Student Projects
Contact Information
University and Department: Penn State, Department of Bioengineering
Team Members: Stefanie Auf der Mauer, Samantha Chan, Peter Chhour, Josh Homa, Vy Pham, Karthik Pisupati
Project Information
Describe the challenge your project is trying to solve.
In collaboration with the Mashavu Project, the respiration group is responsible for developing an inexpensive spirometer, used to measure flow rate. This can be used to diagnose different lung diseases.
Mashavu Project:
In many developing African nations, health care is a rare commodity, that many do not have access to. The reason simply is that there are not enough doctors in the developing nations. In the United States, there is one doctor to 390 people as opposed to Kenya, where the ratio is 1 doctor: 50,000 people. The Mashavu Project plans to overcome problem by using communication technology and telemedicine to remotely diagnose patients. With the startling fact that 97% of people in Kenya have access to a cell phone, the project plans to use the availability of cell phone towers and internet to help spread health care diagnoses to remote regions.
Spirometry:
Spirometry is the measuring of breaths. Generally the patient is asked to perform a variety of breathing patterns depending on the disorder the doctor is looking for. Some patterns may include breathing in deeply and exhaling as full as possible, or breathing normally for a series of breaths. Each test will give the doctor a value that can be used to diagnosis some lung disorders. Some common parameters are Forced Vital Capacity (FVC) and Forced Expiration Volme in one second (FEV1).
Background on Mashavu and East Africa (Nyeri, Kenya)
Every country in East Africa suffers from severe lack of health care professionals. There is only a single doctor for every 50,000 people in East Africa compared to one doctor for every 360 people in the US. Penn State Student, Aaron Fleishman came up with an idea that is based on the promising solution of telemedicine which lead to the creation of the Mashavu project. Trained operators at a Mashavu station on the field collect vital signs of patients with the help of computers and the recorded data is then send via internet to health care professionals, who provide feedback on the patient's health.
Our goal as engineers of the Mashavu project is to create sustainable devices that are technologically appropriate for East Africa, environmentally ben ign, economically sustainable and of course socially acceptable.
Our target customers are children and adults that reside in Kenya, one of many developing countries in Africa. Specifically, the project will be implemented in Nyeri, a town located north of the country's capital Nairobi. The town's population is about 350,000 as for 2008. Nyeri's main industry is farming and being located in fertile highlands water and food is plentiful.
Nevertheless, the majority still lives in poverty and the average income in Kenya is one dollar a day. One of the main social issues that will affect the project is the situation of poverty itself. People are trapped in poverty mainly because the overlap of their economic and social network is large. This induces a fatalistic attitude in most individuals and leads to a failure of planning ahead, which in turn creates more poverty and a marginalized population.
Our Customers
The users of our device include patients and equipment (device/computer) operators, as well as health care professionals. Patients will vary in gender and in age, from children to elderly. We have to be aware that patients might be physically disabled, which could result in difficulties for them to get to the kiosk and could present problems during measurements. In Kenya health care is primarily a female role and technology is dominated by men. Therefore, during the implementation of the project, gender roles will conflict. However, we still expect that the majority of the operators will be women with a low education level, who will not know how to operate the equipment without training.
Aside from patients and operators, our design will consider doctors that will use the recorded data to diagnose disease states.
During this summer, our project is intended for an easy and quick accessible health station (kiosk), but future potential owners will be clinics, schools, orphanages, community centers and entrepreneurs.
Customer Needs
With children and adults of Kenya in mind, the device was guided to respect and meet the needs of our customers. Primary, the team goal was to be able to accurately measure volumetric flow rate to diagnose disease states.
1. The device should be composed of locally available, inexpensive parts.
2. The construction process of the instrument should be relatively easy, so that any repair is facilitated.
4. The device should be easy to operate without much training and the design must incorporate an easy interface with a computer so data can be quickly transfered to doctors who are not in the local area.
5. The device should incorporate a fun aspect during operation
Describe how you addressed the challenge through your project.
Specifications:
1. Cost figures - Materials list and prices:
| Material | per unit cost | |
| Sensor | $ 32.00 | $ 32.00 |
| PVC pipe | $1.20 / 10ft | $ 0.12 |
| PVC coupling | $ 0.23 / coupling | $ 0.46 |
| Coffee Stirrers | $ 1.49/100ct (7 in each) | $ <0.01 |
| Mesh (protoboard) | $ 0.00 (recycled) | $ 0.00 |
| Cotton Cloth | $ 0.20 for (.12m x 1m) | $0.04 |
| total | $32.62+ |
Materials in Kenya:
PVC pipe
Flexible tubes or small diameter straws for sensor
2. Fabrication Process
a. Drilling 2 holes on PVC coupling for sensor prongs to fit in through straws
b. Cutting PVC pipes for 2 sides of device and mouthpiece
c. Sand-paper the connection sites for easy assembly and dissembly
c. Using miller to drill notches for easy dissembly.
