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978-1-4799-6399-7/14/$31.00 ©2014 IEEE
Low Cost Neonatal Incubator with Smart Control
System
Zinat Ara Nisha
Department of Applied Physics Electronics &
Communication Engineering
University of Dhaka
Dhaka-1000, Bangladesh
zinat.ara.nisha@gmail.com
A.H.M Fazle Elahi
Department of Mechanical Engineering
Khulna University of Engineering & Technology (KUET)
Khulna-9203, Bangladesh
fazle.elahi.ashek@gmail.com
Abstract— A neonatal incubator has been designed, modeled
and developed which is incorporated with embedded
temperature and humidity control system. The chamber has two
compartments; larger and smaller. Smaller compartment
consists of temperature and humidity control unit and larger
compartment consists of a mattress where the baby is kept. The
control system components include relative sensors, fans, bulbs,
heater and Arduino Uno microcontroller. For implementation, a
software program has been developed in C which comprises a
code editor. A flowchart is provided to illustrate the logical
expression of the program. The salient features of the model are –
it is entirely microcontroller based, can be locally developed at a
low cost and is a sophisticated version of conventional incubator
systems. The system can control the temperature at the set level
of 36oC to 37oC and relative humidity at the set level of 70% to
75%. At the same time the incubator is free of health hazard. It
can be used commercially in the hospitals as too at home.
Keywords— Neonatal incubator, Neonatal Intensive Care Unit
(NICU), Low cost incubator , Smart temperature control,
Premature Baby, Kangaroo Mother Care (KMC)
I. INTRODUCTION
One of the most sensitive concern of biomedical field is the
premature infant care. Bangladesh is a developing country and
most of the people here lives around the immediate vicinity of
the poverty line. So highly expensive newborn care is not
affordable for them. But the babies who born 2 or more weeks
before the 38 week gestation badly requires intensive care.
Those infants generally have a net body area greater than
normal babies from same age. [1] That means their body heat
loss is higher than normal babies. Also these neonates possess
a net weight less than the normal babies which makes them
unable to keep their body temperature to the required level. In
case of premature babies, it is not possible to control their body
temperature without an external aid. In these circumstances
Kangaroo Mother Care (KMC) is certainly effective which
means to hold a preterm baby skin-to-skin with an adult
especially mother. [2] But sometimes KMC could not be
possible for unavoidable reasons. Firstly, if the mother is too ill
after delivery, she won’t be able to provide Kangaroo Mother
Care (KMC). Some of the mothers are helpless because they
may have reasons such as other children or a job or any
ineluctable cause. If providing KMC is not feasible and the
baby is sent home therefore suffer the complications of
hypothermia, breathing problems, hypoglycemia and even
death [3-4]. To get to a normal growth premature newborns
need a warm, clean and salient environment. The newborns
with complications must be put into a Neonatal Intensive Care
Unit (NICU). NICUs were developed in the 1950s by
pediatricians to provide better temperature support, isolation
from infection risk and also specialized feeding to newborns.
[5] The incubators are designed as an isolated area having an
infant friendly environment without any dust or parasite and
has the ability to control environmental factors like temperature
and humidity to remain them in acceptable levels such as
(36°C-37°C) for temperature, (70%-75%) for relative humidity
[6]. Incubator can also be used for full term babies to give
special medical treatment. Albeit developing countries need the
incubator most, many people living there are not capable of
affording one. So this project provides a luminous solution for
them. The current recommended method of providing infant
temperature regulation in resource constrained settings; the
practice of placing newborns directly onto the mother's chest at
very low cost.
II. PHYSIOLOGY
Babies can be categorized according to their gestation
period; Pre term (less than 35 week gestation), Full term (35 to
42 weeks gestation) and Post term (born after 42 weeks
gestation) [7]. Premature babies are those who are born before
the pre-term. If an infant born before 31 weeks gestation
evaporative water loss is the main reason to heat loss. It’s
because loss of moisture from skin which causes higher
permeability. [8]
Fig. 1. Neutral thermal environment of premature baby
Having difficulties with heat regulation within the body a
newborn child can experience an organ failure. [9] Heat may
loss from the body by four ways; Conduction, Evaporation,
Convection and Radiation. Fig.1 illustrates the ways of heat
loss from an infant body.
A. Thermoregulation in premature infants
The temperature inside the mother’s womb is 38oC
(100.4oF). [10] After birth, the wet baby finds itself in a much
colder environment. So it immediately starts losing heat thus
the thermal protection of the newborn is very much important.
Fig. 2 illustrates the metabolic rate with body temperature of a
preterm baby and normal range of infant body temperature at
which thermo neutrality is achieved. This temperature range is
very narrow and lies between 36.5oC-37.5°C. Thus, the
environmental temperature at which the infant regulates its
body temperature can be considered as the neutral (operative)
temperature [11].
