GlasVent is our DIY (Do it Yourself) emergency ventilator based on the automation of the manual BVM (Ambu-bag) (Fig. 1). The first version of the prototype can be found in our YouTube channel, as well a demo video of the complete prototype tested on a medical dummy. A few groups have demonstrated the manual ventilator by compressing the bag using reciprocal motion, which requires complex control arrangement. Instead, our ventilator uses the slide-crank model (e.g. as in steam engines) to compress the bag (Fig. 1). This has several advantages, most important of which is the better reliability due to the fact that the motor only rotates in one direction. Other advantages include - reduced amount of heat produced, reduced risk of failure in the electronics and the simplified interface with the motor. The simple design of GlasVent ventilator means it can be operated manually by hand or feet (Fig. 2) (e.g. rotating the wheel to maintain a constant tidal volume compared to the conventional BVM) or with help of everyday battery powered tools (electric drill). The battery powering of GlasVent is feasible too for operation outside the grid. These features make it useful for remote and low resource settings. The simplicity of design and easy assembly means it could be used in home or hospitals with minimal training of the user. The delivered tidal volume is controlled with the microcontroller as well as the breath rate (or manual rotating speed) as per the needs of the patient (adults, children). However, our design also allows manual adjustment of the maximum tidal volume, which can be pre-set before deploying the machine with the possibility of adjusting during operation, this is mostly necessary for manual operation. Our aim is to deliver a design that is simple, in terms of materials and implementation, yet robust to sustain continuous operation.
Fig 1. Design of GlasVent emergency ventilator.
Our design can also include features that allow for monitoring of important parameters with precise control as well as fault reporting. For example, airway pressure monitoring is necessary for maintaining optimal pressure as well as to detect when the patient is trying to inhale. We are suggesting the use of a commercially available MEMS-based gauge pressure sensor. Such sensors are designed with medical respiratory equipment in mind and can be easily connected to most BVMs with standard tubing. In the case where the BVM does not have the necessary connection port (most of them do), a simple adjustment adapter can be installed. These pressure sensors allow for facile interfacing with the microcontroller and being factory calibrated means that they can be used right out of the box.
Fig 2. GlasVent used in manual mode similar to sewing machines with a telemedical advise from a medical expert.
The motor and sensor in GlasVent are interfaced using an Arduino microcontroller (see block diagram in Fig. 3). The pressure sensor, along with circuitry on the motor, can monitor if the device is operating correctly and produce warnings otherwise. There is a local control for the breathing rate. Additionally, the Arduino allows connection with a laptop which could be used to provide visual indications of pressure and other status, variables as well as more precise control and modes of operation. The batteries are estimated to operate from full to depleted for about 4 hours, a significant amount of time for a patient to move from his/her residence to hospital.
Fig 3. The block diagram of GlasVent.
Using a laptop or other portable display device makes it easy to provide useful information to doctors and medical stuff. All circuitry in our design uses widely available components for easy prototyping and facile scale-up. Thus, it is built through the adaptation of standard industrial components and/or through using other everyday-life objects whose availability is fast, easy, and universal. Further, it is possible to control several GlasVents using single control devices such as computer or laptop (Fig. 4).
Fig 4. Multiple GlasVent controlled by single portable device such as a laptop.
The GlasVent ventilator primarily uses off-the-shelf electronic components and the cost of various components varies between about £30-150, depending on the type of operation (manual or motorised). The frame of GlasVent can be made of plastic/polymer or metal sheets, which are robust, widely available and are easy to clean. It should be noted that our design is not comparable to commercial ventilators in many ways. For example, the PEEP regulator and the risk of aerosolizing the virus are among the highlighted concerns. However, it appears these could be solved with filters and a manual valves. The system was developed for in house and for emergency use in remote areas outside the grid.
Fig 4. a) B.E.S.T group members working on the prototype. b) GlasVent tested on a medical dummy.
The GlasVent System was tested in an medical dummy and observed its capabilities to deliver constant breathing to the artificial lungs. Figure 5 is a snapshot of the working system. The full demonstration of the GlasVent can be found at the Group's YouTube channel here. The project has been tested for more than 4 hours for its reliability.
In summary, we are hoping to give our best to help meet the requirement arising out of current health crises because of COVID 19. We are happy to share our knowhow related to GlasVent for this noble cause.