AUTOMATIC INSUFFLATOR TESTER
ELEN 119 PROJECT REPORT
Santa Clara University
500 El Camino Real
Santa Clara, CA 95053
February 14, 2010
We would like to thank Professor Tim Healy for his guidance, expertise, and
motivating words. He kept us on track and focused throughout the duration of this
project. Professor Healy emphasized the maturity of not only our engineering skills, but
also our time management and communication skills.
We must also recognize Stryker Endoscopy for their cooperation with the Santa
Clara University curriculum. In particular, Jeff Sears, Al Torabi and Anand
Venkatachalam have been vital contacts and resources for the development of this
1.1 Background Information
On the way to developing new, less invasive surgeries, endoscopy has found itself
at the forefront. Endoscopy has become the way to go when invasive surgical procedures
are necessary since it greatly reduces unsightly scars as well as minimizes interference
with organs not involved in the particular procedure. In general, endoscopy entails
viewing the internal organs by means of a small tube with a light and camera at the end.
This allows precise navigation within the area to be operated on as the image is projected
onto a screen in the operating room.
For this project, a specific type of endoscopy was considered - laparoscopy.
Laparoscopy is the surgical procedure in which a small incision is made in the abdominal
wall through which a laparoscope is placed. This device allows structures within the
abdomen and pelvis to be seen, comparable to the general endoscope. In order to make
maneuvering in the abdomen easier, the area is filled with gas, usually carbon dioxide,
which causes the stomach to expand. This inflation of the peritoneal cavity is referred to
as insufflation, a condition brought about by an instrument called an insufflator.
The insufflator pumps the CO2 peritoneal cavity regulating the pressure, gas flow
rate and temperature of the carbon dioxide entering the abdomen. As one would imagine,
the introduction of foreign elements into the body does not come without risks, and
carbon dioxide insufflation is no exception. Pressure and temperature fluctuations of
carbon dioxide are a main concern because of the possibility of leaking CO2 into the
blood vessel causing obstruction. If the carbon dioxide pressure in the surrounding veins
is higher than the carbon dioxide pressure in the inflated stomach, air bubbles are forced
into the veins. This condition is known as an air embolism and may lead to a Transient
Ischemic Attack (TIA) or even a full blown stroke.
1.2 Problem Statement
Clearly, the working quality and reliability of the insufflator are very important,
as any inconsistency or malfunction may directly affect the carbon dioxide flow. This
may be detrimental to the health of the patient. For this reason, a testing procedure of an
insufflator before it is sent out to a customer has become a major concern for Stryker
Endoscopy. Although current quality testing procedures are satisfactory and the results
are reliable, the tests remain somewhat tedious and time-consuming. Therefore, the
implementation of an automatic tester for the insufflators seems to be a worthwhile
endeavor. Not only would this save time, it also eliminates human inconsistencies due to
different testers performing the inspection.
The objective of this project was to design a system that would perform
automated tests on insufflators. We needed to develop both hardware and software
solutions that worked together.
2) SYSTEM ARCHITECTURE
After developing various designs and evaluating the system process, Figure 2-1
depicts our final proposal. It addresses and resolves most of the problems we ran into.
With control valve #1 in the open position and CO2 tank #1 full, the testing
procedure for insufflation can begin. CO2 gas will flow from the insufflator through
[material] piping, passing through the three inline measuring devices that will provide us
with the exact pressure, flow rate, and temperature of the CO2. A Data Acquisition Board
(DAQ) will collect, record and deliver data from these devices to the computer, enabling
the computer to compare and contrast that data Once data sets are processed
successfully, insufflation is to continue, and control valve #2 is to be opened to release
CO2 gas in the [material] piping and measure flow rate of CO2 appropriately. Flow rate,
and pressure data will be fed to computer for analysis through acquisition board/control.
Insufflation is to cease while allowing control valve #1 and #2 to close. Using a full CO2
tank (#1 or #2) and the pressure control regulator (valve), we can test backpressure. The
pressure control regulator will fill the piping to a set pressure, allowing for Overpressure
and Occlusion testing on the insufflator. Acquisition of this data for further breakdown is
optional through the pressure, flow rate, and temperature meters.
