EC.710 | Spring 2010 | Undergraduate

D-Lab: Medical Technologies for the Developing World

Projects

Nebshair

A breath-actuated, dosage-monitoring attachment for jet nebulizers to treat multiple patients for respiratory illnesses

Team: Caroline Hane-Weijman, Shan Tie, Mary Jue Xu, and anonymous MIT student [GK]

This content is presented courtesy of the students and used with permission.

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Ideas Right Now

by Mary Jue Xu

Our blog begins! Many things have happened over the past few weeks, including speaking to many experts at Children’s Hospital in Boston. (We will post noted from that shortly. In summary, there are three large areas of focus for improving the nebulizer: dosage, interface, and sterilization. We decided to focus on dosage.

Initially, we started off with the idea of capnography, in which we would measure CO2 exhaled to correlate to dosage intake. The design would have to incorporate the fact that CO2 does not directly link to the dosage. For example, maybe the nebulizer outlet is far from the mouth or the patient breaths out too fast. Also, a physician at the Children’s Hospital informed us that a baby’s exhale was not enough to be measured with capnography.

So, it was back to the drawing boards. Right now, we are focused upon an attachment to the current compressed air nebulizers that will allow 1) dosage to be monitored and 2) multiple patients to use it. So off the end of the nebulizer motor, image a the medicine being pumped into a reservoir that stores the vapors. Then several outlets would lead to the individual patient’s interface. The interface would only open or release vapors under the direction of the patient. Maybe this is by a mechanical sensor that needs to sit on the face or maybe this is a one way valve that is breath mediated so that only with the baby’s breath will the vapors be released from the reservoir. Moving on past this part of the interface is a sensor (likely an LED sensor) that can detect and sum up the amount (volume/time possibly) that passes by and will sum up the volume or time and signal when the full dosage has been given. Jose also had the idea to use some kind of sticker on the face that is color changing after receiving a particular dose.

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Problem and Background Information Gathering

by Caroline Hane-Weijman

Just to give some background to our problem and some of the important information we are working with!

Problem Scope

The inspiration for this project came after having visited multiple hospitals, clinics, and health posts in Nicaragua. Currently, the nebulizer is commonly used in developing countries due to the high incidents of respiratory related diseases and infections (the mist from the nebulizer helps unclog liquids found in a sick patient rather than an inhaler). The current nebulizers that are used are air compressors powered by electricity, and the drug most commonly used is albuterol as it is the cheapest. These nebulizers are originally intended for home use but are used for over 30 patients/day in clinics and hospitals, Mothers stand in line with their child until it is their turn to use the nebulizer. These nebulizers do not provide a method for measuring adequate dosage and thus delivery efficacy of the drug to young patients are low, specifically infants. Infants are non-compliant to the face mask that helps administer the drug and the nozzle is just held underneath the infants’ nose without ensuring delivery and wasting a lot of medicine. Additionally, the devices do not have a system to visibly indicate that the device is sterile and ready for use for the next patient, and many are not properly sterilized.

Background

We therefore proceeded to finding more information from experts at Children’s Hospital; including a pulmonologist, respiratory therapist, and a nurse. Below are some important and interesting findings we were able to gather from all three:

Nebulizer Dosage

  • Determined dosage for children
  • Ongoing discussion amongst doctors
  • “Dosage should be same” for a child and adult because more is assumed to be wasted for the child
  • Current dosage is 2.5 mL of premixed albuterol dosage; 0.5 mL parts albuterol and 3 mL of saline
  • Takes around 15 minutes to administer
  • Crying isn’t necessarily bad- children inhale more deeply while crying
  • The way to detect inhaled dosage is through
  • a deposition tracer; using a gamma camera- something that would emit radiation- sensitive photon emitter.
  • Image of the lung to measure how much goes to the lung
  • Ventilation profusion scan
  • Size of dosage particles are very important
  • Too small particles are not helpful and too large will get stuck in upper part of the mouth and not be inhaled
  • Diseases cause under ventilation in areas of your body so medicine cannot be ensured to get into all areas of your body that it may need to- also why size matters a lot
  • Expense of the machine often correlated to how appropriate the size of the particles are
  • Depending on the disease, would ideally like to be able to alter the particle size
  • If sealed mask and if humans breath at a rate faster than the nebulizer administers dosage- can assume 100% is being received