d. Cutting protoboard into circle of inner diameter of PVC coupling
* see Construction page for more details
3. Safety & Sterilization: Design Criteria/Specifications (Mashavu Project: Respiration Design)
Patient owned mouthpieces (PVC) to prevent disease transmission
Sterilize mouthpiece through boiling
Incorporated cloth filter to catch moisture and saliva
cloth can be washed after several uses and reused
4. Ease of Operation
To be determined by customers in Kenya (See Test Plan)
5. Entertainment
Planned to use a sound file of some sort while conducting the measurement
Design Alternatives
Some alternatives we considered:
Chest Strap:
A design used to measure volumetric changes in the lungs, by measuring changes of the chest diameter in patients while inhaling and exhaling. The design incorporated an elastic strain gauge to detect the changes in the chest volume. Due to the design's inability to measure flow rate, the idea was eliminated from consideration.
Velocity/Motion sensing Tube:
This design uses an actually flow sensor to detect the velocity of the flow. From the velocity of the flow, the flow rate could be found. Through research, it was found that actual velocity sensors are generally more expensive and harder to implement correctly. Because of these issues, we decided against using a direct flow sensor to find flow rate.
Dall Tube/Orfice Plate:
Mostly used to measure gas flow through pipelines, the Dall Tube design (similar to a Venturi Meter) measures differential pressure over a significantly constricted region using a pressure sensor. The Dall Tube design requires an area of the pipe to be constricted to create a pressure difference. Creating a pipe with varying diameters would be difficult to recreate in Kenya, due to the availability of parts.
The main goal of this collaboration was to design a device that would aid in the diagnosis of common respiratory problems. Many of the lung problems are defined in terms of lung volume and volumetric flow rate out of the lungs. In order accurately carry out diagnosis, doctors need specific figures about lung volume and volumetric flow rate, so ultimately our device is designed to obtain these values.
Our design concept is a variation of the fleisch-pneumotach; it will measure a differential pressure across a mesh screen. The purpose of the screen is to provide an obstruction to the flow. The resistance value for the mesh screen can be obtained from calibration experiments. Given a pressure difference and a resistance value, volumetric flow rate can be obtained. By integrating the volumetric flow rate over time, a value for lung volume can be obtained.
LabVIEW is a graphical programming language developed by National Instruments. It easily allows recording of signals and measurements from many types of sensors. In addition, it allows the data to presented quickly and formally. For the design, LabVIEW was used to easily interface the respiration device with the computer. Because doctors are not on site, the information must be easily understood and transferable long distances.
LabVIEW programming was created to take inputs from the sensor and convert them to displayable information to the doctors. Specifically, for the respiration device, LabVIEW was used to convert from a differential pressure input which the sensor detected, and report Peak Flow Rate and Forced Vital Capacity. Shown below is the user interface intended for the doctors to see.
While the product is in use, the graph continually displays breathing patterns. The values of Peak Flow Rate and Forced Vital Capacity are displayed next to each respectively graph.
The program operates under 2 different modes. Modes are selected by clicking the "Mode Selection Button"
Normal:
-Measures normal breathing patterns
-The patient should inhale and exhale normally.
Forced Expiratory Volume:
-Measures force expiratory volume
-The patient should inhale deeply and exhale forcibly and quickly
Construction
The goal of construction design is to enable the device to retain its effectiveness using the least amount of hardware, but in the same time satisfying design criteria established in our Customer Needs. It must also be safe and easy for doctors to put and take apart for sterilization and storage.
Material Selection:
We have decided to use PVC material for our design, due to its durability and material strength, but mainly because it is easy to come by, and is inexpensive, which is very well in terms with our Design Criteria.
However, there are concerns about this selection of material, since there has been conflicting sources of whether or not PVC will be abundant in Kenya, should the device require repair or replacement of parts. Bamboo was proposed as an alternative material, since bamboo is readily available in Kenya.
It is difficult for us to locate suitable bamboo shoots to construct our spirometer in State College, thus preliminary experimental testing will be conducted with PVC pipes instead.
Due to the fact that it would be difficult to find hardware that may be easily found in our local department store, we must make our design simple, and with materials that are easily attainable. For this purpose, materials used as the mesh and the filter were secondary materials (originally designed for other functions).
