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Open-source When COVID-19 started spreading around the world in early 2020 (or possibly late 2019; this is not yet certain), one of the big concerns was that there wouldn’t be enough ventilators in hospitals to treat patients who had trouble breathing. Many companies and individuals set about trying to solve this problem; many of them had no medical background, but nonetheless came up with clever solutions. This article describes some of the more interesting ones. by Dr David Maddison 12 Silicon Chip Australia’s electronics magazine siliconchip.com.au Ventilators T Ventilator reliability While the basic engineering of these devices is relatively simple, they are safety-critical devices, as failure can defsiliconchip.com.au CYCLING PHASE TRIGGERING PHASE PRESSURE he media has been awash with reports about COVID19 for the last several months, so we aren’t going to cover basic facts about the disease, many of which are still not known as we write this. Nor are we going to get into the medical side of the issue, eg, which patients should be placed on ventilators or how much it helps. There is some controversy over that point. We aren’t medical experts (Dr Maddison is a different kind of doctor). So we will leave such discussions up to the professionals. But one thing that is clear to us is that a great many people and organisations rushed to help when it was widely reported in the news (rightly or not) that there would be a major shortage of ventilators. Many factories which were previously turning out motor vehicles or other appliances have been converted to produce medical supplies, including ventilators, in a remarkably short time. Some medical manufacturers have outsourced production to other manufacturing enterprises such as car companies, akin to the way many items were produced during wartime, when the usual manufacturers could not satisfy demand. Of course, medical manufacturers who were already producing ventilators have also done what they can to ramp up their own production. One company, Medtronic, has even ‘open-sourced’ all the documentation for one ventilator design, free of charge, to anyone who wants to produce it. Others in the “maker” community have rushed to start projects design and produce their own ventilators. This article is mainly about that last group, ie, open-source hardware and software designed by people who share their information and designs without monetary compensation. Note that, at the time of writing, this area was developing rapidly and so there may be important advances made between then and when you are reading this. If you want to help out, you may be able to find a project to which you can contribute. Given the large number of existing projects, that is probably more helpful than starting your own. If you’re a keen maker, you might also consider becoming involved in developing personal protective equipment (PPE) of various kinds. One example described here is a Powered Air Purifying Respirator (PAPR). Another might be simple and effective masks to wear on the street. Given that there are a vast number of projects, this article cannot possibly cover all of them all. Therefore, we will look at a few that show a sampling of the type of work being done and will provide a list of the remaining projects which while worthy. You can research them yourselves if interested. EXPIRATORY PHASE INSPIRATORY PHASE EXPIRATORY PHASE Fig.1: the four phases of mechanical ventilation. Source: Alex Yartsev. initely lead to a patient death if they are not attended to by medical staff in a short time. The general principles of “reliability engineering” as they apply to medical devices should be taken into account in their design and manufacture. Many of the projects described here are at a very early stage of development, and not yet ready for the clinical environment. What is mechanical ventilation? Mechanical ventilation involves introducing air, with or without extra oxygen, into the patient’s lungs at an elevated pressure with the initiation of breathing cycles caused by either the machine or the patient, or a combination of both. Breathing is maintained by ventilation until the person’s body heals itself and they can again breathe independently. Note we are discussing positive pressure ventilation. Negative pressure ventilation also exists, such as the “iron lung” and similar devices. Those are mostly used for those with neuromuscular disorders. Mechanical ventilation is non-invasive if air pressure is applied via some type of facial mask. It is invasive if air is introduced via the mouth or nose with an endotracheal tube, or through the skin into the trachea via a tracheostomy tube. For invasive ventilation, which is required for more severe cases, the patient has to be sedated and/or paralysed. For non-invasive ventilation via a facial mask, it is possible to use relatively simple machines such as typically used to treat sleep apnea at home. These are either CPAP (Continuous Positive Airway Pressure) or BiPAP (BiLevel Positive Airway Pressure) machines. In CPAP, positive air