|Pump||12 V Vacuum Pump|
|Switch||TIP 120 Transistor|
|Power||12 V 5A DC Supply|
|Tube||6 ft CPAP Tube|
This tech spec was submitted by Joshua Pearce as part of the University Technology Exposure Program.
The COVID-19 pandemic has taken a massive toll on our ways of living. It has placed nations at risk, especially those without a solid medical backbone. Ventilators alone are not enough to sustain support in some countries. The mechanical type also has the potential to damage patients who already have underlying conditions. The forceful distribution of air may cause unwanted pressure in the lungs, risking tissue damage within the organ. Patients must breathe in rhythm with the ventilator to avoid such concerns, not to mention this mechanical device is meant for long-term use—consequently increasing the risks.
With gentlevent, an open source gentle ventilator, patients have a support system that provides calibrated pressure waves aiding breathing. This device targets impoverished patients with respiratory conditions during times of scarcity. While a nonmedical device, gentlevent provides desired performance with the help of basic electronics and commonly-available materials. It can be utilized in low-resource settings for only less than $40.
The 3D-printed system has a mouthpiece connected to an air pump through a short tube. This mouthpiece printed using polylactic acid (PLA) material has a layer height of 0.2mm with a solid infill, weighs 23g, and only costs $0.21. Also, parametric adaptors connect various hose sizes to the output ports. These adaptors are also 3D-printed using an Ender 3 printer for 0.14$ for 12g. For flexibility, three air pumps are tested using different electronic control setups.
In the electric component, the pump control utilizes Arduino Nano since it is easy to integrate despite its low cost. Given single pulse width modulation (PWM) via an output pin, other Arduino devices are also compatible. TIP 120 Darlington transistor provides compatibility in switching, although any NPN transistor or solid-state relay (SSR) works. The resistor divider in the digital input monitors the PWM signal found in the output end.
Gentlevent is preparable in a breadboard—however, connections may be broken, and the traces cannot keep up with the pump’s maximum current. But in cases of scarcity, as the device primarily targets, prototyping in a breadboard allows long-term usage when connections are properly secured. For an improved implementation, perf-board gives a more robust calibration. It is easy to use as it only requires basic soldering. In any case, a 12V DC supplies enough current to run the device motor.
The firmware employs Arduino IDE with its easily-adjustable key parameters. The code is nowhere complex as it only has nine pages, including spaces and comments. Using this code, the device gives three pressure levels, which run by pressing a toggle button. In the case of the turn-on pressure, it is preset to 0 if a button is available. Otherwise, it must be within the normal operating pressure.
Upon starting, the firmware confirms if the calibration has been input. If not, the calibration triggers the pumping by varying the PWM signal, where the user has to measure the resultant pressure using a serial monitor. Once calibrated, the resulting array will be sent to the serial monitor, prompting operation. This array must be copied to the firmware for re-uploading.
The gentlevent shows significant results as it maintains desired operation for at least two hours, proving its value for its target operation during times of scarcity.
A research paper describing the challenge, design, and outcome of the research.