An Open Design for an Air Flow and Pressure Control Circuit for Medical Devices

We report on an air control system with low power consumption for small enclosures with mainly medical applications, such as lung ventilators, APAP machines, PAPR isolation hoods, surgical applications, and aerosol containment. The circuit shared can be built from cost effective, commercially available parts; it represents a pressure control system for positive pressure environments such as hoods used in personal protection equipment (PPE), as proposed in today's COVID-19 epidemic. An essential feature of the approach is that the circuit uses advanced off the shelf modules that include microcontrollers, but the overall design remains analogic. Another contribution is to derive rigorous design equations that bring together the pneumatic and electric nonlinear equations describing an inflatable enclosure, the linearized pneumatic circuits, the power device (fan), and the control loop. We warn that the designs in this paper are for scientific testing only and not for any medical use; no guarantee is implied. See the Warnings and Disclaimer.