ELECTRO-STIMULATOR

ELECTRO-STIMULATOR

GLOSSARY

• Muscle contraction is the physiological process in which muscles develop tension and shorten or stretch (or may remain of the same length) due to a stimulus of previous extension. 
• Endorphin: One of several substances that the body makes that can relieve pain and give a feeling of well-being. Endorphins are peptides (small proteins) that bind with the opioid receptors of the central nervous system. An endorphin is a type of neurotransmitter. 
• Neurotransmitters: chemical substances generated by the body that are responsible for emitting signals (information) from one neuron to another through a process called synapsis.

The electrostimulation is applied by means of an apparatus called 'electro-stimulator' in the most problematic areas, either for the purpose of improving muscular or therapeutic performance. This electrical current causes a contraction in the muscle very similar to the impulses that the central nervous system emits to control the muscular actions.

Muscle electrostimulation devices work depending on the objective pursued when using them, so it is important to choose well the intensity of the discharges that are applied and the area where the electrodes that are directly attached to the skin are placed. The membranes of the cells of the organism are polarized, since there is an unequal distribution of electrical charges between the outside of the cell (positive) and the inside of the cell (negative), where the energy of electrotherapy tries to act precisely. 

Thus, the type of frequency selected in the electrostimulation devices is the key to indicate to our body what type of muscle fiber is being activated or excited, according to the training phase in which we find ourselves, or the health problem that is attempted solve by this technique. 

The lower frequencies are indicated to achieve a relaxation of both the muscle and the person, with an increase in blood circulation and the release of endorphins, but as the band of the electric frequency is raised, the muscle from a typical aspect of aerobic exercise, through a combination of aerobic-anaerobic until reaching anaerobic metabolism, with the highest frequencies, above 50 Hz.

The frequency ranges that can be used in electrostimulation: 

• Range 2-4 hertz: it is a very gentle electrostimulation session, with which the muscle is relaxed, both in case it is overloaded and painful. This band promotes blood circulation and the elimination of toxic substances from the body. 
• Range 4-8 hertz: the session continues to be very smooth, but the body also responds to this electrostimulation. Thus, the organism generates endorphinic substances that contribute to raising the threshold of pain and, therefore, the ability to resist before it. 
• Range 8-12 hertz: although the session is still quite smooth, we begin to notice how the muscle contracts when this frequency range is applied. It is a kind of massage and, therefore, it is accompanied by the benefits of a local massage: intense relaxation in the area, improvement of local blood circulation and muscle oxygenation, as well as a decrease in toxic substances. 
• Range 12-40 hertz: with this intensity the slower muscle fibers are activated, just as it is done with a smooth continuous stroke. It begins, therefore, to work the aerobic capacity of the organism, but without hardly deficit of oxygen.
•  Range 40-60 hertz: this range works mostly intermediate slow fibers, although it can reach some fast, depending on the amplitude. It is one more step of the previous range because it achieves the same effect but expanded: greater muscular resistance and better level of oxygenation. 
• Range 60-80 hertz: this is already a work of strength and development of musculature itself, since both intermediate and rapid muscle fibers are activated.
•  Range 80-120 hertz: fast fibers are activated with great intensity, which improves strength, speed, and also a combination of both.

The electro-stimulator that was developed in practice had a voltage wave, with frequencies from 4 Hz to 14 Hz.

The TENS waves are indicated to reduce pain based on the theory of "GATE CONTROL", that is, the control of the entrance door, which consists of sending the brain a large amount of sensitive sensitive information so that this, the brain, do not receive the information corresponding to the pain. 

The TENS do not make contraction, just a tickling because, when used, they only excite sensory fibers.

    

Frecuencia	Resistencia(K)	Corriente	Voltaje
14	3,10E+05	3,58E-04	2,5
12	3,58E+05	3,74E-04	2,5
10	4,19E+05	3,68E-04	2,5
8	5,32E+05	3,50E-04	2,5
6	6,57E+05	3,58E-04	2,5
4	9,60E+05	3,00E-04	2,5

Electronic diagram and signal 

We use the following electronic diagram to obtain the signal with the desired amplitude and frequency

.

We put the electrodes in the arm and obtained the output of our signal as shown below:  

DEFIBRILLATOR AND PACEMAKER

DEFIBRILLATOR AND PACEMAKER 

GLOSSARY

• Heart rate: number of times the heart beats for one minute.
• Arrhythmias: It is a disorder of the heart rate (pulse) or heart rate. The heart may beat too fast (tachycardia), too slow (bradycardia) or irregularly.
•  Defibrillation: is used in cases of cardiorespiratory arrest, with the patient unconscious, with ventricular fibrillation or ventricular tachycardia without a pulse. They are deadly without treatment. 
• The electrical cardioversion: It is used to reverse all types of reentrant arrhythmias, except ventricular fibrillation. The electric shock is synchronized with the electrical activity of the heart. It can be administered electively or urgently, if the situation compromises the patient's life.

