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Artículo Científico / Scientific Paper |
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https://doi.org/10.17163/ings.n27.2022.02 |
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pISSN: 1390-650X / eISSN: 1390-860X |
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DESIGN AND CONSTRUCTIONS OF AUTOMATED MECHANICAL
VENTILATION EQUIPMENT |
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DISEÑO Y CONSTRUCCIÓN DE EQUIPO DE VENTILACIÓN MECÁNICA AUTOMATIZADA |
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Gilberto
Carrillo1 Jaime
Rodas1 |
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Received: 03-11-2021, Received after review:
06-12-2021, Accepted:13-12-2021, Published: 01-01- 2022 |
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Abstract |
Resumen |
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This document presents the requirements met
for the design, construction and initial validation of a mechanical
ventilation system to be used in patients with respiratory insufficiency, which
in the initial context was due to the COVID-19 pandemics. The design required
the use of computer aided drawing software (Computer Aided Design) CAD and
the construction required the use of installed capabilities in mechanical, electropneumatic, electronic, biomedical and automation
manufacturing of institutes and centers of the Universidad Don Bosco (El
Salvador). The adjustment, configuration and programming tasks were in charge
of research professors specialized in these disciplines. The elements used
for its construction were available in the Salvadoran market, considering the
closure of borders as a government measure to face the expansion of the
pandemics. After the design, manufacturing and commissioning stage,
conditions of the supplied air were measured with the help of professionals
dedicated to the maintenance of medical equipment and with the approval of
internist doctors. The results achieved are those obtained with paramedical
equipment and with first aid equipment, and consequently it has been foreseen
that the equipment can be tested in a subsequent instance with the certified
medical union. |
Este documento presenta los requerimientos cumplidos para el diseño, construcción y primera validación de un sistema de ventilación mecánica para ser utilizado en pacientes con insuficiencia respiratoria, que en el contexto inicial fuera a causa de la pandemia de COVID-19. El diseño requirió el uso de software de dibujo asistido por computadora (Computer Aided Design) CAD y la construcción necesitó el uso de las capacidades instaladas en manufactura mecánica, electroneumática, electrónica, biomédica y automatización de los institutos y centros de la Universidad Don Bosco (El Salvador). Los trabajos de ajuste, configuración y programación estuvieron a cargo de docentes investigadores especialistas en dichas disciplinas. Los elementos empleados para su construcción estaban disponibles en el mercado salvadoreño, considerando el cierre de las fronteras como medida gubernamental ante la expansión de la pandemia. Luego de la etapa de diseño, fabricación y puesta en funcionamiento, se realizaron mediciones de las condiciones del aire suministrado con la ayuda de profesionales dedicados al mantenimiento de equipo médico y con el visto bueno de doctores internistas. Los resultados conseguidos son los que se obtienen con equipos paramédicos y con equipos de primera asistencia, por lo cual se ha previsto que el equipo pueda ser probado en una siguiente instancia con el gremio médico certificado. |
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Keywords: Mechanical ventilation, assisted
respiration, COVID-19, respiratory insufficiency |
Palabras clave: ventilatión mecánica, respiración asistida, COVID-19, insuficiencia respiratoria |
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1Centro de Innovación en Diseño Industrial y Manufactura, Universidad Don Bosco, El Salvador. 2,*Instituto de Investigación e Innovación en Electrónica, Universidad Don Bosco, El Salvador. Corresponding
author ✉: mauricio.gomez@udb.edu.sv Suggested
citation: Carrillo, G.; Gómez, M.; Rodas, J. and
Pimentel, R. “Design and construction of automated mechanical ventilation
equipment,” Ingenius, Revista
de Ciencia y Tecnología,
N.◦ 27, pp. 17-22, 2022, doi: https://doi.org/10.17163/ings.n27.2022.02 |
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1. Introduction At the beginning of 2020, America
becomes the epicenter of the SARS CoV-2 (Severe acute respiratory syndrome
coronavirus-2) [1,2], and in March it is declared a worldwide pandemic due to
the ease of propagation because of the globalization phenomenon [3]. The
first confirmed case in El Salvador was registered that same month. At that
time, different protocols were activated to prevent massive infections in the
population. However, hospitals were getting prepared for the attention of
future patients. With the purpose of
visualizing the possible impact of the pandemics in the country, different
scenarios were considered such as the construction of a specialized hospital
for the attention of patients with COVID-19 (Corona Virus Disease - 2019),
