International Journal of Electrical, Electronics and Computer Systems (IJEECS)
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Computerized Anesthesia Infusion System
1
Prashanth C, 2Mohammed Salman, 3Rohan K.R, 4Govinda Raju. M, 5Roopa. J
1,2,3
8th sem, Dept. ECE, RVCE, 4Assistant Professor, Dept. ECE, RVCE, 5Assistant Professor, Dept. ECE, RVCE
Email: md.salman729@gmail.com
Abstract-In hospitals when any surgery is performed, the
patient must be in anesthetized condition. The anesthetist
administers regulated amount of anesthesia to the patient.
If the injections are given too closely together or a dose of
anesthetic is injected too quickly, a patient may suffer from
an overdose. On the other hand, if the dosage is too less,
then the patient might wake up during the surgery which
results in pain and shock leading to complications. The
dosage and time of which depends on the vital parameters
of the patient such as heart rate, body temperature etc.
Usually, anesthesia is administered manually which may
leads to anesthesia complications due to overdose or under
dose. To reduce the risk of anesthesia complications, a
system which automatically administers the anesthesia has
been proposed in this paper. The proposed system is based
on the anesthetist selecting the type of the surgery and
entering the static parameters (height, weight) of the
patient undergoing surgery on a Graphical User Interface.
The system calculates the initial amount of dosage and the
same is injected. After the initial induction of the
anesthesia, the vital parameters of the patient are
continuously monitored. If these parameters deviate from
the nominal values at any instant during the surgery, the
system recalculates the dosage of the anesthetic and the
same is injected using the syringe infusion mechanism. The
vital parameters are stored in real time for future
reference and analysis in a database.
Index Terms-- Heart Rate, Body Temperature,
Intravenously, Syringe Infusion Mechanism.
I .INTRODUCTION
The process of administration of anesthesia during
surgeries has been a practice which has been followed
since a long time by humans. The main reason for using
anesthesia in operations is to reduce the discomfort
experienced during the course of the surgery. Anesthesia
can be applied using two methods Topically
 Intravenously
such as heart rate, temperature and blood oxygen level
indicates wrong dosage and this needs to be corrected.
Several authors have described the automatic
administration of anesthesia using a closed loop
mechanism. Konrad et al has proposed a system based
on the pharmacokinetic model. This method involves
controlling the muscle relaxation during the injection of
anesthesia [1]. Jin-Oh-Hahn proposes a closed loop
system which exploits the discrepancy between the
measured and predicted clinical effects to make
corrections to the drug-concentration estimate, achieving
improved robustness against variability in the patient
pharmacokinetics[2]. Dr.Thomas Hemmerling proposes
a system called the McSleepy system which acts as an
automated anesthesia system[3]. The system proposed in
[4] involves monitoring the brain activity using platinum
electrodes. The database of about ten common surgeries
contains the dosage levels of the various drugs used
during the surgery and this data is obtained from [4].
The paper is organized as follows-Section II deals with
the motivation for developing such a system and the
factors affecting anesthesia administration. Section III
deals with the design and specifications of the
computerized anesthesia infusion system while Section
IV deals with the implementation details of the various
modules. The sequence of operations is explained in
section V. The results are presented and discussed in
Section VI, followed by the conclusion in Section VII.
II .NEED FOR MONITORED ANESTHESIA
CARE
The process of injection of anesthesia has to be given in
the right amount of dosage as well as the right rate of
injection has to be ensured. In some cases due to human
negligence, the dosage might exceed the optimum value
resulting in an overdose. An overdose of anesthesia
results in: Death, Heart attack, Lung infections, Stroke
etc. Other less severe side effects include Nausea,
Frequent chills, Headache, Loss of appetite. On the other
hand if the dosage is lesser than the optimum value, it
results in under dose leading to experiencing of extreme
stress and strain by the patient. It has been found that in
case of spinal anesthesia, about 25% of the patients still
Intravenous mode of injection involves using an
infusion set to inject the anesthetic into the vein. Topical
mode of injection involves injecting the anesthetic using
a syringe. The measure of the right amount of dosage is
done based on monitoring the vital parameters of the
patient. An abnormal decrease in the vital parameters
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International Journal of Electrical, Electronics and Computer Systems (IJEECS)
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feel pain. The important parameters which are taken into
account during the process are
Heart Rate or Pulse Rate(Dynamic)

