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C11A1 Prototype Build Review

Concept C11A1 - Prototype Build Review

@jd18 15 APR 2020

Positive Comments

  1. Pressure-regulated volume control was the fundamental design criterion, thus the MVP requires minimal software/controller development.

  2. Many Design Criteria Met

    • Must squeeze bag with sufficient volume displacement
    • Must avoid friction between mechanism and bag to lowest degree
    • Must accept placing the bag (Transition from pumping to loading) or a port for manual bag transitions.
    • Must be able to be sterilized and/or used in a sterile environment
    • Must be able to be on it’s own cart or hang from IV Stand - solve limited table space.
    • Must protect the bag from accidental contact from bumps, drops, other equipment
    • Must have the ability to disassemble easily for repair/cleaning
    • Must be able to reach volumes of 1000 per day in industrial facilities
    • Must use as few parts as possible
    • Must Be physically robust enough for rough handling
    • Must have low friction bearings on any high frequency rotating components
    • Must allow sensing for key MVP Specs
    • Must allow for sensing of current actuator location / bag displacement

  3. All the advantages of the OxVent design, without the need for a compressed air supply and expensive proportional valves.

  4. No in-line sensors needed, so extremely simple/inexpensive, items in patient air are all pre-approved.

  5. Patient Pressure and volume are directly controlled, and linear real-time control is possible.

    • Assisted vent is just a code change and expiration P sensor.

  6. Four custom parts so far, simple to print or CNC. Rest of parts are widely available, alternates aplenty, and not currently in COVID-stressed supply chains. Cost could be well under $70. Could save another $20 with an analog pressure sensor (currently digital).

  7. Safety and Cleanability strong positives

  8. Dual motor design allows widely available Nema17 and alternates

  9. MVP testing on an Artificial Lung ongoing.

Neutral Comments

  1. Design Criteria in Question
    • Must be able to replace BVM or similar core pump with ease.
      • Today the clamshell is two cheap parts that need to be sealed around the connections, and thus the Bag. We envision this being a one-way assembly, replaceable after service life for the cost of the bag + pennies for the clamshell.
      • Either the MFR seals and tests on a Bag before shipping or a local user can just "grab another clamshell out of the box" and seal it around a new bag.
      • Or the clamshell is designed with some clamp/release tabs around the edge for reuse.
    • Must have and easy and apparent control interface
      • Propose a control interface attached (but easily removable from) the clamshell
    • Must have simple adjustment for on the fly volume/displacement changes on the device
      • n/a today, but presumably via UI later. 4 buttons and a readout.
      • Design drives V directly, a unique advantage, so this could even be a mechanical adjustment of piston stops.
    • Must have simple adjustment for on the fly pressure changes on the device
      • n/a today, but presumably via UI later. 4 buttons and a readout.
      • Design drives P directly, a unique advantage, so this could even be a mechanical adjustment of piston ring.
    • Must have a small pole (Beacon) indicating alarms and continuous function
      • n/a today. Propose alarm lights on the control interface box
  2. Significant packaging design upgrades needed.
    • Does the piston live with the clamshell or separate?
    • Best material for the piston cylinder?
      • what if PVC not approvable for ICU, even though it does not touch patient or patient air
      • what about standard pneumatic cylinders + linear motors? More expensive, maybe not widely available.

Next Iteration Challenges

  1. Demonstrate MVP mechanics and control.
    • Pressure-regulated volume control inherent in the design. Prove it.
    • Perhaps the piston seal mounts are further refined to allow different amounts of leak/flow under different motions/speeds
    • Perhaps a standard pneumatic cylinder and/or linear actuation, or an inexpensive bellows can be used to increase precision.
  2. Cost / Complexity
    • What's the Mass Production method of choice for the piston?
    • Injection mold tooling for the clamshell?
    • Finalize BOM for all other parts.
  3. Full-out artificial lung and reliability testing ongoing
    • Calibrate piston pressure to P&V at patient, close the loop
    • Imitate and solve all imaginable failure causes and reactions
    • Add battery backup and test fail-over/charge switching
  4. Packaging and UI/UX

Team Lead(s):

Team Gitlab Slack
Acme @jd18 @ Jonathan Kemp
Edited by Trevor Smale