pressure is delivered continuously. In BiPAP, one pressure is maintained during inhalation, but a lesser pressure is applied during exhalation. This bilevel pressure enables more air to be exchanged than with CPAP. CPAP and BiPAP modes are also available on commercial hospital-type ventilators. If there is a lack of hospital-type ventilators, treatment by Australia’s electronics magazine June 2020  13 CPAP and BiPAP is suitable for less seriously ill patients, who can spontaneously breathe but need some assistance. Invasive mechanical ventilation is required for more seriously ill patients. Mechanical ventilators have four phases (see Fig.1): 1) Initiation, controlled by a set trigger variable such as time, airflow or pressure, with the breath initiated either by the machine or the patient’s attempt to breathe. 2) Inspiratory (inhalation) phase, when a volume of gas starts to flow into the lungs controlled by a limit variable such as pressure, flow or volume. Eg, 500mL of gas is allowed to flow into the lungs with limited pressure applied to prevent damage. 3) “cycling”, the moment between when inhalation stops and before exhalation begins. The period is controlled by the cycling variable according to time, airflow or pressure. 4) Expiratory (exhalation) phase with passive airflow out of the patient, often using PEEP (positive end-expiratory pressure) that maintains a positive pressure at the end of expiration to help keep lung alveoli (air sacs) open. Mechanical ventilators can be triggered to cycle as follows: 1) Pressure-controlled ventilation, where inspiration stops when a set airway pressure is reached. 2) Volume-controlled ventilation, where a set “tidal” volume of air is delivered to the lungs and pressure can vary, but a maximum pressure is set to avoid lung damage (barotrauma). 3) Time-cycled ventilation, where the tidal volume (breath volume) is controlled by setting the flow rate and inspiration time. 4) Flow-cycled ventilation, where inspiration is terminated when the flow rate drops to a set level. According to the American Heart Association (AHA), the primary modes of ventilation for COVID-19 patients have a set number of breaths per minute and are: 1) Assist Control (AC), where the patient can initiate breaths, but the machine can also do so at the set rate if the patient does not breathe by themselves. The same tidal volume is delivered for every inspiration. 2) Synchronised Intermittent Mandatory Ventilation (SIMV), whereby a mandatory breath from the machine is delivered with a set tidal volume plus additional breaths by the patient above the set rate are supported. Secondary modes are: 3) Airway pressure release ventilation (APRV), with a positive airway pressure and timed release of that pressure. 4) Pressure regulated volume control (PRVC), a pressurecontrolled mode with a set tidal volume and the inspiratory pressure changing from breath to breath, to achieve the targeted volume. Helpful Engineering There was a recent government-sponsored gathering of amateur engineers, held in Germany over 20-22 March 2020. “Der Hackathon Der Bundesregierung” (siliconchip.com.au/ link/ab18) was dedicated to COVID-19 related projects, with 42,869 people signing up. Out of that meeting arose the Helpful Engineering organisation (www.helpfulengineering.org), which was founded to help people with the COVID-19 crisis. You can join as a volunteer. It currently has over 3400 members such as engineers, developers, doctors and scientists working on over 35 projects. 14 Silicon Chip The object of these treatments is to get enough air/oxygen into the lungs to keep the patient alive but not to overstress infected tissue, possibly causing it to rupture (barotrauma). As the lungs become more diseased, they become less elastic and so more pressure is required to achieve the same level of inflation or volume as a healthy lung. It is therefore essential to monitor pressures carefully and the pressure-volume relationship. Use of CPAP and BiPAP machines for COVID-19 CPAP and BiPAP machines are typically used in the home to treat sleep apnea (where breathing periodically stops during sleep). They provide basic non-invasive ventilation and for COVID-19, have been approved by Australia’s TGA, the US Food and Drug Administration (FDA) and the MHRA in the UK for less seriously ill patients. These machines need to be slightly modified for use on infected patients, with the addition of a filter to prevent the expulsion of contaminated aerosols. There is a medical opinion that the CPAP mode of ventilation is indeed the best for treating COVID-19, see: https://emcrit.org/pulmcrit/cpap-covid/ (by Josh Farkas, associate professor of Pulmonary and Critical Care Medicine at the University of Vermont). CPAP/BiPAP ventilators are widely used in emergency departments. Ventilation parameters The following parameters are among those that should be ideally settable on any ventilator, the first four being a minimum requirement: • Tidal volume (volume per breath). • Number of cycles per minute (respiration rate). • Inhalation/exhalation (I:E) ratio: the ratio of the duration of inspiratory and expiratory phases. 