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Covid-19 UK | Caveat Emptor: Opensource engineering resources only


COVID-19 UK


June 2020

  • The main COVID-19 threat to overwhelm hospitals short on ventilators has passed and thus we are stopping effort to make an open source version.

Historical Information

  • Why are so many ventilators needed?
  • A mildly affected person can recover in 5 days without any medical assistance. A seriously ill person needs ventilator for 6 weeks. In some countries 50% of tested people show no symptoms despite having Covid-19 while they spread it around.
  • A ventilator forces air in and out of lungs.
  • There are lots of settings and technology needed to measure and adjust air flow, pressure, breathing rate, the amount of air sent to lungs and oxygen ratio.
  • Ventilators need certification of hardware, sensors and software before they can be used by a doctor. This step best left to an integrator.
  • Open source can help in parallel manufacture and design of components, electronics, and software for scaling up production.
  • If the medical condition becomes extremely bad, you can make and use your own reduced functionality ventilator if you know what you are doing and accept / manage all risks. With today's off the shelf 3D printers, electronics and sensors, such machines could easily be more advanced than what was available 20 years ago. If the person's condition worsens to the point where not enough oxygen is reaching the brain, the person begin to lose consciousness and needs to be sedated and the air has to be forced directly into the lung through tubes (intubation) to forcefully inflate and deflate lungs to imitate breathing. In UK, 80% of people with COVID-19 and hooked up to a ventilator perish, so may be there is a need for better AI based sensing logged to public anonymized databases for analysis, and AI feedback for rapid change of settings that need to be incorporated to make more advanced ventilators than commonly available on the market.


        Lord Bethell - Minister of Innovation at the Department of Health and Social Care:

        I know people are extremely keen to help. 

        So we’ve set up dedicated hotlines for people to send in their ideas. 

        #Vaccines : Nervtag@phe.gov.uk
        #Ventilators: 0300 456 3565 / ventilator.support@beis.gov.uk
        #Innovation / #tech : DNHSX@nhsx.nhs.uk


  • We offer to do our bit to help during Covid-19 emergency:
    1. Convert parts sent to us into FreeCAD open source parametric designs that can be passed around to make nylon powder 3D printed parts and dxf files for laser cutting.
    2. Convert electronic diagrams sent to us into open source KiCAD drawings and resources permitting create laid out PCB that can be passed around to scale up electronics production.
    3. Convert C/C++ embedded code into state machine code and Arduino compatible library code that is easy to modify to add new features by a greater number of people.
  • The 3 offer of services applies to any parts from any relevant machine. Whether it is ventilator, vaccine research robot automation that require duplication, or some new equipment that needs urgent modifications.
  • We have 1gbit Internet link and 'unlimited' storage for anyone to download the files once finished.
  • No problems if duplicating effort to speed up work and reduce uncertainties.
  • This help is voluntary and no fees for any service.

UK Ventilator Specifications

  • Specifications: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/874279/RMVS001_Rapidly_Manufactured_Ventilator_Specification__PDF.pdf
  • Key points:
    • At least 1 mode of operation
      • Mandatory ventilation mode
      • Optional 2nd mode - pressure controlled or volume of air control
    • Volume control of air
    • 240V mains operation
    • 20 minute battery back up operating at 12V, hot swappable batteries, ideally capable of using a common mix of battery types to minimize run on battery suppliers, uninterrupted operation while cables being unplugged and re-arranged.
    • Avoid EM or RF interference with other equipment
    • Alarms for various conditions
    • 14 day continuous operation minimum requirement
    • Intuitive to use, 30 minute training
    • Adapters to fit to NHS wall mounted gas supply sockets
    • Easy to dismantle and clean all contaminated parts

Open Sourced Files

Segmented hose design - make custom hoses from 3D printed soft materials for testing, or use it to design molds for tooling up and mass production
Parametric design - control dimensions of design from spreadsheet values


Parametric design - control dimensions of design from spreadsheet values. Parametric spreadsheet method avoids having to learn 3D parts design.


Parametric design - control dimensions of design from spreadsheet values. Parametric spreadsheet method avoids having to learn 3D parts design.
  • This part will FDM print without supports for testing purposes.


Parametric design - control dimensions of design from spreadsheet values. Parametric spreadsheet method avoids having to learn 3D parts design.


