mwest_5_22156_tube_thoracostomy_airflow_measurement_and_management-1

Griffith School of Engineering

Griffith University

4001ENG – Industry Affiliates Program

Tube Thoracostomy Airflow Measurement

and Management

Placement Period: 3rd of March to 12th of June

Matthew West s2759009

10th of June Semester 1 2014

Griffith University

Professor Geoff Tansley

Professor Geoff Tansley

A report submitted in partial fulfillment of the degree of 1310 Bachelor of Engineering -

Mechatronics

The copyright on this report is held by the author and/or the IAP Industry Partner. Permission has been granted to Griffith University to keep

a reference copy of this report.

4001ENG – Industry Affiliates Program, Semester 1, 2014

i

EXECUTIVE SUMMARY

Tube thoracostomy airflow measurement and management is an important topic within the

medical field of thoracic surgery. The current method used by the Gold Coast University

Hospital for determining and measuring air leaking from the lungs into the pleural space, uses

the visual inspection method of watching for bubbles in a water chamber. This lack of

precision in the measurement technique, as well as the issue of which sized chest drain

catheter should be installed during Tube thoracostomy surgery is the motivation behind this

project. Therefore the aim of the project is to determine the advantages of bringing new

digital measurement technology to the field of thoracic surgery, determine if there is a viable

market for this technology, and investigate the maximum airflow rates for the currently used

range of chest tube catheters.

This report covers a wide range of research into the field of chest drainage systems which

covers the history and background of currently used chest drains as well as newly developed

digital drainage systems. The report focuses on the process used for the development and

testing of the prototype airflow measurement device. The report is structured around the

project development techniques used to produce a product using off-the-shelf components, 3D

design, and advanced prototyping techniques.

The final product regarded as the main deliverable of the project shown in Figure 0 is the

Pleural Air Leak Measurement Device (PALMD). The PALMD meets all of the requirements

set by the customer, and is capable of being connected to any existing chest drainage system

to accurately measure and displaying the volume of air being removed from a patient by the

current drainage system. The results from the testing of the PALMD show the measured flow

rate of the different sized catheters used in tube thoracostomy surgery. From these results it

can be concluded that a smaller sized chest tube catheter can handle the most severe air leak

volumes.


ii Pleural Air Leak Measurement Device

Figure 0. Pleural Air Leak Measurement Device.


iii

ACKNOWLEDGEMENTS

I would firstly like to thank my IAP supervisor Geoff Tansley for his constant support and

advice throughout the project. As well as the support and vision of Dr Peter Cole, without

whom this project may never have been considered, his vast knowledge and passion have

been essential in the completion of this project.

Throughout this project I have sought input and advice from many of the support staff within

Griffith University and would like to specially thank Milan, my colleague who was working

alongside myself in the lab for his constant advice and counsel. I would like to give a special

thanks to the University’s technical staff Mr Derek Brown for his electronics and components

advice, and Mr Grant Pickering for help with the design, laser cutting, and 3D printing.

Thank you to everyone who has helped me to complete this project and I hope you are all

proud of the achievement, I couldn’t have done it without all of your help.


iv Pleural Air Leak Measurement Device

TABLE OF CONTENTS

1 INTRODUCTION ............................................................................................................. 6

1.1 Background of Surgical Chest Drains ....................................................................... 6

1.2 The Research Question ............................................................................................... 8

1.3 Fluid Dynamics and Air Flow Rates ......................................................................... 9

1.4 Chest Drain Airflow Measurement Technology .................................................... 11

1.5 Purpose of the Project .............................................................................................. 14

1.6 Expected project outcomes ....................................................................................... 14

2 RESEARCHED LITERITURE ..................................................................................... 15

3 PROJECT IMPLEMENTATION ................................................................................. 17

3.1 Project Commission .................................................................................................. 17

3.2 Project Methodology ................................................................................................. 17

3.3 Project Schedule ........................................................................................................ 18

3.4 Project scope .............................................................................................................. 20

3.5 Budget and Resources ............................................................................................... 22

3.6 Product Discovery ..................................................................................................... 23

4 CONCEPTUAL DESIGN .............................................................................................. 24

4.1 Component choice ..................................................................................................... 24

4.1.1 Airflow sensor ...................................................................................................... 24

4.1.2 Microcontroller ..................................................................................................... 25

4.1.3 Power source ........................................................................................................ 26

4.1.4 Display ................................................................................................................. 26

4.1.5 Switches ............................................................................................................... 27

4.1.6 Memory ................................................................................................................ 28

4.1.7 3D design .............................................................................................................. 29

5 COMPONENT SPECIFICATIONS ............................................................................. 29

5.1 Airflow Sensor ........................................................................................................... 29

5.2 Microcontroller ......................................................................................................... 31

5.3 Screen ......................................................................................................................... 32

5.4 Switch ......................................................................................................................... 34

5.5 Power source .............................................................................................................. 34


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6 DESIGN AND CONSTRUCTION ................................................................................ 35

6.1 Internal support structure ....................................................................................... 35

6.1.1 Design ................................................................................................................... 35

6.1.2 Construction ......................................................................................................... 36

6.2 Outer Casing .............................................................................................................. 37

6.2.1 Design ................................................................................................................... 37

6.2.2 Construction ......................................................................................................... 39

6.3 Connection of PALMD’s Components .................................................................... 39

6.3.1 Arduino code ........................................................................................................ 39

6.3.2 Wiring ................................................................................................................... 41

6.3.3 Touchscreen programing ...................................................................................... 42

7 TESTING AND RESULTS ............................................................................................ 45

7.1 Flow sensor calibration testing ................................................................................ 45

7.2 Catheter flow rate testing ......................................................................................... 45

7.2.1 Test Equipment .................................................................................................... 45

7.2.2 Setup ..................................................................................................................... 46

7.2.3 Additional Tests Performed ................................................................................. 48

7.3 Results ........................................................................................................................ 49

7.3.1 Flow sensor calibration results ............................................................................. 49

7.3.2 Catheter flow rate results ...................................................................................... 50

7.3.3 Additional testing ................................................................................................. 52

8 DISCUSION .................................................................................................................... 52

8.1.1 Flow sensor calibration ........................................................................................ 52

8.1.2 Catheter flow rate ................................................................................................. 53

8.1.3 Additional testing ................................................................................................. 53

9 CONCLUSION ................................................................................................................ 54

10 REFERENCES ................................................................................................................ 56

APPENDIX A: FULL RESULTS TABLES ...................................................................... 60

APPENDIX B: ARDUINO CODE ..................................................................................... 70

APPENDIX C: BILL OF MATERIALS ........................................................................... 79

APPENDIX D: USER MANUAL ....................................................................................... 80


6 Pleural Air Leak Measurement Device

1 INTRODUCTION

1.1 Background of Surgical Chest Drains

The modern chest drain can trace its origins back over 2000 years to the ancient Greek

physician Hippocrates. It was Hippocrates who first proposed the method of making an

incision and inserting a metal tube into the chest cavity to drain the fluid caused by empyema

[1-2]. It wasn’t until almost a decade ago that Hippocrates method was adopted for

widespread use by medical professionals. The first widely reported case of the tube

thoracotomy procedure as it is known today, was during the influenza epidemic of 1917. It

was used to collapse the infected lung and remove the pus created by the infection commonly

known as Tuberculosis, this allowed the infected legions to heal [3].

To understand the use of the chest drain in modern surgery a basic understanding of how the

human body works must first be achieved. Within the chest cavity where the lungs are

situated there is a negative pressure or vacuum, this vacuum is essential in keeping the lungs

expanded [4]. When the body undergoes an injury either from an accident, surgery or

infection where air (either from the lungs or outside the body) or fluid (being blood or pus)

enters the chest cavity it creates a pleural space. The pleural space forms in the lining between

the outside of the lungs and the inside of the chest wall as shown in figure 1, restricting the

lungs ability to expand causing pain and difficulty breathing [5].

Figure 1. Pleural space formation within the chest cavity [14].


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If the pleural space expands large enough it can cause the affected lung to collapse and apply

pressure to the healthy lung which in extreme cases can lead to death. [12]

The modern chest drain is designed to remove the fluid and air within the pleural space

allowing the lung to expand as normal [6]. This is achieved by three methods:

Firstly, the pressure exerted by the diaphragm when breathing out, and even more so

when coughing forces air and fluid out through the chest drain tube.

Secondly, if the chest drain system is situated below the patient’s chest, gravity can be

used to drain the fluid.

Lastly, most drains employ a suction method to draw out the fluid and air [6].

Nowadays tube thoracotomy surgery is common practise in hospitals all around the world;

while the modern chest drains used in tube thoracotomy surgery have come a long way in the

past 100 years. The most basic style of chest drain used today by hospitals is the three bottle

system shown in figure 2.

Figure 2. Three bottle basic chest drain system [2].

The catheter tube is now made out of PVC, making it soft and bendable but still rigid enough

to not kink. The new catheter tubes also have multiple drainage holes, a depth marker, a

radiopaque stripe, and come in a wide range of diameter sizes [2][6]. Most of the current

chest drain systems work on the same principles and require a water seal or mechanical



equivalent, the water seal works like a one way valve, allowing fluid and air to be drained

from the patient without letting any air re-enter the pleural space [2].

1.2 The Research Question

The research question being investigated within this report focuses on the different size chest

tubes used by surgeons in today’s tube thoracotomy procedures. There are many different

sized chest tubes available with diameters from 6-40 on the French scale, and the choice of

which size chest tube to be used in surgery is primarily up to the surgeon’s personal

preference.

A tube thoracotomy procedure is performed under the following circumstances [2] [8]:

Spontaneous pneumothorax (large, symptomatic or presence of underlying lung

disease)

Tension pneumothorax (or suspected)

latrogenic pneumothorax (progressive)

Penetrating chest injuries

Hemopneumothorax in acute trauma

Patient in extremis with evidence of thoracic trauma

Complicated parapneumonic effusions (empyema)

Pleurodesis for intractable symptomatic effusions, usually maligant

Chylothorax

Post thoracic surgery

Bronchopleural fistula

The problem lies with the size of the chest tubes put in by the thoracic surgeons. Most

thoracic surgeons prefer to use a large 36-40 French sized catheter as it can handle flow rates

of up to 60L/min [2][11]. The step-by-step method of chest tube insertion in the Advanced

Trauma and Life Support instructors manual, outlines the insertion of a large diameter chest

drain for tension pneumothorax [8]. The larger diameter chest tubes have an advantage over

smaller diameter tubes when it comes to obstructions caused by infected effusions and

clotting blood, though they are significantly more unpleasant for the patient [7].

In the past the use of large diameter chest tubes have been recommended as it was believed

that smaller chest tubes would struggle with blockage from infected fluid and blood clotting

[8-10]. However recent studies have shown that the use of smaller diameter tubes is often just


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as effective as using a large diameter tube [7-8]. This remains a constant debate between

doctors and there is currently no consensus on the optimal size chest tube [8].

As proper chest drain management plays a very important role in post-operative recovery

time. If the chest tube is removed prematurely or its removal is delayed, it can result in an

increased hospital stay for the patient, tying up valuable hospital resources and increasing

costs [6]. Therefore the aim of this research project is, to through the use of mathematical

calculations, and physical measurement of fluid flow rates, determine the optimal size chest

tube for surgeons to use. If a smaller diameter chest tube is equally as efficient as a larger

diameter tube then it will have a noticeable effect on patient’s recovery time, comfort, and

related costs.