Interface

  • Important to allow inhalation through mouth and nose
  • Especially as many children are sick or crying while they are using it so nose is probably stuffed a large percentage of the time
  • Hard to nebulize through mouth while with pacifier
  • Don’t like to use mask; sometimes put it by their face while sleeping but they are not getting full medication
  • Flavors that would taste could help
  • “Bubble masks” in the shape of fish are currently widely used - figures help compliance. The ventilation holes for this mask is located at the bottom which avoids the eyes being too exposed to the medicine
  • Mouthpiece for inhaler is used for 5-6 year-olds and older; mask is used for children under 5 years of age
  • Play therapy is the most effective way of getting a child to comply (role playing on others and yourself to the child more comfortable with the idea)

Type of Medicines

  • Steroids (more expensive)
  • Albuterol
  • Creates side effects like increased heart rate
  • Physical changes occur but difficult to use as a way to monitor since reactions are specific to patient
  • Considered a safe medicine

Ideas for monitoring airflow as a way to monitor dosage

  • Capnography- summing airflow idea
  • Intubation (exist as a color indicator)
  • Aerochamber- Meter dose inhalers/ spacers- they have whistles- at proper speed
  • Video game of trying to stay ball up in the air
  • Balls stay up- to expand lungs- incentive spirometer

Sterilization

  • Cold chemical sterilization
  • Autoclave- would melt the plastic-some plastics are resistant
  • Anything that touches the patient and anything with a backflow (no retrograde flow) should be sterilized
  • Tube that touches compressor does not need sterilization, only the cup needs sterilization
  • Here, mothers will put parts in a breast milk bag, fill with some water and place it in the microwave
  • For multiple patient use: wash with soap and water then boil
  • Ball that would expand and compress depending on heat to indicate sterilization? Color changing indicator?

Three major types of Nebulizers

  • Jet nebulizer (Air compressor as seen in Nicaragua and most commonly used worldwide)
    • Most commonly used here is the Pariproneb with 50 psi pressure (much higher than Nicaraguan which was around 15 to 20 psi)
  • Vibrating Mesh
    • New technology as of a couple of years age
    • Aeroneb Solo System (Not widely used)
      • Very cool!
      • Disposable piece that would cost $40
      • Would break up into adequate particles sizes of 3-5 microns
      • Piece connected to a controller with batteries and frequency generator (set)
      • Can be placed into series with other machines such as ventilators
      • Medicine is gravity fed through a vibrating mesh that breaks up the particles- mesh is a one-way valve
      • Solves dosage problem: device is breath-actuated so whatever medicine is used is ensured to be in the patient.
      • Problem is that reservoir gets clogged if the medicine isn’t breathed in fast enough Brainstorming ways to stop vibrating mesh if too clogged; can possibly be detected through shining an LED through it. Or if controller can only trigger for next breath?
      • Currently used with corrugated tubing can replace with see-through to look at dosage that is in it.
      • Need sealed area
      • Ideas to prolong life of disposable piece is to create a one-way valve mask that can be attached
    • Ultrasonic
      • Widely used before but it would steam copiously and would also “rip” particles rather than just breaking them up into too small particles
      • Stopped being used in the ’80s and ’90s; no considerable efforts have been put into improving technology so still room for improvement and play.
      • Idea: common reservoir with multiple outlets for multiple patient use??
        • Nurse described E-flow compressor
        • Only used for astroneum medicine
        • Works similarly to vibrating mesh
        • Patients having trouble with cleaning it
        • Fun Fact: Teenage patient used it to inhale marijuana!! (what is the world coming to.. :) )

More details coming soon!

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Broken Nebulizer in Nicaragua

by Caroline Hane-Weijman

Broken nebulizer

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Sites and AeroEclipse

by Caroline Hane-Weijman

Some useful sites that were recommended to us by Jose to explore:

Another device Jose helped us come across which almost basically solves our issue… Aeroeclipse!

  • Diaphragm idea that incorporates a breath actuated valve that will direct air from air compressor through medicine when breathing in, and will redirect away while not breathing so only air, no medicine is wasted and therefore dosage delivery can be controlled.