1:2 is a typical setting to mimic natural breathing but can be varied according to several factors. • Pressure-controlled or volume-controlled modes. • Trigger sensitivity to stop the patient fighting against the ventilator if they take their own breath; can be flow-triggered or pressure-triggered. • Rise time of flow in volume-controlled mode, or pressure in pressure-controlled modes. • Inspired oxygen concentration. • For PEEP, pressure measurement at the end of the expiratory phase. • For CPAP, constant airway pressure for inspiration and expiration. • Peak airway pressure. • Plateau pressure. • Expiratory pressure. • Alarms for any fault conditions. • Battery backup. Australian response and regulatory issues While government departments are often painfully slow to move, the Therapeutic Goods Administration (TGA) in Australia says it will take “a proactive stance with respect to repurposing of alternative devices (such as veterinary devices) and rapid establishment of new manufacturing capability.”; see siliconchip.com.au/link/ab14 Via an “expert panel” of ICU clinicians across Australia, the TGA has compiled specifications for the minimum requirements of invasive ventilators for use on COVID-19 Australia’s electronics magazine siliconchip.com.au EXPIRATORY VALVE PEEP VALVE SELF-INFLATING BAG AIR INLET ONE-WAY VALVE AND 02 RESERVOIR SOCKET AIR INLET AND PRESSURE RELIEF VALVES FACE MASK POP OFF VALVE OXYGEN INLET AND TUBING patients and as a guide for manufacturers. See siliconchip. com.au/link/ab15 and siliconchip.com.au/link/ab16 (specifications PDF). Australian ventilator numbers Australia is said to have 2300 ventilators in intensive care units and a further surge capacity of 5000 units. Notwithstanding efforts by the TGA to liberalise regulations for ventilator supply, it has been stated that Australia will have sufficient ventilator numbers to meet demand by more traditional means such as: a) Using existing equipment such as those currently used in veterinary applications. b) Purchasing from overseas suppliers c) Purchasing from existing Australian manufacturers such as Resmed (www.resmed.com.au), with 1000 currently on order. d) The use of a consortium of domestic manufacturers to produce an existing design (the Medtronic unit comes to mind). The Australian Government has also approached Ford in Australia about the supply of ventilators, although this would be presumably via the US parent as Ford Australia no longer manufactures here. In the USA, Ford and other car manufacturers such as Fiat Chrysler, General Motors and Tesla have become involved in the production of ventilators and elsewhere, Ferrari, McLaren and Nissan. Bag Valve Mask (BVM) ventilation Many open-source ventilator projects use a BVM as the basis of a ventilator system. These devices are typically squeezed by hand in an emergency, either by paramedics in the field or medical staff in hospitals (see Fig.2). Many ventilator projects essentially automate the task of squeezing the bag with a machine, rather than by hand, with various parameters such as rate and volume that can be adjusted. Possibly the first proposal to use a BVM in a low-cost ventilator design dates to 2010 in the following paper siliconchip.com.au Fig.2: a typical commercial bag valve mask (BVM). RESERVOIR BAG (PDF format): siliconchip.com.au/link/ab17 Also see the video titled “ApolloBVM Version 1” at https://youtu.be/ u6aDZoBTRwg Before starting on a ventilator project, it is suggested that you read this document, as it includes a spirometer to measure air volume and is thus able to control it. It also has other useful design features. BVM ventilation has some problems, however. Important design considerations It is important to understand that a ventilator is not just a simple air pump; there are many additional requirements. Barotrauma or air-pressure related damage to the lungs is a significant concern. If the air pressure produced by the ventilator is not tightly controlled, it could cause air sacs in the lungs (alveoli) to be damaged or even ruptured. Seriously ill patients who suffer from acute respiratory distress are very susceptible to barotrauma, because many alveoli are blocked with fluid and air cannot enter, causing the pressure in unblocked alveoli to increase even further. So any ventilator must be able to adjust these parameters. Before designing any ventilator, it is crucial to understand the basic principles. In general, the type of ventilation provided by a BVM (whether hand-squeezed or automated) is only suitable for less seriously ill patients with good lungs, for short periods. That’s because the air delivered is volume-controlled rather than pressure-controlled. In commercial ventilators, breathing can typically be triggered by the patient. This is for when the patient can still breathe, but they have difficulty and need some assistance. The machine can trigger by several methods, such as detecting a drop in pressure or by airway flow or electrical activity from the patient’s diaphragm, which is about to contract. Detecting these trigger events requires