1.3 Fluid Dynamics and Air Flow Rates

The volume of air, and rate of flow through the different diameter chest drains can be

calculated using fluid dynamics equations. Since the chest tubes are all made of the same

PVC material, and for calculation purposes are assumed to be the same length, and have the

same design characteristics such as opening friction losses, calculation of the air flow rate

through the different sized tubes can be calculated. To calculate the flow rate of air that each

tube will allow, the following properties must be known:

The length of the pipe

The diameter of the pipe

The pressure difference between the two ends of the pipe

The pressure drop across the pipe

The density of the air

The dynamic viscosity of the air

The minor losses coefficient

The pipe roughness

To allow for realistic calculation without the use of computer aided simulations some

assumptions must be made. With these assumptions an estimation of the flow rate can be

calculated.



If we take an estimated pressure drop across the pipe, we can use equation (1) for

compressible isothermal flow in a horizontal pipe to calculate the volume of flow.

(1)

Where:

p1,2 - pressure on the begging and on the end of pipe line;

w - mass flow rate

v1 - specific volume

f - friction factor ( taken as 3 to account for inward projecting pipe with T style openings)

L - pipe length

D - internal pipe diameter

A - pipe cross section area

With an estimated pressure drop of 1cm H2O gives:

(2)

Therefore: w = 0.000306477;

The volume of airflow can then be found using the formulas (3) and (4).

(3)

(4)

The estimated values used for preliminary flow calculations can be checked and updated once

the prototype device is used to accurately measure the volume of air flow and velocity of air

flow in the catheter. This will then allow for a more accurate prediction of the friction forces

and pressure drop.


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1.4 Chest Drain Airflow Measurement Technology

To back up the calculated flow rates achieved from the research question a prototype flow rate

measuring device will be designed and created. The prototype measuring device will serve a

dual purpose in that it will not only back up the calculated flow results, but will also serve as a

more accurate measurement device for use in the hospital for patients who have undergone

tube thoracotomy surgery.

At the moment the main method used for determining and measuring air leaking from the

lungs into the pleural space uses the visual measurement of ‘‘bubbles in a water chamber’’

[12] which can be seen in figure 3.

Figure 3. Atrium Oasis water seal air leak meter.

As air leaks form the lungs into the pleural space it is sucked out by the chest drain. As the air

is sucked out by the chest drain it passes through a water seal, which both visually shows the

flow rate of the air as bubbles through the water, and stops air from returning into the pleural

space.

Since the range of the airflow leak under normal breathing is known to be between 0.005

SLPM (5mL/min) and 0.9 SLPM (900mL/min) [13], a thermal mass flow sensor can be used

to measure the relatively slow flow rate of air. With electronic sensors we are now able to

accurately measure the flow rate of the air leak, and thus calculate the volume of air that is

leaking from the lungs over a certain time period. This will give doctors a much clearer



picture of how the leak is progressing, not only will it show how big the leak is, but it will

also show the rate of change over time. This will give doctors a the ability to better manage a

prolonged air leak, and is expected to contribute to better patient care and reduced costs for

both the hospital and the patients.

Digital Thoracic Drainage Systems (DTDS)

The most common complication after lung surgery is still considered to be air leaks [13-17].

With the current level of technology used in air leak detection it is not uncommon for

physicians to disagree on the presence of an air leak while inspecting the water chamber for

bubbles [15].

With the digitalization of many areas of life becoming a fast growing industry it was

inevitable that a Digital Thoracic Drainage Systems (DTDS) would be created to fill the gap

in the market. The first digital airflow measurement device created for the measurement of

pleural air leaks was the AIRFIX in 2006 shown in figure 4 [16].

Figure 4. AIRFIX Digital airflow measurement device [16].

The AIRFIX device was designed to attach to the chest drain that is currently being used by

the patient and record the flow rate of air. The device uses “mass airflow” sensor technology

to measure a range of 0 – 5000 mL/min with an accuracy of ± 5%, and was used in a trial with

208 patients [16].


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Since the introduction of the AIRFIX device in 2006, a few other companies have developed

their own Digital Thoracic Drainage Systems. In 2008 the Swedish company, Millicore

developed the world’s first FDA approved digital air leak measurement system, the Digivent

shown in figure 5 [15].

Figure 5. Digivent Thoracic drainage system [15]

The newest known device to enter the market is the Thopaz thoracic drainage device made by

Medela shown in figure 6. The Thopaz is an all in one drainage unit with a removable fluid

catchment container, and inbuilt suction pump to allow for patient mobility [15]. The device

contains all of the digital measurement technology required and displays the airflow results on

an LCD screen on top of the device.

Figure 6. Thopaz Thoracic drainage system [18].



1.5 Purpose of the Project

The purpose of this project was split into two tasks, the first task was to give doctors at the

Gold Coast University Hospital a more accurate way of quantifying post thoracic surgery air

leaks. The projects main task was to develop a device capable of determining the presence

and severity of an air leak by displaying a quantifiable value of the volume of air leaking per

minute. This was to be achieved through the use of off-the-shelf components, new digital flow

sensor technology, an open source micro-controller, and advanced prototyping techniques.

The second task of this project relates to the research question, the purpose of the second task

was to determine the flow rates of the different size chest tubes used by surgeons in today’s

tube thoracotomy procedures. There are many different sized chest tubes available with

diameters from 6-40 on the French scale, and the choice of which size chest tube to be used in

surgery is primarily up to the surgeon’s personal preference. Though the use of the Pleural Air

Leak Measurement Device (PALMD) developed in task one, the flow rate for the different

sized chest tube catheters were examined under controlled conditions to determine the

relationship between size and flow rate for each of the tubes.

1.6 Expected project outcomes

Since this project was broken down into two distinctive tasks, a research question and a

prototype measuring device, the expected outcomes for each task will be different.

The expected outcomes for task one (the prototype measuring device) will be of both a

physical and academic nature.

It is expected that the completion of this project will result in a completed device for

use in post-thoracic surgery pleural airflow measurement, capable of measuring the

volume of air leaking from the lungs into the pleural space.

To accompany the prototype a user manual will also be created to ensure the correct

use of the device.

A full in depth report covering the background, design, test results, and conclusions

will be delivered as the final project outcome.


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The PALMD device will act as a prototype for use in the hospital to generate awareness for

the possibility of new technology in the field of post-thoracic surgery.

The expected outcomes for task two (the research question) will be of an academic nature.

A report on the effects of drainage flow rates for different diameter chest drains is

expected.

The report will include the results from the PALMD developed in task one.

2 RESEARCHED LITERITURE

The research phase of the project started with an investigation into the working principles of

the current chest drain technology being used. The research question evaluated within this

report requires an investigation into the airflow ranges of the different sized chest tube

catheters. The problem lies with the size of the chest tubes put in by the thoracic surgeons.

There is a vast field of medical journal articles of the effects of different sized chest tubes.

Chest tubes. Indications, technique, management and complications [2], is a review article on

chest drain technology, that backs up the theory that most thoracic surgeons prefer to use a

large 36-40 French sized catheter. This is believed to be due to the fact that it can handle flow

rates of up to 60L/min [2].

The journal article, BTS guidelines for the insertion of a chest drain [8], is an internationally

recognised set of guidelines for the safe insertion of a chest drain. The section of the article on

drain size states that “small bore drains are recommended as they are more comfortable than

larger bore tubes, but there is no evidence that either is therapeutically better”, and that the

use of small bore catheters as small as 9 FR have been successfully used to treat

pneumothoraces, however a large bore tube is recommended for a hemothorax [8].

The aim of the journal article, treatment of malignant pleural effusion: pleurodesis using a

small percutaneous catheter. A prospective randomized study [7], is to compare a 10FR

catheter to a 24FR catheter for performing pleurodesis. The results show that there was no

significant differences in operation between the two sizes, though the smaller 10 FR catheter

was found to be more pleasant for the patient than the larger 24 FR catheter.



For the development of the prototype device journal articles on the Digital Thoracic Drainage

Systems were used to find the relative information on the existing technology in this field. To

create a quality prototype the issues with the old chest drains must be examined.

The journal paper, postoperative chest tube management: measuring air leak using an

electronic device decreases variability in the clinical practise [19], examines the chest tube

withdrawal criteria and personal observation bias caused by traditional drainage systems. The

paper focus on the issue that there is currently no set guidelines or method for the

management of chest tubes after lung resection surgery, or for the use of suction [19]. This

paper examines the results obtained from study of two thoracic surgeons, every morning the

two surgeons evaluated the decision to remove a patient’s chest drain blinded to the other

surgeon’s decision. The study was performed on 61 cases (35 with a digital drainage device

and 26 with a traditional device) with the agreement rate of the two surgeons being 58% for

the traditional group, and 94% for the digital group. The results published in this paper show

that the use of DTDS increases the agreement of when to remove a chest drain, by giving the

two surgeons a quantifiable value for the air leak not subject to interpretation [19].

The journal paper, the benefits of digital thoracic drainage system for outpatient undergoing

pulmonary resection surgery [17], examines the benefits that a digital thoracic drainage

system (DTDS) can offer over conventional drainage systems. The paper focus on the issue of

a prolonged air leak after pulmonary resection surgery, which is one of the most frequent

complications of lung surgery [17]. There are currently a number of articles that promote the

use of DTDS, and claim that it will allow for the drains to be removed earlier, and the patients

to be discharged sooner. This paper puts that theory to the test with the use of testing on

selected patients. Three patients that developed a prolonged air leak after surgery were chosen

for the trial. On the 7th, 7th, and 5th postoperative day patients 1, 2, and 3 respectively were

given the option to be discharged with a DTDS to monitor their status. 6 days after being

discharged the drain was removed from patient 1, while 15 days after being discharged the

drain was removed from patient 2, and 3. The authors found that DTDS is safe, comfortable

and well accepted by patients, it was also clear that the use of DTDS resulted in a shorter

hospital stay [17].

The journal article, AIRFIX: the first digital postoperative chest tube airflowmetry – a novel

method to quantify air leakage after lung resection [13], examines the use of a thermal mass


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flow meter in quantifying bed-side air leaks as managed by conventional thoracic drainage

systems. The AIRFIX digital airflow measurement device was the first device created to

measure and record the volume of postoperative chest drain airflow [13]. The study conducted

in this paper was a clinical evaluation of the AIRFIX system on 204 patients with an air leak

between 150 and 250 mL/tidal volume. The device was used to measure the range of air

leakage for a variety of breathing maneuvers, such as, normal breathing, forced breathing, and

coughing. The results from this study show the range of airflow measured under different

breathing maneuvers to range from 5-900 mL/min [13].

3 PROJECT IMPLEMENTATION

3.1 Project Commission

The project was commissioned as an internal IAP project proposed by Dr Peter Cole, Head of

Thoracic Surgery at the Gold Coast University Hospital, and supervised by Professor Geoff

Tansley, Head of the School of Engineering, Griffith University.

The Project was commissioned to determine the advantages of bringing new digital

measurement technology to the field of thoracic surgery and determine if there is a viable

market for this technology.

Currently the insertion of a chest drain is common practice with Australia, with Australian

hospitals performing over 12,000 tube thoracostomy procedures per year [20]. The

development of the PALMD is to act as a trail device, designed to gauge the market response

and determine the requirements for a mass produced device.

3.2 Project Methodology

The first task before the project planning began was to do research into the field of thoracic

drainage. The working principles of the existing chest drains on the market needed to be

understood. As well as the medical symptoms related to the use of chest drains, and lung

function.

