Mechanical Ventilator (second report)

Mechanical ventilator manual link designed: https://drive.google.com/file/d/1uRV9ktVYHOwRvqs9B8ZddRuZ2AVFL2I7/view?usp=sharing

Mechanical Ventilator

BackGrounds

A ventilator is a machine designed to mechanically move air in and out of the lungs to intermittently or continuously assist or control pulmonary ventilation, This device is primarily used in intensive therapy to help improve the patients breathing by regulating the flow of gas in the lungs.

Objectives of the design of a Mechanical Ventilator

1. Supply control of ventilation.
2. Enable the exchange of gases.
3. Reduce respiratory work.
4. Facilitate muscle recovery (weaning).
5. Allow sedation, anesthesia

Basic Concepts

Figure 1: general scheme of operation of a uci ventilator

Figure 2: Patient Breathing Circuit

In an intensive care ventilator (ICU) we use oxygen and high pressure air. Once filtered, the pressure of each gas is reduced and stabilized to an optimum value, and then each one is dosed separately by means of proportional valves, in order to obtain the gas mixture in the amount and proportion necessary to ventilate to the patient. This is achieved by insufflating said gas during the inspiratory phase.

Mechanical Ventilation Modes

Conventional Ventilatory Modalities:

1.  Assist-Control Ventilation (ACV) : Total assisted-controlled mechanical ventilatory support is the most basic form of MV, it is used in those patients who present a considerable increase in ventilatory demands and who therefore need total replacement of ventilation. The assisted-controlled modality allows the patient to initiate the cycling of the ventilator starting from a preset value of respiratory frequency (f) that ensures, in the event that this one does not make inspiratory efforts, the ventilation of the patient.
2. Synchronized Intermittent-Mandatory Ventilation (SIMV): The synchronized intermittent mandatory ventilation allows the patient to perform spontaneous breaths interspersed between the mandatory cycles of the ventilator, the word synchronized refers to the waiting period that the ventilator has before a mandatory cycle to synchronize the inspiratory effort of the patient with the insufflation of the ventilator. When used with high f covers the patient's ventilatory demands, being comparable to conventional assisted-controlled ventilation. Used with low frequencies, the SIMV allows the progressive disconnection of the Mechanical Ventilation (VM).
3. Pressure-Controlled Ventilation (PCV) - Pressure Support Ventilation (PSV):  It is an assisted modality, limited to pressure and cycled by flow, which modifies the spontaneous ventilatory pattern, that is, it decreases the respiratory rate and increases the circulating volume. The ventilator provides a ventilation aid, programmed from the support pressure level. The pressure remains constant throughout the inspiration, and in parallel the flow decreases progressively until reaching the level that allows the start of expiration. This partial support modality is widely used, since it allows to synchronize the respiratory activity of the patient with the ventilator when responding to changes in the patient's ventilatory demand. In addition, it preserves respiratory work and reduces the need for sedation and healing, thus facilitating the disconnection of the VM.

Alternative Modalities

1. Peep: Positive end-expiratory pressure (PEEP) is a mechanical technique that is often used when ventilating an unconscious patient. This technique includes the addition of a quantity of pressure in the lungs at the end of each breath. The patient's ventilation process causes a degree of desufflation in the lungs; between breaths, the lungs contain less air than usual. By adding positive pressure at that time, we try to reinfuse the respiratory tract.
2. Continuous Positive Airway Pressure (CPAP):  It is a spontaneous breathing modality with PEEP, in which a supraatmospheric pressure is maintained throughout the ventilatory cycle. The flow must be high to guarantee a high gas supply, higher than the requirements of the patient and small pressure oscillations (<5 cm H2O) so as not to cause excessive respiratory work.
3. Airway Pressure Release Ventilation (APRV):  It combines the positive effects of continuous positive airway pressure (CPAP) with the increase in alveolar ventilation obtained by the transient decrease in airway pressure from the level of CPAP to a lower level. Ventilation with pressure release provides long periods of insufflation, interspersed with brief periods of pulmonary deflation. It is a mode of partial ventilatory support cycled by the ventilator or by the patient and in which during the period of insufflation the patient can breathe spontaneously. Its main advantage lies in the fact that the pressure in the airway can be set at a modest level, and furthermore as the pressure is maintained during a longer period of the respiratory cycle an alveolar recruitment occurs. In theory, short periods of deflation do not allow alveolar collapse, but it is sufficient for the exchange of gases not to be affected by the CO2 clearance.