Fig. 2. Heat losses from premature baby
Thus there is no accurate ambient temperature that is suitable
for new born babies without considering all factors such as
gestation period, body mass, size etc. [12] The new born baby
cannot regulate its temperature like an adult. It therefore cools
down or heats up much faster and is able to tolerate only a
limited range of temperature. The smaller the new born the
greater the risk. Thermal stability improves gradually as baby
increases in weight. [13] As the difference between warm
womb temperature and the ambient is very high, most of the
heat loss occurs just after the birth of newborn. [14] Incubator
can offer shorter hospitals stay to millions of premature babies
and can enable infants who might have faced a lifetime of
severe disability.
III. METHODOLOGY
This project emphasizes on developing an infant incubator
especially for premature babies. Entire chamber of the
incubator is constructed using Acrylic sheet as it is more
advantageous over glass and plastic. This material is less
dense – its density can range from 1100-1200 kg/m3. It is very
much less than the density of glass which ranges 2420 to 2790
kg/m3. [15] Transportation and assembling of acrylic materials
are consequently easier and cheaper. Main chamber consists of
two compartments. Larger compartment keeps the baby in and
smaller compartment comprises of control units. The control
unit section has three portions. The lower portion is the
heating unit. Heating unit consists of an incandescent bulb and
a 12V dc fan. There are slits on the joining wall of the unit.
The fan exert air flow which becomes heated by the bulb heat
and passes through the slit to the baby room. The dc fan and
bulb starts running when the baby room temperature reduces
from 37oC and stops when the sensor gives the signal that the
baby room temperature is above 37oC. The upper portion has
two subsection. One is cooling unit and the other is humidity
control unit. Some ice are kept in the cooling unit to reduce
the temperature when it goes beyond 37oC. A 12V dc fan is
attached outside the cooling chamber to flow the air stream to
the baby room in order to confine the temperature within
37oC. The humidity control unit has the capacity to collect the
molten water from the ice of cooling chamber. It contains a
heater and a 12V dc fan. When humidity sensor sense the
humidity level below 70% this unit automatically starts. It
runs no later than the humidity level reaches at 75%. There is
an exhaust fan on the outside of the baby chamber which
ensures the continuous flow of air. The whole system is
controlled by an Arduino microcontroller program. The supply
current is provided by using transformers, rectifiers, bridge
and relays with 220V AC current.
IV. DESIGN AND CONSTRUCTION
One of the most important elements in a newborn's
survival is the infant’s temperature regulation. The newborn
baby is readily a mature homoeothermic, but the range of
environmental temperature over which an infant can operate
successfully is severely restricted. The infant’s body
temperature should be maintained at 36oC-37oC. Another
important element is humidity regulation. The dehydration of
infant with 31 or less weeks of gestation, treaties in ambient
with relative humidity in 20 %, exceed 200 ml/kg/day. To
provide a baby friendly environment the relative humidity
must be maintained within 70% to 75% RH. [16] Keeping in
mind about the above problems related to the infant we need
to design such an incubator system that controls the
temperature and humidity of the environment where the
newborn baby is rested. Fig. 3 shows the block diagram of
total control system unit through which the incubator would
run to get optimum temperature and humidity.
Fig. 3. Block diagram of temperature & humidity control system
The Design Requirements of infant incubator are to provide
the infant with the bare necessities, these are: (i) An ambient
temperature of 36⁰C-37⁰C (ii) Humidity greater than 70%RH
and (iii) sterile air supply. The proposed system of a neonatal
incubator contains following portions:-
(a) Structure development of incubator
(b) Temperature control system
(c) Humidity control system
(d) Control Unit
(e) Cost Analysis
A. Structure development of incubator
It is better that the incubator is light in weight so that it can
be portable at the same time provides strong support for the
components used and can bear the weight of the infant.
Isolation of the compartment where the baby is kept from the
controlling unit is a necessary requirement. The incubator
design can be divided into four subsystems: structural support,
enclosure, shell, and bed. The structural support is the device
that accommodate the other subsystems and the preterm infant.
Design Parameters: Length 80 cm, Height 30 cm, Width 30 cm
thickness of material 5mm. Control unit inside the box has a
dimension of 10 cm x 30 cm x 30 cm. The control unit is
responsible for holding the heat exchanger and the electrical
components needed for the incubator to work. The shell is
responsible for retaining the heated air, preventing airborne
infections from reaching the preterm infant, and venting the
stagnant air. The bed is intended to keep the preterm infant in
place. Fig. 4 depicts the rendered image of the 3D model of
incubator structure designed by Computer Aided Design.