Once the process of the air leak was understood a solution could be made to address

the problem.



The current digital thoracic drainage devices would be used as a base starting point

and benchmark for this project.

The major components for the prototype would need to be ordered early as a long

delivery time is expected.

The device will be made primarily from off-the-shelf components and materials

available within the University’s lab.

Once the prototypes components are assembled it will be used to measure and supply

the data required for the research question.

The data for the research question will be assessed using Microsoft excel spreadsheets

and graphs.

The project will be managed like a prototype development project primarily, with the

research question being addressed using the finished prototype device.

3.3 Project Schedule

The project schedule was developed as part of the IAP requirements Project Planning Report.

The first three weeks of the project were spent doing research to gain the knowledge required

for the project, and to complete the project planning report. Part of the project planning report

required that a Gantt chart be created to organise the tasks essential to completing the project,

this can be seen in figure 7 below.


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Figure 7. Gantt chart of tasks required to complete the project.

The development of the Gantt chart required that possible problems be predicted and

compensated for very early on in the project. Each task required to complete the project was

given a completion date and estimated time required, taking into consideration delays such as

buying components from overseas. Extra time was allowed for the design tasks to allow for

multiple redesigns if necessary.

Concurrent engineering techniques were utilised in the planning of the Gantt chart to ensure

that all tasks could be completed within the timeframe given. The final report task runs almost

the entire length of the project, starting after the planning report task ends. Organising tasks

by running them parallel is a good way to handle tasks that are not dependent on each other.

Sequential planning was used for the design, and testing tasks as they require the previous

task be completed before moving on to the next task.

Throughout the project all tasks progressed as planned with the exception of the parts

acquisition task. This problem was expected and extra time was assigned to the parts

acquisition task to account for delays in the delivery of components. This however was not

sufficient as some component delays were longer than expected and some components have



still yet to be received. This caused the project to fall behind schedule in the final construction

and testing phase. With unforeseen delays a back-up plan was considered in case the parts

didn’t arrive in time. The delays caused by parts accusation caused the project testing phase to

be greatly reduced; however much of the testing could be done without all of the components

present.

3.4 Project scope

The scope of the project was initially defined by the customer, Dr Peter Cole. The project

scope was to:

To develop a device that can measure the volume flow rate of air, leaking from the

lungs after a chest drain has been installed.

To assess the flow rate capabilities of the different sized chest tube catheters used in

tube thoracostomy surgery.

There are many methods that can be used to determine the scope of the problem, for this

project a prioritized requirement table was used, listing the required tasks and additional tasks

that were to be implemented in order of importance for the construction of the prototype

device.


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D or W Requirements Importance (1-10)

D Measure airflow 10

D Display air flow rate 10

D Washable with alcohol 10

D Connect to existing chest drains 10

D Doesn’t inhibit normal operation 10

D Instruction manual 10

D Safe 10

W Battery powered 7

W Aesthetics 7

W Easy maintenance 6

W Alarm 5

W Compact 5

D: Demand (10)

W: Wish (9-1)

Table 1. Prioritised Requirements of the prototype device.

With the use of the prioritised requirements table for the prototype device as shown above in

table 1, a user requirement specification sheet was made to list the minimum requirements

required to successfully complete the project. The user requirement specification sheet shown

below in table 2, was signed by the customer, the IAP industry supervisor, and myself giving

this project a clear and defined unchanging minimum scope.



User Requirement Specifications (√ or X ) (√ or X )

Pleural Air Leak Measurement Device

(PALMD)

A prototype device to measure the volume of air flow

exiting the water seal drainage bottle

Prototype must be washable with alcohol chlorhexidine

Powered by an internal rechargeable battery (usb

connection)

Air flow rate to be displayed on LCD screen

Alarm when major prolonged air leak is detected

Instruction manual, to explain the use of all features

Research Question

Mathematical calculations to show predicted flow rates of

different size chest tubes

Experiment designed to measure the actual flow rates of

different size chest tubes

Report showing both calculated and measured flow rate

results, to determine if a smaller sized chest tube can be as

effective as a larger sized one at removing air.

Designers Signature Customers

Signature

Supervisors

Signature

Table 2. Prioritised Requirements of the Pleural Air Leak Measurement Device (PALMD)

3.5 Budget and Resources

There was technically no set budget for the project, though a cost effective approach was

taken to the design and development of the prototype.

The component selection was heavily influenced by cost/benefit analysis as shown in tables 3-

6, the cheapest option was not always the best option.

Most of the resources required for the construction of the project’s prototype, such as 3D

modeling software, and lab hardware including the acrylic laser cutter, and 3D printer were

made available by Griffith University. This allowed the projects costs to be kept relatively


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low, as only the components needed to be purchased, for a full list of components see the bill

of materials in appendix C.

3.6 Product Discovery

To create a successful new project the ‘product discovery’ method shown below in figure 8

was used to determine what the prototype needed to be succesful in the market.

Figure 8. The product discovery method [21]

The ‘product discovery’ method shows that for a successful project choice there must be a

hole in the market for it, described by one of the three areas:

Technology push – the development of the PALMD fits this category with the use of

the MEMS technology in the airflow sensor and the advancement in the the inteigent

touchscreen LCD.

Market pull - the development of the PALMD will determine if the cost of the device

will compare to the added benefits of the device.

Product change – in todays society everything is going digital, the PALMD will use

digital electronics to replace the outdated technology currently being used in tube

thoacostomy surgery.

The PALMD project meets the all three of the requirements that the ‘product discovery’

method defines for a successful project choice, and therefore the project was approved for

manufacturing.



4 CONCEPTUAL DESIGN

Figure 9. Component diagram

The component diagram shown in figure 9 shows how each of the PALMD’s components will

connect together.

4.1 Component choice

4.1.1 Airflow sensor

The airflow sensor can be considered the most important component in this project. The main

function of the device is to measure the volume of air that is being removed from the pleural

space by the chest drain. Therefore choosing the correct sensor for the task was of high

priority.

There are many different methods for determining airflow, from mechanical systems such as

turbines and Anemometers, to more advanced electronic methods such as vane and hot wire

mass air flow sensors. For this project it was decided that the best type of airflow sensor

would be a thermal mass air flow sensor.

To determine the best sensor for the purposes of this project table 3 was created.


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Flow Sensor

Sensirion

SFM4100

Mass Flow

Meter for

Medical

Gases

Sensirion

SFM3000

Low-

Pressure-

Drop Flow

Meter

Honeywell

Zephyr™ HAF

Series – High

Accuracy ±50

SCCM to ±750

SCCM

Honeywell

Zephyr™ HAF

Series – High

Accuracy 10

SLPM to 300

SLPM

Range 0 to 20 l/min +/-200slm

(bidirectional)

0 SCCM to

±750 SCCM

(bidirectional)

0 SLPM to 10

SLPM

Connection

Type

Digital I²C

interface

Digital I²C

interface

analog (Vdc),

Digital I²C

interface

Digital I²C

interface

Accuracy 0.15% FS or

3% MV 2% MV ±0.25 %FS 3.50% FS

Power 3.5 V – 9.0 V 5 V 5 V 3 V to 10 V

Cost $280.00 $199.00 $93.69 $100.00

Table 3. Flow sensor comparison.

From information gathered in the research phase of the project it was determined that the

maximum airflow that the sensor had to be able to measure was 7 Liters/minute [13] as

produced by a patient blowing into a closed system, this produced the highest pressure in the

lungs and therefore the highest leak volume possible. Under normal breathing the range of air

flow was between 0 SCCM and 1,000 SCCM [13], this produced a problem in determining

the required range of the sensor and as such a range of 10 SLM was chosen to accommodate

any leak that could be encountered by normal operation.

4.1.2 Microcontroller

The current market for microcontrollers have made the Raspberry Pi, and Arduino

microcontroller platforms extremely easy to use. For this project the Arduino Leonardo

microcontroller was chosen due to the designer’s previous experience with this particular

platform and the availability of the Leonardo board.



4.1.3 Power source

The PALMD is designed to use an electronic digital airflow sensor, microcontroller, and

digital display. Therefor the issue of power is critical to the design and operation of the

device. To determine the best option for powering the device table 4 was created to compare

the different methods available.

230V

Mains

Power

Rechargeable

Batteries

USB

power

pack

Weight NEG 100g 150g

Size NEG Medium Small

Capacity NEG 2300mAh 5600mAh

Cost $10 $ 20 $10

Portability poor good good

Recharge

method NEG 230V mains USB

Table 4. PALMD Power options

To determine the best method for powering the PALMD the operating environment must be

considered. The PALMD is required to operate in the hospital environment, therefore 230V

mains power would seem like the obvious choice as power points are common in hospital

rooms. The only downside to 230V mains power is the portability issue, as the device will

need to remain attached to the patient for up to a week, portability is very important. For this

reason the USB power pack was chosen as it is cheaper than the battery alternative, has a

higher capacity and the USB cable used for recharging can also be used to retrieve the data

from the microcontroller.

4.1.4 Display

The display is essential in meeting the minimum requirements of the project scope. The data

measured by the airflow sensor must be displayed in a way that is easy to read and interpret.


Matthew T West 27

To determine the best option for displaying the data table 5 was created to compare the

different methods available.

7

Segment

Display

LCD TFT

LCD

Touchscreen

LCD

Weight Light Light Light Heavy

Size Medium Small Medium Extra Large

Cost $10 $20 $30 $240

Function Low Low Medium High

Appearance Basic Basic Medium High

Table 5. PALMD Display options

To give the PALMD a high tech feel and appearance the touchscreen LCD was chosen. The

screen is the only part of the device that the customer will be using to interact with the device,

therefore it had to display the data in the most easily accessible way. The most simple and

cost effective method would have been to use a standard 2 line LCD panel though this did not

fit with the design idea of producing a new and exciting product to act as a proof of concept

prototype. The touchscreen LCD was chosen for its high level of function and appearance, as

it is believed that it will remind the users of a smart phone and allow for many different

results to be displayed.

4.1.5 Switches

Switches are an important component in any device and there role in the PALMD is essential

in the devices ability to complete its intended task. The choice of which switches to use for

the device rely on multiple factors, such as environment and purpose. To determine the best

option table 6 below was created to compare the different types available.



Switch

Type

Round

Rocker

Switch

Spst Led

Illuminated

- Paddle

Switch

Miniature

Dpdt

Panel

Mount

Switch

Spdt

Miniature

Toggle

Switch

Cost 7.95 4.95 1.25 6.95

Hole Size 20mm

Hole

20mm

Hole 35x13mm 6mm

IP65 Yes Yes No Yes

Appearance Good Good Bad Average

Illuminated Yes Yes No No

Table 6. PALMD switch options

Since the device requirements specify that the device will be cleaned with alcohol and used in

a biologically hazardous area, an IP65 certified switch would be required. The device will

require two switches, one to act as a power ON/OFF switch, and one to act as an LCD screen

ON/OFF switch, the round rocker switch was chosen to be the most appropriate choice.

However the SPDT Miniature Toggle Switch was purchased due to its small hole requirement

and availability.

4.1.6 Memory

As part of the devices additional feature the data collected from the devices sensor can be

stored in memory, so that it can be accessed at a later time for research purposes. The Arduino

Leonardo microcontroller has a small amount (1 KB) of EEPROM memory on board [22],

this works out to be only enough space to record approximately 250 samples. For more

storage space a bigger EEPROM chip was chosen. A 24LC256 Integrated Circuit microchip

was chosen due to its 32KB memory size and I2C connection type.