  • A thin heating wire such as nichrome wire is mounted between the two cone supports into the middle of the air flow.
  • The wire is retained with fire cement which is packed to fill the cone; which on setting resists heat and is non-conductive.
  • To minimize the possibility of hot wire touching plastic, the mounting hole diameter of the cone support is increased to allow a ceramic ferrule to be inserted, through which the wire is threaded. The ceramic ferrule and wire is retained by applying fire cement to fill the cone until it sets.
  • The wire is heated to about 50 degrees. The temperature of air flow before entering the sense chamber is taken.
  • The hot wire is cooled by the airflow. The amount of cooling depending on temperature difference and airflow. Airflow can be measured as a change in resistance of the wire.
  • By careful calibration, a solid state hot wire sensor can measure airflow without using any moving parts.
  • Example of how it works - https://www.youtube.com/watch?v=rCzw6ottMe4
  • Circuit ideas - https://www.electroschematics.com/measuring-air-flow/
  • Parametric design - control dimensions of design from spreadsheet values. Parametric spreadsheet method avoids having to learn 3D parts design.


  • The design is being worked on and will be uploaded soon as it is ready.
  • The diagram shows a ball valve with a voice coil for pulling magnet1 and releasing it at high frequency. The ball valve is held permanently closed by pushing force of magnet 2 against magnet 1. This avoids using a mechanical spring and allows the voice coil to operate at high frequency. The coil is energized and pulls magnet 1 back allowing a pulse of air to exit through the ball valve. The outlet is at a lower pressure than inlet, and thus the ball valve will try to close of its own accord from the rushing air. The mark space ratio of coil on to coil off determines the volume of air released per pulse. Using higher frequency pulses allows finer control of the release of air. By varying the mark space ratio, high pressure air can be converted to low pressure air flow suitable for inflating lungs at a slow pace.
  • The valve can operate in reverse where the outlet is connected to a high vacuum. By pulsating the voice coil, air is slowly drawn out of the lungs and into the high vacuum. Pressure sensors can ensure the lung is not completely emptied of air, and that a positive pressure inside the lung is always maintained to keep the lung inflated against external air pressure.
  • The 3D printing has to be done mostly in nylon powder.
  • The ball valve cup needs to be very accurate and a smooth surface otherwise it will leak air. It should preferably be made from softer materials. Most likely the part is made with injection molded nylon.
  • The design file has a BSP 1/4 inch thread profile and helix to generate nuts and bolts. For testing purposes, these nuts and bolts are good to go to make pneumatic connectors, and can even make good prints with FDM printer!! If you do generate threads, FreeCAD slows down considerably due to the huge number of polygons it needs to handle when updating design changes from spread sheet or sketches. For that reason, threads will be added after design work is completed.
  • A 2nd hand SLA 3D printer with grey resin and elastic resin has been ordered. The printer may be good enough to make fully functional voice coil actuator ball valve. The ball valve cup needs to be redesigned to be printed from the elastic resin to give air tight operation. The BSP pipe threads will always leak air - they are always meant to be used with thread sealant such as PTFE tape.


Solid State Ventilator Design

  • Above is a diagram for 'solid state' ventilator using solid state hot wire air sensor, solid state pressure sensor such as BMP280 and use of an always off ball valve driven by voice coil that is near enough solid state with hardly any moving parts. There is spring resistance in the ball valve but implemented by a pair of repelling magnets to allow the voice coil to operate at high frequency letting tiny amounts of air through with each pulse. The oxygen and air arrive at high pressure. The vacuum is high suction. Each of the 3 supply line is shared between all ventilators making the device very cheap to make and the software easy to write. There are no pulsating ventilator bags with this system although one could be added to visually show the inflation and deflation. Everything to the left of the coupler is the solid state ventilator and could be made to reside in a shoe box size unit. The coupler can be larger hoses or if intubing, the hose can be the smallest possible because the high pressure air, high pressure oxygen and high vacuum can deal with the resistance of small diameter hose.
  • For long duration unattended use, a ventilator also needs a nebulizer. The purpose of the nebulizer is to vaporize medicines to 5 to 15 micron droplets and add it to the air flow. This can be achieved with pressurized air (makes a lot of noise) or a solid state ultrasonic vaporizer commonly used for fog generating machines.
  • To make the air comfortable to breathe, the output temperature needs to be regulated with a heating element or cooling element. The simplest of all heating/cooling solid state element is a Peltier cooler. One Peltier can be used as both cooler and heater depending on direction of current flow with a H-bridge circuit.
  • Reading the hot wire sensors, reading pressure sensors, and sending out PWM signals to operate the voice coil to create a breathing profile is relatively mundane task for Arduino or a clone such as ST-Duino. Since there is no software out there for open source ventilators, we hope to make the software soon and release it fully open sourced. It will be much simpler than a portable ventilator because there are no pumps to control and no secondary functions.
  • A solid state ventilator has no moving parts or settings to manually adjust. Every adjustment is handled by sensors and actuators connected to a microcontroller board. All data can thus be captured and uploaded to cloud for AI to inspect changes in medical conditions and note how those conditions have been handled, learn from the data, and adjust other ventilators through AI more quickly than humans can do on a minute by minute basis.