strengthening the installed capacity of existing hospitals, oxygen supply,
possible medication for treating patients, training and hiring of medical
staff for attention of patients, among other actions. In this last case, it
is evident that when a patient requires personalized attention with an
equipment for manual assistance of respiration, the medical or auxiliary
staff assisting him/her cannot care other patients, thus becoming a human
resource unavailable for assisting people; this impact may be reduced if an
automated equipment easy to install and easy to use in emergencies is
supplied. The expectation of a
possible shortage of equipment for respiratory assistance motivated
researchers to propose alternative systems of mechanical ventilation [4,5]
from auxiliary manual breathing units (AMBU) [6, 7]. This initiative sought
the collaboration between the Industrial Design and Manufacturing Innovation
Center (CIDIM, Centro de Innovación en Diseño Industrial y Manufactura) and the Research and Innovation Institute in
Electronics (IIIE, Instituto de Investigación
e Innovación en Electrónica), with the management of special resources of
the Energy Research Institute (IIE, Instituto de Investigación en Energía) and the support from the collaboration of the
United States Embassy in El Salvador. To determine the
best design of the system, and considering the strengths and capacity of the
centers and institutes, it was stated that it fulfilled the following
requirements: · Take advantage of the existence of
a manual reviver [8] used by paramedics and internist doctors. · The reviver should be operated
using two systems, one electropneumatic and another
electronic. · Structural accessories should be
easy to manufacture in metal-mechanic shops. |
· The acquisition of the specialized
monitoring sensors would be handled through the American Space UDB of the IIE
[9], due to the national quarantine that made difficult the imports by local
industries. 2. Materials and methods The basic fundamental of the
designed system is an electropneumatic control
system that drives a manual reviving equipment. The operation signals are
controlled by a programmable logical controller, that receives electric
signals from sensors that monitor the heart rate and the level of oxygen
concentration in the air supplied. The first design
stage consisted of meetings between technical researchers and intensive care
doctors from the Hospital San Rafael. The control variables that should be
monitored in patients were determined in these meetings; these variables
include the air volume according to the consistency of the patient, the
number of cycles per minute required by patients according to their clinical
picture, the ventilation pressure, the positive end-expiratory pressure
(PEEP) [4], [10], the air flow, and the inspiratory-to-expiratory (I/E)
ratio. Another important requirement is that the system should operate in
three types of cycles: volume-cycled, pressure-cycled and combination of
both. However, with the approval of the intensive care doctor it was chosen
the volume-cycled, since it is a simple and effective operation mode, always
taking into account that it is an emergency measure [11]. The design should
provide appropriate ventilation for patients prior to releasing a specific
ventilator [12], and thus it was considered the tidal volume and the
respiratory rate that would maintain patients stable [13]. The tidal volume
was determined based on a ratio with the ideal weight of patients and it is
calculated taking as reference the weight of the person: IBW (ideal body
weight, kilograms) men [14]: 50 + 2.3*(size in
inches – 60) or 50 + 0.9*(size in cm
– 152,4) IBW (ideal body
weight, kilograms) women: 45.5 +
2.3*(size in inches – 60) o 45.5 +
0.9*(size in cm – 152,4) With respect to
respiratory rate, the inspiration and expiration cycle is related to the age
of patients, according to the behavior shown in the curve of Figure 1. |
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Figure 1.
Respiratory cycles Figure 1 shows the
I/E ratio [15], inspiration [16] (insufflation) and expiration (exhalation),
which may be adjusted to 1:3. But if the patient condition is preexisting
asthma [17] or exacerbation of chronic obstructive pulmonary disease, it may
be adjusted to 1:4. After obtaining the
operation requirements, the structural design was carried out with the aid of
CAD software [18] and 3D printing light manufacturing [19], with the result
presented in Figure 2.
(a)
(b) Figure 2. Design of the system with the aid of CAD software Figure 2 shows the
design obtained of the structural system and of the electropneumatic
system. Figure 2(a) shows the structural distribution to hold the reviver,the location of the
access points to the inlet and outlet air connections, together with the
valves that regulate the reviver pressure, the mobile door, the cover with
the set of buttons and the information display. |
Figure 2(b) shows
the distribution of the electropneumatic control
system constituted by the 5/3 bistable electropneumatic valve, unidirectional flow regulators,
pressure regulator, programmable logic controller (PLC), ventilator, electric
and pneumatic adapters, supports and configuration of the structural base.