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Background Discussion on the Capnography Technology

by Shan Tie

The use of capnography was first considered as a way to monitor dosage. Caroline had initially discovered this technology in the context of its usage for anesthesia and intensive care. The capnogram directly measures the inhaled and exhaled concentration or partial pressure of CO2 produced by the patient. Furthermore, the device can indirectly measure the amount of arterial CO2.

There are five major physical methods for detecting CO2; however, the least expensive and most popular method for CO2 detection involves using IR technology.

The actual device interface includes a mask that contains an IR light source, some filters and focusing lenses, and an IR detector. The IR source shines IR light through the cloud of CO2 particles produced by the patient. CO2 selectively absorbs 4.3 micron IR light. The absorption amount is directly correlated to the CO2 concentration and thus the amount detected can be compared to a known standard of CO2.

The information that the capnography provides includes CO2 production, pulmonary perfusion, alveolar ventilation, respiratory patterns, and CO2 elimination. These data is presented as the inspired and/or expired CO2 plotted over time (Kodali, capnography.com).

This technology initially appealed to us because it was a technology that had concepts based very much like the pulse oximeter, is already interfaced with a mask, and is used to measure gas production. Our belief was that if we could place the sensor close between the drug outlet of the mask and the nose of the patient, the patient’s breathing can be monitored by his CO2 production and we can assume due to proximity of the drug outlet to the patient’s nose, that he would be effectively breathing the medicine. We can then use this to track the breathing of the patient over time and count up the amount of time that his CO2 production was above a minimal threshold (to account for adequate breathing) until it totally 10 minutes.

After speaking with Brian Walsh, a respiratory specialist at the Children’s Hospital Boston, we discovered some limitations in using capnography. We intended on using this technology for patients under 5 years of age. Currently, the capnograhy either directly measure the CO2 in the mask or takes measurements from side stream line that pulls out samples from the mask. Unfortunately, the amount of CO2 production by these young patients will be too low for any capnography device made cheaply to detect. Furthermore, the capnography device requires a near perfect seal between the patient and the mask. However, the current masks contain vents to allow the release of the CO2 and a perfect seal for infants is nearly impossible. Given these limitations, we decided we needed a more feasible and reliable method for monitoring dosage.

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Background on Vibrating Mesh Technology

by Shan Tie

During our visit to speak with Brian Walsh, he introduced a new nebulizer that is based on vibrating mesh instead of the standard air jet from the compressor pump.

The new aerosolizing technology was implemented in a nebulizer made by a company called Aerogen. The structure of the device is a thin mesh material with ~1000 holes. The device is battery powered to cause the mesh to vibrate at 100,000 times a second. This vibrating motion is a sieve-like motion that draws the albuterol liquid sitting above the mesh through the holes like a pump and effectively aersolizing the liquid droplets into consistently sized, aerosolized particles (Aerogen.com). The aersolized drug will then fall down due to gravity and will collect in the chamber of the nebulizer until the patient actively inhales the drug.

This technology seemed promising because it addressed two major pitfalls in the current nebulizer design. One, it created uniform aersolized particles such that it is of a breathable size that will allow for effective delivery of the medicine to the appropriate areas of the patient lung. Second, the breathe-actuated feature of the device allows for more accurate monitoring of dosage because no medicine is actively pushed out of the chamber without the patient breathing it in- thus leading to a lower medicine loss and allows for more accurate measure of how much drug is breathed in.

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Ultrasound Nebulizer Background

When we visited Brian Walsh and Chris Hug, they also mentioned a type of nebulizer that operated by sending ultrasonic waves through the drug. These were developed around 30 years ago, and consist of a piezoelectric plate which transmits high-frequency vibrations through a liquid. These devices output a far higher volume of nebulized material than traditional jet nebulizers, and since the frequency can be very easily controlled do not have the problem of varying particle size encountered by jet nebulizer. At first we had the idea to utilize the high-volume output by collecting it in a reservoir from which multiple patients could be nebulized. However, we were told that though the particle size was uniform, it could often be too small - meaning that either that the particles would only be effective on deep-lung conditions or that they would not settle in the lungs at all but be immediately exhaled. In some cases, the ultrasonic nebulizers actually ripped up the molecular structure of the drug, rendering it useless.

We decided that considering the far higher cost of ultrasonic nebulizers they may not have much advantage over the jet method - especially since clinics in Nicaragua already have air compressors and compressed air outlets.