Defibrillation is based on the abrupt and brief application of a high voltage electric current to stop and reverse the rapid cardiac arrhythmias (sustained ventricular tachycardia, ventricular fibrillation); situations in which the number of heartbeats increases excessively or a disorganized electrical activity occurs, because some area or focus of the heart 'triggers' impulses in an uncontrolled manner, which are not effective or produce a hemodynamic instability (deterioration of the vital signs) that can lead a person to cardiac arrest.

The defibrillator is indicated in patients with cardiac arrest, loss of consciousness and ventricular fibrillation. When the heart beats so many times and so disorganized, it can not pump blood and therefore its activity 'stops'. Under these conditions, death ensues in a few minutes if the arrhythmia does not stop. The only measure that can prevent this outcome is electrical defibrillation.

 It is also indicated in patients with a history of myocardial infarction or dilated cardiomyopathy who have poor ventricular function who have not suffered any cardiac arrest, but who are at high risk of suffering from a dangerous cardiac arrhythmia (primary prevention).

The pacemaker is an electronic device that sends impulses to the heart to maintain the normal rhythm. An artificial pacemaker is an electronic device designed to produce electrical impulses in order to stimulate the heart when physiological or normal stimulation fails. These impulses, once generated, need a conductor cable (or electrocatheter) that stands between them to reach their goal. In this way, a cardiac stimulation system consists of a generator of electrical impulses (or pacemaker itself) and a cable.

Pacemakers, in general, are indicated for heart rhythm disorders with abnormal decrease in heart rate. And there are two main causes of an abnormal fall in heart rate:

• The inability of the sinus node (cell group where the electrical impulse that gives rise to a heartbeat originates) to produce a sufficient number of impulses per minute: also called 'sick sinus syndrome or sinus node disease'. When the nodule fails, its trigger frequency decreases (number of pulses / minute) and sometimes there are long pauses in which the heart stops beating for a few seconds. Pacemaker implantation is indicated if symptoms such as syncope (loss of consciousness), heart failure (difficulty in breathing, swelling in the legs) or angina (chest pain) occur, as long as these symptoms are secondary to bradycardia.
• The failure of the conduction of the impulses produced by the sinus node to the heart muscle: if atrioventricular AV node disorders occur (cardiac cells specialized in the formation and conduction of cardiac electrical impulses) and of the distal conduction system, The indication of implanting a pacemaker depends on the severity of the disorder and the patient's symptoms. If there is a complete atrio-ventricular block (no conduction of any of the impulses produced by the sinus node), the pacemaker is indicated; if it is of the second degree (there is no conduction of some of the impulses produced by the sinus node), it will only be applied if there are symptoms, and if it is of the first degree (all impulses are driven but with a decrease in the transmission speed) , it is not implanted. There are other circumstances in which its use is indicated.

Types of pacemakers 

Temporary pacemaker: the generator is not implanted in the patient, and can be:

•  Transcutaneous (usually included in some defibrillators): the electrodes are placed on the skin, one in the anterior part of the chest (negative electrode) and another in the back (positive electrode). 
• Intravenous (endocavitary): the electrodes are placed through a central vein to contact the endocardium. Permanent pacemaker: the generator is implanted subcutaneously.

Permanent pacemaker: the generator is implanted subcutaneously.

Pacemaker and Defibrillator code

we declared the pin of input of a button and the size of arrays 

when the button is pressed, we set a discharge of 500 ms according to the value of voltage that the person selected.

In the circuit, we show the correct connection of capacitors from where we get the voltage.

To perform the defibrillation voltage multipliers are used, these are electronic circuits composed of rectifier diodes and capacitors to raise an AC voltage to a DC voltage. The voltages used were: 18, 140 and 260 V.

For show the vector of ECG that we read from signal generator, we did with the next code where we read 80 data in total where the time between data is 1 ms, and the sampling frequency was 125 Hz. 

NEWBORN INCUBATOR

NEWBORN INCUBATOR

GLOSSARY

• Bililuces: Blue fluorescent lights used to treat jaundice.

• Bilirubin: A yellowish waste product that is formed when red blood cells break down

• Blood gases: Levels of oxygen and carbon dioxide in the blood. 

• Jaundice: Yellowing of the skin and eyes due to the accumulation in the blood of a waste product called bilirubin.

