Piston Ventilator

grabcad

The design centers around a 2-foot-long, 4-inch-diameter PVC pipe and an internal 3-D printed piston that is moved by a linear actuator housed within the pipe. As the piston rises, air is sucked through a readily available CPR one-way flapper valve with a built-in filter. The piston is pushed down, allowing air to travel into a hose leading into a hospital bed Ambu or Laerdal bag. An HME filter is connected to the breathing port on the Ambu bag to retain humidity and act as a viral filter for the air entering the patient, also filtering exhalation air to protect healthcare workers. From the HME, an intubation tube enters the patient, providing critical air and oxygen. Utilizing the Ambu bag allows for an adjustable PEEP valve to be easily attached, along with an oxygen port, mixing chamber, and non-electronic exhalation control valving. In the event of a ventilator failure, manual Ambu ventilation can begin immediately due to the system's inline design. The system HMI features a 3.5-inch Nexion touchscreen that provides setting adjustment and parameter monitoring, compatible with an Arduino that controls the actuator through an H-bridge. To sense pressure differential between ambient air and patient air, a Honeywell sensor is incorporated, allowing for breath assist mode and pressure mode along with pressure monitoring. An ultrasonic sensor trains on the piston to detect speed/position and calculate flow rate, feeding into the command to end the stroke and return depending on the mode. The system aims to be cost-effective, space-efficient (entirely housed in a single PVC cylinder), and easy to build using mostly readily available parts with others 3-D printed. The mechanical portion is mostly prototyped, while electronics are in development. Ideally, an Ambu bag incorporating a pop-off valve will be used. The system can achieve a range of 0 to 1.2 liters tidal volume per stroke and a maximum 30 BPM at 1.2 liters, increasing with lower tidal volumes. A simple Piezo buzzer alarm is included, while all systems run on 12V DC from a 120V AC converter brick, allowing for various backup batteries. The system can be hung on the side of a hospital bed, and PVC can be replaced with see-through acrylic as an alternative at higher cost. Double O-ring seal lubrication uses food-grade, odorless grease. Material costs are approximately $200 USD. On April 29th, design files will be submitted to GrabCad. From May 1st, the mechanical portion will be completed. By May 14th, electrical and coding work will be finished, followed by prototype evaluation and tweaking from May 15-25.