    Respiratory Curves: in the different ventilation modes mentioned above, flow, pressure and volume curves are used in time to have a detailed analysis of the operation of the mechanical ventilator.

Figure 3: Respiratory Curves (flow,pressure and volume)

      According to figure 3:

      Flow Curve: Starts according to the flow pattern selected at the beginning of inspiration. In assisted or pressure-controlled respirations, the flow is slowed and in volume-oriented modalities, quadratic flow is generally used. At the end of the inspiration, the flow becomes 0, and is inscribed below the X axis, which represents the expiration that constitutes the most important portion of the curve, it must be linear starting from the maximum expiratory flow to the baseline, before of the next breath (expiratory pause time). In the different ventilation modes mentioned above, flow, pressure and volume curves are used in time to have a detailed analysis of the operation of the ventilator.

     Volume Curve:Should be correlated with the previous ones, indicates some of the problems already mentioned in the previous curves.

   Pressure Curve:This should ascend smoothly. In ventilations controlled by the ventilator, the pressure curve starts from the final expiratory pressure and in those triggered by the patient, an initial negative inscription indicates the inspiratory effort. In the pressure curve the autopeep is not observed because it is disguised, it must be suspected when the inspirations begin very early on the expirations (high respiratory frequency) or the patient has conditions having autopeep (bronchial asthma, COPD, small caliber tube).

      

    Design

Interface Desing

Figure 4: Design Control panel

    The design of the mechanical ventilator for adults was developed through the implementation of an interface called the control panel, where the ventilatory control modes are selected, parameters are entered and the respiratory curves are observed. everything named above is implemented in the LabView programming software.

     Electric Diagram

Figure 5: Electric Diagram Mechanical Ventilator

Figure 6: Mechanical Ventilator Electric Block Diagram

the mechanical ventilator consists of two control modes that are pressure and volume, in the pressure mode, the inspiratory time value is entered, which is an important consideration to take into account when ventilatory support is started, giving the relation between the duration of inspiration and expiration. dynamic parameters are established as the maximum and minimum pressure known as PEEP, the range of pressure was established between 40-100 mmHgO, which in the theory corresponds to 5-30 cmH2O, the results to be obtained will be the pressure and volume curves, where the volume is a function of the pressure.

For the volume control, parameters such as maximum volume and minimum volume are established, the volume control carries an inspiration-expiration relationship through the control or implementation of flow. At the beginning of the mechanical ventilation, a flow must be established that ensures an inspiratory time of around 1 second (0.8-1.2 s), which is equivalent to programming a peak or maximum flow of about 60 l / min (40-80 l / min), but in the design made the system flow is constant In this case the volume control is determined taking into account pressure parameters, the volume range was established between 50 and 600 ml.

The ventilatory system has a self-test as verification test of ventilator operation, in which auditory alarm operation, patient detection, patient breathing system in operation is reviewed. On the other hand, it has two auditory and visual alarm systems. The visuals are observed as LEDs on the control panel, the alarm systems are due to high pressure and valve obstruction.

Programmed Design

The programming in LabView consists basically of three buttons that are the selection to the self-test, control pressure and volume control, which is then directed to a cycle while doing three processes, insufflation, time of inspiration, expiracion and inspiration, annexed to this is find the programming of the alarms with conditionals.

Mathematical Desing

Pressure

Figure 6: Linearization Pressure

Figure 7: Linear Regression Pressure

Volume

Figure 6: Linearization Volume

Figure 9: Linear Regression Volume

The previous linearizations observed in Figure 8 and 9, are made to implement the equation of the line obtained in the programming within each of the cycles.

The pressure linearization was obtained by measuring the voltage at different pressure values, which was indicated by the manometer. for the volume as it was reacted as a function of pressure, the maximum voltage was taken at a maximum pressure and the minimum voltage at a minimum pressure and each one at a volume value.

Results

Control Pressure

Figure 10: Curves Control Pressure

Pressure wave: It is written starting from zero or the value of the PEEP as an upward wave during inspiration until reaching the maximum pressure. An inspiratory pause can be seen if programmed, then falls during expiration to the level of the final expiratory pressure. The respiratory effort is inscribed as a negative deflection before the wave described.

Volume wave: In it, leakages or leaks are observed well, when the expiratory wave does not reach the baseline.

