The ventilator was designed to be affordable and easy-to-build, providing an open-source hardware description to allow free replication. The prototype was built using off-the-shelf materials available via e-commerce: a high-pressure blower and its driver (WM7040, Ning Bo Feng Hua Wei Cheng Motor Factory, Zhejiang, China), two pressure transducers (XGZP6847005KPG, CFSensor, Wuhu, Anhui, China) and an Arduino Nano controller with a digital display. Pressure and flow were continuously measured at the outlet of the ventilator and fed into the controller which was provided with a custom-made code to detect inspirations and expirations and to accordingly trigger the inspiratory and expiratory pressures generated by the blower. The ventilator can operate in timed or spontaneous timed (ST) mode (spontaneous breaths of patients are assisted and if the patient’s effort is not detected a timed breath is triggered according to a rescue frequency). The retail cost of this ventilator prototype was below 75 US$, and includes all required electronic circuits and power source. Noteworthy, this cost could be considerably reduced by wholesale purchasing. All the technical information and detailed circuit schematics and controller code required to build this ventilator (including optional enclosure by conventional 3D printer) is available for release under free terms following the open-source hardware approach in the online supplement (Technical_Description.zip) . Figure 1 shows external and internal images of the prototype.
Click on the “Figures & Data” tab to download the
Technical_Description.zip file that includes the simple Arduino sketch, and schematics and PCB in Altium. (Current developer releases of KiCad include the ability to read some Altium files.) They include files to print an enclosure but recommend metal for electromagnetic shielding.
Internally, it points to http://www.ub.edu/biofisica/dwn/Technical_Description_ventilator.zip for any additional updates.
The Arduino sketch depends only on the standard PID and LiquidCrystal libraries. It’s not hard to read but it helps to know a little spanish since some of the identifier names are in spanish and others in english.