• Premature baby: A baby born before 37 completed weeks of pregnancy.

• Phototherapy: Treatment for jaundice whereby the baby is placed under blue fluorescent lights, sometimes called "bililuces." 

• Radiant heater: an open bed with an upper heating element to keep the baby at a warm temperature. 

INCUBATOR

The incubator is a closed chamber that has the purpose of providing an environment conducive to the maturation of premature or newborn babies. It is made of transparent material, has a padding to put the baby to bed and has air intakes and windows.

In addition, they include control systems that allow to know in real time the weight, the heart rate and the brain activity of the child. That is, indicate minute by minute the actions performed by the baby's body.

Functions of the incubator

There are certain characteristics that an incubator must have in order to effectively meet its objective. These are the main ones:

• Servocontrol: it is a sensor that sticks on the baby's skin to measure its temperature. If it is low, the incubator automatically emits heat. If it is high, it does the opposite. 
• Isolation: one of the essential tasks of these devices. The air filters that the incubator has keep away the germs and allergens that are outside. That is why it is such an important element for babies with problems in their immune system. 
• Humidity sensors: in the same way in which the temperature is controlled, the humidity inside the appliance is measured. If there is very little, dehydration of the baby could be favored. 
• Oxygen source: with the aim of preventing respiratory diseases in neonates, the incubator offers an environment with a high oxygen content.
•  Assisted breathing: in severe cases where babies can not breathe on their own, they are incubated and a pump is placed to help them complete this process mechanically.
•  UV rays: the ultraviolet light in the incubator, which is administered in moderate amounts, is used for the activation of endogenous vitamin D and to combat jaundice, which is the yellowish color seen in the skin of some newborns

The incubator provides the fundamental tools for the control of newborn functions. It also allows isolating it from environmental threats that can cause complications in beings so small and, often, defenseless. 

The most common cases in which it is necessary to place the baby in an incubator are:

• Birth of premature babies: it is considered premature to that baby who has not exceeded 37 weeks of pregnancy. This can be caused by several reasons, such as high blood pressure of the mother or complications in the final phase of pregnancy. The incubator allows you to shelter them until their development is completed.
•  Low birth weight: babies underweight are considered to be those with less than 2.5 kilograms at birth. Whether it is a birth on time or premature, the incubator is responsible for protecting the baby while it is delivered orally or by infusion the nutrients that your body needs. 
• Difficulties to maintain the temperature: as it has a constant temperature, the incubator allows to counteract this deficit.
•  Deficiencies in the immune system: until they develop the capacity of self-defense against pathogens, babies - usually premature babies - are conserved in this environment free of germs and microbes that may represent a threat to their health.

There are four main types of incubators depending on where the heat comes from:

•  The closed ones have a glass cover that completely covers the baby and does not expose it to the ambient air. The heat comes out from the bottom, where the baby is lying. Its main characteristic is that the baby is not subjected to cold currents and will not lose liquids by evaporation because it is in a medium in which the air is also hot.
•  The open ones are also called radiant heat because there is not a wall that covers the baby, but in the upper part, at a reasonable distance, there is a tower that has a source of radiant heat.
• Stationary Incubators: In this group are the incubators that are located in the areas of emergency, intensive care, intermediate care and temporary care and eventually in areas assigned to physiological care.
•  Transfer incubators: as the name implies, are equipment used to transport neonates either within the medical unit or outside the medical unit. Said transport can be land or air. In general, they are lighter and smaller in order to facilitate their mobility and handling to enter or exit emergency vehicles, operating theaters, x-ray rooms, etc.

POWER STAGE 

The power stage is designed to control the inmersion resistor and the hot resistor, when the arduinos send 5v to the power stage, the resistors turn on and begin to generate temperature and humidity.

NEWBORN INCUBATOR DESIGN 

NEWBORN INCUBATOR RESULTS 

Call libraries to LCD, DHT11 and matricial keyboard

Code of the Keyboard we declared a pair of constants rows and columns of the keyboard, and columns of the keyboard, and ones arrays for indicate to the library what pins of arduino correspondence to rows and columns of the keypad.
We defined what symbols corresponding to each position of the keys too.

To read the humidity and temperature the sensor brings its own library, as shown below.

Characterization of the fans

To start, the user set the weight and week's gestation as shown in the following tables

Temperature

Humidity

According to the tables, a linear regression is calculated to control the humidity and temperature values through the speed of the motors controlled by the PWM, as shown below.

