At present, neonatal incubators can be found in practically all hospitals and clinics; these are increasingly safe and easy to control by medical personnel.
Each one of the mechanical and physical components that they form the incubator, as well as the sensors that measure the different variables must be synchronized and in perfect functioning so that the microenvironment of neonate will not be disturbed. Two fundamental components of a neonatal incubator are the dome and the chassis.
The dome is essential to maintain the necessary means for the newborn. Porsu part, the chassis contains the source of power and sensors that alert in case of failure, for the protection of the newborn.
The cover or dome is responsible for isolating the baby and creating a barrier between the external environment and the microenvironment generated by the incubator; This means that it protects it from situations such as drafts, low temperatures, among others. The cover must meet certain special characteristics; It should allow the visibility of the baby and be made of a material that does not react with oxygen, to avoid corrosion in cases where oxygen therapy is necessary. Generally, an acrylic material containing a certain percentage of polypropylene and other polymers is used, and
approximately 6mm thick, enough to isolate the external environment of the microenvironment of the incubator. The standard measurements of an incubator are 90cm long, 40cm wide and 45cm high [4].
The chassis is the metal base of the incubator. In it are the different sensors and the source of power, and on it is located the mattress holder. It must be constructed with a resistant material that supports the weight of the neonate and the dome, in addition to being highly heat resistant, so that it does not deform easily due to the temperatures that are registered both inside the incubator and in the chassis [3].
Principles of Operation
Most incubators provide heat to babies through the flow of hot air, this heat is transferred mainly by convection. The heating and humidification systems are located below the incubator compartment. The circulation of the air is achieved thanks to a fan or a turbine that takes it from the outside and passes it through a heating element and a temperature measuring device, then passes over a water tank used to moisten the air (if it is required) before pushing it into the camera where the patient is.
TEMPERATURE :
Likewise, incubators have a heating element or heat unit that is activated by an electrical signal, which is proportional to the difference between the measured temperature and the reference value pre-established by the operator [5].
It is defined as the range of environmental temperature, in which the metabolic rate (oxygen consumption) is minimal and thermoregulation is achieved without vasomotor control.
Within this range, the RN is in equilibrium with the environment. The normal body temperature of the newborn implies the recording of the temperature when the state of thermoneutrality is achieved, even when the definitions of normal temperature vary.
The current recommendations of the American Academy of Pediatrics and the American College of Gynecology and Obstetrics are 36.5 and 37.5 ° C for axillary and rectal temperatures respectively; for abdominal skin temperature is 36 to 36.5 ° C.
HUMIDITY:
In the premature, the amount of heat that can be lost by the mechanism of evaporation is particularly important. This occurs in the form of insensible water losses and is known as PTEA. The contribution of the PTEA to the thermal stability of the RN is complex and depends on many factors. The anatomical characteristics predispose it to these losses, but the most significant factor in this process is the relative humidity of the surrounding air. Within the physiology of the RN, what is more important is the increase in the permeability of the skin, due to its thinness and immaturity.
Desing
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figure 6: Dimer electric circuit
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figure 7: Electric Circuit
Figure 7 shows the electrical diagram that was used to sense and display the temperature and humidity, to control the speed or power of the fans and to generate the alarms (visual and audible) corresponding to temperature and humidity outside the ranges normal The incubator consists of three fans, an internal fan that circulates the steam and hot air, and two external fans, one extractor and another that enters fresh air from the external environment. The speed of the fans depended on the error that existed between the sensed value and the value entered by the keyboard. To generate hot air we used a dry resistance that reached 100 ° c, and generate water vapor using a submersible resistance, both are fed with 110v A.C. To control the temperature, only the fans were needed, to control the submersible resistance it was necessary to use a dimmer (figure seven) as well.
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ResultsAfter making the code and the model, we related a corresponding PWM value of the fans with a temperature and humidity value taken by default, giving the following tables (table 1,2):
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Table 1: Humidity Characterization Table
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| Table 2: Temperature Characterization Table |
The points that
were obtained after characterizing the motor were related in a linear manner:
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| figure 2: Temperature Characterization |
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figure 3: Humidity Characterization
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to maintain the temperature and humidity to the desired value entered by means of a keyboard, it is programmed by means of an error control between the difference of the temperature and humidity sensed and the temperature and humidity that one wants to obtain in the system, so if the difference it is zero the PWM of the fans is very low and if the difference is 1 or greater than 1 the PWM of the fans increases to control temperature or humidity, depending on the mode in which it is.
four alarms were programmed consisting of high and low temperature, high and low humidity, when an alarm is activated either by high temperature or by high humidity the fans are activated with the maximum of PWM that is to say with the value of 255, so that the temperature or humidity decrease as quickly as possible and return to the set value. When the low temperature or humidity alarm is activated, the speed of the fans decreases so that the heat of the dry resistance concentrates more and the temperature increases, when the variables stabilize the PWM returns to its set value.
The completely finished model can be seen in (figure four). To control the incubator, an alphanumeric keyboard is used, to display the information an LCD screen was used, located on the breadboard but not on the model. When the incubator is connected, the screen shows a selection or start menu (figure five), from this menu the user will select the operating mode of the incubator either by temperature or humidity and enter the corresponding value between a range of 35 - 39 degrees for temperature and 45-85% for humidity, depending on the operating mode selected, the other variable behaves constantly, maintaining a set value of 50% for humidity and 37 ° c for temperature.
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| figure 4: Finished Model |
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| figure 5: Start Menu and display of variables |
Conclusions
The current incubators must have the capacity to warm the newborn by means of modern control systems that prevent thermal oscillations of the machine and, therefore, the child. They should also have the alarm systems of excessive and low heating of the appliance and the child as well as cooling, detection of power and operation failures. have the ability to provide the desired humidity and the ability to easily clean both the accessories and all parts of the apparatus.
an important aspect is the easy access to child without the need to disturb him and the possibility monitoring.
In the construction of a real incubator, the quality standards are much higher, but the approach with the prototype developed establishes important bases to reach a team that meets the clinical standards.
BIBLIOGRAPHY
[1] Castrillón B., Ajito E., Barrios A., Solórzano E., Tarrillo J.
Burbuja Artificial Neonatal (BAN). II Congreso Colombiano de
Bioingeniería e Ingeniería Biomédica, Bogotá,
[2] Bayona D., García M., Sandoval J., Reyes F. Diseño e
Implementación de una biomáquina para niños prematuros. II
Congreso Colombiano de Bioingeniería e Ingeniería Biomédica,
Bogotá
[3] Zaragoza I., Gómez Y., Cabrera A. Diseño y construcción de un
prototipo de incubadora controlado por lógica difusa. Memorias
II Congreso Latinoamericano de Ingeniería Biomédica, 2001.
[4] Food and Drug Administration. Neonatal and neonatal transport
incubators–Premarket notifications (1998)
[5] Pardell, X. (2019). Incubadora Neonatal - Apuntes de Electromedicina Xavier Pardell. Retrieved from https://www.pardell.es/incubadora-neonatal.html
[6] Zamorano-Jiménez, C., Cordero-González, G., Flores-Ortega, J., Baptista-González, H., & Fernández-Carrocera, L. (2019). Control térmico en el recién nacido pretérmino. Retrieved from http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0187-53372012000100007