advanced software and a suitably powerful CPU (an Arduino might not be up to it). It is important to avoid the patient fighting against a Australia’s electronics magazine June 2020  15 Connection to test lung Bag compressor plate Single-use self-inflating bag Backing plate Piston compresses self-inflating bag Gas reservoir of self-inflating bag from enough people, it should be possible. Another important feature required for ventilators is an alarm system, to alert medical staff to failures. As with any engineering project, it is essential to first talk to the people who are going to use the device to determine their requirements. Ventilator projects Pneumatic cycling unit Expiratory time control Inspiratory time control “Waste” oxygen from pneumatic drive unit fed to gas reservoir of self-inflating bag Fig.3: a computer rendering of the Dingley automated BVM device described in 2010. mandatory breath produced by the ventilator, as this can cause barotrauma. To help prevent alveoli collapsing, a ventilation technique known as Positive End Expiratory Pressure (PEEP) is used, in which a constant positive pressure is maintained in the lungs. However, this requires very fine control of air pressure and most BVM squeezing designs cannot achieve this. For invasive ventilation, the upper airway is bypassed. This usually warms and humidifies incoming air. If dry, cold air is introduced to the lungs, this can cause damage. So, in this case, the air has to be artificially warmed and humidified. If oxygen is being added to the air, that also has to be controlled. Another critical factor is the ability to sterilise components and filters air to stop exhaled virus particles from entering the hospital environment. It is certainly challenging to come up with a cheap, massproduced ventilator design. But with enough commitment We have selected a range of products to look at, based on different designs. This list includes some based on an automated means to squeeze a bag valve mask (BVM), an oximeter ‘hack’, the use of an Android device for control, fluidic logic, an electric screwdriver as the drive mechanism, the use of a compressed gas supply with valving, bellows, the use of personal protective equipment such as a respirator to protect a caregiver, and the repurposing of CPAP devices. The Dingley BVM-based ventilator This design by Dingley et al. (UK) is from the year 2010 and is titled “A low oxygen consumption pneumatic ventilator for emergency construction during a respiratory fail- UK MHRA ventilator specifications For those interested in developing a ventilator, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has developed a detailed set of specifications for a “Rapidly Manufactured Ventilator System”. The specifications provide recommendations for ventilation functions (at least one ventilation mode and preferably two, with control of oxygen concentration), gas and electricity supply, infection control (must be cleanable), software stability, monitoring and alarm features and ease of use (must require no more than 30 minutes of instruction and pass a usability standard). Parts must be available in the UK supply chain. The specifications are intended for devices “used in the initial care of patients requiring urgent ventilation”. For ventilators produced under this specification: “(i)t is proposed these ventilators would be for short-term stabilisation for a few hours, but this may be extended up to 1-day use for a patient in extremis as the bare minimum function. Ideally it would also be able to function as a broader function ventilator which could support a patient through a number of days, when more advanced ventilatory support becomes necessary”. The PDF document is available at siliconchip.com.au/link/ab1r The United States’ FDA (Food and Drug Administration) has also relaxed regulatory guidelines for ventilators to assist in their more rapid production, and these are available at www.fda.gov/ media/136318/download See the main body text of this article for the Australian TGA guidelines. 16 Silicon Chip Australia’s electronics magazine Fig.4: the AgVa ventilator as mounted on a stand with accessories and a humidifier unit. The Android tablet controller is visible at the top and the ventilator unit itself is behind that. siliconchip.com.au Fig.5: a close-up of the Israeli-developed AmboVent 1690.108 control panel, with the BMV drive mechanism visible at the bottom. It is controlled by an Arduino Nano, and the drive mechanism is powered by a car window lift motor (Dorman model 742-600). Fig.6: a rendering of the AmboVent 1690.108. The box contains the control electronics and the drive mechanism for the bag valve mask. The device at the left is an oxygen reservoir, to aid in the delivery of extra oxygen when necessary. ure pandemic”. It seems to be tailor-made for COVID-19. This was a rare case of planning for such a contingency. The device is described at siliconchip.com.au/link/ab19 and also see Fig.3. See the videos titled “World’s cheapest ventilator” at https://youtu.be/Y 92mDYfRGs and “AgVa Advanced Ventilator Demo Video 2019 March” at