 

PUMP INFUSION

PUMP INFUSION 

GLOSSARY

• Cannula: Short rubber tube or other material that is applied to various medical and laboratory devices, such as that used in medicine to evacuate or introduce fluids into the body.
• Occlusion: Closing or narrowing that prevents or hinders the passage of a fluid through a pathway or conduit of the organism.
• Peristaltic: The peristaltic movement or peristalsis, is what has the property of achieving contraction, and in the field of Biology can be defined as a successive series of contractions that are made in the process of digestion.

Operating principle

An infusion pump is an electronic device capable of supplying, through its programming and in a controlled manner, a certain substance intravenously to patients who, due to their condition, require it.

The use of these devices is very important because they reduce the percentage of human errors in the intravenous drug supply, regulating in a rigorous way the flow of liquids inside the patient under a positive pressure generated by the pump.

The pumps provide greater accuracy and safety in the infusion of drugs than traditional flow control methods (controllers), are capable of exceeding small occlusion pressures, can overcome the resistance of the antibacterial filters and arterial lines to the infusion and They can infuse drugs with great precision at very low speeds.

Types of infusion pumps

Peristaltic pumps: They work by pressing a flexible bag or tube to produce movement of the liquid that is inside a container. Two modalities can be found within this classification, linear peristaltic pumps and rotary pumps. Linear peristaltic pumps have a line of finger-shaped discs that compress the tube into a wave form of continuous motion, forcing fluid out of the container toward the patient. Rotary peristaltic pumps use a rotor that presses the liquid into the tube through rollers through a semicircular passage.

Syringe pumps: Preferred when it is required to supply low volumes and low flow rates. These pumps push the plunger of the syringe at a controlled rate to deliver the substance to the patient. The supply rate can be continuous or in steps that provide boluses in a certain time. The syringe is placed in the pump with the plunger fitted on the plunger holder. As the embolus advances, the syringe empties.

CONTROL AND SECURITY FUNCTIONS IN INFUSION SYSTEMS

Currently, most infusion systems have the following functions:

1. Total volume to be infused
Infusion pumps allow the user to select the volume to be infused (VTBI). If this limit is reached before the liquid source ends, most pumps trigger an alarm and continue to infuse liquid into a minimal infusion form known as KVO (keep vein open), for the purpose of prevent the intravenous or intra-arterial cannula of the patient from being blocked by thrombi.

2. Alarms

• Drip alarm. It is activated in case the drip chamber registers an increase or decrease in the programmed flow rate, or a speed of the medication has been introduced during the programming which may result in a delivery profile that is too low for that medication.

• Air alarm In some systems also called vacuum alarm. The sensor can be found inside or outside the system. Record the presence of air in the infusion tube. The delivery of the pump container size is complete, or the pump has detected 2 ml of air in the line.

• Battery alarm. In infusion systems that have their own rechargeable power source when connected to the power source, this device is activated when the power reserve is close to a critical level of operation, after which the pump devices are inaccurate or, not functional.

• Standby alarm. Also called reminder alarm. It works with a time device that triggers an audible alarm when the infusion is temporarily suspended.

• Volume alarm Used in most infusion pumps, by means of audible and / or visible devices. It is activated when the infusion of the volume selected by the user is completed. Start infusion in KVO mode.

• Alarm due to overuse of air-liquid discharge. In multiple infusion pumps, this device is operated when the specified purge limit of the system has been exceeded.

• Alarm by occlusion. The system detects an occlusion between the pump and the patient.

The alarm conditions are detected by ultrasonic or pressure transducers, and optical sensors. In some pumps a sensitive device is placed in the drip device of the infusion set.

Many infusion devices contain self-diagnostic programs to facilitate the initiation of an infusion and to alert the user of existing problems or impairments.

Characterization of the sensor 

To know how the engine works, we did a characterization, where we measured the amount of volume thrown in a minute with different pwm.  

the regression was this: 

In the regression equation the variable "x" is replaced by "volume/tiem", so that when the user wants work for more than one minute, the machine works correctly.  

Programming Code 

Call libraries to LCD and matricial keyboard

Code of the keyboard, we declared a pair of constants rows and columns of the keyboard, and ones arrays for indicate to the library what pins of arduino correspondence to rows and columns of the keypad. 

We defined what symbols correspondence to each position of the keys too. 

First, we pass the characters to numerical value, after we create a void to save in a matrix the numerical values and with this is with the that we can able to work. 

To start, the user set the volume, if this volume have a values between 11ml and 1000ml, we save the volume value in the variable “volumenval”. 