Figure 2-1 System Schematic
After the test is completed and the required data is obtained, the pressure control
regulator will close and block CO2 from entering the [material] piping and insufflator.
Control valves #1 and #2 are to open and allow remaining CO2 gas in the system to exit.
The following represents hardware specifications and hardware configurations for
components we would use in building this project. The selection of the hardware was
based on the need to satisfy specific criteria for different testing conditions. There were
essentially seven hardware components we decided on, namely, the flow meter, pressure
meter, temperature probe, controlled valves, data acquisition board, control module and
the pressure control valve.
3.1 Gas Flow Meter/Pressure Meter:
Gas-flow/pressure meters are used for measuring the flow or quantity of a moving
gas. The basis of flow-meter selection is having a clear understanding of the
requirements of the particular application. Examples of criteria that a flow meter might
include are accessibility of data output, precision and accuracy to within a certain
percentage, proper physical dimensions, compatibility, durability and an ease of
In addition, understanding and accounting for the pressure inconsistencies along
the tube length is critical. We could situate these electronic meters at the entrance of the
gas cylinder or place several of pressure meters along the length of the tube. The idea is
to position them as to obtain the most accurate pressure or flow rate. However, we
decided it would be better if we had a flow element that measures pressure drop along a
certain length before entering the gas cylinder.
Figure 3-1 Gas Flow Meter
A laminar flow element for airflow measurement is an ideal choice. When air
flows through it, the result will be a differential pressure proportional to the flow. This in
turn can be measured and evaluated by an electronic differential pressure transducer (< 1
mbar for the measuring range). Advantages in addition to the low-pressure loss, are rapid
response, possibility of bidirectional operation and wide measuring span.
Figure 3-1 Laminar Flow Element
The principle of the LFE is based on Poiseuille´s law, which states that the flow in
a thin pipe is proportional to the pressure loss per unit of length, provided the flow is
laminar. This ensures that selecting an appropriate pipe diameter will result in a
Reynold´s number below 2000. For low flow volumes, a single thin capillary may be
used. To achieve a wider flow range, many of these capillaries are arranged in parallel,
increasing the maximum volume that can be measured, while the pressure drop remains
3.2 Temperature Probe
This instrument would be compact, durable and accessible to the data acquisition
system. NTC probes 401 AC for intra abdominal pressure (YSI. Inc., Yellow Springs.
OH): and K probe T-430-2R for insufflation hose temperature (AHLBORN, holzkirchen,
3.3 Controlled Valves
Control valves are devices for closing or modifying the passage through a pipe,
outlet, inlet, or similar items, in order to stop, allow, or control the flow of media. These
valves are used throughout industry in many applications. Important specifications to
consider when searching for control valves include diameter, working pressure, and
Figure 3-2 Control Valves
Servo valves provide closed loop flow or pressure response to an electrical or
electronic control signal. They can be positioned anywhere to control the amount,
pressure and direction of fluid flow. The distinction between servo valves and
proportional valves is inconsistently defined, but in general, servo valves provide a higher
degree of closed-loop control. Both types of valve are used for control in pneumatics,
hydraulics, gas and water transport, and other specialized applications
3.4 Data Acquisition Board/Control Module
A hardware interface needs to accumulate all data from several components and
interpret those results for computer use. Sensor output acquired by the board must be sent
to the computer in a usable format.
Figure 3-3 National Instruments – PCI-6052E Multi-Functions DAQ Device
The Agilent 34904A module for the 34970A Data Acquisition/Switch Unit gives
the most flexible connection path between the device under test and the test equipment,
allowing different instruments to be connected to multiple points on the DUT at the same
time. Rows or columns may be connected between multiple modules to build 8 x 8, 4 x
16 or larger matrices, with up to 96 cross points in a single frame.
3.5 Pressure Control Regulator (Valve)
Pressure regulators are used to reduce the pressure to a lower pressure sub-system
or to regulate system pressure to a desired value. The types of pressure regulators
available are backpressure, vacuum pressure, differential pressure, and pressure reducing
regulators for specific kinds of fluids like oil and fuel. The most important parameter to
consider when specifying pressure regulators is the regulating or adjustment range. This
is the limit of adjustment control on the pressure range. Common media types include
air, gas, and hydraulic fluids.
