Overview
Objective: To investigate the feasibility of producing low-cost mechanical ventilators using widely available materials in Cambodia
According to worldometers, the number of new cases of COVID-19 worldwide is linearly increasing, and developing countries like Brazil, India, Iran, Pakistan, Mexico, and Bangladesh are facing thousands of new cases in one day. A ventilator designed by a group of researchers from MIT has published open-source specifications and designs in e-vent. This team has interviewed several doctors and ventilator operators about the situation of the patients suffered by Covid-19. They gathered the best information in terms of clinical specification and operation of a ventilator for such patients and published it on the website. They have analyzed and come up with the best Ventilator design at a low cost that could help Covid-19 patients. Our design is mainly based on this design. In addition, we have successfully made our own pressure sensor for use with our ventilator. Our ultimate goal is to get our ventilators in use for those who will need them. Because the ventilator is produced with local materials mostly available in Cambodia, the same one can be produced almost anywhere in the world as long as we provide automatic control system design and program code that guarantees the safety of operation.
The ventilator being proposed by our ITC team is an automated Ambu bag. A conventional Ambu bag or a bag resuscitator works with a person (a doctor, nurse, technician, or another health worker) squeezing the Ambu bag by hand to inflate the patient lungs until a mechanical ventilator becomes available. This is done by intubating a patient (inserting a tube into the patient’s airway) and then pumping air into the lungs by squeezing and releasing the Ambu bag. Our automated Ambu bag (based on the MIT model) would essentially add an automated process that will replace the person squeezing the Ambu bag. The health-related risks of conventional Ambu bag includes air inflating the stomach, lung injuries from over-stretching, lung injuries from over pressurization, and hyperventilation (too many breaths per minute). To avoid these problems, our ventilator is equipped with components that can adjust breaths per minute (BPM), tidal volume, Inhale/Exhale time ratio. Our control program operates according to the adjustable parameters input by the operator. A pressure sensor is also used to detect over-pressurization. Our ventilator can operate in two modes, Volume Control and Assist Control (see our latest update ventilator in the video below).
For Volume Control mode, the amount of tidal volume is adjusted according to the percentage of squeezing Ambu bag. For a particular BPM, the amount of air entering and getting out of the lung may not be the same. The Plateau Pressure may increase or decrease over a period of time since the lung compliance of each patient is different from one another. So, the pressure sensor detects the Plateau Pressure for monitoring and alarming (sound, and message) in accordance with the safety condition provided in the list of alarms. If the pressure is higher than PIP, the ventilator stops operation and raises an alarm sound as well as an alarm message. The alarm notification will allow the operator to learn and make adjustments to the relevant parameter before restarting the ventilator.
For Assist Control mode, the inhale phase is triggered by depressurization below PEEP pressure. The Plateau Pressure and PEEP pressure are monitored. If any of the pressure is out of operation range, alarm sound and message are raised. Since the lung compliance of each patient is different from one another, the amount of air volume entering may be too low or too high. A flow meter (design based on different pressure at an orifice) is used to measure the amount of air volume. The amount of air volume is monitored and alarm conditions are set accordingly.
Next steps
1. Conduct a test with a certified artificial lung.
2. Purchase medical-grade air tubes for a clinical trial with an animal.
3. Application for approval from national health authority for conducting a test on a human.
4. Establish a supply chain for all components that need to be ordered from abroad such as DC motor, Ambu bag, air tube, and strain gauge + amplifier.
5. Conduct durability test.
6. Design manufacturing process for mass production.
Barriers facing
1. New technical team members need to be recruited as the old team members graduated and left the laboratory. The new members need some time to learn.
2. A group conducting a study on supply chain and logistics has not been formed.
3. A good collaboration with a group of doctors in order to conduct experiments on animals and humans has not been established.
Remark: The current design of this version has a limited level of safety, i.e. for conscious patients only. Although it can operate automatically, it cannot guarantee total safety for unconscious patients. A new version of the design for use with unconscious patients needs to be considered. The new design must have a current sensor and feedback controller to remedy some fault operations. It needs further study and investigation in technical detail for this design.