INFUSION PUMP

PERISTALTIC INFUSION PUMP

BackGrounds

Figure 1: Infusion Pumps

The infusion pump is an electronic device capable of providing, by means of its programming and in a controlled manner, a certain substance by intravenous (para-arterial infusions) or oral (enteral infusions) to patients whose condition requires 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. To assess the competitiveness of a device, characteristics such as accuracy in the amount of substance infused (normally with errors of 5%), accuracy in the established time interval, ease of use and programming, safety alarms are taken into account. etc.

Feeding

Normally the pumps work both with the power supply of the electric network and with internal battery. If the pump runs on the mains and is disconnected or fails, it automatically switches to battery power. Before reaching the exhaustion of the battery the pump gives an alarm signal.

Drive mechanism

Part of the team responsible for carrying out the pressure in the administration set to achieve the perfusion of the liquid. It is usually composed of a motor controlled by a microprocessor that generates impulses proportional to the perfusion flow. The motor normally moves a piston or peristaltic mechanism that performs the pressure on the administration set.

Venocolysis device

Figure 2: venoclysis device and its parts

Its use is in the medical area since it is a device intended to enter intravenously, either peripheral or central, the continuous infusion of fluids. Normogotero that is made with different types of medical grade plastic and whose main feature is to provide a drip between 28 and 32 drops per minute.Microgotero that besides having medical grade plastic, has a metal cannula that offers a drip of 56 to 64 drops per minute.

Types of Infusion Pumps

Peristaltic Pumps

Figure 3: Parts of a Peristaltic Infusion Pump

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

Figure 4: example syringe pump,https://www.pardell.es/curso-bombas-.html 

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.

Rotating Peristaltic Pumps

It is perhaps the least accurate of all pump systems and is not generally used in the intravenous application of medications. Its use is focused more on the administration of food, as is the case of parenteral nutrition. The rotary pump is also widely used for the infusion of blood in the operating room, during the implantation of a bypass or in blood banks for the processing or separation of plasma cells.

Implantable Infusion Pump

Figure 5: Implantable Infusion Pump http://www.sonivega.com/ELECTROMEDICINA/Paginas/BOMBAS_DE_INFUSION..html

An implantable intrathecal infusion pump for pain is a way to alleviate some types of long-term (chronic) pain or pain caused by cancer. Send an analgesic medication through a thin, flexible tube A small electronic device is used to control the pump.

Security - Alarms

The infusion equipment must have minimum safety measures:Accuracy of operating data: the equipment must maintain the accuracy established by the manufacturer or higher. The most usual precision values ​​are between 3 and 10%.

Opening maintenance rate, TMA (also known as MVA, maintenance of the Open Vein): these are predetermined low values ​​of the perfusion rate in order to keep the patient's duct open.

Maximum perfusion pressure: maximum pressure that the equipment can generate under conditions of total obstruction at the end of the patient's duct.

The minimum alarms that a pump must carry are the following:

• Food Alarm
• Obstruction Alarm
• Air Detection Alarm
• Empty Container Alarm

DESING

electrical diagram:

figure 6 electical diagram

For the design of the infusion pump a peristaltic motor is used, which from the control of PWM sent from the arduino, which allowed the amount of fluid to be released, for this the characterization of the motor was made as shown in figure 6 On the other hand, the mode of operation of the prototype carried out consisted of entering the parameters of volume and time, and from this, determining the flow that would be released by the motor, the control of the exhausted liquid alarm was made from the use of electrodes that when in contact with the fluid closes the surgeon and sends a 1 to the arduino and when the liquid is finished the circuit is opened causing a zero to be sent to the arduino allowing it to be detected when the fluid runs out, On the other hand to stop the bubbles was made use of a barrier sensor that allowed analogously to determine when there was one.

RESULTS

After making the code and the model began to relate the value of PWM with the flow, to do this we post the volume pumped by the engine in a given time (one minute), giving the following table (table 1):

Table 1: Characterization table.

The points that were obtained after characterizing the motor were related in a linear way, and when tests were carried out, lags of up to 5ml were obtained, therefore, the trend line was changed to an exponential one (figure 7).

Figure 7: Characterization.

The fully finished model can be seen in figure eight. To control the infusion pump an alpha numeric keyboard is used, to visualize the information an LCD screen was used. When the pump is connected, the screen shows a selection or start menu (figure nine), from this menu the user will select the volume to enter in a certain time, which determines the flow. According to table 1, the operating range of the pump is between 0.183-1.066 ml / s. The pump only goes into operation when the time and volume values are entered.

Figure 8: Finished model.

Figure 9: Start Menu.

A for cycle is used to carry out the operating time, and if conditions were used to execute the alarms. When any of the alarms was activated, the pump stopped, showed the alarm on the screen and activated a buzeer (audible alarm) until the problem was resumed.

CONCLUSIONS

1. The infusion pumps generate mechanical pressure to move the fluid through a tube to the patient's vascular system, helping to administer the fluids with more precision, this causes a greater accuracy in the drip rhythm than the gravity systems, saving time since it is not necessary to be regulating the drip flow.
2. The infusion pump precisely administers the infusion despite: the patient's movement, patient's arm position, inadequate catheter fixation, catheter bracing or equipment conveyor tubes, resulting in optimal administration, generating an early recovery decreasing patient complications.
3. To generate the alarms in the code, interrupts can be used. To perform the alarms in this case, we used conditional if nested within a for cycle in which the main function is executed.

BIBLIOGRAPHY

1. Bowcutt M, Rosenkoetter MM, Chernecky CC, Wall J, Wynn D, Serrano C. Implementation of an intravenous medication infusion pump system. J Nurs Manag 2008 03;16(2):188-197.
2. Bombas infusión (Apuntes Electromedicina SEEIC), Xavier Pardell, 2012.

ELECTROSURGICAL

ELECTROSURGICAL

BackGrounds:

An electrosurgical unit (ESU) delivers high-frequency electrical current through an active electrode to produce cutting and coagulation effects on tissues. The frequency of electrosurgery for cutting is between 100 kHz and 5 MHz, which is within the radio frequency (RF) band [1].

At the beginning of the procedure, the passive electrode (or return electrode) is attached to the patient’s body. The surgeon then applies the active electrode to the surgical site to achieve the surgical effect. The active electrode is usually a very small tip electrode, while the return electrode has a large contact surface area with the patient [1]. 

The surgical effect is due to heat created by the RF current at the tissue–active electrode interface. The degree of heating in the tissue depends on the resistivity of the tissue as well as on the RF current density.

Three different tissue effects can be created by an electrosurgical current at the active electrode site: desiccation, cut, and fulguration. 

MODES OF ELECTROSURGERY

monopolar:

The current flows between two electrodes, completely surface different The active electrode has a very small surface to favor the increase of the applied current density, in this way the desired cutting or coagulation effect is obtained. The passive electrode has a very wide surface, ensuring that the current density through it is very low.

figure 1 passive electrode position

bipolar:

the current flows between two electrodes of the same surface, allowing to control in this way the path that runs through the applied current and thus delimiting the tissues that will suffer the desired effect. This mode is usually used basically to produce a coagulation effect.

There are different mixtures between cutting and coagulation producing the waveforms shown in figure 2

figure 2 blend waveform

 Design:

electrical diagram:

figure 3 electrical diagram

To perform the electrobisturi it was necessary to use a signal generator to modify the cut signal in this case an XR2206 was used, on the other hand to control the coagulation signal, a timer 555 was used together with the XR2206 to control this The PWM of the signal, on the other hand to join the stage of high power with the low one was used a relay a tip 122 which is designed for amplifiers of general use and low speed switching.

Mathematical Desing

In order to find the required frequencies, the first thing is to determine the frequency of the generator. Formula 1 was used, where the value of the capacitor was always fixed and the value of the resistor was in our case, a potentiometer was used, the capacitor value was 0.01uF and the value of the ponciometer was 100K

  (1)

To calculate the pulse for coagulation, equation 2 was used, which allows to calculate the pulse frequency of the timer.

(2)

Results:

As a result we obtained the graphs of figure 3 and 4 where we can see that when in cut mode the wave is continuous and the sine wave determines the frequency at which the cut will be made since we use the frequency that comes from the network would not be enough to cut, on the other hand in the other figure you can see that the sine wave is not continuous because to do the coagulation it is necessary to have these times in this way only heats the scalpel allowing the wound to be cauterized more not that it reaches to make the cut. in the coagulation graph there is the same frequency as the cut, varying the time that will be that frequency.

figure 3 graphic coagulation

figure 4 graphic cut

CONCLUSIONS

It was possible to carry out an electrobisturi model capable of helping us to understand the principle of operation of the same, on the other hand it was possible to add new concepts to our lexicon.

It is very important to be careful when determining the frequencies and voltages used because they can cause harm to the patient and the manipulator.

BIBLYOGRAPHY

Juntadeandalucia.es. (2012). Electrobisturíes. [online] Available at: http://www.juntadeandalucia.es/servicioandaluzdesalud/hinmaculada/intranet/view_pdf.asp?id=116022 [Accessed 3 Mar. 2019].

Asit.org. (2019). principles electrosurgery. [online] Available at: https://www.asit.org/assets/documents/Prinicpals_in_electrosurgery.pdf [Accessed 4 Mar. 2019].