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Design Update: Playing with Nebulizer Reservoir

  1. Drilling holes in Tupperware reservoir

Caroline bought some Tupperware that we could use for vapor reservoirs. Today in D-Lab, we drilled a hole in the bottom to serve as a connection to the medicine chamber. Grace is also going in later today to drill holes in the side of the Tupperware® to place a laser and photo detector.

  1. Condensation in the reservoir

Playing around with the nebulized vapors in the Tupperware®, we noticed a few things. There was condensation buildup on the side, and we wondered if a non-static coating would ameliorate the problem. Also, pressure could build up in the reservoir if closed, so we need to think about whether multiple users would prevent this pressure build up or whether there needs to be some release valve.

  1. Learning about how to measure vapor size

There seems to be multiple ways to measure vapor size. Paul H. talk to us about the one way he does so for the Aerovax project. A laser sits on a stand and shoots a beam of light towards a photosensor. If particles are in the way, then they will diffuse the light and less light will reach the sensor. The larger the particles–> more light scattered–>less light detected by the photosensor–>lower resistance in the detector–> higher voltage outputted and recorded. Paul built and wired this system that we will use.

We want to measure relative vapor size of particles coming out from the nebulizer directly compared to particles that have been sitting in the reservoir to see whether time in a reservoir causes clumping of particles. This is important because Dr. Brian Walsh of the Children’s Hospital mentioned that particle size will dictate efficient delivery of the medicine in to the lungs. So we want to ensure that our reservoir is not changing the particle size.

Today, we were orientated to the setup and we plan on doing some tests during the week.

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Background on Anti-Static Coating for the Reservoir Surface to Minimize Aerosol Particle Coagulation

by Shan Tie

Anti-Static Methods

Chemical solutions to static electricity: http://www.explainthatstuff.com/howantistaticcoatingswork.html

Glass pipes with a protective antistatic coating: (PDF)

The optimal composition of the applied film is found to be: 50% SnCI~.5H20 with a concentration of 1% SbCI3.

Anti-static coating and its method of preparation:

This patent talks about composition of anti-static material composed of a synthetic resin base without any metallic particles. However, it is in the context of using this coating for the fuselage of airplanes; therefore it might be a bit more than what we need for coating our nebulizers.

%%%

Found various anti-static sprays:

  1. Endust Anti-static spray

  2. Static Guard Anti-Static Spray 5.5 oz (156 g)

  3. Aeros anti static spray (END096000) Category: Surface Cleaners

Found various anti-static tape:

  1. 3M 40PR 1/4 in x 72 yd Clear Anti-Static Tape

  2. Dadas Tapes 1662-05 - Anti-Static Transparent Tape, 3" Core, 1/2" …

  3. Botron B1651 (1/2"x36yd Clear ESD Tape) - 1/2"x36yd Clear ESD Tape

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Pictures of our Reservoir Prototyping Round 1

by Caroline Hane-Weijman

Vapor laser sensor connected to the Arduino can measure particle size and concentration

We need to explore a valve system so that the pressure does not get too high inside the reservoir.

Next step: Build the patient tube with a one-way valve and another vapor sensor!

Experimental setup with patient tube, one-way valve, and second vapor sensor

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One-Way Valves
by Mary Jue Xu

Designs for valve cut-outs

Part of our design is to have a breath-actuated one way valve. In other words, a valve that will open only when the patient breaths and only opens one way.

At first, our group was looking online to try and find one way valves to buy. The majority of them that we saw were used for CPR, so we were concerned that those valves required more pressure than a baby’s breath could open.

Then in class Jose introduced us to a way of simply making one way valves cheaply. The D-Lab health team from last year also worked on this as well, so I talked to one of their members, Luvena. Their team used a thin plastic bag for the valve and cardboard cut-out rings adapted to whatever tubing being used. A problem the group ran into was that the flap did not close completely.

Shan and I tried some one way valves. For holders, Caroline had the idea of using the bottleneck part of water bottles and the O-rings on the top as holders. Also, Caroline and Grace found mesh to put behind the flap so that it would allow air flow one way but prevent the flap from opening both directions. They chose white mesh because they thought it would look cleaner to patients.