https://youtu.be/ lm79Q3H4Rp8 AgVa tablet-based ventilator AmboVent Even before COVID-19, there was a severe shortage of ventilators in countries such as India, which motivated inventors there to design a simple and cheap ventilator using an inexpensive Android tablet for its control electronics and monitoring. The company has several ventilator models, but is currently producing only their AgVa Advanced model; see www.agvahealthcare.com and Fig.4. Design work by roboticist Diwakar Vaish and neurosurgeon Deepak Agrawal started in 2016. It costs about US$2000 (around AU$3000), which is much cheaper than Western units (around US$10,000/AU$15,000) or more. Production has increased from 500 per month to 10,000 or more, working around the clock. India’s biggest automotive manufacturer Maruti Suzuki is helping to produce these. The device is self-contained and can be set up anywhere with no other infrastructure such as compressed air, and is suitable for long-term use at home for the chronically ill. The Indian government has banned the export of these units; it is available for purchase now, but only in India. The AmboVent was designed by a team of 40 professional engineers, makers, doctors and innovators in Israel and is a bag valve mask-based device. It was designed for mass production at low cost with offthe-shelf materials (Figs.5 & 6). Its name is derived from the common (commercial) name for a bag mask valve, Ambu bag, and the word “ventilator”. Their website is at siliconchip.com.au/link/ab1a Documentation with the entire blueprints, mechanical and electrical designs, source code and medical/engineering test reports is at https://github.com/AmboVent/ AmboVent See these videos for more information: https://youtu.be/4f6rNCI8iv4 https://youtu.be/xohUDG607s0 https://youtu.be/NeeeegF7KVk (first test on an animal) Andreas Spiess oximeter ‘hack’ During ventilator treatment, it is necessary to monitor blood oxygen levels and heart rate. A simple and inexpensive way to do this is with the use of cheap and readily-available Fig.7: Andreas Spiess with a pulse oximeter (green readout), ESP32 module for Bluetooth data acquisition and an OLED display showing the data acquired by the ESP32. siliconchip.com.au Australia’s electronics magazine June 2020  17 Fig.8: the Breathing Aid concept, where multiple patients connect to a central system. Fig.9: a computer rendering of the Dyson TTP CoVent attached to the side of a hospital bed. pulse oximeters. Such devices use light beams of two different wavelengths, passed through thin areas of the body such as fingers or earlobes, to determine the level of oxygenation in the blood and the pulse rate. We published an article describing in detail how pulse oximeters work in the January 2016 issue; see siliconchip. com.au/Article/9765 Some people working on ventilator projects looked at making hardware interfaces to these devices, but since many are equipped with Bluetooth, YouTuber Andreas Spiess decided to decode the Bluetooth signal to extract oxygenation, pulse and perfusion index data. So it was an entirely software-based project. He used a low-cost Arduino-enabled ESP32 microcontroller with built-in Bluetooth as the listening device (see Fig.7). Also see the video titled “BLE Oximeter Hack with ESP32 for COVID-19 Projects” at https://youtu.be/FIVIPHrAuAI depth article in the August 2019 issue (siliconchip.com. au/Article/11762). A.R.M.E.E. ventilator The A.R.M.E.E. (Automatic Respiration Management Exclusively for Emergencies; https://armeevent.com/) is a fluidic-logic based device, based on a design from the US Army in 1965. It is similar to the Worldwide Ventilator discussed later. For a detailed description of fluidic logic, see our in- Fig.10: the ventilator mechanism by JoergSprave using a plywood frame and gears, an electric screwdriver as the power source and a soft drink bottle as a substitute for the bag valve mask. This should be regarded as a source of ideas, not a working device. 18 Silicon Chip Breathing Aid Breathing Aid (www.breathing-aid.org/homeen) is a German project and uniquely, is a centralised system designed to support multiple patients simultaneously. See Fig.8 and the video titled “Breathing Aid” at https://youtu. be/Wee6FnA_eao Dyson and TTP UK vacuum cleaner manufacturer Dyson (www.dyson.com), in partnership with technology company TTP (www.ttp.com), have designed a ventilator called the CoVent. They received an order for 10,000 units from the UK Government. It uses a motor and HEPA filters from Dyson’s vacuum cleaner designs and is designed to conserve oxygen via rebreathing (see Fig.9). It is also intended to be simple to use. Electric blower-based portable emergency ventilator This device is from the University of Utah and was designed in 2013. You can download a PDF file describing it from siliconchip.com.au/link/ab1b Fig.11: the COVIDIEN Puritan Bennett PB560 ventilator. The complete plans have now been released by Medtronic, allowing it to be replicated or be used as the basis of another model. Note that Medtronic purchased the company COVIDIEN in 2015; the name has nothing to do with