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4.1.7 3D design

The design of the PALMD required that a 3D model be created, for use in a rapid prototyping

3D printer. There are many good 3D modeling programs on the market including, AutoCAD,

Solid Works, and Inventor. Originally solid works was chosen as it is the preferred software

within the market at the moment. After the initial 3D design, the software was switched to

Autodesk Inventor due to the designer’s skill level difference between the two systems.

5 COMPONENT SPECIFICATIONS

5.1 Airflow Sensor

The most important component in this project is the airflow sensor. There was a lot of choice

when choosing the best sensor for the task. The best performing sensor was the Sensirion

SFM4100, however with a cost of over $280 the much cheaper $100 Honeywell ZephyrTM

Digital Airflow Sensor: HAF Series–High Accuracy model was chosen due to its ability to

perform all required tasks and its low cost comparison between the other options.

The Honeywell ZephyrTM Digital Airflow Sensor: HAF Series–High Accuracy model chosen,

shown below in figure 10 was the model with a 10 SLPM (Standard Liters Per Minute) flow

range.

Figure 10. Honeywell ZephyrTM Digital Airflow Sensor (10SLPM)

The advancement in digital sensor technology over the past few years has made it much

simpler to implement a sensor like the ZephyrTM Digital Airflow Sensor into a prototype

device.

The Honeywell ZephyrTM Digital Airflow Sensor: HAF Series operates on the heat transfer

principle to measure mass airflow as shown in figure 11 below.



Figure 11. Mass airflow technology working diagram [23]

They operate on MEMS technology and consist of temperature-sensitive resistors deposited

with thin films of platinum and silicon nitride. The MEMS sensing die is located in a precise

and carefully designed airflow channel to provide repeatable response to flow [24]. As air

flows through the device heat is transferred from the heater element to the temperature-

sensitive resistors allowing for a precise measureable signal.

The key features of the Honeywell ZephyrTM Digital Airflow Sensor are [24]:

The sensor is compensated over the calibrated temperature range of 0°C to 50°C [32°F

to 122°F], meaning that for programing, temperature fluctuations are automatically

compensated for by the sensor.

The sensors digital output is linear which allows for easy calibration of the device,

figure 12 shows the graph of the digital output value for the full scale flow percentage.

Figure 12. Nominal Digital Output [24].

http://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Bilder/Sensirion_calorimetric_principle.gif


Matthew T West 31

The device has a high level of accuracy as shown by figure 13, and a resolution of

0.002 SLPM, making the device adequate for the purpose of this project.

Figure 13. Accuray and Total Error Band [24].

The airflow sensor will be connected to the microcontroller board through an I2C connection

which allows for a measurement reading response time of 1ms. The maximum sink current of

the SDA and SCL lines are 2mA, therefore SDA and SCL lines must be connected to pull-up

resistors. Two 4.7kΩ resistors were needed to be connected between the VDD and the SDA

and SCL lines.

5.2 Microcontroller

The Arduino Leonardo microcontroller board was used to run the PALMD. The Arduino

platform was chosen due to its easy to use software and hardware, for a simple prototype

device such as this projects PALMD the Arduino’s open source platform fits the requirements

perfectly.



Figure 14. Arduino Leonardo microcontroller board [22]

The Arduino Leonardo microcontroller board as shown above in figure 14 is used in the

prototype to read the airflow value from the sensor and send the data in a useable fashion to

the screen. The Arduino board runs off a 5V power supply and can supply the needed power

and current requirements of the airflow sensor.

The 1KB EEPROM memory on the Leonardo board is not sufficient for long term

measurement storage options, however an external EEPROM chip can be connected through

the digital I2C pins.

5.3 Screen

The 4D systems uLCD-43-PT (Resistive Touch version) 4.3" TFT Intelligent Display shown

below in figure 15 was chosen for the prototypes display. The 4.3" touchscreen was chosen

due to the vast amount of customizability of the system, and lift of included features in the

device.


Matthew T West 33

Figure 15. SK-43PT-AR (Starter Kit) [25]

The uLCD-43-PT is a new system on the market that is designed to be a stand-alone graphical

user interface. The touchscreen not only offers a digital display capable of showing the air

flow rate but comes with a wide range of additional features such as [26]:

On-board audio amplifier with a tiny 8Ω speaker for sound generation and WAV file

playback.

480 x 272 VGA resolution, RGB 65K true to life colours, TFT screen with integrated

4-Wire Resistive Touch Panel

14KB of flash memory for user code storage and 14KB of SRAM for user variables,

or 14KB shared user code and program variables.

On-board micro-SD memory card adaptor for multimedia storage and data logging

purposes. HC memory card support is also available for cards larger than 4GB.

Display full colour images, animations, icons and video clips.

4.5V to 5.5V range operation (single supply).

Weight ~ 79g.

The touchscreen is the component that is used to bring the whole PALMD together, by

incorporating the on board speaker, data logging features of the micro-SD card, and master

I2C ability to control the Arduino microcontroller, the screen becomes the controller for the

entire device.



5.4 Switch

The SPDT Miniature Toggle Switch shown in figure 16 was chosen due to its availability,

size, and IP 67 rating.

Figure 16. SPDT Miniature Toggle Switch [27]

The IP 67 ingress protection rating of the switch is one of the most important features as the

switch will control the power for the device and may come in contact with alcoholic cleaning

substances. An IP 67 rating means that the switch is, totally protected against dust ingress (6),

and protected against immersion between 15cm and 1M (7) [28].

5.5 Power source

The Portable External Battery USB Charger Power Bank shown in figure 17 was chosen to

power the PALMD due to its many advantages over standard battery packs.

Figure 17. Portable External Battery USB Charger Power Bank [29]


Matthew T West 35

The key features of the power bank are [29]:

Shock drop resistance

Capacity: APP5200-5600 mA

Charge Time: 10 hours

Size:90mm *40mm*20mm

USB charging

Output: 5V 1A

These features make the power pack the best choice for the PALMD to accommodate

charging, data retrieval, and the minimization of internal wiring complications.

6 DESIGN AND CONSTRUCTION

6.1 Internal support structure

6.1.1 Design

The internal support structure of the PALMD is used to secure all of the prototypes

components and act as a testing platform for use before the final product is assembled.

The internal support structure was designed using Autodesk Inventor CAD software, a shelf

style structure was designed with 3 levels. The internal support structure was made out of

3mm acrylic Plexiglas and designed to clip together. Figure 18 below shows the CAD

drawing of the top view of all the internal support structure pieces.



Figure 18. Internal support sructure pieces

6.1.2 Construction

The top face of each piece was exported as an .STL file and cut from the 3mm plexiglas using

a laser cutter. The laser cut pieces were connected together and the device’s components

atteched to there respective shelves as seen in figure 19 below.

Figure 19. Assembly of the internal support structure.


Matthew T West 37

6.2 Outer Casing

6.2.1 Design

The center ring of the case was also designed using Autodesk Inventor CAD software. The

center ring makes up the middle of the device, containing the device’s connection plugs to the

chest drain system. The center ring piece was designed in two parts as seen in figure 20

below, that connect together to form the ring.

Figure 20. Outer ring 3D design of the PALMD

The front and back face’s of the device shown in figure 21 below, were made of 3mm acrylic

Plexiglas to allow for internal viewing of the device while in the prototype phase. The front

face has a hole cut out of it, so that the touch screen can protrude through the front of the

device and be accessed by the user.



Figure 21. Front (left) and back (right) faces of the PALMD

The entire case fits together to produce a nice clean looking concealed measurement device,

the product was designed to connect in-line with a currently used chest drain system. The full

3D design representation of the outer case of the PALMD shown in figure 22 shows the outer

ring connected with the front and back face plates. The top of the device shows the connection

to the vacuum hoses and USB connection slot.

Figure 22. full outer casing 3D design of the PALMD


Matthew T West 39

6.2.2 Construction

The center ring was made using an FDM 3D printer and connects around the internal support

structure. The center ring contains all of the devices external connections including the USB

connection cable, and power switches.

6.3 Connection of PALMD’s Components

The PALMD construction started with the connection of the various components. The first

components to be connected were the Arduino and the airflow sensor.

6.3.1 Arduino code

The Arduino code is very easy to grasp the basic concepts, and is widely used by hobbyist for

creating personalized projects. For this project the code was required to initialize the airflow

sensor and take readings at set intervals, and use the data to produce an output that can be

displayed to an LCD screen and easily interpreted by the customer.

The Arduino Platform contains many code libraries and example codes, which make the tasks

required very easy to accomplish.

Before starting the code for the PALMD the flow chart shown below in figure 23 was created

to visualize the code structure.



Figure 23. Code structure flow chart for reading and displaying sensor data

The code was designed to make use of sub-routines, and as such each task was separated into

its own sub-routine.

The request data sub-routine uses the Arduino’s inbuilt “wire” library to request 2

bytes of data from the airflow sensor using the I2C connection. When the two bytes are

received they are converted into a single value to which is related to the volumetric

flow rate measured by the sensor.

If the “zero device” button has been triggered by the user then the measured value is

used as the zero value for calibration.

The “calibrate” sub-routine takes the data value sent by the sensor and scales it to

represent the actual flow rate, it then sums up the 10 measurements taken each second

and returns the one second average.


Matthew T West 41

The “minute average” sub-routine takes the value returned from the calibrate routine

for 60 cycles and sums it up, it then returns the 1 minute average of the flow rate.

The “display data” sub-routine sends the output of the “calibrate” sub-routine and the

“minute average” sub-routine to the LCD display.

A “check screen” subroutine will be run before all of the others once the LCD touchscreen is

connected to check the status of the touchscreens digital buttons. As a button is pressed on the

touchscreen it will trigger a flag event in the arduino code to select the correct sub-routines to

execute.

The full version of the Arduino code can be found in appendix B.

6.3.2 Wiring

The wiring within the device was basic, since the airflow sensor, Arduino, and touchscreen

were connected by I2C, the wiring was minimal. Basic 22 gauge solid core hook up wire was

chosen to connect all of the components.

The connection between the airflow sensor and the Arduino board required a wiring harness

be created as shown in figure 24. The wiring harness was used to connect into the pins of the

airflow sensor and contain the 4.7kΩ resistors for the SDA and SCL lines.

Figure 24. Wiring harness created to connect the airflow sensor to the arduino



6.3.3 Touchscreen programing

The visual display for the touchscreen was created using 4D systems ViSi-Genie workshop

environment. The display works by creating the screens you wish to display by adding

backgrounds, buttons, gauges, and text. For the development of the PALMD 5 screens were

made to fulfil the basic functions required as seen below in figures 25-30.

Figure 25. Start screen of PALMD

The start screen contains the choice of two buttons the airflow volume button leads to the

“real time airflow measurement” screen shown in figure 26. The additional features button

leads to the “additional features” screen shown in figure 28.

Figure 26. Real time airflow measurement screen of PALMD


Matthew T West 43

The “real time airflow measurement” screen shows the current airflow, updated every second

on the gauge. The average airflow rate displayed using the numerical display can be changed

using the “settings” button.

Figure 27. Average airflow rate settings screen of PALMD

The “average airflow rate settings” screen shown in figure 27 is used to select the time

interval for measurement display on the “real time airflow measurement” screen.

Figure 28. Additional features screen of PALMD

The “additional features” screen shown in figure 28 is used to show all of the PALMD’s

additional features that were not required by the scope of the project.



Figure 29. Airflow data screen of PALMD

The “airflow data” screen shown in figure 29 is used to trigger the arduino code to store the

measured airflow data for viewing and retrieval purposes.