Then the user set the time(minutes) in which he wants the volume to be entering into the patient, if the time is between 1 and 60, the time will save into a variable “tiempoval”,  then  we convert this time to seconds and we put this value and the value of "volumenval" in the sensor characterization equation to start to work. 

we did two alarms to the pump infusion, this alarms are occlusion and  when the machine haven't enough water. this alarms were do with two infrared sensors that were located in strategic parts of the machine. 

ELECTROSURGICAL UNIT

ELECTROCAUTERY

GLOSSARY

• Coagulation: process by which the blood loses its liquidity becoming a gel, to form a clot. This process potentially results in hemostasis, that is, in the cessation of blood loss from a damaged vessel, followed by repair.
• Electrode: device such as a metal plate or a small needle that conducts electricity from an instrument to a patient undergoing treatment or surgery. The electrodes can also carry electrical signals from the muscles, brain, heart, skin or other parts of the body to the recording devices to help diagnose certain conditions.
• Galvanic skin response (GSR): also an electrodermal activity (EDA) and skin conductance (SC), is the measure of the continuity of skin characteristics, for example, conductance, caused by variation Of the sweating of the human body. 
•  Hemostasis: is the ability of an organism to make blood in the liquid state remain in the blood vessels. Hemostasis allows the blood to circulate freely through the vessels and when one of these structures is damaged, it allows the formation of clots to stop the hemorrhage, later repairing the damage and finally dissolving the clot.
• Impedance: Apparent resistance of a circuit equipped with capacity and self inductance to the flow of an alternating electric current, equivalent to the effective resistance when the current is continuous. 
•  Tissue damage: type of injury or injury suffered by the skin. A cut, a bruise or a burn.
• Vascularization: Presence and disposition of the lymphatic blood vessels in a tissue, organ or region of the organism. The way in which the vessels are distributed in a certain organ.

The electrocautery

Also called electric scalpel, surgical unit or HF device, is an electrical device that converts electrical energy into heat to cut, remove or coagulate soft tissues such as meat, thanks to currents that are above 200,000 Hz. 

These frequencies are used because they only produce heat and, if lower frequencies are used, they could interfere with the nervous processes of the body.

The operation of the electrocautery: 

It circulates high frequency current and moderate or high intensity between two electrodes applied to the body. This causes that heat is generated in the place applied and cut (electrosection) or coagulate (electrocoagulation) the tissue.

 The currents can be of two types: direct current or alternating current. In direct current, also called galvanic current, there is a continuous and one-way exchange of electrons between two opposite poles. 

In the alternating current, the exchange of electrons is bidirectional and the magnitude and direction vary cyclically in a sinusoidal manner

Effects of the current on the tissue: 

When the current is applied to human tissue, the following effects occur:

•  Faradic effect: the alternating current of low or medium frequency provoke stimulations in muscles or nerves, something that can produce tetany, premature ventricular fibrillation, or in the worst case, death. The maximum impact occurs when the current is about 100 Hz, and decreases as the frequency increases, because with high frequencies its harmful effect is lost.
•  Electrolytic effect: an ion current is produced in the tissue caused by the electric current. With direct current the positive ions would move towards the negative pole and the negative ions towards the positive pole, causing tissue damage. For this reason direct current is not used. Instead, with the alternating current the ions are displaced permanently changing direction, something that does not cause any damage to human tissue. 
• Thermal effect: it is produced with high frequency alternating current, something that is used in current electrocautery and that avoids the two previous effects.

Types of electrocautery 

The surgical units have two modes of operation: 

• Monopolar mode: It has a large surface electrode, called a return electrode, and a smaller one called an active electrode. The current density that is generated at the contact point of the active electrode is high, which is why a large amount of heat is concentrated in it. 

Active electrode Depending on the shape of this electrode, one effect or another is achieved on the tissue. If the contact surface is smaller, the current density increases, and with it the generation of heat at the contact point, which results in a cut. In contrast, a larger contact surface is used to coagulate the tissue.

Return electrode The return electrodes have a low contact impedance with the skin, have a large surface ranging from 100 to 200 cm² and are very adhesive. It can be of two types: solid, which have a continuous conductive surface, or split, consisting of two pieces to be able to monitor the contact between the electrode and the skin. It should be placed in muscular masses with good vascularization, preventing parts of the body with irregularities and with a lot of bone. In case it is placed preventing a good contact between the electrode and the skin, it can cause an increase in the contact impedance and lead to burns.

•  Bipolar mode:The current is applied between the two tips of an instrument, which are usually clamps or scissors. The current generated between the two tips causes heat to be generated, which is delivered to the fabric. The bipolar electrosurgical units have a lower power density than the monopolar ones, and this means that they can not produce cuts in the tissue (except for some exceptions). With them, hemostasis can be performed using modulated or unmodulated current. It is usually used in endoscopic applications or to seal vessels.