In class, Shan and I found that one large flap was better cutting the circle into four flaps. The four-flap system had a lot more leakage if everything did not align during assembly. Also, three-way flaps were held too tightly on the rings.

As Grace will explain in her post, Ryan, an instructor from D-Lab was kind enough to lend us some pressure valves that open upon reaching a certain pressure. We have decided to hold off on the manually made one way valves for now. Since our design is unique in that it is all pressure modulated, we are first focusing on proof of principle before we think about decreasing costs and local manufacturing.

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Preliminary Vapor Quantity Testing
by Shan Tie

One of the things we mentioned as an important feature for our new nebulizer design was to incorporate a better method for measuring dosage. Our design will attempt to address that by adding a breath-actuating feature (medicine only flows out when a patient inhales) in conjunction with a vapor sensor near the mouthpiece to sum up the times when vapor is passed through from the reservoir to the patient.

Today, Mary and I worked on creating the physical breadboard and the Arduino code for our sensor. The sensor itself consists of a LED light, a light sensor, the Arduino, and the breadboard. The set-up of our system works off of the current system created by Paul and his team. Our physical construction will be described in more detail by Mary. A modification we included in our design was to replace the laser light source with a LED light. The original design needed a LED light because the sensor was placed at a much farther distance away from the light source and the detection threshold of the sensor depended on a minimum level. However, after speaking with Paul, we realized that the distance we will be working with (the diameter of a tube, ~2 cm) is small enough to allow us to use a LED light. We modified the Arduino code from Paul’s original detector and added code that specified turning on the LED.

Arduino code:

int redPin = 7; // sets the output serial port for the LED light

int sensorPin = 0; // sets the input serial pin

int sensorValue = 0; // sets the initial input value at the pin as 0

void setup() { // how to start the set-up code

pinMode(redPin, OUTPUT); // defines the output variable name as “redPin”

pinMode(sensorPin, INPUT); // defines the input variable name as “sensorPin”

Serial.begin(9600); // defines the “baud” rate (transfer of data rate)

}

void loop() { // how to start the operating code

digitalWrite(redPin, HIGH); // defines the digital output from the arduino board to the LED

sensorValue = analogRead(sensorPin); // defines analog output from the sensor as “sensorValue”

Serial.println(sensorValue); // displays the sensorValue in a running stream of numbers

}

We created a special testing tube for our sensor and LED (Mary will describe). We tested the sensitivity of our sensor by flowing nebulized water into our test tube and observing the output measures from our sensor. Our system is very stable without any aerosolized particles flowing–in our test run, the output signal was 437. When we ran nebulized water, the level rose to 452. When we stopped flowing air into it, the levels never returned to the initial baseline value (443)– this is due to a degree of condensation that remains both on the walls of the tube and on the sensor and LED light. When we resumed flowing nebulized water, the signal output rose to 455. However, the changes between when the nebulizer is on and off were 15 and 12, respectively. This seems to show that there is consistency in our devices in our preliminary tests.

Next steps:

It will be interesting to carry out the previous experiments further and see if the change remains consistent once the walls becomes saturated.

We will need a way to sum up the amount of particle that flows through over time.

We need to create a standard for the amount of particles flowing through based on the output.

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Vapor Sensor: Physical Setup
by Mary Jue Xu

Vapor sensor setup

Today we made an tested our first prototype of a vapor sensor. It was really excited to get the Arduino code, wiring, and initial test set up. The idea behind the vapor sensor is to measure dosing. By measuring interference of a light to a photodetector, we can tell how much time and possibly volume of vapor the patient has breathed in from the breath-actuated nozzle.

We initially sought help from Paul H, who works for IIH on the Aerovax vaccine. I remember seeing him testing vapor size earlier this semester.

Today to build the initial vapor pressure prototype, we connected 4 tube ends with black electrical tape. Then we placed the photodetector and the LED light in tubes facing each other. We covered those two tubes with black tape in order to block out ambient light. This way, the photodetector could pick up the LED light more accurately. So vapors flow through one direction and the sensor picks up data in the perpendicular direction.