Figure 30. Measured flow rate screen of PALMD

The “measured flow rate” screen shown in figure 30 is used to display the recorded airflow

data in a graph over time. This will allow an easy visual representation of the air leak’s

progression.

The 4D systems ViSi-Genie workshop was designed with the connection and use of the

Arduino platform considered. 4D systems has produced a ViSi-Genie arduino library which

makes reading and writing of data between the arduino microcontroller and the LCD

touchscreen extremely easy.


Matthew T West 45

7 TESTING AND RESULTS

7.1 Flow sensor calibration testing

The digital thermal mass flow sensor used in the PALMD outputs a temperature compensated

linear value for the airflow rate. To check the calibration of the sensor, the test rig shown

below in figure 31 was set up supply a known volume of air to the system. The 60mL syringe

was used to measure the sensor value for known volumes of air from 60mL/min to

360mL/min in 60mL/min steps.

Figure 31. Syringe calibration test setup.

To achieve the required results the minute average was set to use the measurements taken

from the first 10 seconds of measurement and extrapolate for the minute average. Therefore a

10 mL volume over 10 seconds is equivalent to 60 mL/min, and 60 mL volume over 10

seconds is equivalent to 360mL/min.

7.2 Catheter flow rate testing

The testing phase of the project was scheduled to take place as one of the last task in the

project. The finished prototype measuring device would be used to measure the airflow

through the different sized chest tube catheters so that the flow range of each catheter could

be assessed.

7.2.1 Test Equipment

Prototype PALMD



Laboratory vacuum tap

6mm plastic tubing

8mm rubber tubing

11mm rubber tubing

Atrium oasis dry suction chest drain

Laptop running Arduino and excel software

USB to micro USB connection cable

Heimlich valve

32 FR, 28 FR, 24FR, 18FR, and 14FR catheters

7.2.2 Setup

The testing system was set up as shown below in figure 32.

Figure 32. Test setup for catheter airflow measurement

The vacuum tap is connected to the atrium oasis chest drain which is used to both,

simulate an actual operating chest drain, and control the vacuum level using the inbuilt

continually adjustable dry suction control regulator shown below in figure 33. [30]


Matthew T West 47

Figure 33 . Atrium oasis continually adjustable dry suction control regulator.

The PALMD was connected between the Atrium chest drain and the catheter which

was connected to the Heimlich valve as shown in figure 34 below.

Figure 34. 32 FR Catheter connected to a Heimlich valve.

The laptop was used with the Arduino software to read the airflow measurements from

the PALMD through the serial monitor, and record the data into an excel spread sheet.

The full results tables can be found in appendix A.

The different sized catheters tested were 32 FR, 28 FR, 24FR, 18FR, and 14FR, as

shown below in figure 35 along with the 1 way heimlich valve.



Figure 35. Range of commonly used catheters in tube thoracostomy surgery, and a hiemlich

valve.

For each of the five catheters the vacuum controller was initially set to -10cm H2O, and the

flow rate measured every second for a minute with the minute average being displayed at the

end. After each test the vacuum was increased by -5cm H2O up to -40cm H2O and the test

repeated.

7.2.3 Additional Tests Performed

The PALMD was also used to determine the flow ranges required for each step in the atrium’s

water seal flow scale. The atrium water seal shown below in figure 36, has a scale of 1-5 to

visually show the severity of an air leak. With the use of the PALMD the actual volumetric

flow rate for each indicator can be examined.


Matthew T West 49

Figure 36. Atrium water seal during testing.

7.3 Results

7.3.1 Flow sensor calibration results

Table 7. Flow sensor calibration test data

Volume

(mL/min)

Sensor

value

Difference

(per 60mL)

360 2050 71

300 1979 68

240 1911 71

180 1840 72

120 1768 70

60 1698 67

0 1631 0



Figure 37. Flow sensor calibration test data trendline.

7.3.2 Catheter flow rate results

Vacuum

(cmH2O) -10 -15 -20 -25 -30 -35 -40

Catheter Size Volume of airflow (mL/min)

14 FR 4338 5757 7015 8161 9132 9832 10698

18 FR 6515 8427 10447 11983 12534 12534 12534

24 FR 9813 12534 12534 12534 12534 12534 12534

28 FR 11592 12534 12534 12534 12534 12534 12534

32 FR 11902 12534 12534 12534 12534 12534 12534

Table 8. Airflow rates measured using PALMD.


Matthew T West 51

Figure 38. Airflow rates measured using PALMD

Figure 39. Computer calculated estimated flow rates



7.3.3 Additional testing

Figure 40. Measured flow rate for each indicator level on the atrium water seal.

8 DISCUSION

8.1.1 Flow sensor calibration

The syringe method was the used to test the calibration of the flow sensor due to its ease of

use, accuracy and its repeatability of testing. The linear output of the flow sensor shown in

figure 12 from the product data sheet gives a starting point of 0 mL/min for a sensor output of

1638. This number was seen to change depending on the position of the sensor and its angle

to the horizontal plane.

Since the output is known to be linear the syringe test method was used to determine the ratio

of the sensor data number to the actual volume of air. As seen in table 7 there was a difference

of between 67 and 72 for a 60mL/min increase in airflow. The data collected in table 7 was

plotted on the graph seen in figure 37 and the function of the trendline was calculated.

The function y = 69.798x + 1561 shows the step size relationship between the volume of airflow

and the sensor output as 69.798 for a 60mL/min increase.

This formula was then used in the Arduino code to calibrate the sensor.


Matthew T West 53

8.1.2 Catheter flow rate

The scope of this project was split into two parts the construction of the PALMD and the

evaluation of the flow rate of different sized chest drain catheters.

The PALMD was used to measure the flow rate of air through the different sized chest tube

catheters currently used by the local hospital. The PLAMD was designed to handle the

relatively low flow rates associated with pleural air leaks and therefore was not capable of

giving an accurate reading of the maximum flow rate for any of the tubes larger than the 14

FR catheter. From figure 38 it can be seen that the flow rate of the 14 FR catheter increases

linearly with respect to the vacuum applied to the system. If we compare the 14 FR catheter

flow rates in figure 38 to the 5 mm diameter tube represented in the estimated calculation

figure 39 it can be seen that they follow the same linear pattern and approximate range. This

shows that the estimated pressure drop in figure 39 is slightly lower than we would see in the

real world as the 14 FR catheter has an internal diameter of approximately 4 mm.

From a comparison of the PALMD measured airflow and the computer calculated estimated

flow rates it can be seen that the flow rate increases linearly with respect to pressure, and

exponentially with respect to internal diameter.

For the purpose of chest drain management the size of chest drain catheter chosen must be

able to remove all of the air leaking from the lungs, if more air is leaking into the pleural

space than the catheter can remove then further surgery will be required. The results recorded

in table 8 and figure 38 show that all of the catheters tested were able to achieve flow rates of

over 10 L/min, which is the maximum the PALMD can measure. From these results we can

determine that the all of the chest tubes measured would be effective in handling even the

largest prolonged air leak.

8.1.3 Additional testing

The current method used to determining the severity of an air leak using the atrium oasis chest

drain is to visually inspect the water seal chamber air leak monitor for the presence of air

bubbles. The air leak monitor as seen in figure 36 has a graduated scale from 1-5, with 1

representing a low rate of air leak and 5 representing a high rate of air leak.

Using the PALMD the vacuum pressure was slowly increased to determine the airflow range

of each step in the graduated scale. It can be seen in figure 40 that an air leak of over 4L/min

is required to move from the 1st marker to the 2nd marker. This makes the need for a more

accurate measurement device such as the PALMD apparently clear. With such a large range



covered by the graduated scale the differences in personal opinion on the severity of an air

leak are unavoidable.

9 CONCLUSION

The most common complication after lung surgery is still considered to be air leaks [14-18].

The current level of technology being used for the detection and measurement of a pleural air

leak is clearly outdated when compared to its digital counterparts. With the introduction of

Digital Thoracic Drainage Systems the quantification of an air leak becomes as simple as

reading the value from the device.

The prototype pleural air leak measurement device was developed as the main deliverable of

this project and was designed to test the viability of digital measurement technology within

the local thoracic surgery market. The PALMD was created using off-the-shelf components,

sourced from a range of international companies. The PALMD was designed to use current

cutting edge technology in the fields of airflow measurement, LCD display, microcontrollers,

rechargeable power packs, and advanced prototyping equipment.

The PALMD was designed to make use of the advanced prototyping equipment supplied by

the university, and as such the device was modeled using 3D CAD software. The PALMD’s

casing and support structure were created using the universities laser cutter and 3D printer.

The finished PALMD when connected in series between the currently used chest drainage

system and the vacuum source, measures the flow rate of the air leaving the system every

100ms and displays on the screens analog gauge the 1 second average which is updated every

second. The display also shows in numerical form the 1 minute, 5 minute, 15 minute, or 30

minute average flow rate.

The finished PALMD prototype was tested by supplying a known volume of air into the

system and comparing this with the result displayed on devices screen. The PALMD was also

used to measure the flow rate of air through the different sized chest tube catheters. The

results obtained from this experiment show that there is a linear relationship between the

vacuum pressure applied to the system and the flow rate, and an exponential relationship

between the chest tubes internal diameter and the flow rate. From the results it can be


Matthew T West 55

concluded that for the drainage of an air leak the 14 FR sized chest tube is able to handle even

the largest of possible air leaks.

The cost associated with the procurement of the PALMD’s high quality components, and the

3D printed casing, make the PALMD too expensive for mass production, the cost to benefit

ratio would need to be much greater for the project to be commercially viable. However the

completion of this project has opened up the possibility for a new project to be commissioned.

The new project could be to take the features offered by the PALMD and create a low cost

alternative, with mass production and marketing in mind, as it is believed that this will be a

high growth area in the future.



10 REFERENCES

[1] Hippocrates, and F. Adams, “The genuine works of Hippocrates,” New York. W. Wood

and company, 1849.

[2] Miller, K. Scott, and S. A. Sahn, "Chest tubes. Indications, technique, management and

complications." CHEST Journal 91, no. 2 (1987): 258-264.

[3] D. Bouros, “Pleural Disease Volume 186 of Lung biology in health and disease,” New

York: CRC Press, 2004.

[4] W. A. Sirokman, "AUTOMATED PROVISION OF". United States Patent US

2003/0212337 A1, 13 November 2003.

[5] E. A. Graham, and R. D. Bell, "Open pneumothorax: its relation to the treatment of

empyema," The American Journal of the Medical Sciences, vol. 156, pp. 839-871, 1918.

[6] C. S. Rajan, "Tube Thoracostomy Management,” Medscape, Dec 17, 2013. [Online].

Available: http://emedicine.medscape.com/article/1503275-overview. [Accessed 20 march

2014].

[7] P. Clementsen, T. Evald, G. Grode, M. Hansen, G.K. Jacobsen, and P. Faurschou,

“Treatment of malignant pleural effusion: pleurodesis using a small percutaneous catheter. A

prospective randomized study,” Respiratory Medicine, vol. 92, Issue 3, pp. 593–596. 1998.

[8] D. Laws, E. Neville, and J. Duffy, “BTS guidelines for the insertion of a chest drain,”

Thorax, An International Journal of Respiratory Medicine, vol. 58, pp. 53-59. 2003.

[9] DR Harriss, and T.R. Graham, “Management of intercostal drains,” British journal of

hospital medicine, vol. 45, pp. 383–386, 1991.