Control Volume

Figure 11: Curves Control Volume

The pressure limit of each cycle increases or decreases depending on the circulating volume of the previous cycle. A certain VT and the advantages of the pressure controlled are ensured, since they limit the pressure in the adjusted value. Figure 11 shows the inspiration and expiration without inspiratory pause in the volume graph.

Conclusions

1. For better results in the control modes, more parameters should be taken into account such as the RR, that is, a complete timbre of inspiration to inspiration, by which the inspiratory and expiratory time of the patient is determined.
2. In the volume control to obtain more optimal results, it is necessary to have a way to control the amount of flow because when a volume level is set with a certain time the flow rate must be handled to obtain the desired volume in time required.
3. In conclusion, an easy-to-assemble fan simulator model was designed to understand how a hospital-grade mechanical ventilator works. With this tool it is possible to instruct doctors about the ventilation issue and its different control modes, so that at the moment it is used a device of these can understand its operating principle.

Bibliography

MacIntyre, NR., et al. Mechanical Ventilation, 2nd ed. 2009.

Marco Ranieri, Rocco Giuliani, Tommaso Fiore, Michele Dambrosio, Joseph Milic-Emili. Volume-Pressure Curve of Respiratory Sistem Predicts Effects of PEEP in ARSD: Occlusion versus Contant Flow Technique. Am J Respir Crit Care Med.; Vol 149. pp 19-27, 1994. 

Benito S.: Sustitución total de la ventilación. En: Net A, Benito S, eds. Ventilación mecánica. 3ª ed. Barcelona: Springer-Verlag Ibérica; 1998. 

T

ELECTRICAL SAFETY – PATIENT SECURITY (report one )

BACKGROUND

an electric current is an ordered movement of free charges, usually electrons a crossing of a conductor of material in an electric circuit. the electric current can be of two types, alternating current and direct current, this depends on the movement of the electrons.

Direct current: movement of electrons in the same direction, it is used by all devices that work with batteries or batteries, or which are connected to a power source.

Alternating current: the movement of the electrons changes direction every so often, Alternating current is used by all devices connected directly to the electrical network.

Figure 1: Movement of electrons through time

for the operation of any device, equipment and technology, it is necessary to access the electrical network for current consumption, this is done by means of sockets.

A socket is formed by two elements: plugs and receptacle, which are connected to each other to establish a connection that allows the passage of electric current.

Figure 2: Electrical Outlet

the frequency that the current sockets in Colombia handle is 50-60 hertz, this means that in the sockets and terminals of any device turned on, the positive and negative poles are inverted 50-60 times in a second. It means that the electrons are changing direction successively and what is transmitted are vibrations.

the manipulation of current brings with it danger for the health, for this reason it is important to have rules that regulate all the electrical installations.As an example, there are different electrical symbols and colors that identify risks in the RETIE:

Figure 3: main graphic symbols




Figure 4: Classification and colors for warnings

The most common electrical risk factors are electric arcs, absence of electricity, direct contact, indirect contact, short circuit, static electricity, defective equipment, overload, etc.

and finally, when an electric shock accident occurs, the following steps must be taken:

1. First, call the emergency services.
2. Do not touch the person until you are sure you are not in contact with any electrical source.
3. If you are in contact, look for ways to cut the power. It may be a switch or it may be that the cable has to be cut, in which case it will be done with a well insulated tool and with the proper protectors and insulators. Make sure you do not wear wet clothes and if you are standing on puddles or wet floors.
4. If you can not find a way to cut off the current, you will use a wooden object, plastic (a chair, a stick ...) or any non-conductive element of electricity to separate the victim.
5. If it is a high voltage line, do not approach more than six meters while there is electric current. Try to cut the flow of electricity and only then approach.
6. Once separated from the current and secured the victim, avoid moving as far as possible, especially the neck and head, as it could have some spinal injury.
7. Check your degree of awareness and breathing. In case you do not breathe, proceed to perform cardiopulmonary resuscitation maneuvers
8. Treat burns with water or saline to clean them, and cover them with sterile gauze or clean cloths.

DESIGN
a current socket consists of three basic parts: the phase, the neutral and the earth. The neutral is a conductor with potential 0 or potential difference 0. Its function is precisely to create an imbalance, a potential difference that allows the existence of electric current by the Phase conductor, this term refers to the active conductor, that is to say the conductor that transports the electric current normally from the network to a socket or switch. The ground, or ground, is a conductor with a protection function, The objective is to conduct possible overvoltages to ground.

These three drivers are classified in single-phase installations: They are the most common in homes, and are characterized by transporting the current through a single phase. They usually have one phase, one neutral and one ground.