COVID-19. Australia’s electronics magazine siliconchip.com.au Fig.12: ventilators in production at Medtronic. Fig.13: the Minimum Universal Respirator (MUR). Electric screwdriver-powered ventilator However, it is best to register at the first link to ensure you get the latest files. The third release contains the source code. There’s a lot to explore in those file sets. One commentator expressed a concern that there might be difficulty getting some parts as this is a ten-year-old design, but we don’t know for sure whether that is a problem. If some parts are unavailable, appropriate substitute components would likely be available, or modifications can be made to utilise currently available components. Medtronic stated that “Our hope is that manufacturers and engineers will use this intellectual property to inspire their own potentially lifesaving innovations.”. This is from YouTuber JoergSprave. It uses an electric screwdriver as a power source (see Fig.10). See the video titled “Saving Lives With a Drill?” at https://youtu. be/1ZwsNOvOUoE Jeff Ebin’s prototype This is not a published design, but you can see photos of BVM-based prototypes and some useful documentation at siliconchip.com.au/link/ab1c Medtronic Medtronic (www.medtronic.com) is a major international medical products company that includes ventilators among its product portfolio. It has ramped up ventilator production by more than 40% but is also assisting by releasing the plans of one of its ventilator products for free use. On March 31, Medtronic announced that it was publically sharing all the design specifications for its Puritan Bennett 560 (PB560) ventilator model, which was first introduced in 2010 and sells for US$8,000 (about AU$12000; see Figs.11&12). The plans include product and service manuals, design requirement documents, manufacturing documents, manufacturing fixtures, PCB drawings, mechanical drawings, 3D CAD files, schematics and software. This enables the exact replication of the entire machine or parts could be used as the basis for another design. You can register to download the files at siliconchip. com.au/link/ab1d or download the first two ZIP file releases from siliconchip.com.au/link/ab1e and siliconchip. com.au/link/ab1f Fig.14: the Open Source Ventilator block diagram. siliconchip.com.au MUR (Minimal Universal Respirator) The MUR (www.mur-project.org) is a French project run by four designers with many other contributors. It is designed to be easily reproducible with off-the-shelf components and can run off any air source (see Fig.13). Its documentation is available from siliconchip.com.au/ link/ab1g Open Source Ventilator Project The Open Source Ventilator Project (siliconchip.com.au/ link/ab1h) is from the University of Florida. It does not use a bag valve mask, but instead uses a compressed air supply to provide airflow. It uses components such as exhalation valves based on bicycle inner tubes, an inspiratory valve based on an Orbit 57280 from a lawn irrigation system and a Bosch BMP280 air pressure sensor (see Figs.14-15). It is designed to be built quickly, with hardware and electronics store supplies for a parts cost less than US$300 (AU$450). To build one in Australia, you would have to find equivalent plumbing components to the imperialsized ones. See the video titled “Open Source Ventilator Project System Integration Test” at https://youtu.be/KhgUCOhOCNM Fig.15: the pneumatic section of the Open Source Ventilator. Australia’s electronics magazine June 2020  19 Important resources for ventilator designers Coronavirus Tech Handbook (siliconchip.com.au/link/ab1t) is is a crowd-sourced library with thousands of expert contributions. Essentials of Mechanical Ventilation, 2nd edition, Dean R. Hess and Robert M. Kacmarek, McGraw Hill, 2002 Principles and Practice of Mechanical Ventilation, 3rd edition, Martin J. Tobin, McGraw Hill, 2013 (siliconchip.com.au/ link/ab1u) The Ventilator Book, William Owens, 2012, First Draught Press or watch a “live stream” of its endurance testing at https:// www.twitch.tv/cssalt The design files can be downloaded from http:// siliconchip.com.au/link/ab1i PopSolutions OpenVentilator This Brazilian project (siliconchip.com.au/link/ab1j) recognises a possible shortage of bag mask valves, especially in small villages in Brazil, and therefore uses an alternative system with bellows (see Figs.16 & 17). The documentation is at siliconchip.com.au/link/ab1k and see the video titled “OpenVentilator (Spartan testing version)” at https:// youtu.be/5DkFc5B6lGQ Powered Air Purifying Respirator (PAPR) The PAPR (http://siliconchip.com.au/link/ab1l) is intended for caregivers rather than patients, and allows them to have a contamination-free air supply, so they don’t get infected (Fig.18). See the video titled “Low-Cost Powered Air-Purifying Respirator (PAPR)” at https://youtu.be/oS6GA83nbds Fig.17: an early prototype of the OpenVentilator. Rice OEDK Design: ApolloBVM The ApolloBVM is from Rice University in the USA; see their website at siliconchip.com.au/link/ab1m It uses a bag valve mask with two Arduinos, one to control the motor and one for