Fig. 4. 3D model of the incubator
B. Temperature Control System
The temperature is sensed by DHT11 sensor. It is
connected to the Arduino Uno. In the circuit arrangement of
the control system. Signal pin of the sensor is connected to the
analog input pin A0 of the microcontroller. These are
connected through relays with the digital output pin 10 and 9 of
Arduino board. Each Relays are of 5 volts and are interfaced
with the Arduino Uno through relay drivers. Here NPN
transistors are used as relay drivers. Arduino Uno is the
controller used here. The program is written to control the bulb
and fans. When the temperature in the chamber falls down
below 36oC the bulb glows and fan associated with the bulb is
turned ON so that that the hot air is blown to the compartment
B through the slider. The cooling unit consists of an Aluminum
vessel containing ice and a 12 v dc fan. This fan is connected
with the digital output pin 7 of the Arduino board through a
relay. Whenever the temperature in the chamber goes beyond
37oC the bulb automatically switches off and the fan in the
cooling unit turns ON. Cool air is blown to the compartment B
until the desired temperature is achieved. Fig. 7 shows the
constructed view of incubator’s temperature controlling unit.
Fig. 5(a) and 5(b) are heating and cooling portions
respectively.
5(a) 5(b)
Fig. 5. 5(a) Heating unit with incandescent bulb, 5(b) Cooling unit with ice
C. Humidity Control System
At one side of the cooling unit a small compartment is
built to serve the purpose of controlling humidity. In this
compartment there is a 100 watt heater and a 12 V dc fan
connected with the digital output pin 6 and 13 respectively.
When the relative humidity falls below 70% the bulb glows.
As a result water is turned into vapor. The fan placed behind
the heater helps to blow the vapors to the small compartment.
If relative humidity exceeds over 75% an exhaust fan placed
outside of the compartment exhausts the air outside of the
incubator. Here the humidity is sensed by the same sensor
DHT11. Fig. 6 depicts the real constructed image of the
incubator humidity control unit. This sensor is so beneficial
because it can render signals for both temperature and
humidity.
Fig. 6. Constructed view of the incubator with humidity control unit
D. Control Unit.
The Arduino Uno is a cross platform application written
in Java, and is derived from the Uno for the Processing
programming language and the Wiring project. For
implementation, a software program has been developed in C.
It includes a code editor with features such as syntax high
lighting, brace matching, and automatic indentation and is also
capable of compiling and uploading programs to the board
with a single click. [17] The logical expression for the
program is provided at Fig. 7.
Fig. 7. Logical expression for Arduino program
E. Cost Analysis
The project aims to a cost effective neonatal incubator with
consistent performance. Total cost of the prototype
construction is enumerated below.
TABLE I. COST OF CONSTRUCTION FOR INCUBATOR
Product
Cost (BDT)
Acrylic sheet
1000
Arduino Uno
1400
Temperature and
humidity sensor
750
LCD display(16×4)
252
Relay(4)
120
12 V dc fans(4)
240
100 W incandescent
bulb
60
Heater
100
Connections and
accessories
300
Total Cost
4222
The amounts are in Bangladeshi taka and given according to
the particulars used. Cost of the prototype construction is so
less than the commercially available incubator. Thus the
designed incubator would be available for all at a low cost.
V. RESULT AND DISCUSSION
A. Temperature Control Unit
The major concern of this incubator is to control the
temperature of the baby room and maintain it within the
desired range 36oC to 37oC. Fig. 11 exemplifies the process
control by Arduino UNO microcontroller. Here a whole day
(24 hour) data of controlled temperature is inset with the
ambient temperature of the same day.
Fig. 8. Temperature variation in the incubator for control system
At 00:00 am the temperature of atmosphere was low and
almost constant up to morning 6:00 am. Then it rises with the
day time and again lowered at and after 5:00 pm. But the
system for keeping preterm baby safe and sound the
temperature is needed to be constant within the range. The
incubator constructed has been efficient at doing this and the
graph shows that it kept the temperature of the baby
compartment at 36oC to 37oC irrespective of ambient
temperature.
B. Humidity Control Unit
Humidity is another critical factor for preterm infants. Fig.
12 depicts the humidity control by Arduino microcontroller
system and its variation with the ambient humidity.
Fig. 9. Humidity variation of the neonatal incubator and it’s ambient
The baby room is maintained within the RH level of 70% to
75% though the humidity in the immediate vicinity of the
incubator varies from 30% to 80% at different time of the day.
VI. CONCLUSION
Every year, about 1 million infants in the developing
world die due to prematurity complications. Premature infants
are born before the developing organs are mature enough to
allow normal postnatal survival. To provide a sound
environment for the baby temperature in an infant incubator
must be maintained at a proper level, generally set at 37oC.
The developed system is one of the most practical solutions
for addressing the lack of proper care for infants, affected
preterm and other complications in impoverished regions. The
system is capable of providing the most crucial aspects of
patient care at a cost low enough. The prototype is capable of
maintaining a proper environmental temperature (36oC-37oC)
and humidity (70%-75%) for a patient, which are the primary
functions of an incubator. Once set, the temperature and
humidity are maintained automatically by the microcontroller
based system which makes the system easy to operate. The
proposed model can be further improved by using a voice
detection system using DSP to detect if the baby’s crying.
Emergency oxygen supply mechanism should be incorporated.
Solar power can be used as an alternative power source.
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