frequency utilized is shortwave therapy at 27,000 Hz.

• The existing classification system for electrical currents is outdated and does not reflect current practices or realities in physiotherapy.

Critique of Current Classifications

• The need for an updated classification system is emphasized due to contradictions present in the current framework.

• It is suggested that many physiotherapy texts have copied this outdated classification without revisions or updates.

Understanding Impulse Duration and Characteristics

Components of Impulse Representation

• In graphical representations of interrupted impulses, three key components are identified: rise time (pendiente de ascenso), maintenance time (mantenimiento del impulso), and fall time (pendiente de descenso).

• The concept of pause duration between impulses becomes relevant only when dealing with interrupted sequences; continuous impulse sequences do not incorporate pauses.

Physiological Impact on Nerve and Muscle Cells

• Progressive dependent impulses can lead to accommodation capacity in healthy tissues, raising depolarization thresholds in muscle or nerve fibers.

Graphical Representations of Electrical Currents

Continuous vs. Interrupted Impulses

• A constant direct current (monophasic), depicted graphically as stable over time without intensity variation, differs significantly from impulse representations.

Understanding Galvanic Current and Impulses

Representation of Galvanic Current

• The graphical representation of galvanic current differs from impulse representations previously discussed, emphasizing a constant state without variations in intensity over time.

• The inclined zones on the sides illustrate the increase in intensity until reaching the desired therapeutic value, highlighting the importance of gradual adjustments.

Characteristics of Impulses

• To achieve a steady flow of electrons at therapeutic levels, one must manually adjust intensity in both ascending and descending patterns; this is distinct from impulse forms since galvanic current lacks frequency.

• Key concepts include:

• Duration of Impulse: Time an impulse lasts.

• Duration of Pause: Time between impulses.

• Amplitude/Intensity: Height of an impulse.

• Period of Impulse: Total time from one impulse to the next, combining duration and pause.

Types of Current Waves

• A sequence of alternating current impulses shows positive and negative phases. This includes:

• Symmetrical biphasic currents with zero galvanic component.

• Variable currents that change intensity over time, illustrated through sinusoidal waveforms rather than rectangular ones.

Frequency and Period Definitions

• Discussing period definitions involves understanding:

• Frequency relates to how often impulses occur within a given timeframe.

• Duration specifics for both impulses and pauses are crucial for effective application in therapy.

Practical Applications in Therapy

• The definition remains consistent regardless if there are pauses or not; it focuses on the total time between successive impulses. Understanding this allows flexibility in treatment methods without compromising effectiveness.

Understanding Impulse Frequency and Period

Calculating Impulse Frequency

• The frequency of an impulse can be calculated by dividing 1000 milliseconds by the impulse period, which is also measured in milliseconds. This relationship highlights the importance of understanding both impulse duration and phase interval as part of the overall impulse period.

Inverse Relationship Between Period and Frequency

• There exists an inverse proportionality between period and frequency; as one increases, the other decreases. The impulse period is defined as the time from one impulse to the next, expressed in time units. Understanding this relationship is crucial for manipulating electrical currents effectively.

High vs Low Frequency Currents

• A clear distinction exists between high-frequency currents (without phase intervals) and low-frequency currents (with pauses). This difference affects how impulses are delivered and perceived in practical applications.

Impact of Impulse Duration on Period

• When increasing the number of impulses within a given timeframe (e.g., from 10 to 50), adjustments must be made either to reduce individual impulse duration or shorten pauses, thereby influencing the overall concept of period. This adjustment reflects directly on how frequency impacts both duration and pause length.

Practical Example with Equipment Setup

• An example involving laboratory equipment illustrates that if more items (camillas) are added without changing their size or spacing, it necessitates reducing either their length or distance apart, affecting both impulse duration and pause length accordingly. This serves as a metaphor for understanding electrical impulses in practice.

Frequency Calculation Examples

Calculating Frequency from Impulse Duration

• To calculate frequency based on known parameters: if the impulse period is five milliseconds, then using this value allows for determining a frequency of 200 Hz (impulses per second). This calculation emphasizes how precise measurements lead to accurate frequency assessments.

Graphical Representation of Periodicity

• A graphical representation can illustrate three periods of impulses totaling fifteen seconds when each has a five-millisecond duration, reinforcing concepts around cycles and timing in electrical stimulation contexts.

Acomodation in Neuromuscular Tissue

Effects of Consistent Stimulation

• Neuromuscular tissue exhibits accommodation when exposed to rhythmic stimuli over extended periods without variation in parameters; this phenomenon underscores the need for modulation to maintain effective stimulation levels during therapy or treatment protocols.

Modulation Techniques

Understanding Modulation in Electrical Therapy

Key Concepts of Modulation

• The concept of "limuitarza" duration and pause duration is introduced, emphasizing the importance of timing in electrical therapy.

• Discussion on producing a specific effect (ey WOMAN) alongside modulation techniques.

• Manual vs. automatic modulation: Therapists can manually adjust parameters like frequency, impulse duration, or intensity to prevent accommodation, while devices can automatically change these settings.

Frequency and Impulse Duration

• Frequency and phase duration are inversely proportional; higher wave frequency leads to different calculations for impulse emission based on known parameters.

• The ability to alter the rhythm of impulse emissions allows for varying numbers of impulses per second over specified time intervals.

• Example provided with a frequency of five impulses per second over 15 seconds, followed by two impulses per second in subsequent intervals.

Examples and Applications

• An example illustrates calculating parameters from a known sequence of impulses with zero pause duration, highlighting common modulation patterns available in devices.

• A graphical representation shows three impulse periods indicating abrupt changes suitable for chronic pathologies.

Understanding Automatic Changes

• Explanation of how neuromuscular tissue accommodates to stimulus variations; cycles take one second to switch values under certain conditions (1:30 ratio).

• To avoid sensory or motor accommodation, electrical current modulation is employed strategically during therapy sessions.

Types of Modulation Techniques

• Different types of modulation are discussed: manual adjustments by therapists versus automatic device functions that progressively transition through parameter ranges.

• Manual modulation involves changing parameters between two hertz values over six seconds to maintain therapeutic effectiveness without causing accommodation.

• The second form focuses on varying the intensity of impulses automatically based on device capabilities and user preferences for effective treatment outcomes.

• The third type addresses impulse duration variation aimed at enhancing therapeutic efficacy while preventing sensory or motor adaptation effects.

Conclusion on Theoretical Concepts

Modulation Frequencies and Their Applications

Understanding Modulation Frequencies

• The concept of modulation frequency is introduced, highlighting a scenario where two impulses are emitted per second, indicating an interrupted emission pattern.

• A modulation ratio of 1.1 is explained, where one frequency (5 Hz) is followed by another (2 Hz), showcasing the variability in impulse emissions.

• The specifics of a 1.1 modulation cycle are detailed, emphasizing the transition between two frequencies within a second and its implications for chronic pathologies.

Different Modulation Patterns

• Another modulation pattern is described, where frequencies alternate every 30 seconds between 2 Hz and 5 Hz, allowing for smoother transitions compared to abrupt changes.

• This pattern is termed "1.30," indicating that it takes one second to switch from one frequency to another while maintaining each frequency for 30 seconds.

Smooth Transition in Modulation

• The "6.6" modulation method is presented as the most gradual approach, transitioning through all parameters between two set values over six seconds both ascending and descending.

• Unlike previous methods that toggle between extremes, this technique allows for continuous variation across all parameters during the cycle.

Intensity Variation in Impulses

• A new form of modulation focuses on changing the intensity of impulses either manually or automatically, with options available based on device capabilities.

Duration Changes in Impulses