the user controls (Fig.19). Later versions will have a third Arduino. It has two redundant motors for safety. Free registration on the site is required to download the construction files. The device has settings for adult, child and pediatric uses with an adjustable ratio of inspiratory to expiratory time (I:E ratio), variable positive pressure, tidal volume and respiratory rate. It was inspired by an early student-designed ventilator from 2018-19. The total parts cost is expected to be under US$250 (around AU$375), with a majority of the components being off-the-shelf types. The remainder are 3D printable or laser-cut. The design team is working with a major manufacturer to mass-produce it, but anyone can manufacture it; you Fig.16: a computer rendering of the Pop Solutions OpenVentilator. Fig.18: the components of the PAPR, designed for caregivers or other at-risk individuals. (Inset) wearing the PAPR. 20 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.19: the Rice OEDK ApolloBVM device. Note the bag valve mask in the centre of the unit. can even make one yourself. University College London Mercedes HPP This comes from a collaboration between engineers from University College London, clinicians at University College London Hospital and engineers at Mercedes-AMG High Performance Powertrains (HPP), who build Formula One engines. They have developed a CPAP device by reverse engineering a device which was out-of-patent and made improvements to it. The UK National Health Service has already approved it. The device took under 100 hours from the time of the first meeting to production of the first device. As of 29th March 2020, 100 machines are to be produced for clinical trials and production will be rapidly expanded if they are successful. It is reported from Italy that about 50% of patients are suitable for CPAP treatment rather than the more invasive mechanical ventilation, so that mechanical ventilators can be reserved for the more seriously ill. A CPAP machine may be all a patient needs to recover if they are still capable of breathing by themselves, but if not, they will have to be transferred to mechanical ventilation. To better understand the difference between a CPAP machine and mechanical ventilation, read the article at Fig.20: the Open Breath Italy ventilator siliconchip.com.au/link/ab1o Also see the video titled “Mercedes F1 helps upgrade CPAP to fight coronavirus” at https://youtu.be/Ofpa7-ugY38 Open Breath Italy The Open Breath Italy ventilator (www.openbreath.it) is another BVM-based device (see Fig.20). Vortran GO2VENT The GO2VENT (Gas Operated Ventilator; www.vortran. com/go2vent) is operated by compressed air or oxygen only, with no electronics, and is disposable – see Figs.21 & 22 and the video titled “VORTRAN GO2VENT Training - Device Overview” at https://youtu.be/uCMqDvpPzgw Worldwide Ventilator The Worldwide Ventilator (www.worldwideventilator. com) uses a fluidic device, specifically a bistable fluidic amplifier. This uses no moving parts to switch between the inhalation and exhalation phases (see Figs.24 & 25). It works in both assisted and automatic breathing modes, Fig.22: the GO2VENT attached to a patient. Fig.21: the Vortran model 6123 disposable ventilator device for emergency use. It runs on a supply of compressed air or oxygen with no electronics. siliconchip.com.au Australia’s electronics magazine June 2020  21 Fig.23 (right): the original US Army Emergency Respirator from 1965. Fig.24 (below): a computer rendering of Revision 14 of the Worldwide Ventilator, inspired by the Army Emergency Respirator. so if someone can breathe by themselves to some extent, it will assist them. If they cannot breathe by themselves, it can automatically fill the lungs and then allow them to exhale followed by an inhalation cycle once again. It does this with fluid logic alone and no moving parts or electronics. Three screws on the device enable the setting of the inhalation and exhalation pressure and the exhalation duration. The device itself requires only an external air supply, plus a face mask or endotracheal tubes, and optionally an oxygen and humidification system. The inspiration for this device came from the “Army Emergency Respirator” device invented in 1965 at what was then called the Harry Diamond laboratory of the US Army (mentioned above and see Fig.23). You can see a video of the Worldwide Ventilator titled “Worldwide Ventilator - April 6th Update” at https://youtu.be/St7oJl5TjEg and you can download the project files from siliconchip.com.au/link/ab1p Project Pitlane Project Pitlane involves a group of seven Formula 1 racing teams working together to produce ventilators and other medical equipment that’s in short supply. See the video at siliconchip.com.au/link/ab1q for more information. Triple Eight Race Engineering Australian company Triple Eight Race Engineering (http:// tripleeight.com.au/) was in Melbourne for the Grand Prix, but it was then cancelled. So they decided to build a ventilator (Fig.26). They consulted medical specialists, intensive care unit specialists and Queensland government departments. They started designing the ventilator on 20th March and had a prototype ready by 30th March. It uses a pincer mechanism around a bag valve mask to produce the airflow. See the video titled “Triple Eight’s emergency venti- Fig.25: the inhalation and exhalation cycles on the Worldwide Ventilator device. The air supply flows from the left to either the patient or to the exhaust when the patient exhales. It naturally oscillates between the inhalation and exhalation cycles, or it will assist the patient to breathe by helping them inhale or exhale as the patient desires. Switching between the inhalation and exhalation modes is due to the bistable nature of the “gate”, at the junction of the main channels. lator project” at https://youtu.be/987rfTSLfJk VentilAid VentilAid (www.ventilaid.org) is an open-source ventilator project from Poland. It uses 3D-printed parts so that it can be produced anywhere that a 3D printer is available. It requires just a few other basic parts, for a total cost of around €50 or AU$90. The device is under constant development and they are asking for contributors. Visit the website for more details. The latest documentation and printer files are available at https://gitlab.com/Urbicum/ventilaid Also see the video titled “VentilAid open-source ventilator that can be made anywhere locally” at https://youtu. be/t9mFWhHW3sc VentSplitter The VentSplitter (http://ventsplitter.org/) is a 3D-printed device designed to allow one ventilator to be used by two or more patients (see Fig.27). Ideally, their lung capacities and ventilation requirements would be matched, but if they are not, the difference can be compensated for by flow limiters. What to do with these ventilators after COVID-19? After the current COVID-19 crisis, there is likely to be huge numbers of surplus ventilators. As there is a shortage of ventilators in Third World countries, many could be donated to such places. Or they could be kept in storage for the next pandemic, which is inevitable. We just don’t know when! 22 Silicon Chip Fig.26: the Triple Eight Race Engineering ventilator. Australia’s electronics magazine siliconchip.com.au Other ventilator projects These are other projects of which we are aware, but had no room to cover. (Google the names for more information!) Fig.27: a pair of 3D-printed ventilator splitters. 3D printer files (in STL format) can be downloaded from the website. This type of system has the advantage that an existing commercial ventilator can be used and no mechanical or software development is required. The parts are extremely simple and cheap. See the video titled “VentSplitter - 2 Person Ventilation” at https://youtu.be/LLS4t0YblrA YouTube DIY ventilator Finally, YouTuber “HowToLou” has an interesting YouTube video entitled “DIY Ventilator” at https://youtu.be/ Z7Wbt5_PW-E (see Fig.28). It is remarkable for its simplicity and use of readilyavailable parts although, at the date of writing, it lacks electronics to control speed and other parameters. However, like many of these projects, the basic design is an excellent starting point. The quality of some or all of the components would have to be improved to meet medical standards. SC Fig.28: YouTuber HowToLou with his ventilator made with a motor, a bellows pump and a painter’s respirator mask. siliconchip.com.au DRM127 Ventilator/Respirator Protofy Team OxyGEN S-VENT, crowdsourced-ventilator-covid-19 The Open Ventilator, BlueVent3d OpenVent-Bristol V1.0 Zephyr Open Source Ventilator MIT 2010 (Husseini et al.) CaRE-VENT, Saving Babies’ Lives Starts With Aquarium Pumps And Ingenuity RespiraWorks Gtech Ventilator MIT E-Vent VentilatorPAL Open source ventilator Pakistan openventilator - KiCad Translation and update of the Medtronic OpenVentilator CoronavirusMakers The Pandemic Ventilator (older) Cuirass-Ventilator, SparkVent YACoVV - Yet Another (SARS-)CoV(-2)Ventilator IMPROV: Inexpensive Maker-Made Piston-Respiratory Open-Source Ventilator Ad Hoc Ventilator MIT Low Cost Ventilator, Dr Mujeeb ur Rahman design Hackaday Rex Ventilator V1 Automatic ambu ventilator Pandemic Ventilator Open Ventilator Project OpenVentilator, Simple device from www.POMO.cl Acute-19, COVID19 Respirador (Vaccarini) The Breathing Project Cuirass Ventilator the DIY way 1M Ventilators MVP, Open Source Ventilator Ireland Low-Cost-Medical-Ventilator Pandemic Ventilator Project Mechanical Ventilator Milano (MVM) OxVent Illinois RapidVent Automatic Resuscitator Open Source Covid-19 Ventilator Canada Vortran-Type Pneumatic Ventilator Low Cost Medical Ventilator Low-Cost Automated Emergency Ventilator Low-Cost Ventilator Wins Sloan Health Care Prize Projecto EAR Celso Project Open Air LEITAT1 Respirator, Respirador RESP19 OperationAIR CoroVent Inspiramed Ventilador Foscal y Unab Vanderbilt University Commodore Open-Source Ventilator v3.1 PREVAIL NY, DIY-Beatmungsgerät [Respirator] OpenLung Emergency Medical Ventilator Inspire OpenLung COVID-19 Rapid Manufacture Ventilator BVM Ambubag for £80 OpenVent-Bristol, low-cost-medical-ventilator VentCore DIY Ventilator Part 1 (YouTube video) Umbulizer Australia’s electronics magazine June 2020  23