Piston Ventilator

Engineer: Luis Marina
General Description:
The design centers around a 2' long 4" diameter PVC pipe and internal 3-D printed piston which is moved by a linear actuator (also housed within the pipe). Air is sucked through a readily available CPR one way flapper valve with a built in filter as the piston rises. As the piston is pushed down air travels into a hose which leads 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, as well as to filter exhalation air to protect healthcare workers. From the HME, an intubation tube enters the patient- providing critical air/oxygen. Utilizing the Ambu bag allows for an adjustable PEEP valve to be easily attached, and also provides an oxygen port, mixing chamber, and non electronic exhalation control valving. In the event of a ventilator failure, because it is inline with the system- manual Ambu ventilation can begin immediately. The system HMI features a 3.5" Nexion touchscreen which can provide setting adjustment and parameter monitoring. The latter is compatible with the Arduino, which controls the actuator through an H-bridge. To sense the pressure differential between the ambient air and patient air, a Honeywell sensor is incorporated. This way, breath assist mode and pressure mode can be incorporated along with pressure monitoring. To detect piston speed/position and calculate flow rate an ultrasonic sensor is trained on the piston. This reading will flow into the command which  can tell the piston to end the stroke and return (depending on mode). Overall, the system is intended to be cost effective, space efficient (entirely housed in a single PVC cylinder), and easy to build with mostly readily available parts (others to be 3-D printed). Currently, the mechanical portion is mostly prototyped and the electronics are in development.
 
Other Notes:
 
Ideally an Ambu bag which already incorporates a pop off valve will be used.
 
Range of  0 to 1.2 liters tidal volume per stroke.
 
Max 30 BPM @ 1.2 Liters (increases with lower tidal volumes).
 
Simple Piezo buzzer alarm.
 
All systems run on 12V DC (from a 120V AC converter brick), allowing large variety of backup batteries.
 
Can be hung on side of hospital bed.
 
PVC can be replaced with see through acrylic as alternative if desired (higher cost).
 
Double O ring seal lubricated with food grade no odor grease.
 
Material Cost ~ $...