Temperature(Dynamic)

Saturated Blood oxygen Concentration(Dynamic)

Body Mass Index(Static)
rate of the pulse is observed and measured by tactile or
visual means on the outside of an artery and is recorded
as beats per minute or BPM. This paper demonstrates a
technique to measure the heart rate by sensing the
change in blood volume in a finger artery while the heart
is pumping the blood.
III. COMPUTERIZED ANESTHESIA
INFUSION SYSTEM
Fig.2 Principle involved in measurement of Heartbeat
through fingertip
Fig.1 Block Diagram of CAIS
As seen from Fig. 1, the block diagram of the
Computerized Anesthesia Infusion System (CAIS)
consists of the following blocks
Heartbeat Sensor to monitor the heartbeat of the
patient

Temperature Sensor to
temperature of the patient.

Oximeter to monitor the saturated blood oxygen
level.

Microcontroller which is used for storing the
sensor values and also for controlling the actuation
mechanisms (infusion set and syringe).

Computer System on which the database regarding
the dosage for various surgeries is created, the vital
parameters of the patient are stored and the user
interface is created.

Actuation Mechanism
components-

Syringe Mechanism which is used during the
Induction phase of the surgery.

Infusion Set which is used during the Maintenance
phase of the surgery.
monitor
which
the
body
includes
It consists of an infrared LED that transmits an IR signal
through the fingertip of the subject, a part of which is
reflected by the blood cells. The reflected signal is
detected by a photo diode sensor. The changing blood
volume with heartbeat results in a train of pulses at the
output of the photo diode, the magnitude of which is too
small to be detected directly by a microcontroller.
Therefore, a two-stage high gain, active low pass filter is
designed using two Op-Amps to filter and amplify the
signal to appropriate voltage level so that the pulses can
be counted by a microcontroller. The wavelength of the
led used is 910nm while the photodetector should have
maximum sensitivity in the same range. Furthermore,
the led should be isolated from the photodetector to
prevent crosstalk. The IR sensor has a range of about
10cm and is powered using the voltage from the
microcontroller.
2
Fig.3 Signal Conditioning Circuit
Fig.3 shows the signal conditioning circuit used for
amplifying and filtering the photodetector output.
A.
Heartbeat Sensor
Typically, the signal from the photodetector is in the
range of a few 100 µV. The two stage amplifier has a
Heart rate is the number of heartbeats per unit of time
gain factor of 10000 and also includes a low pass
and is usually expressed in beats per minute (BPM). The
amplifier with a cut-off frequency of 2.5 Hz. Fig.4
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shows a representation of a typical heartbeat signal and
its variation with respect to time.
IV. IMPLEMENTATION
The system is developed using the Atmega 328P
microcontroller. The database of the surgeries is
developed on the LabVIEW software. A database of ten
common surgeries is developed for the prototyping
stage.
A.
Heart Beat Sensor
The heartbeat sensor however gives the output in the
form of pulses. For the purpose of counting the pulses, a
counter is initialized and the number of pulses is counted
for a period of 15 seconds. The count value is then
multiplied by 4 to get the heart beat pe minute(BPM).
B.
Fig.4 Typical Heartbeat Signal
B.
Temperature Sensor
The process of measurement of body temperature is
done using the LM35 sensor which produces an output
which is linearly proportional to the Centigrade
temperature. The LM35’s low output impedance, linear
output, and precise inherent calibration make interfacing
to readout or control circuitry especially easy.
C.
Pulse Oximeter
Pulse oximetry is the non-invasive measurement of the
oxygen saturation (SpO2). Oxygen saturation is defined
as the measurement of the amount of oxygen dissolved
in blood, based on the detection of Hemoglobin and
Oxyhemoglobin. Two different light wavelengths are
used to measure the actual difference in the absorption
spectra of HbO2 and Hb. Deoxygenated and oxygenated
hemoglobin absorb different wavelengths. Hemoglobin
(Hb) has a higher absorption at 660 nm and oxygenated
hemoglobin (HbO2) has a higher absorption at 940 nm.
A photodetector in the sensor perceives the nonabsorbed light from the LEDs. This signal is inverted
