The hyperlink for Ref 82 needs revising as it links to an error page.



One the first paragraph of page 4 ‘breadth’ has mistakenly been used in place of ‘breath’. Additionally there are some minor grammatical errors toward the end of this same paragraph that need amending, specifically the sentence starting with ‘texts area available for the ……..’



Generally speaking, it would have been very useful to contextualise much of the discussion with annotated diagrams of several key open source innovations, to give the reader a real feel for the types of devices in development. Indeed, this is typical of many academic based reviews of the scientific and gray literature. Unfortunately, this has not been the case in the present manuscript and I would invite the author to consider such an amendment.

The manuscript presents a review of open sources ventilators with particular emphasis towards applications in the COVID-19 pandemic during the early phases of 2020. Given the submission date of the manuscript, which has coincided with the emergence of the COVID-19 pandemic, the review is very topical, in addition to being thought provoking and insightful. COVID-19 disease is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), where the presenting symptoms of a patient are predominantly based upon respiratory ailments, requiring ventilation based equipment to treatment the most severe of cases. As the virus infiltrates a greater frequency of the general population, the availability of ventilation based products has rapidly become one of the primary causes for concern not only in developing, but in developed economics. Given the disruption of standard medical device supply chains during a pandemic, a viable alternative to meet the demand for ventilation equipment from healthcare providers is to turn to communities of designers, engineers, industrial specialists and knowledgeable maker enthusiasts to develop easily accessible, low-cost and open source alternatives to traditional devices. The manuscript is therefore a vital piece of documentation to assist researchers in global efforts to create ventilator alternatives. Equally, the manuscript does an exceptional job at highlighting the current state of the art in this area with balanced and considered conclusions throughout.It is noted that the article is based on the premise of discussing ventilator technology which are deemed open source. As review manuscripts generally attract a wider target audience that scientific bodies of work, it would seem appropriate for the author to define what is meant by open source, for the benefit of unfamiliar readers. Indeed, one may see general scientific publications are open source information by virtue of the information being in the public domain. However, it is clear that the authors perception of this would require a deeper level of ‘disclosure’ of the innovations presented by various research groups to allow for ready duplication and adoption of such systems. This is starkly evident later in the manuscript during discussions of existing literature. Therefore, the distinction of what constitutes open source in this context should be explicitly defined, ideally within the introduction.In light of the rapidly evolving nature of the pandemic and the volume of initiatives that are attempting to provide viable, often, open source solutions, there is likely to be some developments that have not been addressed in the review. Generally, the author has done an exemplary job of drawing the readers attention to many of the most topical and noteworthy examples. However, one would imagine as we approach the end of the pandemic period that there is likely to be a wealth of additional technologies which will have surfaced and so perhaps a follow up review may be justified, ideally inviting multiple authors involved in such projects to contribute. It is however noted that certain information within the manuscript has since evolved, specifically relating to the comment in the first paragraph of the introduction, where it is mentioned thatUpon further development of this story, the company had made official statement to clarify that they did not attempt to sue the party which made ventilator valve parts but had primarily withheld designs based upon medical device regulation. Although withholding designs during this particular circumstance when supply chain needs could not be met resulting in potential mortality of patients, there is an argument to disclose such information despite legal implications. However, this is very much different to the notion of the company suing the Italian firm. At the time of writing the article this would not have been known to the author, but given the controversial nature of the comment, I would request the author to reword this sentence to reflect the final outcome of this case study.During the introduction when discussing the very many technologies available to the open source community, the discussion preferentially revolves around the use of rep-rap 3D printing, under the notion of digital fabrication technologies which have distributed manufacturing potential. This is a very important point to make by the author as distinctions are made as to why this approach would provide added value within the context of a pandemic. In particular, designs may be shared both at a national and international level using internet based data transfer, while leveraging manufacturing and technical capacity closer to the point of use. Such capacity has long been utilised by the open source community, providing strong resilience in instances when typical supply chains are disrupted, as would be the case during a pandemic. However, this discussion appears to be somewhat incomplete for readers who are unfamiliar with this approach of manufacturing. More specifically, it may be useful for future readers to hear some mention of other digitally driven distributed technologies, such as milling/CNC machining, laser engraving/etching and other digitally controlled tools. Indeed, several of these technologies would serve to reduce or eliminate the perceived limitations of 3D printing both in terms of manufacturable materials and speed of manufacturing. Please could the author include some additional discussion here to contextualise available options to the open source community with respect to digital and distributed manufacturing.The author