Three-phase installations: They are more common in shops, industrial buildings and factories, within this type there are several configurations:

Tripolar (three conductors): gray, brown and black (the three phases).

Tetrapolar (four conductors): gray, brown and black (the three phases) and blue (neutral).


Pentapolar (five conductors): gray, brown and black (the three phases), yellow-green (earth) and blue (neutral)

Figure 5: three phase socket

Figure 6: single phase socket

      DEVELOP

Regulate electrical outlet   

Ground System	Voltage  (V ac)
PH-Neutral	115,9
PH-Ground	115,9
Ground-Neutral	0,18

 No regulate electrical outlet

Ground System	Voltage  (V ac)
PH-Neutral	117,7
PH-Ground	117,7
Ground-Neutral	0,23

The white outlets (no regulated) are of a general electrical circuit. Orange outlets (regulated) come from another circuit of which the ground wire is not of the general network, it is an isolated ground wire and it is also because the phase comes from a UPS. This insulated ground cable is to protect the equipment that is connected to this circuit.

EFFECTS OF ELECTRIC CURRENT ON THE HUMAN BODY

When some part or parts of the human body come into contact with two points or objects between which there is a potential difference (voltage), the passage of an electric current through the body is established, which can produce very different effects, from a slight Tingling to death as shown in table 3

CURRENT (mA)	EFFECTS
0-0,5	Does not cause physiological damage or sensations.
0,5-10	Does not cause physiological damage but causes sensations of tingling, cramping and movements caused by reflexes.
10-15	Threshold of not letting go, causes pain and muscle contractions.
15-25	With this current the body begins to present contractions in extremities, respiratory distress, increase blood pressure, this current is the limit of tolerance by the body.
25-50	Start of ventricular fibrillation, unconsciousness, increase in blood pressure.
50-200	The ventricular fibrillation occurs, produces burns, initiation of electrocution
200-1000	Reversible cardiac arrest, also produces burns and unconsciousness, risk of death
1000-5000	Severe burns, cardiac arrest with high probability of dying

table 3: effects of electric current

Electrical shock can occur when touching elements subjected to tension, such as cables or bare metal bars (direct contact), or objects, normally harmless, whose voltage is due to faults and insulation defects (indirect contact).

keep in mind that low frequency alternating current (50 - 60 Hz) that is distributed through the network can be up to 3 or 5 times more dangerous than continuous. highlighting that this current is the one we are most exposed to because it is what we find in homes, stores, etc.

CONCLUSION

Nowadays the technology is advancing rapidly and a lot of these advances are electronic so they use an electric source, many of them a current outlet for that reason it is very important to know how it is conformed the current outlets and what happens when you enter contact with different intensities.


In the hospital environment, only vital equipment must be connected in the regulated outlets, that is, machines that provide vital support to the patient.

The electrical risks are related to the electrical systems of the machines, because we are in permanent contact either in our place of work, study, homes, etc., if they come into contact with people or facilities can cause injuries and damage.

with respect to the measurements made, the voltage difference found is approximately 3 volts and is an ideal difference, so it is concluded that the connections are made correctly.

BIBLIOGRAPHY

Gordejuela, L. and &rarr;, V. (2017). Efectos de la corriente eléctrica en el cuerpo humano (II): La edad de la gran potencia. [online] Los Mundos de Brana. Available at: https://losmundosdebrana.com/2014/11/25/efectos-de-la-corriente-electrica-en-el-cuerpo-humano-ii-la-edad-de-la-gran-potencia/ [Accessed 2 Feb. 2019].

Insht.es. (2019). corriente eléctrica: efectos cuerpo humano. [online] Available at: http://www.insht.es/InshtWeb/Contenidos/Documentacion/FichasTecnicas/NTP/Ficheros/301a400/ntp_400.pdf [Accessed 2 Feb. 2019].

RESOLUCIÓN NO. 9 0708 de AGOSTO 30 de 2013, REGLAMENTO TÉCNICO DE INSTALACIONES ELÉCTRICAS (RETIE).

GLOSSARY

GLOSSARY

GLOSSARY REPORT ONE

This glossary will be complemented with each one of the guides that will be made

Voltage: also called "potential difference" and more familiarly "voltage" is related to the work capacity that an electric charge can perform.

Intensity: is the amount of electricity "electric charge" that circulates through a conductor per unit of time.

Electrocution: occurs when said person dies due to the passage of current through his body.