Figure 3-4 Pressure Control Regulator
4.1 Purpose of the Software
The purpose of developing software was to produce:
A) a way to control the insufflator by issuing it commands
B) a way to obtain data and measurements from the insufflator
C) a way to control the black box by issuing it commands
D) a way to obtain data and measurements from the black box
E) all the command functions and data acquisition functions to simulate a fully
automated test of the insufflator. This is done by calling the functions in a
specified sequence which mimics the manual test procedure.
LabVIEW is the graphical development environment for creating flexible and
scalable tests, measurements, and control applications rapidly and at minimal cost. With
LabVIEW, engineers and scientist interface with real-world signals, analyze data for
meaningful information, and share results and applications. Regardless of experience,
LabVIEW makes development fast and easy for all users.
The advantage of using this software is that everything is displayed graphically
and the user does not need to learn the syntax of the language. We found it relatively
easy to maneuver within LabVIEW because we could see all the variables, comparators,
boxes and connections and we did not have to learn syntax. Understanding the meanings
of the actual functions and which of them we needed to incorporate into our design
proved a bit more challenging. We also had a few setbacks when we realized that the
student version we were using did not have all the functions we needed, for example,
some of the component descriptions were not accessible.
Similar to C++ and other programming languages, LabVIEW is capable of
declaring variables, comparing values, collecting input, and displaying output. The
programmer can make case statements and execute loops of code. In addition, lines of C
and Matlab code can be integrated and executed in the program, which could be useful.
This section goes over the command functions of the Insufflator, which are on the
front panel of the machine. The command functions simulate a user pushing the buttons
on the front of the machine.
Ideally, each of these functions would consist of written code that issues
commands to the Insufflator. Upon calling these functions, the commands will be sent
through a channel, connected to the back of the Insufflator. Every task will be activated
through this port.
The tasks that the insufflator is capable of include Start/Stop, Increase/Decrease
Pressure, Set Pressure, Increase/Decrease Gas Flow Rate, Set Gas Flow Rate, and Reset.
Each of these tasks will be implemented by its own function.
Insufflator Command Functions
Increase/Decrease Gas Flow Rate
Set Gas Flow Rate
Figure 4-1 Insufflator Command Block
Black Box Command Functions
Measure Gas Flow Rater
Open Valve / Close Valve
Data Acquisition Functions
Data Acquisition Functions are the functions we will use to retrieve
measurements and data from the insufflator. These functions let us know whether the
insufflator is working properly. We compare the acquired data with the standard values
in the Quality Inspection Procedure (QIP), and this data is sent to the output as well as a
pass or fail statement for the test. The Insufflator is capable of obtaining measurements
in pressure, gas flow rate, gas consumption, temperature, and also displays text messages.
Insufflator Data Acquisition Functions
Get Desired/Actual Pressure
Get Desired/Actual Gas Flow Rate
Get Gas Consumption
Read Software Revision
Figure 4-2 Insufflator Data Acquisition Block
Black Box Data Acquisition Functions
Get Gas Flow Rate
4.4 Pseudo-code Test Procedure
The most important step in the translation of the manual testing procedure to an
automated one is to have the steps done by the designed “black box”. It was obvious that
this is where the software would become important as it would give commands to both
the insufflator and the black box. It then compares data inputs to ensure the proper
working condition of the insufflator. A pseudo-code based on the QIP was the first step
towards this automation. By generating the list of commands to be applied to both the
testing and tested device, we had to decide on a software program that could control both
devices as well as analyze and log the data. The software evolved from pseudocode
using C++ language into implementation using LabVIEW.
National Instruments’ LabVIEW was chosen and we proceeded to generate the
command functions. These commands, such as “Set Pressure”, were implemented in our
elementary design and were then made into one unit referred to as the Command Func
component. These commands would be applied to both the black box and the insufflator.
The second of the two parts involved in the implementation of the pseudo-code is
the data acquisition list of commands for the devices. Our data acquisition component,
Data Acqui, was designed with example commands such as “Get Pressure”.
In the main page of our control system, the output values of the pressure values
for example, of both the tester and the insufflator are compared on a true/false basis.