presents an eloquent attempt to discuss both the academic and non-academic ventilation systems, citing many interesting studies and raising most of the key facets of each respective technology. Following from the previous comments regarding the open source nature of a given study, it is highlighted that sadly many academic studies, though presenting some remarkable feats of engineering, simply do not provide sufficient information to allow for other researchers and experts to duplicate a respective ventilation system. This is indeed a shame and highlights perhaps a necessity for researchers to adopt a more open frame work of reporting academic findings and equally for reviewers to encourage and accept such ways of reporting. In light of major global health catastrophes such as pandemics, such openness within the literature may in fact prove advantageous to hasten innovations to tackle the detrimental effects on a given population.The discussion on the current open source efforts appears to cover several of the major projects to the awareness of this reviewer, but more crucially provides a good cross section of important developmental aspects to inform the reader. As highlighted previously, given the rapidly evolving nature of the pandemic and the wiliness and passion of researchers and technical experts, new attempts to create ventilation products are arising on a weekly, if not daily basis from groups around the world. Therefore, in this reviewer’s opinion, to cover all such attempts would be impractical but also unnecessary given that the overlap of technical development with existing projects. As with the previous section, it would have been good to present annotated diagrams and a summary chart/table of the systems broken down into the primary attributes that fulfil the requirement for ventilation. In reading this section it was difficult to surmise how these efforts were truly moving towards a functional ventilation device. One of the more noteworthy examples from Rice University, with credible data to back the developments to date was sadly hindered by component failure after only a 11-hour evaluation period, which falls considerably short of a functional ventilator. Clearly, several if not all examples highlighted by the author raise several notes of caution toward open source design, namely the clarity and robustness of evaluation, which lacks the rigour of typical academic scrutiny in addition to the lack of standardisation of components which are suitable for purpose. Arguably, the author to varying degrees’ highlights this by stating the case studies in question are either in the very preliminary stages of investigation, show a lack of relevant performance data or a Bill of Materials (BOM) which enables scrutiny of the components employed. I believe there is a missed opportunity of discussing these elements in greater depth, which is vitally required if open source ventilators are to truly enter mainstream acceptance and use. I would very much welcome further discussion on limitations with appropriate recommendations, which both do not stifle the breadth of design ideas by the community, but also provide substantiative guidance to direct those involved to be mindful of critical milestones and ‘codes of best practise’ during the journey from inception of idea to final working and ‘usable’ ventilator. For example, looking at open source efforts for Personal Protective Equipment (PPE) we see that the 3D Printing community rapidly converged towards the preferential use of PETG polymers for manufacturing, owing to the factors of mechanical stiffness providing a semi flexible yet robust part, and importantly biocompatibility for limited human contact and being food grade to allow ease of decontamination. Equally, strict protocols were developed to minimise contamination of parts during printing, handling and shipping to both reduce the spread of the virus within the supply chain and to follow some element of best practise, similar to constraints set by medical device companies upon their manufacturing procedures. It would be very useful to the open source community if the author would share their thoughts in more explicit detail to provide a template that could be built upon for future efforts, outlining best practise from initial design ideation to working prototype. Arguably, the imperative of this is much greater than with PPE given potential intrusive nature of ventilation systems providing a clear route to internal infection through the lungs.One element that appears to be missed in the present review is an overview of current commercial systems and evaluation of their performance characteristics to be both efficacious and crucially to prevent unintended harm to a patient. The author does cite an existing review of commercial ventilators by Pham, and so it would be unnecessary to conduct a repeat of this work. However, what would be relevant in the present manuscript is a discussion focusing on the regulatory and quality assurance aspects and how these would align and differ in the approach of open source ventilation systems. Indeed, commercial devices must adhere to the very strictest regulatory scrutiny to be classified and used as a medical device, particularly given the invasive nature of their operation to either supplement or take complete control of a patients breathing. As such there are tightly regulated frameworks of ‘fail safes’ to ensure that every component used falls within acceptable usage limits, that construction of such devices follow strict regimes for assembly and minimisation of contamination, that tests are conducted to evaluate the working performance of each device, that there is a robust training and best practise usage protocol, amongst many other safety measures and supply chain demands. Arguably, one of the biggest reservations by the commercial sector regarding open source hardware for medical device technology are the lack of process control, quality assurances and regulations regarding technological development and best practise. It would be valuable for the readers to have some insight into what safety and evaluation procedures that are conducted and how such measures would be replicated in open sources systems in general terms, highlighting key challenges which can be built upon for the future discussion.The final sections of the review offer an exceptional summary of