Ventricular fibrillation: consists of the anarchic movement of the heart, which stops sending blood to the different organs and, even if it is in motion, it does not follow its normal rhythm of functioning.

obtenido de https://www.icba.com.ar/pacientes/educacion-para-pacientes/enciclopedia/fibrilacion-ventricular

Tetanization: we understand the uncontrolled movement of muscles as a result of the passage of electrical energy.

Threshold of perception: Minimum value of intensity that causes a sensation in a person.

Threshold of reaction: Minimum current that produces a muscular contraction.

No-drop threshold: Maximum value of the intensity for which a person can be released from electrodes that cause the current to pass. In alternating current it is considered that this value is 10 mA, for any time of exposure.

Ventricular fibrillation threshold: Minimum value of the intensity that can cause ventricular fibrillation. It decreases substantially when the duration of the current passage extends beyond a cardiac cycle. It is the leading cause of death from electrical accidents.

UPS (Uninterruptible Power Supply): It is a source of electrical supply that has a battery in order to continue giving energy to a device in the case of electrical interruption. 

Neuter It is a zero potential cable, that is, it has no electrical charge or voltage. Exactly the same as the ground wire, that's why the current flows and closes the circuit.

Phase This term refers to the active driver, that is, the driver that transports the electric current normally from the network to a socket or switch in our house or office.


Electric discharge Decrease in electrical charge of a body. But that decrease is always equivalent to the passage of charge to another body, which creates an electric current between the two.

GLOSSARY REPORT TWO

Ventilation modes: Relationship between the different types of breathing and the variables that constitute the inspiratory phase of each breath (sensitivity, limit and cycle). Depending on the workload between the ventilator and the patient there are four types of ventilation: mandatory, assisted, spontaneous.

Volume: In volume controlled ventilation mode, a specific volume (circulating or tidal) is programmed to obtain an adequate gas exchange. Usually a tidal volume of 5-10 ml / kg is selected in adults.

Respiratory frequency: It is programmed depending on the ventilation mode, tidal volume, physiological dead space, metabolic needs, level of PaCO2 that the patient should have and the degree of spontaneous breathing. In adults it is usually 8-12 / min.

Flow rate: Volume of gas that the ventilator is able to provide to the patient in the unit of time. It is between 40-100 l / min, although the ideal is the one that covers the patient's demand.

Flow pattern: The fans offer us the possibility to choose between four different types: accelerated, decelerated, square and sinusoidal. It is determined by the flow rate.

Inspiratory time Inspiration-expiration relationship (I: E). 

Time inspiratory is the period that the ventilator has to provide the patient with the tidal volume that we have selected. Under normal conditions it is one third of the respiratory cycle, while the remaining two thirds are for expiration. Therefore the ratio I: E will be 1: 2.

Sensitivity or Trigger: Mechanism with which the ventilator is able to detect the respiratory effort of the patient. Normally it is placed between 0.5-1.5 cm / H2O

FiO2: It is the inspiratory fraction of oxygen that we give to the patient. In the air we breathe is 21% or 0.21. In the MV, the lowest possible FIO2 will be selected to achieve an arterial O2 saturation greater than 90%.

PEEP: Positive pressure at the end of expiration. It is used to recruit or open alveoli that would otherwise remain closed, to increase the average pressure in the airways and thereby improve oxygenation.

Alarm Systems: These provide the ability to control the patient, the circuit and the equipment. They should be precise, simple when programming and interpreting, ideally audible and visual and should inform when the upper or lower limits are exceeded. They can be active, if they automatically activate security mechanisms, or passive, if they only notify.

GLOSSARY REPORT THREE

Cauterization: is a clinical term used to describe the body burn used to extract a part of it. The main forms of cauterization used today are: electrocautery and chemical cauterization.

Electrofulguracion: Procedure that uses electric current to kill cancer cells. The tumor and the surrounding area are burned and then extracted with an acute instrument. It is used for the treatment of superficial precancerous lesions.

Pure wave: The pure wave is the sinusoidal, which delivers the distribution network and is generated by rotating machines (alternators).

Cushioned wave: it is a wave whose amplitude decreases with time eventually reaching zero

Incision: Cut made in a body or surface with a sharp or sharp instrument.

Coagulation: process by which the blood loses its liquidity becoming a gel, to form a clot. This process potentially leads to hemostasis, that is, the cessation of blood loss from a damaged vessel, followed by repair

GLOSSARY REPORT FOUR

Bolus: Amount of liquid in ml that you want to administer to the patient at the maximum rate of infusion.