Basic Functions Test
This test checks the initial values of the Insufflator when it is plugged in, but not
turned on. The values of desired pressure, desired gas flow rate, actual pressure, actual
gas flow rate, and total gas consumption that are displayed on the Insufflator screen are
compared with what they are suppose to be, according to the QIP-096 form. This test
only uses the data acquisition functions. If all of the values match, then the test passes.
Gas Flow Rate Test
This test checks the gas flow rate of the Insufflator. The Insufflator is turned on
and the gas flow rate of the insufflator and the tester is commanded to set the gas flow
rate to the desired pressure. If both devices give the same output values, the test passes
for the low pressure command and the tester continues to the next testing value. If there
is a failure at a point along the gas flow rate test, the error message is generated and the
This test makes sure the gas consumption meter is working. This test is done after
the gas flow rate test, and checks to see that the amount of gas consumed is greater than
zero at this point. A pass or fail value is recorded. Then, the reset gas consumption
function is called, and the gas consumption is checked again to make sure its zero. If it is
zero, then it passes.
This test checks that the pressure of the insufflator is indeed the value to which it
is set. The insufflator executes this test if the Gas Consumption Test has passed. If the
value of the pressure of the insufflator is that of the tester, the test passes.
Veress Needle Test
The Veress needle test checks that the actual flow rate through it is the same as
that of the insufflator tube. This part of the test has not yet been implemented into the
design of the tester.
Heater Board Test
The Heater Board test makes sure that the temperature of the insufflator is being read
properly and generates an error message upon overheating.
5.1 Data Acquisition
Data acquisition is the processing of multiple electrical inputs from devices such
as sensors, timers, relays, and solid-state circuits for the purpose of monitoring, analyzing
and/or controlling systems and processes. Data acquisition instrument types include
computer boards, instruments or systems, data loggers or recorders, and I/O modules.
Computer boards are self-contained printed circuit boards with full data acquisition
functionality, which are typically plugged into a backplane or motherboard, or otherwise
interfaced directly with a computer bus. Instruments or systems are fully packaged with
input and output, user interface, communications capability, etc. They may include
integral sensors. Data loggers and data recorders are data acquisition units with the
instrument functionality of data storage capability. Input modules are devices (module or
card) configured to accept input of sensors, timers, switches, etc. for use in the data
acquisition system. This will allow for acquisition of actual data from the pressure
sensor, flow rate sensor, thermometer and possibly pressure control valve/regulator. I/O
modules have both input and output functionality. Digital or discrete I/O includes on-off
signals used in communication, user interface, or control. This will allow for quick and
complete control over the pressure control regulator and the control valves.
Common form factor for data acquisition devices include IC or board mount,
circuit board, panel or chassis mount, modular bay or slot system, rack mount and stand-
alone. Common device specifications to consider when searching for data acquisition
products include differential analog input channels, digital I/O channels, sampling
frequency, resolution and accuracy. Common signal inputs available for data acquisition
products include DC voltage, DC current, AC voltage, AC current, frequency, and
charge. Specialized inputs include encoder, counter or tachometer, timer or clock, and
relay or switch. Transducers and excitation are also important to consider when
searching for data acquisition. Many products have integral sensors or transducers.
These sensors can have voltage or current excitation. Common outputs for data
acquisition products include voltage output, current output, frequency output, timer or
counter output, relay output, and resistance or potentiometer output.
Common applications for data acquisition products include general lab or
industrial, environmental, vehicular, marine, aerospace or military, seismic or
geotechnical, weather or meteorology, and medical or biomedical.
5.2 Signal Conditioning
Signal conditioning includes the amplifying, filtering, converting, and processing
required to make sensor output suitable for reading by computer boards. It is primarily
utilized for data acquisition in which sensor signals must be normalized and filtered to
levels suitable for analog-to-digital conversion so they can be read by computerized
devices. Signal conditioning type, form factor, device specifications, signal inputs,
sensor inputs, specialized inputs, transducers and excitation, outputs and user interface
are all important to consider when searching for signal conditioning devices. Other
specifications to consider include application software, memory and storage, network
specifications, filter specifications, amplifier specifications, and environmental
Types of devices that use signal conditioning include signal filters, instrument
amplifiers, sample-and-hold amplifiers, isolation amplifiers, signal isolators,
multiplexers, bridge conditioners, analog-to-digital converters, digital-to-analog
converters, frequency converters or translators, voltage converters or inverters,
frequency-to-voltage converters, voltage-to-frequency converters, current-to-voltage
converters, current loop converters, and charge converters.