the state of art in the field of open source ventilators, highlighting several challenges and opportunities in this space. The author rightly highlights the very early stages open source ventilations systems currently are at and that we should not expect these systems to be working within a clinical setting in the immediate future. Despite this, I for one feel optimistic given the current work that is underway, our ability to access a wealth of digital knowledge, alongside the availability of hardware and manufacturing resources at our disposal. Arguably, the open source community has never been better equipment to make positive impact on the world during the COVID-19 pandemic. It is also the opinion of the reviewer that there remains many more opportunities for both growth of the open source community and to leverage the expertise synergistically with other academic groups to more rapidly advance our preparedness for emergency situations.Reflecting upon the manuscript, I could not help but feel there are differing schools of thought that of the traditionalist and the open source innovator. The traditionalist will operate with robust scientific rigour but will provide limited information scientific manuscripts, be open to patent and potentially restrict free flow of concepts and with respect to medical technology will strictly follow medical regulatory frameworks. The open source innovator is generally driven by an overwhelming sense of openness and transparency in their work, with the belief this will help proliferate and see ideas adopted faster for anyone’s benefit, albeit on some occasions operate with a naivety towards regulatory and best practise aspects. Initial discussions by the author drew distinction between efforts of the academic and non-academic communities, which very loosely are comprised of these two types of innovators, with the exception of a few ‘maverick’ academic groups. However, there was little discussion of strategies as to how these two communities may come together in cooperation and bridge any perceived differences in thinking. Clearly the academic community prides its outcomes based on empirical evidence, the careful scrutiny of data, alongside objective design performance metrics, attributes that the authors clearly outlines as shortfalls of the general open source community. Conversely, the non-academic community provides a wealth of creativity, ingenuity, alongside technical prowess, finding often remarkable and highly efficacious solutions working with limited resources and minimal dependency of specific supply chains. I would therefore strongly welcome the author to add further discussion towards strategies on how both communities, which for the most part work independently, could align agendas to realise opportunities that transcend the sum of the two parts. Indeed, I think it more critical for the open source community, based upon the reflection of the author, to be more engaged in traditional scientific process and to incorporate this into their thinking to hasten product development for evaluation.One element that gave me considerable food for thought, was the notion that developing nations have a perceived advantage during global health emergencies due to their more relaxed legal and regulatory frameworks to deploy open source ventilator systems. I am not entirely convinced that this is the case and indeed the author makes several valid arguments to the contrary, mainly that the technology is not significantly mature to function as intended and without consequence. Such suggestions can indeed have several unpleasant connotations from a legal and ethical standpoint and so I would encourage the reviewer to consider an amendment to this comment. Ultimately, I believe it was not the authors intension to imply this given previous discussions, however the context of this point should be framed better.Overall, despite the sombre theme of the review, the author has done an admirable job of bringing together all the relevant themes relating to open source ventilation systems. One of biggest take home messages from the review is how much potential exists with the open source community to provide cost effective, robust and timely medical device solutions, which may be far less susceptible to supply chain disruption and leverage a greater capacity for localised fabrication using the distributed manufacturing model. This capacity can only be realised by continued development of existing open source projects, increased dialogue with academic groups to work collaboratively to validate and iteratively improve ventilation system concepts for maximum efficacy. Equally, there is a clear need for regulatory reform which appreciates the evolving circumstances during a global health crisis and could provide an alternative framework to leverage capacity outside of typical medical supply chains to supplement efforts on the ground, as and when appropriate. What this framework should look like is another debate entirely, but this article makes an elegant argument for the debate to be had.Despite the infancy of open source ventilation systems, much potential exists and it is an exciting time for developers to continue their efforts towards working solution. It is exciting to see what may be a paradigm shift in how we perceive and operate globally in the medical device sector, particularly in light of the recent issues during the COVID-19 pandemic, which have decimated supply chains, while the shear volume of cases has put a drain on medical resources. The pandemic has already seen the use of open source designs, manufactured in a distributed manner, make impact to supplement shortfalls in PPE equipment. Could the same in time be true for ventilator technologies based on the balance of growing demand and available resources? Only time will tell. I reiterate the relevancy of the article by the author and the manuscript has been a very thought provoking document to read and digest. I would whole heartedly recommend this article for publication and encourage researcher and technologist in the field to draw inspiration from the insightful and thought provoking arguments outlined. I do welcome a time when the lessons we are learning during the pandemic lead to a more caring and equitable world for us all, and it feels from a technological standpoint, that open source innovation will be part of that story.