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Photos of Testing

Testing the nebulizer

Breadboard circuit

Complete setup

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Prototyping and Testing
by Caroline Hane-Weijman

We spent the day in D-Lab playing with all the wonderful toys Rob provided us to create the different modules of our designing and testing them. The main three components we worked on today were:

Vapor Sensor- This is to measure dosage received by the patient after the breath-actuated one-way valve

Solenoid Valve- This valve is placed before the nebulizer cup as a way to divert the compressed air flow from going through the medicine when the pressure inside the reservoir gets too high.

System Pressure monitoring of the System- This looked at the interplay between the air compressor, pressure of the reservoir, and the activation/“cracking” of the one-way valves.

We got a lot of testing done and have these components at least working separately. Next step–> Put it together!

I looked specifically at the System Pressure monitoring of the System. We drove the air compressor by a voltage source, connected it to the nebulizer cup (using any type of connectors we could make work), placed a Vernier Gas Pressure sensor inside the reservoir that communicated with a LoggerPro and the accompanying software, and connected the reservoir to a tube with a one-way valve placed at the end. We were exploring 0.07 psi and 1.5 psi valves. The following labeled photograph shows the experimental setup!

Experimental setup

Observations

  • Reservoir Lid pops when the reservoir is at approximately 104.4 kPa
  • Found that around 102. kPa the 0.07 psi valves opened. i.e. would open very easily and before medicine was able to get through the tubing
  • Used a 1.5 psi valve, which before could not be breath actuated, but after pumping pressure through it and kept the pressure in the range of 102 kPa and 103 kPa, was able to be breath actuated- want to go with this valve for now.
  • Coagulation is a problem- by the time it reaches the outlet tub it condenses again.
  • The system kept leaking which is why the pressure was constant while flowing air through the system without opening the valve, however when we made attempts to seal these leaks, the pressure would quickly increase and pop the lid of the container.
  • While sealing leaks, pressure was able to be maintained relatively constant when we activated the valves (breathed in) which is positive. The highlighted portion of the graph below shows consistency due to breathing in (while the others are due to leakage). Peaks occur when the lid pops off the container.

Pressure-vs.-time data

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General Project Overview & Ryan Assistance

Recently we refined our final design idea to the point where we know exactly what we need to build and what tests we need to run - as shown in the wonderful blog posts below. Much of this was due to the help of Ryan, who lent us pressure control equipment and gave us some great ideas for our setup and experimentation.

The general ethos behind our final product is that we’re proving the concept of our design with high-quality equipment that can be scaled down in cost and complexity if the concept proves to work. Our overall goal is to create a nebulizer that:

  1. Can be used on multiple patients

  2. Is very efficient in its use of medicine

  3. Allows some level of dosage monitoring

The way we decided to do this was to create a nebulizer with a central reservoir from which multiple patients’ tubes could feed off. It also aims to be breath-actuated by the patient, i.e. medicine only comes out if the patient breathes in. To do this, we want to use one-way valves on the end of each patient’s tube and control the pressure in the reservoir such that it is just under the cracking point of the one-way-valves. This way, the patient only needs to apply a little pressure by breathing in for the valve to open and them to receive the medicine.

The way the pressure can be kept at this rate is through a control system run through the Arduino. The Arduino takes input from a pressure sensor in the reservoir and based on that decides whether to open or close a valve between the air compressor and the nebulizer cup. If the pressure is too great, the valve opens and directs the compressed air away from the nebulizer. As pressure starts to go down, the valve closes, letting more air through the nebulizer cup. With an effective control system the pressure in the reservoir could be kept reasonably constant.

Fancy equipment that Ryan has given us:

  • Several different one way valves, with different cracking pressures (0.07psi, which is adult breathing pressure, 1.5 psi, and I think a 10 psi. Note: all of these can be breath actuated, the pressure on the other side just has to be a little bit lower than the cracking pressure. One of our experiments will be to determine whether a high or low pressure reservoir works better). The one current problem with these one way valves is way they fit in line with the pipes - we don’t really have good couplings for them. Some investigation and hardware store shopping is needed.
  • A fancy 3-way solenoid valve. Basically what this does is it receives an input from the Arduino, (on or off) and depending on what that input is switches the flow of air from one outlet to another. This goes behind the nebulizer - the input is the compressor air, one output is the nebulizer, and one is left to the open air. So when we need to decrease pressure, the Arduino will tell the valve to switch to the open air output.