Device specifications that are important to consider when searching for signal
conditioning instruments include differential analog input channels, digital I/O channels,
and accuracy. Differential channels use the difference between two signals as an input
while common mode is filtered out. In some systems, differential inputs are a
combination of two single-ended inputs. In this case, twice the number of differential
channels would be available as single-ended inputs. Digital or discrete channels are used
for low-level on-off signals used in applications such as communication, user interface,
Signal inputs accepted by signal conditioners include DC voltage and current, AC
voltage and current, frequency and charge. Sensor inputs can be accelerometer,
thermocouple, thermistor and strain gauge or bridge. Specialized inputs include encoder,
counter or tachometer, timer or clock, and relay or switch. Outputs for signal
conditioning equipment can be voltage, current, frequency, timer or counter, relay,
resistance or potentiometer, and other specialized outputs.
5.3 Using Software to Drive the Hardware
National Instruments provides powerful algorithms and functions designed
specifically for measurement analysis and signal processing. You can easily integrate
these into your applications and virtual instruments created by LabVIEW. By using these
functions, you do not have to write your own algorithms in order to turn raw data into
critical information. To make sense out of raw data you need to manipulate, process, and
analyze acquired data and extract information. With NI software you can:
Extract information from acquired data and unique measurements
Generate, modify, process, and analyze signals
Add intelligence and decision-making capabilities to your applications
Perform inline and offline analysis
Use common-purpose as well as specialized tools and add-ons
Academic Analysis Examples
6) ETHICAL ISSUES
6.1 Should the amount of healthcare provided be equal
amongst everybody regardless of economic status?
Stryker Endoscopy is a front-runner in the biomedical instrumentation field.
Their highly advanced products and systems are paving a path towards fully automated
medical machines, which will revolutionize operations and medical procedures
worldwide. However, with such technological advancements a hefty price is also
attached. Thus, the ethical question arises on whether or not the amount of healthcare
provided should be equal amongst all persons regardless of economic status.
If one considers healthcare a benefit, then it should be available to everyone
equally and/or distributed fairly. There is a definite degree or minimal standard of
healthcare every person should receive. Society should ensure that all persons are
adequately cared for based on basic survival and health. However, beyond that line,
where extra medical practices are involved, it is not the responsibility of those who can
afford the advanced procedures to hold back because another cannot. It is also beyond
means to ask the health care industry to be responsible for everyone and provide
everyone with the exact same treatment beyond the minimal amount needed for basic
survival. Such actions would contradict many characteristics Americans appreciate about
capitalism, and does not reward, nor reprimand, those who have earned or not earned
what they have worked for.
The larger issue of affording healthcare resonates to the question of is it ethical to
charge so much for healthcare? If healthcare were cheaper, or made more affordable, the
problem of providing equal amounts of healthcare would be drastically minimized
because more people would be able to afford more.
6.2 Responsibility of Manufacturer versus Consumer
Most would assume any product distributed by any company would be of the
highest caliber and standard attainable for that company. Thus, it would make it
Stryker’s ethical responsibility to distribute a product with the highest level of quality
possible. If this is an ethical obligation or a standard which simply reflects the morale of
the company is debatable. Some may argue that device standards should be on a parallel
sliding scale and would require a higher demand for accuracy and quality the more
dangerous or life-threatening procedure the device is being used for. Like all companies,
however, Stryker Endoscopy must deal with the cost, time and other business aspects of
producing a product and making maximum profits. Therefore, requiring better products
straight out of production would most likely increase the cost of the product. It is
extremely likely that the Stryker, as well as most other companies, would not appreciate
this burden on their profit and finances.
However, is it ethical to put all of the responsibility on the manufacturer/producer
rather than place some on the consumer? Where can we draw the line of burden? It is
understood that each situation is independent and influential details will alter the outcome
of each respectively. Of course, it may be worth thinking about.
6.3 Is capitalism unethical?
Think about it…