Types of electric wave generated by the electrocautery 

All high-frequency electrosurgery equipment generates an oscillatory wave known as a sine wave. There are two types of waves, damped sine waves and pure sine waves.

• Damped sine wave (damped): A damped sine wave is a waveform that occurs as a group of oscillations, the first oscillation of the group presents the maximum amplitude followed by a train of small waves. This type of wave has a wide effect on living tissue, which results in excessive heat generation and of coagulation. When the wave is more cushioned, the coagulation and tissue destruction effect increases. As a result, the greater the damping in the wave, the greater the hemostasis.

• Sine wave undamped (undamped) or pure An undamped sine wave is a pure, balanced and symmetric wave, in which the amplitude in all oscillations is the same. A pure sine wave produces an effect in the highly focused tissue, which results in tissue separation with very little coagulation. Since it produces very little damage to the tissue or coagulation, there is no significant hemostasis.

• Wave mixture (moderately damped) The most common form used for cutting current it is usually a mixture of a pure sine wave and a damped sine wave. The combination of both waveforms simultaneously allows to cut with hemostasis. With the proper balance in the mix, the cut can be performed with satisfactory hemostasis and minimal tissue damage.

MECHANICAL VENTILATOR

MECHANICAL VENTILATOR

Glossary

• Inspiratory capacity (CI): The amount of air a person can breathe, starting at the level of a normal expiration and distending their lungs to the maximum (3,500 ml approximately). CI = VC + VRI
• Total lung capacity (CPT): The volume of air in the respiratory system, after voluntary maximum inhalation. It corresponds to approximately 6 liters of air. It is the maximum volume at which the lungs can expand with the maximum possible effort (approximately 5,800 ml). CPT = VC + VRI + VRE + VR
• Vital capacity (CV): Is the amount of air that is possible to expel from the lungs after having inspired completely. They are around 4.6 liters. CV = VRI + VC + VRE
• Mechanical ventilation: or positive pressure ventilation is a procedure that supplements the patient's respiratory function or assists him or her to carry it out.
• Residual volume: the amount of air left in a person's lungs after exhaling completely.
• Respiratory frequency: is the number of breaths a person makes per minute. The frequency is usually measured when a person is at rest and simply consists of counting the number of breaths for one minute each time the chest is raised.
• Tidal volume (VT, or TV): is the amount of air that is displaced along normal inhalation and exhalation, in other words, the amount of air that is breathed throughout normal breathing. In a healthy young adult, the tidal volume is approximately 500 ml per inspiration or 7 ml / kg body mass.

Respiratory Physiology

VENTILATION AND RESPIRATORY MECHANICS: Pulmonary ventilation is the functional process by which gas is transported from the subject's surroundings to the pulmonary alveoli and vice versa. This process can be active or passive depending on whether the ventilatory mode is spontaneous, when it is performed by the activity of the respiratory muscles of the individual, or mechanical when the ventilation process is performed by the action of an external mechanism. 

The level of ventilation is regulated from the respiratory center according to the metabolic needs, the gaseous state and the acid-base balance of the blood and the mechanical conditions of the lung-rib cage complex. The objective of the pulmonary ventilation is to transport oxygen to the alveolar space so that the exchange with the pulmonary capillary space occurs and evacuate the CO2 produced metabolic level.

Inspiratory Time and Relationship I: E: the inspiratory time is regulated taking into account how much time the patient requires to deliver the volume or pressure programmed. It should also be noted that it is not too short to generate discomfort in the patient, nor too long that hinders the time to exhale and generate a PEEP car by not being able to complete the delivery of the gas supplied in the inspiration.

 The relationship between inspiration and expiration or I: E, is usually 1: 2, so if, for example, we program FR at 20 per minute, we will have the inspiration in 1 second and the expiration in 2 seconds, if we do changes in this I: E ratio we will also have to change the flow velocity, so that it can fulfill the inspiratory time as previously explained, without problems in the inspiration, in many fans we have a built-in program that makes the changes automatically.

Gas delivery method: there are basically two ways: 

• To by volume: each respiratory cycle is delivered with the same level of flow and time, which determines a constant volume independent of the patient's effort and the pressure that is generated. The flow wave will generally be a square wave, since the delivery of the flow is constant, some equipment allows to change it to descending or sinusoidal, in order to decrease the inspiratory pressure. They can be controlled totally, partially or spontaneously. 
•  To by pressure: each respiratory cycle will be delivered in inspiration at a preselected pressure level, for a certain time. The volume and flow vary according to the impedance of the respiratory system and the strength of the inspiratory impulse. The most frequent form of flow delivery will be in descending ramp. In this modality, the changes in the compliance of the thoracic wall as well as the resistance of the system will influence the corresponding tidal volume. Thus, when there is greater resistance and less compliance, the volume will decrease and increase if compliance improves and resistance decreases. They can be controlled totally, partially or spontaneously.

Next, we will describe the most frequent ventilatory modes: 

• Volume controlled ventilation (CMV): All breaths are controlled by the ventilator and offers tidal volume (VT) and respiratory rate (FR) predetermined. It does not accept the initial stimulus of the patient so its use is reserved for patients who do not have spontaneous inspiratory effort or are paralyzed. 
• Advantages of CMV: it provides total ventilatory support (tidal volume and constant respiratory frequency), then it controls the minute volume and determines the PaCO2 and the ventilatory pattern.
•  Disadvantages of CMV: ventilation support does not change in response to increased needs, can generate discordance (asynchrony) with the ventilator, so for better coordination may require sedation and paralysis; As a consequence, a variable peak pressure (PIP) can appear and there is also a high risk of cardiovascular compromise. 
• Controlled assisted ventilation (AC): The breaths are delivered as programmed in tidal volume, peak flow and waveform, as well as the base respiratory frequency. The respirations initiated by the machine or the patient are delivered with these parameters, the sensitivity can be adjusted so that the patient can generate a higher respiratory frequency than the programmed one
• Advantages of AC: we will have a Minimal Ventilation (VM) minimum assured, also the volume will be guaranteed with each breath. A better chance of synchronization with the patient's breathing will be given, which then can send its frequency.
•  Disadvantages of AC: if the spontaneous frequency is high, respiratory alkalosis can occur, high pressure can also be generated in the upper airways and have associated complications. Excessive patient work if the flow or sensitivity are not programmed correctly. There may be poor tolerance in awake patients, or without sedation. It can cause or worsen the PEEP car. Possible respiratory muscle atrophy if this form of support is prolonged for a long time.

Constant values 

• Running volume: 500 ml 
• Inspiratory reserve volume: 3,000 ml (with inspiratory effort)
•  Expiratory reserve volume: 1,100 ml (with expiratory effort) 
• Residual volume: 1,200 ml Vital capacity: inspiratory reserve volume (3,000 ml) + expiratory reserve volume (1,000 ml) + circulating volume (500 ml) = 4,500 ml
•  Inspiratory capacity: circulating volume (500 ml) + inspiratory reserve volume (3,000 ml) = 3,500 ml 
• Expiratory capacity: circulating volume (500 ml) + expiratory reserve volume (1,000 ml) = 1,500 ml 
• Total lung capacity: vital capacity (4,500 ml) + residual volume (1,200 ml) = 5,700 ml 

A person at rest performs 12 breaths per minute; if 500 ml is mobilized at each air inlet and outlet, 6000 ml will be mobilized in one minute.

Programming Code

Call libraries to LCD and matricidal keyboard 

Code of the keyboard, we declared a pair of constants rows and columns of the keyboard, and ones arrays for indicate to the library what pines of arduino correspondence to rows and columns of the keypad.

We defined what symbols correspondence to each position of the keys too.

First, we pass the characters to numerical value, after we crate a void to save in a matrix the numerical values and with this is with the that we can able to work.  

If the key is the number one, the machine will start the test, which will trigger the alarm, the compressor and the pressure on the sensor that is appropriate.

We prove the compressor sending a pulse to the pin of compressor and reading this pulse in the pin 22, if pin 22 is high, the compressor be working.

We prove the alarm sending a pulse to the pin of the led and buzzer, this buzzer will sound and led will turn on, also we ask if the  person listen the buzzer for continue to the test.

We prove the pressure sending a pulse to the compressor and to the two-electro valve, thus insufflating the pump and we will check the pressure reading the analog voltage of pressure sensor in the pin A0 of us arduino, if the pressure is the indicated to the input, the pressure will be ok. 

After the pressure was ok, the mechanical ventilator will be able to work.                                             If some parameter of the test its incorrect the test will repeat.

If the key is the letter “B” the person ingress to the adult ventilation. 

If the key is the letter “C” the person ingress to the pediatric ventilation

If the key is the letter “D” the person ingress to the newborn ventilation

After this, the person put the weight according to the patient; this weight will serve us for the mode of ventilation by volume due to the current volume it is gave by 7ml/Kg, so the weight will multiply for seven and we will get the correct volume  for work, but if the mode is of the pressure, the person should put the pressure in mmHg according to the patient 

Getting physiology graphs.