using an inverting operational amplifier (Op-Amp) The
resulting signal represents the light that has been
absorbed by the finger and is divided in a DC
component and an AC component. The DC component
represents the light absorption of the tissue, venous
blood, and non-pulsatile arterial blood. The AC
component represents the pulsatile arterial blood.
The saturated blood oxygen level is measured by using
the relation:
R=log(Iac)λ1/log(Iac)λ2
Where, Iac represents the current equivalent of the light
intensity at wavelengths λ1(660nm) and λ2(940nm).
The ratio R can be used to calculate the saturated blood
oxygen level based on an empirical formula.
Temperature Sensor
As mentioned in Section III, the body temperature is
measured using an LM35 sensor. The ADC value
obtained from the temperature sensor is passed through
a low pass filter to remove the high frequency noise.
Also, the temperature in degree Celsius is obtained using
the formula:
Temp.(inoC)= (ADC Value)*Vref*100/1024
C.
Pulse Oximeter
The pulse oximeter consists of two LED’s namely red
(660 nm) and IR(910 nm). The current equivalent of the
received light intensity is measured in each of the cases.
The ratio of the received intensity of the red to infrared
is found. The saturated blood oxygen level is found out
by comparing the ratio against a standard lookup table.
D.
Induction Phase Syringe
There are two phases on anesthesia injection during a
surgery. The first one is the induction phase, which is
mainly to put the patient to sleep and this dosage is
calculated depending on the type of surgery and the
weight of the patient. The second one is the maintenance
phase, where anesthesia is constantly administered
throughout the surgery at the right flow rate so as to not
cause an under/ an over dosage.
This section covers the implementation of the induction
phase mechanism.
A crankshaft mechanism has been devised, where, upon
the selection of the dosage, the syringe’s plunger
automatically gets pushed and the drug is delivered to
the subject. The actuator that is being used is a Servo
motor. The plunger in the syringe needs a linear
actuation in order to move in and out of the syringe.
This conversion of angular to linear motion is done
using a mechanism similar to that of a crank shaft,
where we are using a steel rod of 1.5mm thickness to
connect a servo arm to the plunger. Fig.5 shows the
design and principle of operation of the syringe
mechanism.
A ratio of 1 represents a SpO2 of 85%, a ratio of 0.4
represents SpO2 of 100 %, and a ratio of 3.4 represents
SpO2 of 0 %.
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Fig.5 Syringe Mechanism
E.
Infusion Set Mechanism
During every surgery, the most important parameters of
the anesthesia induction are the volume of the dosage
and the flow rate of the anesthetic. In the proposed
system, while the volume of the dosage is taken care of
by means of the syringe, the flow rate is maintained
using the infusion set mechanism. The infusion set
consists of a standard infusion set used in hospitals and a
solenoid valve which is used to control the flow. By
fixing the amount of time for which the solenoid is
open , the size of the drop us made constant. Further, by
varying the amount off-time period the variation in the
flow rate is achieved.
Fig.7 GUI of Database of CAIS
A driver (L293D) is used along with a battery to excite
solenoid. Fig.6 shows the solenoid valve and its design
of the infusion set mechanism.
Fig. 8 GUI showing sensor values
V. SEQUENCE OF OPERATIONS
The basic algorithm of the CAIS is as follows
The first step is to select the type of surgery on the
GUI. The static parameters of the patient like age,
weight, height are to be entered. The system
calculates BMI(body mass index),which in turn
helps in calculating the precise dosage to be given
to the patient for the induction phase

When induction phase is selected on the UI, the
dosage of the drug to be injected is calculated by
LabVIEW is sent to the microcontroller using the
VISA toolkit through UART protocol

The microcontroller sends suitable PWM signal to
the servo motor that’s connected to it which moves
the plunger of a syringe to a precise distance and
hence injects the calculated dosage accurately into
the patient

When maintenance dosage is selected on the UI,
the dosage per minute is calculated.