(a)
(b) Figure 3. Construction of the electropneumatic system Figure
3 shows the finalized structural (a) and electropneumatic
(b) systems, ready to carry out tests and measurements. It is important to
remark that all control system elements installed were found at the place,
since imports to El Salvador were not possible as a consequence of the
confinement due to COVID-19 pandemics. This enables replicating the system
without difficulty, in case it is required. A
SIEMENS LOGO version 8.0 micro-PLC was used to control the process. It can
handle 4 digital outputs, better known as output to relays, which are used to
govern the valves and electrovalves required by the
system. Similarly, the buttons enable to control the number of repetitions
per minute demanded by the patient and according to the criterion of the
treating physician. The
control system was designed according to the plot of the respiration process
shown in Figure 1, where |
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the specialist may determine if
the patient requires 12, 14, 16 or more repetitions per minute for his/her
treatment. It should be mentioned that the code is versatile enough to be
modified at any moment, and configure it in the cadences required by
internist doctors. The PLC has a
display where the specialist may see the selected value of repetitions and
the buttons are marked to avoid confusions. The electropneumatic
system is prepared to receive compressed air from the hospital
infrastructure, and thus it has been anticipated that this air is used as
pneumatic supply to the control electrovalves. The system design
was prepared to place programmed control processes in the PLC, to enable
specialists to be certain about the number of repetitions that they are
selecting for the patient. At this moment the system is open-loop, because
the sensors required to implement the corresponding control loops are not
available. However, appropriate sensors may be installed in a subsequent
version such that the system self-regulates based on the information provided
by the sensors, thus transforming it into a close-loop system. Figure 4 shows the
connections between the PLC and the different parts of the respirator.
Figure 4. Configuration of the PLC 3.
Results and
discussion Due to the agreement between the diagrams and the final equipment, it is considered that the conceptual prototype may be easily reproduced, both its structural and electropneumatic components. Measurements were carried out by the INFRA personnel in El Salvador, to conduct operation tests and verify that it complies with the parameters indicated by the internist doctor. They are responsible of performing maintenance |
of
assisted mechanical ventilation equipment, with the use of specialized
equipment.
(a)
(b) Figure 5. Equipment for measuring
operational parameters Figure 5 presents the
measurement equipment: (a) verifies that it is a Certifier FA TSI High Flow
Module [20] and (b) presents the detected value of 0.301 liters of air and
15.2 blows per minute (BPM). The values shown are in agreement with the ones
indicated by internist doctors for patients with ages between 25 and 40
years, with 15 to 19 inspirations per minute, values that can be regulated
through PLC programming and varying the flow regulator, establishing
predefined pushbuttons for such parameters and for medical conditions of
patients. In addition, measurements were carried out with the NI ELVIS [21]
equipment of the University Biomedical Laboratory, which was used to build a
plot from the signals detected by sensors, that coincides with the data
obtained by the INFRASAL specialists. Table 1 shows the
data measured with the TSI equipment, indicating the respirations per minute
(RPM), the minimum and maximum air volume given in milliliters, the minimum
and maximum air flow in liters per second, the minimum and maximum air
pressure in cm H2O. The equipment was configured for 15 and 19 RPM, es requested by specialists. When configured for 15 RPM,
the volume transfer obtained was between 290 and 330 ml, the flow varied from
2.5 |
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to 3 l/s and the pressure reached
a value of 42 cm H2O. On the other hand, when the equipment was configured
for 19 RPM, a volume transfer between 270 and 320 ml was obtained, the flow
varied from 2.5 to 3 l/s and the pressure reached a value of 40 cm H2O [22,
23]. In both cases, the values obtained are considered appropriate. Table 1. Measurements carried out with the TSI equipment
4.
Conclusions Some of the strong proficiencies
of the Universidad Don Bosco are in the areas of electronics, automation and manufacturing,
and thus this work proposes the design of a mechanical ventilation system
assisted by automatic control systems. The support provided
by the American Space UDB was key to obtain electronic elements that were not
available at the moment due to the closure of borders as a consequence of the
pandemics, but that are necessary for developing automatic and medical
equipment, which enables to give a fast response to face worldwide
challenges. Improvements may be
implemented in the design and the prototype which makes it more complex,
efficient, precise, but which enables applying it to a larger number of cases
that arise at the medical level. The systems designed
and constructed are versatile, because they may be configured according to
the requirements of doctors and patients in short time, both face-to-face and
remotely. Different programs may be simultaneously loaded in the PLC, such
that pressing different buttons or changing the position of a knob, different
programs may be called for the operation of the pneumatic cylinder (cycles,
stroke length) according to the requirement of each patient. Another advantage of
the PLC is that different clinical sensors may be connected to it, and with
the interpretation of such signals changes in the operating conditions of the
pneumatic control system are automatically activated. The system
constructed may be used for studies in medicine, manufacturing, electronics,
automation, both in continuous training of specialists, and in graduate and
undergraduate studies. The objective is always to provide humanitarian aid. The physical model
constructed may be a reference for future development of mathematical and
simulation |
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