The global needs for ventilators in the context of the Covid-19 pandemic.
What it does
A stand alone ventilator that can operate without the need of air supply. It can operate in 3 distinct modes: Tidal Volume control, Pressure control, and Assisted mode. With a maximum tidal volume of 800 ml, the ventilator can deliver from 8 to 35 breaths per minute in different inspire/expire ratios from 1:5 to 5:1. The system includes a safety valve set at 60 cm H2O pressure and a PEEP valve (5-20 cmH2O), The ventilator integrates 2 HEPA 16 filters for the intake air and outtake. It can be supplied with O2 via the intake port through a standard Venturi tube. The O2 fraction depends on the Venturi tube selected by the operator
How I built it
The system consist in 3 blocks:
- Mechanical pump
- Onboard computer (OBC)
- Human interface unit
The mechanical pump is made out of a water PPR pipe as the main body material. The piston and other plastic parts are made of POM (Acetal). The pump driving mechanism use a typical 3D printer Z axes components with minor adaptations. A standard NEMA 17 stepper motor controlled by an Arduino board is used and a dedicated software was developed in order to implement the operational modes imposed by medical personnel by a set of requirements. A standard PEEP valve is used as a unidirectional valve for the intake path while the outtake flow is regulated by an ambu-bag expiatory valve which integrates a PEEP valve, a unidirectional flow valve and an expiatory valve. The ventilator integrates 2 HEPA 16 filters for the intake and exhaust airflow.
The OBC controls the pump as a function of the input parameters: tidal volume, air pressure, flow rate, breaths per minute, inspir/expir ratio FiO2 fraction. The OBC also acts as a connection between the human interface unit and the mechanical pump, reading the air pressure and flow sensors output and sending them to the human interface module. The input parameters for the OBC are set by the medical staff using six rotary encoders.
Human interface unit
This block consists of a raspberry-pi computer with a 7 inch display. A custom application has been developed for a graphical display of both the input parameters and sensors readings. We've continuously received requirements and feedback from doctors and medical staff in order to develop an intuitive interface close to the ones that are already installed in the hospitals.
Challenges I ran into
With at least half of the team working from home, integrating mechanical engineering with electronics and software development is not an easy job. Moreover, we've spent a lot of time researching the mechanical ventilation operation principles. It was also very difficult to find available medical staff for consolidating our requirements and for giving us a continuous feed back during the implementation phase.
Accomplishments that I'm proud of
Our experience in space engineering proved very useful. At system level, we've run the VentilaThor project as a typical spacecraft development project.
What I learned
To design a low friction pump made out of material approved for medical use.
What's next for VentilaThor@RISE
Register for approval at national level asap.