[10] R.L. Quigley, “Thoracentesis and chest tube drainage,” Critical Care Clinics, vol. 11, pp.

111–126. 1995.


Matthew T West 57

[11] E.R. Munnell, and E.K. Thomas, “Current concepts in thoracic drainage systems,” The

Annals of thoracic surgery, vol. 19, pp. 261-268. 1975.

[12] Atrium Medical Corporation, “A personal guide to managing dry suction water seal chest

drainage,” Hudson: Atrium Medical Corporation, 2013.

[13] Anegg U, Lindenmann J, Matzi V, Mujkic D, Maier A, Fritz L, Smolle-Jüttner FM,

"AIRFIX: the first digital postoperative chest tube airflowmetry--a novel method to quantify

air leakage after lung resection.," European Journal of Cardio-thoracic Surgery, vol. 29, pp.

867-872, 2006.

[14] Odlarmed, Medical Blog, (Accessed 2014, May). Pleural space formation within the

chest cavity. [Online]. Available: http://odlarmed.com/wp-content/uploads/2009/02/15208.jpg

[15] R. Cerfolio, ctsnet, “Clinical Use of a Digital Air Leak System”, 8 April 2008. [Online].

Available: http://www.ctsnet.org/portals/thoracic/newtechnology/article-13. [Accessed May

2014].

[16] Anegg U, Lindenmann J, Matzi V, Maier A, Smolle-Jüttner FM, “AIRFIX®: Technical

Features of the First Digital Airflow Measurement Device for Bedside Use,” [Online].

Available: http://www.ctsnet.org/portals/thoracic/newtechnology/article-12

[17] Mier J.M, Fibla J.J, Molins L. “The benefits of digital thoracic drainage system for

outpatients undergoing pulmonary resection surgery.” [Online]. Available:

http://www.ncbi.nlm.nih.gov/pubmed/21680137

[18] Medela, Thopaz, (Accessed 2014, May). Thopaz Thoracic drainage system. [Online].

Available: http://www.medela.com/IW/en/healthcare/products/thoracic-drainage/thopaz.html



[19] Varela G, Jiménez M.F, Novoa N.M, Aranda J.L. “Postoperative chest tube management:

measuring air leak using an electronic device decreases variability in the clinical practice,”

European Journal of Cardio-thoracic Surgery, vol. 35, pp. 28-31, 2008.

[20] Reddy, C., Hardman, A. D. and Tharion, J. (2007), TS16P TUBE THORACOSTOMY:

THE IMPORTANCE OF SWING. ANZ Journal of Surgery, 77: A96. doi: 10.1111/j.1445-

2197.2007.04133_16.x

[21] D. Dao, Product Definition [Lecture Notes], [Lecture Notes], Griffith University Gold

Coast, 2013.

[22] Arduino (Accessed 2014, May). Arduino Leonardo [Online]. Available:

http://arduino.cc/en/Main/arduinoBoardLeonardo

[23] Sensirion, Mass Flow Control with CMOSens®, (Accessed 2014, May). Principle of

CMOSens® Mass Flow Controllers & Sensors [Online]. Available:

http://www.sensirion.com/en/technology/gas-flow/

[24] Honeywell Zephyr TM, (Accessed 2014, May), Digital Airflow Sensors: HAF Series–

High Accuracy, [Online]. Available:

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0sensors%20haf%20series%20%28high%20accuracy%29

[25] 4dsystems, (Accessed 2014, May), SK-43PT (Starter Kit). [Online]. Available:

http://www.4dsystems.com.au/product/uLCD_43/

[26] 4dsystems, (Accessed 2014, May), uLCD-43 Datasheet. [Online]. Available:

http://www.4dsystems.com.au/product/uLCD_43/

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=list


Matthew T West 59

[28] Access Communications, (Accessed 2014, May), IP (Ingress Protection) Rating for

Equipment and Enclosures. [Online]. Available:

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[29] Ebay, (Accessed 2014, May), Portable External Battery USB Charger Power Bank,

[Online]. Available:

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84.m1497.l2648

[30] Atrium Medical Corporation, “A personal guide to managing dry suction water seal chest

drainage,” Hudson: Atrium Medical Corporation, 2013.



APPENDIX A: FULL RESULTS TABLES

32 FR

Vacuum

(cm H2O) -10 -15 -20 -25 -30 -35 -40

Time(s)

1 11893 12534 12534 12534 12534 12534 12534

2 11908 12534 12534 12534 12534 12534 12534

3 11957 12534 12534 12534 12534 12534 12534

4 11910 12534 12534 12534 12534 12534 12534

5 12012 12534 12534 12534 12534 12534 12534

6 11871 12534 12534 12534 12534 12534 12534

7 11921 12534 12534 12534 12534 12534 12534

8 11844 12534 12534 12534 12534 12534 12534

9 11973 12534 12534 12534 12534 12534 12534

10 11887 12534 12534 12534 12534 12534 12534

11 11840 12534 12534 12534 12534 12534 12534

12 11882 12534 12534 12534 12534 12534 12534

13 11811 12534 12534 12534 12534 12534 12534

14 11876 12534 12534 12534 12534 12534 12534

15 11864 12534 12534 12534 12534 12534 12534

16 11927 12534 12534 12534 12534 12534 12534

17 11914 12534 12534 12534 12534 12534 12534

18 12000 12534 12534 12534 12534 12534 12534

19 11913 12534 12534 12534 12534 12534 12534

20 11910 12534 12534 12534 12534 12534 12534

21 11925 12534 12534 12534 12534 12534 12534

22 11941 12534 12534 12534 12534 12534 12534

23 11871 12534 12534 12534 12534 12534 12534

24 11877 12534 12534 12534 12534 12534 12534

25 11903 12534 12534 12534 12534 12534 12534

26 11790 12534 12534 12534 12534 12534 12534

27 11872 12534 12534 12534 12534 12534 12534


Matthew T West 61

28 11859 12534 12534 12534 12534 12534 12534

29 11829 12534 12534 12534 12534 12534 12534

30 11955 12534 12534 12534 12534 12534 12534

31 11940 12534 12534 12534 12534 12534 12534

32 11955 12534 12534 12534 12534 12534 12534

33 11905 12534 12534 12534 12534 12534 12534

34 11950 12534 12534 12534 12534 12534 12534

35 11892 12534 12534 12534 12534 12534 12534

36 11948 12534 12534 12534 12534 12534 12534

37 11957 12534 12534 12534 12534 12534 12534

38 11921 12534 12534 12534 12534 12534 12534

39 11849 12534 12534 12534 12534 12534 12534

40 11929 12534 12534 12534 12534 12534 12534

41 11856 12534 12534 12534 12534 12534 12534

42 11950 12534 12534 12534 12534 12534 12534

43 11948 12534 12534 12534 12534 12534 12534

44 11905 12534 12534 12534 12534 12534 12534

45 11925 12534 12534 12534 12534 12534 12534

46 11843 12534 12534 12534 12534 12534 12534

47 11926 12534 12534 12534 12534 12534 12534

48 11931 12534 12534 12534 12534 12534 12534

49 11858 12534 12534 12534 12534 12534 12534

50 11884 12534 12534 12534 12534 12534 12534

51 11881 12534 12534 12534 12534 12534 12534

52 11889 12534 12534 12534 12534 12534 12534

53 11879 12534 12534 12534 12534 12534 12534

54 11857 12534 12534 12534 12534 12534 12534

55 11891 12534 12534 12534 12534 12534 12534

56 11817 12534 12534 12534 12534 12534 12534

57 11910 12534 12534 12534 12534 12534 12534

58 11949 12534 12534 12534 12534 12534 12534

59 11931 12534 12534 12534 12534 12534 12534

60 11964 12534 12534 12534 12534 12534 12534



minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

11902 12534 12534 12534 12534 12534 12534

28 FR

Vacuum

(cm H2O) -10 -15 -20 -25 -30 -35 -40

Time(s)

1 11626 12534 12534 12534 12534 12534 12534

2 11674 12534 12534 12534 12534 12534 12534

3 11589 12534 12534 12534 12534 12534 12534

4 11526 12534 12534 12534 12534 12534 12534

5 11580 12534 12534 12534 12534 12534 12534

6 11525 12534 12534 12534 12534 12534 12534

7 11584 12534 12534 12534 12534 12534 12534

8 11644 12534 12534 12534 12534 12534 12534

9 11647 12534 12534 12534 12534 12534 12534

10 11676 12534 12534 12534 12534 12534 12534

11 11604 12534 12534 12534 12534 12534 12534

12 11591 12534 12534 12534 12534 12534 12534

13 11637 12534 12534 12534 12534 12534 12534

14 11567 12534 12534 12534 12534 12534 12534

15 11496 12534 12534 12534 12534 12534 12534

16 11599 12534 12534 12534 12534 12534 12534

17 11558 12534 12534 12534 12534 12534 12534

18 11640 12534 12534 12534 12534 12534 12534

19 11511 12534 12534 12534 12534 12534 12534

20 11615 12534 12534 12534 12534 12534 12534

21 11629 12534 12534 12534 12534 12534 12534

22 11478 12534 12534 12534 12534 12534 12534

23 11606 12534 12534 12534 12534 12534 12534

24 11610 12534 12534 12534 12534 12534 12534

25 11584 12534 12534 12534 12534 12534 12534


Matthew T West 63

26 11610 12534 12534 12534 12534 12534 12534

27 11591 12534 12534 12534 12534 12534 12534

28 11685 12534 12534 12534 12534 12534 12534

29 11573 12534 12534 12534 12534 12534 12534

30 11738 12534 12534 12534 12534 12534 12534

31 11605 12534 12534 12534 12534 12534 12534

32 11525 12534 12534 12534 12534 12534 12534

33 11592 12534 12534 12534 12534 12534 12534

34 11627 12534 12534 12534 12534 12534 12534

35 11604 12534 12534 12534 12534 12534 12534

36 11522 12534 12534 12534 12534 12534 12534

37 11511 12534 12534 12534 12534 12534 12534

38 11642 12534 12534 12534 12534 12534 12534

39 11647 12534 12534 12534 12534 12534 12534

40 11630 12534 12534 12534 12534 12534 12534

41 11530 12534 12534 12534 12534 12534 12534

42 11641 12534 12534 12534 12534 12534 12534

43 11650 12534 12534 12534 12534 12534 12534

44 11555 12534 12534 12534 12534 12534 12534

45 11633 12534 12534 12534 12534 12534 12534

46 11571 12534 12534 12534 12534 12534 12534

47 11529 12534 12534 12534 12534 12534 12534

48 11556 12534 12534 12534 12534 12534 12534

49 11480 12534 12534 12534 12534 12534 12534

50 11610 12534 12534 12534 12534 12534 12534

51 11580 12534 12534 12534 12534 12534 12534

52 11608 12534 12534 12534 12534 12534 12534

53 11593 12534 12534 12534 12534 12534 12534

54 11551 12534 12534 12534 12534 12534 12534

55 11546 12534 12534 12534 12534 12534 12534

56 11635 12534 12534 12534 12534 12534 12534

57 11505 12534 12534 12534 12534 12534 12534

58 11653 12534 12534 12534 12534 12534 12534



59 11563 12534 12534 12534 12534 12534 12534

60 11643 12534 12534 12534 12534 12534 12534

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

11592 12534 12534 12534 12534 12534 12534

24 FR

Vacuum

(cm H2O) -10 -15 -20 -25 -30 -35 -40

Time(s)