Our mesh, for instance, was made out of an old protoboard used for circuit building. Although protoboards can be made of many different materials other than the G-10 type that we've used in our design, the material does not matter as much as the size and density of the holes. But since protoboards are designed to have a certain consistency to these parameters universally, this was not a huge concern in terms of calibration and accuracy of measurement.
The process of selection of filters was a rather tedious and troublesome one, which required much calibration and testing, so as to choose the filter material with least resistance to enhance the sensitivity of our measurements, but in the same, be water absorbent enough to serve the physical purpose as a filter. Three different filter materials were tested. Results show that the cotton cloth gives us least resistance than the others. Cloth also proved to be the best filter, since it can be easily washed and sterilized, and thus minimizes disposable waste.
Fig.1: Prototype for Spirometer
- PVC pipe - 3/4"
Schedule 40
Outer Diameter = 1.050"
Inner Diameter = 0.804"
Price = $1.20 (per 10ft)
Provider: HARVEL PLASTICS, INC. (http://www.harvel.com/index.asp) - PVC Coupling - 429-007HC
Schedule 40
Assembled Depth = 2.1"
Assemble Height = 1.3"
Assembled Width = 1.3"
Fitting Size = 3/4"
Price = $0.23
Provider: HARVEL PLASTICS,INC. (http://www.harvel.com/index.asp) - Flexible tubes
Outer Diameter= 0.2"
Price = $0.19 per yard
* A coffee stirrer was used as an alternative in our prototype device - Differential Pressure Sensor
Dimensions = 1.4" x 1.2" (length x width)
Pressure range = -25 kPa to +25 kPa (-3.6 psi to +3.6 psi)
Voltage Range = 0 to 5 V DC
Price = $32.00 - Mesh Materials
1) G-10 Protoboard
Price = $1.05
2) Plastic Knitting Web (2 sizes)
Price = $ 0.40 - Cardboard tube for sensor housing
- Cotton Cloth (with rubber band to secure filter)
Wrapped around the PVC pipe connector
Dimension = 3 in x 3 in
Estimated total price of device = approximately $35 USD
Road Blocks with Construction:
A major difficulty we had come across with the construction design mainly had to do with the size and geometry of the fastener. The fastener is the most important part of our construction design; it serves as the backbone of the device, which securely holds the 2 PVC pipes, the mesh, and the sensor in place. Our goal in construction is to design the device in a way that makes it easy to dissemble and assemble for repair, sterilization and storage; thus our device has to be tightly held together when in use, but in the same time easy to take apart afterward.
After much research and construction trials, we have come down to our last resort, that is to use a commercial PVC coupling, for only a PVC coupling was sturdy enough to hold the pipes in place, yet allow the device to be easily dissembled. We understand that the coupling may be hard to replace in Kenya, but its durable material strength diminishes the like
Another concern with the construction was the filter material selection. After testing among three different materials, the cotton cloth gave us the lowest resistance. Though this may be the case, it is only viable to the specific cloth we got from a local department store. Thus, should the cloth break or be not longer functional, it would be difficult to find an identicle cloth of the same cotton / polyester consistency and threadcount. These are parameters that are taken into account during calibration. An air compressor was used to supply steady air flow during calibration, but the likelihood of finding an air compressor in Kenya is quite low, therefore the difficulty of re-calibration has stricken us as an issue.
Conclusion:
The end goal of this project was to design a device that can help diagnose common lung disorders of the Kenyan patients. There exists a need for such a device as cases of lung disorders are on the rise in Africa1,2,3. The first step in designing our device was to identify customer needs: a device that is safe, sterilize-able, made from locally available materials,cost effective, and is easy to use. Specifically, our device must be able to produce information about lung volumes (values such as Forced Vital Capacity (FVC), Forced Expiratory Volume (FEV)) and flow rates since most common disorders can be diagnosed with this information.
We considered several design alternatives before settling on the concepts found within the Fleisch-Pneumotach. The idea is that the presence of a mesh resistor will cause a pressure differential which is proportional to flow rate; the pressure differential will be measured by our sensor. To test the feasibility of our design concepts, we constructed finite element models to analyze the air flow in the tube. The result we are looking for is a drastic difference in the pressure across the mesh resistor. After verifying that our design concept will work through COMSOL post-processing, the construction process began.
After discussion with our context manager and Khanjan, we found that pvc tubings and connectors are available in Kenya, and would be ideal materials for our spirometer. Holes were drilled before and after the mesh resistor, which was made of a piece of circuit board, in order to integrate the sensor. We tested our device by comparing our results with Biopac (a commercial spirometer) system. A syringe pump was used to provide a constant volume for comparison, since regular breathing is too sporadic and would have a high level of variability. The results from both devices were similar. The next step is to test the device in Kenya and get customer feedback to improve the design. The product thus far can be seen below:
