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.