The various vital parameters are obtained from the
sensors in real time and are used by the
microcontroller to calculate the change to be made
with the anesthesia flow rate, so that the parameters
are maintained at their nominal values.

The flow rate is controlled using a solenoid-valve
which is engaged and disengaged for a particular
duration. Hence the duration for which the liquid
Fig.6 Solenoid Valve
F.
Software and Database Design
The software design is done using the LabVIEW
software by National Instruments. The design involves
the creation of a user interface where the surgeon has to
enter the various static parameters. The database of
surgeries containing the dosage levels at the two stages
of the surgery is also created. For the prototyping stage,
a database of ten common surgeries is taken each from
the major departments of medicine. The list of surgeries
considered is shown in Table 1. The Figure 7 shows the
front panel of the database.
The user is also provided with GUI to show sensor
values during the surgery.
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flows is controlled and the flow rate is controlled.
Maintenance is continued throughout the duration
of the surgery
VI. RESULTS AND DISCUSSION
The results can be categorized into three separate parts
Sensor Interfacing

Database and Dosage Calculation

Actuation Mechanism
The sensor interfacing involves designing a PCB to
mount all the sensors and calculating the various
parameters of the patient and sending this information to
the GUI. For each of the sensors, the validation is done
using the commercially available modules i.e for
temperature sensor a thermometer, heartbeat and
saturated blood oxygen level, an oximeter is used.
The dosage calculation is done using the parameters
entered at the beginning of the surgery such as weight
and the duration of the surgery. The dosage string
includes both the induction and the maintenance dosage.
These values are sent to the microcontroller at the
beginning of the surgery. Table 1 shows a list of the
surgeries considered for the prototype.
process, the system plays a very important role of
assisting the anesthesiologist thereby reducing the risk
of anesthesia overdose. The user interface provides an
easy way of interaction for the user. The database
developed is easily scalable and can include more
surgeries.
The patient health monitoring feature is also included
within the system which involves storing the vital
parameters of the patient in a spreadsheet file. This later
assists in the report generation and analysis.
Future improvements include using a wireless mode of
communication such as Zigbee, GSM to transmit the
sensor values. Also by introducing more intelligence
into the system, the system can be made autonomous.
REFERENCES
[1]
Konrad S. Stadler, Peter M. Schumacher.
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Jin-Oh Hahn, Guy A. Dumont and J. Mark
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Table 1 List of Surgeries
Surgeries considered in our prototype
Intracranial Surgery
Spinal Reconstruction
Atrial Septal Defect
Face Lift and Neck Lift
Arteriosus
Cardiopulmonary Bypass
Caesarian Section
Nephrectomy
Arm Surgery
Lobectomy
The actuation mechanisms are calibrated and tested
under various situations. For the syringe mechanism, a
rotation of about 110o will cause the complete recoiling
of the syringe. On the other hand, the solenoid valve has
an on time of 50ms and about 20 drops make upto
1ml.The off time depends upon the dosage value being
injected.
VII. CONCLUSION
The project provides a means of automating the
anesthesia injection process by using the syringe
mechanism and the infusion set mechanism. The
proposed system shows a working prototype of the
anesthesia administration system. Also, the system
consists of a database which contains the drug dosage
values for different modes of surgery. By introducing
different modes of operation namely the induction phase
and the maintenance phase, the various stages of the
surgery are accounted for. By automating the induction
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[10]
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