Flow: Is the result of dividing the total volume in milliliters and the total time in hours and / or minutes, the units given for the flow are milliliters / hour.

Peristaltic Movement: Rhythmic, undulatory and automatic movement performed by different parts of the digestive system to advance food.

Figure 1: Example Movement Peristaltic 

Peristaltic pump: Is a type of positive displacement hydraulic pump used to pump a variety of fluids.

Figure 2: Example Movement Peristaltic Pump

Percursor: It is understood that it is a syringe pump.

Real Time: Is the elapsed time it has taken the infusion pump to administer the liquid corresponding to the actual volume.

Rank: Flow interval, volume or time limited by one minute and a maximum to be programmed.

Total Time: It is the time in hours and / or minutes defined to administer to the patient the corresponding total volume.

Time Remaining: It is the difference between the total time and the real time, in units of time in hours and / or minutes that are lacking in order for the remaining volume to be administered to the patient.

GLOSSARY REPORT FIVE

Phototherapy: It is a treatment for jaundice, which involves placing fluorescent lights on the baby's bed to help disintegrate the bilirubin.

Incubator: It is a special closed cradle with controlled temperature to keep the baby.

Neonate: Is a newborn infant until 6 weeks of age.

Neonatology: Branch of medicine that is responsible for the study and care of the newborn.

Premature delivery: It is when the contractions cause the cervix (the lower opening of the uterus) to thin and open, within three weeks of the estimated date of birth.

Newborn at full term or mature: is one who was born between 37 or 42 weeks of gestation.
Newborn preterm, premature or immature: Is one who was born before 37 weeks of gestation.
Post-term or post-mature newborn: Is one born after 42 weeks of gestation.

GLOSSARY REPORT SIX

Cardiac Wave Form:

Power: source of power is the device that converts alternating current (AC), in one or more continuous currents (DC), which feeds the various circuits of the electronic device to which it is connected

Energy: source of renewable energy that is obtained by the movement of electrical charges that occur inside conductive materials

ECG: graphic representation of the electrical activity of the heart in the function of time, which is obtained, from the body surface, in the chest, with an electrocardiograph in the form of a continuous tape.

Heart frequency: Measure the number of times the heart at the last minute. After 10 years, a person's heart rate should be between 60 and 100 beats per minute while at rest.

Bifasica Wave: Wave composed of two phases of opposite polarity

Monofasica Wave: They discharge unipolar or single-phase current, that is, a single direction of current flow. Within this group there are two waveforms, the monophasic damped sinusoidal in which the current flow returns to zero gradually and the monophasic truncated exponential in which it is electronically terminated before the current flow reaches zero.

Unicameral: a cardiac chamber

Bicameral: two cardiac chambers 

Galvanic resistance of the skin: The galvanic skin response (GSR), also called electrodermal activity (EDA) and skin conductance (SC), is the measure of the continuous variations in the electrical characteristics of the skin, for example the conductance, caused by the variation of the sweating of the human body

GLOSSARY REPORT SEVEN

Electrotherapy: application of energy from the electromagnetic spectrum to the human organism, to generate desired and therapeutic biological responses on the tissues.

Electricity: physical property of matter, consists of that negative, or positive interaction between protons and electrons of matter.

Polarity: property that some physical agents have to accumulate their effects in opposite points of certain bodies.

Current intensity: a magnitude that reflects the level of electricity that a driver passes through in a certain time span.

Frequency: physical phenomenon that repeats cyclically a certain number of times during a second of time, and can range from one to millions of cycles per second or hertz.

Impedance: resistance to the passage of an alternating current.

Power: speed at which energy is consumed.

Anode: electrode with positive charge.

Cathode: negative electrode.

Electrode: end of a conductor in contact with a medium, which leads or receives an electric current.

Pulse width: type of voltage signal used to send information or to modify the amount of energy that is sent to a load.

Biphasic: impulse that deviates in a direction of the isoelectric baseline and then deviates in the opposite direction to the baseline by doing two phases per impulse.

Monofasica: in a direction of the isoelectric baseline and returns to the baseline for a fine amplitude with identical phase characteristics.

Electrophoresis: technique for the separation of molecules according to the mobility of these in an electric field.

Short wave: use for therapeutic purposes of high frequency currents between 10 and 300 megacycles with a wavelength comprised between 30 meters and 1 meter.