Progress and Deficiencies

  • Hose, sleeve adapter, hose splitter, air filter, solid state hot wire air flow sensor parts 3D print OK.
  • Notice a few designs released on Internet - STL files - time consuming if it needs modifications as they are not original design files.
  • No open source software for ventilator control found yet - still in stone age. Here is a list of features required:
    • What we probably need is two hoses per mask for ventilation control using 3 air pressure sensors.
    • Pressure sensor of atmospheric air
    • Incoming air timed with breathing detected by pressure drop
    • Separate outgoing air sucked out, but not completely - using pressure sensor to maintain slight pressure above atmospheric pressure to keep lung inflated
    • Some kind of cheap to make hot wire air flow sensor to measure total volume of air, and the air temperature of air going into the sensor.
    • Clear large menu display
    • Large buttons / keypad to operate the display
    • Notice now that due to shortages of ventilators, some have split the air hoses to connect multiple people.
      • One giant source of air supply and vacuum pump could be split endlessly to many people. All we would need then are a small number of sensors and control box per person instead of one ventilator per person. Special air valves needed to regulate high pressure air into lung pressure air needed to make this system work. The software need less effort to write.

Open Source Ventilator Resources


Open Source Mask Resources


No comment


Sensors and Components


Sources for Information


Big Data


Repair Manuals of Existing Ventilators


Certification


Bleeding edge know how


Desperate Measures


News


Government Policy Ideas and Technology Ideas

  1. Governments all around the world need to bulk purchase utility output electric, water, gas, telecom and pay for it directly so that the public are not being invoiced for it. Tell banks/landlords to stop invoicing. So no one is getting unnecessary bills during emergency. Some of it happening in finance sector with interest holidays already 😀. And at least one country has gone towards cancelling utility payments. But the majority of countries and civil servants are blasé towards this source of cash drain and piling on huge debts on families for what purpose exactly?
  2. Roll out UBI funded by VAT during emergency - this is largely happening in some countries 😀. Other countries should step up to the task and copy.
  3. Move the public into Internet of Fiber Era. Strip genocidal telecom and cable companies of rights to sue governments and local authorities in opposing roll out of fiber and only use their revenues to invest and fiber to reduce future billing. The telecom and cable companies have been hugely responsible for preventing home working for best part of a decade and through that has assisted with spread of virus on a genocidal scale.
  4. Begin roll out of Crowd Governance through Internet. It is 24/7 always on efficient decentralized governance to allocate resources. These new ideas use online crowd checking to prevent cheating and becomes more powerful than anything before it.
  5. Make centrifuge beds to empty lungs of fluid build up. We asked UK government funding agency £100k for 80% of the costs, at the time when up to £250k was available per project. That was rejected with rule changes that limit it to 50K, with up to 100% funding for projects. Not the best thing for UK Civil Service to be doing while 1000 people a day are expiring in UK.
The idea of the centrifuge is to exploit known lung drainage pattern during infection. Due to gravity, the lungs drain to the bottom with fluids causing lungs to change and become sponge like soaking up fluids and literally drowning the lung. Patients are tilted to allow fluids to drain, but the maximum effect is only about 1g and far less if the person is in a lying down position. Spinning creates extra forces to drain lungs. Plan is up to 3g with this machine. With a set of laser mirror to detect anything falling off the beds and onto the floor. It can take up to 4 months to make this centrifuge. Something simpler could take a lot less time, but that then requires another 4 months again to scale up. With modern parametric design and production methods, the entire device complete with laser floor scanning to detect fallen objects to stop the centrifuge could be designed and finished in under one month but may require a lot more resources than £100k to make it happen.




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Page last modified on July 21, 2020, at 01:32 PM