This does require wiring up some circuitry - the solenoid valve cannot run on the low (5 V) Arduino voltage, it needs at least 12 V. Though this is now made a lot easier by the fact that Ryan has given us all the necessary parts and a picture of a working breadboard in his lab that uses the same circuit.

Ryan advised us that when testing the solenoid valve, instead of hooking it up directly to receive input to the pressure sensor, we should use a ‘fake’ pressure sensor input into the Arduino (e.g. a pot) that we can directly control to check the code works instead of relying on the pressure sensor straight away.

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D-Lab Showcase!
by Caroline Hane-Weijman

Yesterday, D-Lab had its end of the year showcase at the MIT Museum, featuring all the D-Lab class projects. D-Lab Health gave the other classes a run for their money :) The neb team managed to get all the individual components working, including the solenoid valve, the pressure sensor, and the vapor sensor (all with code), before the showcase, although it was a rush to the finish! Shan did a great job representing our team in the one-minute pitches, and people seemed to like the idea.

We still need to work on the interplay between the components but we were having issues with leakage in the system and therefore the pressure in the system was relatively constant when we tried to seal the end of the tube. We also have to retrofit the tiny valve to the large tube for the mask- but for demonstration purposes on Wednesday we are considering showing it as two different components as we do not have the opportunity to get the right diameter valve in time. We will continue working until Wednesday— come see us present in class in detail!!

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Vapor Quantity Testing Part 2

Vapor sensor also includes the ability to turn on a “dosage LED”- in other words, this light turns on when the total amount of time the patient is inhaling medicine satisfies a requisite number. Currently, the code takes in a given threshold value that determines when the patient is inhaling medicine and also a set dosage time of 10 seconds. In reality, the threshold number will need to be calibrated closer to the levels that is seen from a person’s inhalations and to take into account noise from humidity in the air and inaccuracies in the measurements. Furthermore, the dosage time will be actually ~10 minutes to correspond with current standard dosage times (it’s shorter here for proof-of-concept needs).

Arduino code:

int redPin = 7; // sets the output serial port for the sensor Red LED light

int dosePin = 4; // sets the output serial port for the dosage dose LED light

int sensorPin = 0; // sets the input serial pin

int sensorValue = 0; // sets the initial input value at the pin as 0

int lastsensorValue=0; // defines the variable to store the last sensorValue

int threshold = 300; // set by user as the baseline value needed to reach for nebulized medicine

long startTime; // defines the start time

long elapsedTime; // defines the elapsed time

int total=0; // defines the variable the sums up the time for when the sensorValue is above threshold value

int fulldosage = 10000; // defines the dosage time (in milliseconds) for a complete dosage

void setup() { // how to start the set-up code

pinMode(redPin, OUTPUT); // defines the output variable name as “redPin”

pinMode(dosePin, OUTPUT); // defines the output variable name as “dosePin”

pinMode(sensorPin, INPUT); // defines the input variable name as “sensorPin”

Serial.begin(9600); // defines the “baud” rate (transfer of data rate)

}

void loop() { // how to start the operating code

digitalWrite(redPin, HIGH); // defines the digital output from the arduino board to the LED

digitalWrite(dosePin, HIGH);

sensorValue = analogRead(sensorPin); // defines analog output from the sensor as “sensorValue”

if (sensorValue >= threshold && lastsensorValue <= threshold){

startTime = millis();

}

if (sensorValue <= threshold && lastsensorValue >= threshold){

elapsedTime = millis() - startTime;

//Serial.print( (int) (elapsedTime / 1000L));

}

lastsensorValue = sensorValue;

total = total + elapsedTime;

elapsedTime = 0;

if (total >= fulldosage) {

digitalWrite(dosePin, HIGH); // turns on dosage dose LED only when the desired time is fulfilled

}

else{

digitalWrite(dosePin, LOW); // ensure that dosage dose LED is OFF when the desired time is NOT fulfilled

}

Serial.println(sensorValue);

}

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Mini Update

As few days ago, we presented our design in class. It was a lot of fun showing our design and seeing other groups’ work.

This summer, we will be in China, New York, and Boston, so maybe some of us can continue building and testing over the summer!

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Course Info

Instructor
Departments
As Taught In
Spring 2010
Level
Undergraduate
Topics
Learning Resource Types
Design Assignments with Examples
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