1 9737 12534 12534 12534 12534 12534 12534

2 9702 12534 12534 12534 12534 12534 12534

3 9798 12534 12534 12534 12534 12534 12534

4 9781 12534 12534 12534 12534 12534 12534

5 9841 12534 12534 12534 12534 12534 12534

6 9844 12534 12534 12534 12534 12534 12534

7 9815 12534 12534 12534 12534 12534 12534

8 9764 12534 12534 12534 12534 12534 12534

9 9792 12534 12534 12534 12534 12534 12534

10 9838 12534 12534 12534 12534 12534 12534

11 9893 12534 12534 12534 12534 12534 12534

12 9816 12534 12534 12534 12534 12534 12534

13 9906 12534 12534 12534 12534 12534 12534

14 9766 12534 12534 12534 12534 12534 12534

15 9744 12534 12534 12534 12534 12534 12534

16 9815 12534 12534 12534 12534 12534 12534

17 9763 12534 12534 12534 12534 12534 12534

18 9764 12534 12534 12534 12534 12534 12534

19 9788 12534 12534 12534 12534 12534 12534

20 9768 12534 12534 12534 12534 12534 12534

21 9817 12534 12534 12534 12534 12534 12534

22 9812 12534 12534 12534 12534 12534 12534

23 9831 12534 12534 12534 12534 12534 12534


Matthew T West 65

24 9757 12534 12534 12534 12534 12534 12534

25 9788 12534 12534 12534 12534 12534 12534

26 9767 12534 12534 12534 12534 12534 12534

27 9792 12534 12534 12534 12534 12534 12534

28 9853 12534 12534 12534 12534 12534 12534

29 9820 12534 12534 12534 12534 12534 12534

30 9786 12534 12534 12534 12534 12534 12534

31 9829 12534 12534 12534 12534 12534 12534

32 9803 12534 12534 12534 12534 12534 12534

33 9774 12534 12534 12534 12534 12534 12534

34 9808 12534 12534 12534 12534 12534 12534

35 9825 12534 12534 12534 12534 12534 12534

36 9794 12534 12534 12534 12534 12534 12534

37 9738 12534 12534 12534 12534 12534 12534

38 9839 12534 12534 12534 12534 12534 12534

39 9851 12534 12534 12534 12534 12534 12534

40 9864 12534 12534 12534 12534 12534 12534

41 9795 12534 12534 12534 12534 12534 12534

42 9809 12534 12534 12534 12534 12534 12534

43 9841 12534 12534 12534 12534 12534 12534

44 9873 12534 12534 12534 12534 12534 12534

45 9812 12534 12534 12534 12534 12534 12534

46 9862 12534 12534 12534 12534 12534 12534

47 9786 12534 12534 12534 12534 12534 12534

48 9886 12534 12534 12534 12534 12534 12534

49 9857 12534 12534 12534 12534 12534 12534

50 9787 12534 12534 12534 12534 12534 12534

51 9886 12534 12534 12534 12534 12534 12534

52 9799 12534 12534 12534 12534 12534 12534

53 9797 12534 12534 12534 12534 12534 12534

54 9906 12534 12534 12534 12534 12534 12534

55 9864 12534 12534 12534 12534 12534 12534

56 9836 12534 12534 12534 12534 12534 12534



57 9826 12534 12534 12534 12534 12534 12534

58 9838 12534 12534 12534 12534 12534 12534

59 9839 12534 12534 12534 12534 12534 12534

60 9838 12534 12534 12534 12534 12534 12534

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

9813 12534 12534 12534 12534 12534 12534

18 FR

Vacuum

(cm H2O) -10 -15 -20 -25 -30 -35 -40

Time(s)

1 6542 8426 10456 11975 12534 12534 12534

2 6427 8457 10456 11973 12534 12534 12534

3 6560 8441 10436 11979 12534 12534 12534

4 6511 8450 10450 11977 12534 12534 12534

5 6465 8437 10467 11971 12534 12534 12534

6 6504 8397 10461 11979 12534 12534 12534

7 6539 8423 10445 11973 12534 12534 12534

8 6528 8426 10427 11979 12534 12534 12534

9 6495 8402 10445 11967 12534 12534 12534

10 6564 8416 10457 11991 12534 12534 12534

11 6510 8457 10437 12021 12534 12534 12534

12 6547 8455 10462 11978 12534 12534 12534

13 6515 8418 10459 12018 12534 12534 12534

14 6450 8414 10464 11946 12534 12534 12534

15 6526 8444 10440 11982 12534 12534 12534

16 6539 8409 10452 11982 12534 12534 12534

17 6535 8414 10439 11976 12534 12534 12534

18 6501 8437 10411 12022 12534 12534 12534

19 6503 8444 10438 11985 12534 12534 12534

20 6489 8400 10451 11984 12534 12534 12534

21 6479 8444 10422 11980 12534 12534 12534


Matthew T West 67

22 6501 8364 10454 11962 12534 12534 12534

23 6494 8437 10458 11985 12534 12534 12534

24 6504 8420 10456 11996 12534 12534 12534

25 6514 8409 10444 11980 12534 12534 12534

26 6548 8438 10417 12001 12534 12534 12534

27 6509 8418 10448 11970 12534 12534 12534

28 6495 8463 10433 11979 12534 12534 12534

29 6479 8441 10461 11971 12534 12534 12534

30 6541 8458 10452 11963 12534 12534 12534

31 6495 8419 10478 11959 12534 12534 12534

32 6498 8385 10455 12019 12534 12534 12534

33 6506 8412 10435 11995 12534 12534 12534

34 6509 8435 10447 11969 12534 12534 12534

35 6535 8422 10439 11988 12534 12534 12534

36 6522 8401 10459 11966 12534 12534 12534

37 6477 8430 10475 11972 12534 12534 12534

38 6560 8463 10452 11959 12534 12534 12534

39 6544 8440 10426 11998 12534 12534 12534

40 6539 8442 10419 11980 12534 12534 12534

41 6550 8457 10447 11993 12534 12534 12534

42 6493 8361 10446 12009 12534 12534 12534

43 6544 8422 10423 11996 12534 12534 12534

44 6465 8423 10495 11988 12534 12534 12534

45 6528 8445 10453 11977 12534 12534 12534

46 6551 8465 10444 11974 12534 12534 12534

47 6550 8466 10436 12014 12534 12534 12534

48 6477 8423 10407 11979 12534 12534 12534

49 6492 8441 10445 12015 12534 12534 12534

50 6535 8380 10446 11998 12534 12534 12534

51 6520 8394 10457 11970 12534 12534 12534

52 6554 8439 10442 11959 12534 12534 12534

53 6508 8426 10487 11982 12534 12534 12534

54 6528 8403 10425 11994 12534 12534 12534



55 6478 8429 10428 11986 12534 12534 12534

56 6540 8405 10448 12019 12534 12534 12534

57 6531 8447 10490 11981 12534 12534 12534

58 6496 8423 10436 11981 12534 12534 12534

59 6555 8438 10422 11989 12534 12534 12534

60 6506 8436 10471 11973 12534 12534 12534

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

6515 8427 10447 11983 12534 12534 12534

14 FR

Vacuum

(cm H2O) -10 -15 -20 -25 -30 -35 -40

Time(s)

1 4367 5777 7044 8141 9086 9856 10644

2 4366 5772 7000 8154 9156 9860 10643

3 4356 5756 7035 8134 9155 9806 10653

4 4343 5723 7029 8178 9142 9828 10667

5 4347 5745 7000 8158 9145 9859 10661

6 4327 5753 7015 8173 9148 9845 10648

7 4373 5723 7023 8158 9131 9821 10646

8 4335 5780 6992 8181 9140 9871 10679

9 4380 5754 6975 8165 9122 9854 10720

10 4329 5725 7045 8173 9150 9819 10714

11 4362 5769 7020 8159 9139 9833 10742

12 4295 5748 7066 8175 9132 9835 10698

13 4368 5789 7009 8152 9152 9822 10706

14 4332 5706 7005 8177 9138 9815 10704

15 4292 5749 6986 8182 9139 9856 10689

16 4347 5779 7018 8154 9140 9853 10727

17 4389 5761 6994 8141 9149 9846 10697

18 4339 5748 7034 8152 9109 9839 10669

19 4321 5728 7010 8174 9173 9841 10714


Matthew T West 69

20 4316 5778 6998 8160 9123 9816 10700

21 4352 5747 7045 8157 9119 9799 10689

22 4336 5776 7005 8202 9126 9863 10726

23 4312 5812 7034 8149 9148 9797 10682

24 4323 5790 6998 8148 9170 9799 10713

25 4325 5769 6989 8148 9111 9812 10702

26 4336 5787 7016 8122 9090 9847 10711

27 4347 5773 7017 8161 9091 9829 10697

28 4321 5722 7029 8154 9118 9839 10731

29 4346 5749 7020 8135 9130 9843 10715

30 4367 5808 7047 8157 9105 9837 10716

31 4356 5764 7037 8106 9152 9833 10701

32 4338 5729 7011 8120 9130 9809 10694

33 4316 5767 7038 8176 9104 9830 10681

34 4341 5754 7003 8177 9081 9795 10694

35 4369 5729 7029 8130 9152 9804 10676

36 4350 5768 7035 8140 9125 9827 10724

37 4344 5772 7036 8179 9124 9829 10698

38 4307 5754 7028 8178 9152 9804 10724

39 4354 5741 6992 8171 9115 9837 10674

40 4334 5762 7019 8175 9151 9838 10700

41 4354 5760 6980 8158 9163 9826 10707

42 4318 5776 7016 8164 9141 9824 10708

43 4324 5758 6999 8184 9151 9836 10706

44 4299 5760 7049 8186 9130 9848 10727

45 4331 5762 7001 8156 9139 9862 10734

46 4323 5771 7008 8111 9144 9825 10668

47 4324 5728 7041 8208 9139 9821 10699

48 4358 5751 7030 8179 9088 9822 10735

49 4351 5750 7028 8154 9129 9864 10693

50 4330 5782 7007 8171 9148 9819 10711

51 4289 5776 7006 8154 9125 9833 10719

52 4346 5740 7013 8176 9110 9858 10699



53 4326 5782 7037 8177 9131 9820 10675

54 4359 5714 7009 8162 9101 9869 10699

55 4349 5767 6977 8141 9121 9853 10720

56 4342 5729 7002 8181 9127 9813 10720

57 4301 5768 7002 8139 9159 9827 10724

58 4321 5718 6994 8141 9149 9819 10705

59 4330 5769 7007 8190 9133 9847 10719

60 4365 5750 7021 8178 9139 9817 10669

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

minute

average

4338 5757 7015 8161 9132 9832 10698

APPENDIX B: ARDUINO CODE

#include <genieArduino.h>

#include <Wire.h>

#include <EEPROM.h>

#include <stdio.h>

int fivemin = 0;

int val = 0;

int count = 0;

long number= 0;

long average= 0;

int hbit =0;

int lbit =0;

long sum = 0;

long minsum =0;

long pminsum =0;

long averagevolume =0;

long minuteaverage =0;

long bminsum =0;

long bpminsum =0;

long baveragevolume =0;

long bminuteaverage =0;

long cminsum =0;

long cpminsum =0;

long caveragevolume =0;

long cminuteaverage =0;

long dminsum =0;

long dpminsum =0;

long daveragevolume =0;

long dminuteaverage =0;

long averagevalue = 500;

int fiveminstore =0;

int flag1 = 0;

int flag2 = 0;

int flag3 = 0;


