S04: DESIGN, BUILD AND EVALUATION OF A LOW COST, PANDEMIC VENTILATOR USING NON-VENTILATOR SUPPLY CHAIN PARTS
Gordon Gibby, MD; David Lizdas, BS; Anthony DeStephens; William Johnson; Sean Niemi, PhD; Ilana Zarour; Sean Kiley, MD; Jennifer Nichols, PhD; Patrick Tighe, MD; Samsun Lampotang, PhD; University of Florida
Introduction: In the early days of the COVID-19 pandemic, a shortage of up to 950,000 ventilators was predicted for the US. Unable to predict exactly when the surge in ventilator demand would occur and whether new assembly lines for full-featured ventilators would deliver in time and in the numbers required, many ventilator projects were started, including ours, aiming to bridge the time gap when the US population might lack ventilators.
Methods: To not interfere with traditional ventilator supply chains that were already stretched, we opted to design and build our ventilator with equivalent non-ventilator parts, like solenoid-controlled sprinkler valves for flow control of high pressure gas, water pipes and Arduino microcontroller boards. We kept parts count low to produce a minimal, inexpensive but safe design. All parts must be inexpensive and readily available in 100,000s. The overall design must not require special tooling or assembly lines to assemble in volumes of 100,000s. A pandemic being global, we selected an open source project that volunteers could contribute to and benefit from worldwide. We chose an open architecture design (OS-Vent) whereby the design is localized to use equivalent, locally available parts or modules. We are seeking Emergency Use Authorization (EUA) from the FDA for PanVentTM, a fixed-design variant.
The software coded by authors in groups.io. using the Arduino free integrated development environment runs on an Arduino Nano. The software executes a continuous loop with modules for user-interface, alarms checking, and ventilator control. The main ventilator control loop makes repeated measurements from I2C-based sensors at up to 40 Hz. We included backup modes and stringent protection for I2C failures. A watchdog timer restarts the system if a hardware or software failure occurs, and ceases using failed hardware. Instantaneous battery backup provides more than 1 hour battery operation.
We evaluated ISO 80601-2-80 ventilator performance on test lungs (Michigan Instruments TTL 1600) with variable compliance (C), airway resistance (R) and a ventilator analyzer (Citrex H5, imtmedical ag).
Results: OS-Vent and PanVentTM provide time cycled (rate of 10 - 30 bpm; I:E: 1:1, 1:2, 1:3), volume controlled (250 - 600 ml tidal volume), pressure limited (15 – 60 cm H2O pressure limit) continuous mandatory ventilation (CMV) with assist control (-4 to -15 cm H2O trigger) with active PEEP (0 – 20 cm H2O) and inspiratory pause (25% of inspiratory time).
The PanVentTM flow diagram is in Fig. 1. Cost of goods is $300 but less in 100,000s. Assembly time is 2 person hours or less per PanVent. A PanVentTM has ventilated a test lung continuously for 5 weeks. Fig. 2 displays flow and pressure plots at C = 0.1 l/cm H2O, R = 20 cm H2O/l/s.
We disseminated build instructions, bill of materials, software at https://simulation.health.ufl.edu/technology-development/open-source-ventilator-project/ and GitHub https://github.com/CSSALTlab/Open_Source_Ventilator.
Conclusion: We built a low cost (<$300) and scalable (≤ 2 hours assembly time without special tooling or assembly lines from widely available parts) emergency use ventilator. Continued testing and review to meet the requirements for EUA of the PanVentTM is ongoing.