In this case, we can see pressure and volume graphs and their values depends of each patient. In this mechanical ventilator we used a MPX-5100 pressure sensor, giving us a change of voltage when the pressure change in the airways. To Characterize the voltage vs Pressure, we divide it in three cases depending the patient.

Newborn Patient.

 The pressure limit of a newborn patient in this mechanical ventilator is 60mmHg, where the voltage at this value is 0.44volts. Making a linear regression, we have the next Equation:

Replacing in the equation m =230.77, for that reason the linear regression is:

Respect to the volume graphs, we make it depend the pressure value, we can have a volume value with a specific pressure value, in this case, for a newborn patient the pressure limit is 60mmHg and  the maximum volume value is given by the maximum weight in the system (5Kg-35mL), for that reason in this case the linear regression is made between pressure and volume with the following equation:

Replacing the values, we get y=0.5833x where y is the volume to know and x is the pressure value given by the sensor.

Pediatric Patient

The pressure limit of a pediatric patient in this mechanical ventilator is 80mmHg, where the voltage at this value is 0.54volts. Making a linear regression, we have the next Equation:

Replacing in the equation m =222.22, for that reason the linear regression is:

Respect to the volume graphs, we make it depend the pressure value, we can have a volume value with a specific pressure value, in this case, for an adult patient the pressure limit is 80mmHg and  the maximum volume value is given by the maximum weight in the system (65Kg-455mL), for that reason in this case the linear regression is made between pressure and volume with the following equation:

Replacing the values, we get y=5.6875x where y is the volume to know and x is the pressure value given by the sensor.

Adult patient

The pressure limit of an adult patient in this mechanical ventilator is 100mmHg, where the voltage at this value is 0.62volts. Making a linear regression, we have the next Equation:

Replacing in the equation m =227.27, for that reason the linear regression is:

Respect to the volume graphs, we make it depend the pressure value, we can have a volume value with a specific pressure value, in this case, for an adult patient the pressure limit is 100mmHg and  the maximum volume value is given by the maximum weight in the system (220Kg-1.540L), for that reason in this case the linear regression is made between pressure and volume with the following equation:

Replacing the values, we get y=10.26x where y is the volume to know and x is the pressure value given by the sensor.

Power Stage

The power stage is designed like in the picture, the first part is composed by an optocoupler 4n25, it receives the Arduino’s pulse to turn on the compressor , the optocoupler has the function to isolate the ground system of the Arduino from the voltage source, them with a tip122 and a 2n2222a transistor, the current increases and go to a relay, the relay activate the compressor and the electro valves  with a different Arduino pin.  When the compressor is on, one electro valve is on, that is the inspiration process and them, after 1 or 2 seconds, depending the I:E relationship the compressor and the electro valves turn off and the second electro valve turns on completing the expiration.

MAINTENANCE MANUAL MECHANICAL VENTILATOR

To perform the respective maintenance of the equipment it is necessary to take into account the following recommendations: 

1. . It is necessary to disconnect the equipment. 
2.  Uncover the equipment carefully without disconnecting any of the cables.
3.  Aspirate the equipment to remove dust, speck etc. (Use masks) 
4.  Perform a visual inspection (damaged capacitors, loose resistors, loose cables etc). 
5.  Download the equipment streams.
6.  Check the type of power supply of the equipment, if enough voltage and current is arriving:  Compressor: 110-120 V                                 Sensor and relay supply: 12 V   
7.  Check the hoses are well connected 
8. Turn on the equipment
9. Check that there are no loose wires in the arduino.
10. Check if the arduino is connected to a power supply (USB port or charger)
11. Connect the patient simulator ballon
12. Perform the test to check the state of the equipment
13. Check for oxygen leaks
14. Check in the flow sensor is working correctly
15. Test all keyboard keys.

MECHANICAL VENTILATOR USER'S MANUAL

The mehanical ventilator has an LCD where it will indicate the keys that each procedure represents, as can be seen in the following image.

Where A is used to enter the process.

It is necessary to connect the compressor to the 120 V socket and the sensor, electrovalves to 12 V (protoboard elements) Wait for the team to pledge Perform the test recommended by the equipment before performing its respective operation, as you can see in the following video

After the equipment confirms that it is in optimal conditions to start ventilation, the user can choose the following patient options:

B: Adult patient, where the weight range that can be entered is 66-220 kg 

C: Pediatric patient, where the weight range is from 6 - 65 kg 

D: Neonatal Patient, where the weight range is 1-5 Kg

 After entering the type of patient to be ventilated and the weight it is necessary to choose what type of ventilation you want: 

* Pressure 

# Volume