Matthew T West 71

int flag0 = 0;

int flag4 = 0;

int flag5 = 0;

int flag6 = 0;

int flag7 = 0;

int flag9 = 0;

int flag8 = 0;

int setting1 = 0;

int setting2 = 1;

int setting3 = 0;

int setting4 = 0;

int set1 = 0;

int set2 = 1;

int set3 = 0;

int set4 = 0;

unsigned long currentMillis = 0;

unsigned long previousMillis = 0;

unsigned long minuteMillis = 0;

int interval = 200;

long minute = 60000;

long pvolume =0;

long volume = 0;

int zero = 1638;

Genie genie;

void setup()

delay(4000);

Wire.begin(); // join i2c bus (address

optional for master)

Serial.begin(9600); // start serial for

output

Serial1.begin(9600); // Serial0 @

200000 (200K) Baud

genie.Begin(Serial1);

genie.AttachEventHandler(myGenieEvent

Handler); // Attach the user function Event

Handler for processing events

void loop()

genie.DoEvents();

while (1)

unsigned long currentMillis = millis();

if(currentMillis - previousMillis >=

interval)

previousMillis = currentMillis;// save

the last time interval

measure ();

screenupdate();

myGenieEventHandler();



/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

void myGenieEventHandler(void)

genieFrame Event;

genie.DequeueEvent(&Event);

//If the cmd received is from a Reported

Event (Events triggered from the Events

tab of Workshop4 objects)

//If the cmd received is from a Reported

Event (Events triggered from the Events

tab of Workshop4 objects)

if (Event.reportObject.cmd ==

GENIE_REPORT_EVENT)

if (Event.reportObject.object ==

GENIE_OBJ_4DBUTTON) // If the

Reported Message was from a Slider

if (Event.reportObject.index == 6) // If

Slider0

flag0 = 1; // Receive the event data

from the Slider0

Serial.println("CALIBRATE");

Serial.println(set2);


Slider0

setting1 = 1;

setting2 = 0;

setting3 = 0;

setting4 = 0;

Serial.println("setting 1 min");


Slider0

setting1 = 0;

setting2 = 1;

setting3 = 0;

setting4 = 0;



Slider0

setting1 = 0;

setting2 = 0;


Matthew T West 73

setting3 = 1;

setting4 = 0;



Slider0

setting1 = 0;

setting2 = 0;

setting3 = 0;

setting4 = 1;


/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

long measure()

request();

zerodevice();

calibrate();

minutevolume();

bminutevolume();

cminutevolume();

dminutevolume();

return previousMillis;

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

int request()

if (flag1 == 0)

// Serial.println("request");

flag2 = 0;

Wire.requestFrom(0x49, 2); // request 6

bytes from slave device #2

while(Wire.available()) // slave may

send less than requested

byte data = Wire.read(); // receive a

byte

if (flag2 == 0)

// Serial.println("hbit");

hbit = data;

if (flag2 == 1)

// Serial.println("lbit");

lbit = data;

flag2 = 2;



if (flag2 == 2)

number = hbit*254 +lbit;

// Serial.println("number1");

// Serial.println(number);

return number;

flag2 = 1;

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

int zerodevice()

if (flag0 == 1)

zero = number;

flag0 = 0;

return zero;

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

long calibrate()

//Serial.println("number");

//Serial.println(number);

// Serial.println("zero");

//Serial.println(zero);

int volume = map(number, zero,

zero+11667, 0, 10000);

//Serial.println("volume");

//Serial.println(volume);

//Serial.println("flag3");

// Serial.println(flag3);

if (flag3 <= 5)

// Serial.println("average1");

sum = pvolume + (volume);

pvolume = sum;

//Serial.println("sum");

//Serial.println(sum);

flag3 = flag3 + 1;

// Serial.println("flag3");

// Serial.println(flag3);

if (flag3 == 5)

// Serial.println("average2");

averagevolume = (sum /5);

pvolume =0;

sum =0;

flag3 = 0;


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flag4 = flag4 +1;

//Serial.println("time seconds");

//Serial.print("time ");

//Serial.println( flag4);

//Serial.print("volume ");

Serial.println(averagevolume);

// Serial.println(averagevolume);

return averagevolume;

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

int minutevolume()

if (flag3 == 0)

if (flag4 <=60)

minsum = averagevolume + pminsum;

pminsum = minsum;

//Serial.println("minsum");

//Serial.println(minsum);

if (flag4 == 60)

minuteaverage = minsum /60;

Serial.println("minute average");

Serial.println(minuteaverage);

minsum = 0;

pminsum = 0;

flag4 = 0;

flag5 = flag5 +1;

return minuteaverage;

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

int bminutevolume()

if (flag4 == 0)

if (flag5 <=5)

minsum = baveragevolume + bpminsum;

bpminsum = bminsum;



if (flag5 == 5)

bminuteaverage = bminsum /5;

Serial.println("5 minute average");

Serial.println(bminuteaverage);

bminsum = 0;

bpminsum = 0;

flag5 = 0;

flag6 = flag6 +1;

return bminuteaverage;



/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

int cminutevolume()

if (flag5 == 0)

if (flag6 <=3)

cminsum = caveragevolume + cpminsum;

cpminsum = cminsum;



if (flag6 == 3)

cminuteaverage = cminsum /3;


Serial.println(cminuteaverage);

cminsum = 0;

cpminsum = 0;

flag7 = 0;

flag7 = flag7 +1;

return cminuteaverage;

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/

int dminutevolume()

if (flag6 == 0)

if (flag7 <=2)

dminsum = daveragevolume + dpminsum;

dpminsum = dminsum;



if (flag7 == 2)

dminuteaverage = dminsum /2;


Serial.println(dminuteaverage);

dminsum = 0;

dpminsum = 0;

return dminuteaverage;

/**********************************

**********************************

**********************************


Matthew T West 77

SCREEN READ

**********************************

**********************************

**************************/

void screenupdate()

if (flag3 == 0)

if (averagevolume > -200 &&

averagevolume <1000)

if (flag9 == 1)

genie.WriteObject(GENIE_OBJ_FORM, 1

, 0);

flag9 = 0;

genie.WriteObject(GENIE_OBJ_COOL_G

AUGE, 0, averagevolume+200);

if (flag4 == 0)

if (minuteaverage >= 0 )

genie.WriteObject(GENIE_OBJ_LED_DI

GITS, 0, minuteaverage);

flag8 = 1;

if (averagevolume > 1000)

if (flag8 == 1)

genie.WriteObject(GENIE_OBJ_FORM, 6

, 0);

if (averagevolume >= 9999)


AUGE, 1, 9999);

if (averagevolume <= 9999)


AUGE, 1, averagevolume);

if (flag6 == 0)

if (minuteaverage >= 9999)


GITS, 1, 9999);

if (minuteaverage <= 9999)



flag9 = 1;

flag8 = 0;

if (setting1 == 1)

if (flag4 == 0)

if (minuteaverage > 0)







if (setting2 == 1)

if (flag5 == 0)

if (bminuteaverage > 0)


GITS, 0, bminuteaverage);


GITS, 1, bminuteaverage);

if (setting3 == 1)

if (flag6 == 0)

if (cminuteaverage > 0)


GITS, 0, cminuteaverage);


GITS, 1, cminuteaverage);

if (setting4 == 1)

if (flag7 == 0)

if (dminuteaverage > 0)


GITS, 0, dminuteaverage);


GITS, 1, dminuteaverage);

/**********************************

**********************************

**********************************

SCREEN READ

**********************************

**********************************

**************************/


Matthew T West 79

APPENDIX C: BILL OF MATERIALS

Item Quantity Name Material/Source Price/Unit Cost ($

AUD)

1 1 Honeywell Airflow sensor DigiKey 100 $100

2 1 Arduino Leonardo GUGC 30 30

3 1 USB power pack Dick Smiths 40 40

4 1 4D LCD display Mouser 200 200

5 2 Spdt Miniature Toggle Switch Jaycar 7 14

6 2 Outer ring FDM plastic 0 0

Internal support structure

7 1 Back face 3mm Plexiglas 0 0

8 1 Front face 3mm Plexiglas 0 0

9 1 Base 3mm Plexiglas 0 0

10 2 Side support 1 3mm Plexiglas 0 0

11 2 Side support 2 3mm Plexiglas 0 0

12 1 Arduino shelf 3mm Plexiglas 0 0

13 1 Display shelf 3mm Plexiglas 0 0

14 1 Assorted nuts and bolts GUGC 0 0

15 1 22 Gauge single core wire GUGC 0 0

16 1 Solder GUGC 0 0

17 2 4.7 kΩ resistor GUGC 0 0

18 1 Heat shrink Jaycar 0 0

19 1 USB extension cord Jaycar 0 0

20 1 USB Hub Jaycar 0 0

21 2 palstic angle bends Bunnings 0 0

22 1 11mm rubber tubing GUGC 0 0

Total Component Cost $ 384

Estimated Total Device Cost $ 584



APPENDIX D: USER MANUAL

Pleural Air Leak Measurement Device

User Manual


Matthew T West 81

The Pleural Air Leak Measurement Device

Features:

• 0 – 10L/min airflow measurement range

• 4.3” LCD touchscreen display

• USB connection

• Rechargeable battery

• 5600mAh battery capacity

• 0.5% Accuracy (0% FS – 14.3%FS)

• 3.5% Accuracy (14.3% FS – 100%FS)

1. Catheter connection inlet valve

2. Catheter connection outlet valve

3. USB connection cable

4. Power switch

5. LCD touchscreen

1 2 3 4

5



How to use

*** DEVICE MUST BE KEPT HORIZONTAL WHEN MEASURING AIRFLOW ***

1. Turn on power switch.

2. Turn on LCD screen power switch.

3. Block both (1) and (2) inlet and outlet

valves.

4. Press LCD screen button “AIRFLOW

VOLUME”.

5. If the “REAL TIME AIRFLOW

MEASUREMENT” gauge does not read

zero ( 0 ).

6. Press LCD screen button “SETTINGS”.

7. Press LCD screen button “CALIBRATE”.

8. Press LCD screen button “BACK”.

9. Connect the outlet tubing of chest drain to

(1) the left hand tube connector.

10. Connect the inlet tubing of the vacuum

source to (2) the right hand tube connector.

The volume of airflow will be displayed on

the LCD screen.


Matthew T West 83

ADITIONAL FEATURES

If not on the home screen

1. Press LCD screen button “HOME” in the top

right corner of the screen.

1. Press LCD screen button “ADDITIONAL

FEATURES”

2. Press LCD screen button “AIRFLOW DATA”

“RECORD AIRFLOW DATA” stores the

measured airflow rate to the devices memory

The “RED” LED will illuminate when

recording.

“DOWNLOAD AIRFLOW DATA” sends the

stored airflow data to the USB serial

connection.

The “BLUE” LED will illuminate when

sending.

1. Press LCD screen button “ADDITIONAL

FEATURES”

2. Press LCD screen button “MEASURED

FLOW RATE”

Shows the last 6 hours of measured data as

a graph.



Airflow measurement display

When on the “REAL TIME AIRFLOW

MEASUREMENT” screen

1. Press LCD screen button “SETTINGS”

The average airflow rate displayed on the

“REAL TIME AIRFLOW

MEASUREMENT” screen can be set to

display the average every minute, 5

minutes, 15 minutes, or 30 minutes.

The “REAL TIME AIRFLOW

MEASUREMENT” gauge displays the

average for every second.

mwest_5_22156_tube_thoracostomy_airflow_measurement_and_management-1

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