Modular Design in The Ventilator Crisis: Why It Matters

Flexibility of Treatment

It is not the place of engineers to tell doctors how to treat patients. It can be the place of engineers to give doctors every tool possible in sufficient quantities that they can make decisions as free from scarcity as possible. Particularly in the developing world, scarcity may limit the way patients are treated, thus producing far worse outcomes. In all cases and everywhere, we know that keeping patients strong through supportive care, in every stage of disease severity, will improve outcomes. Respiratory support can occur at many levels.

Local Shortfalls and Supply Chain Shortfalls

The need for mechanical ventilators in this pandemic is unpredictable, but we can say with certainty:

  1. There will be local shortages even if worldwide demand is met.
  2. When a health care system, including ventilators, is overwhelmed, outcomes will be worse. In other words, more people will die.

Supply Chain Resilience

Ideally, we would have supply chain resilience. Nobody can make a Sensirion flow sensor better than Sensirion; but nobody should die because they cannot get one. We, as engineers, should construct a system which is resilient to supply chain disruption. We should not aim for perfect substitutability, but we should aim for graceful degradation. This is a term of art which can be put more colloquially: the system should bend, not break.

Modularity = Resilience

By modularity, we mean that the system consists of a system of parts, called modules, which can be interchanged in a LEGO® brick -like fashion. The concept is of course familiar. It may even be present within the product lines of major firms, but until now they have had little incentive to reveal, or open that modularity.

Parallel = Fast

Modular design also lends us an advantage in the timeline of design and development of crisis interventions. By effectively modularizing the problem space, individual project teams are each able to concentrate their efforts on one piece of the engineering puzzle, and thus all of the research, development, user and lab testing, and all other stages necessary for each of these designs happens concurrently. Since the scope of each module is simplified relative to an overall ventilator design, this development and testing process would likely be expedited and can be more precisely tailored to the nature of that specific component’s task.

Softening = Versatility

For the last 50 years, machines and parts of machines have been getting more electronic control. One could say that they have been getting smarter. We prefer to say they have been getting softer, in the sense of software as opposed to hardware. As the machines and even tiny, inexpensive parts of machines have gotten softer, they have become more versatile. (This is why it may be possible to “jailbreak” a given CPAP machine to turn it into a BPAP machine or simple invasive ventilator.) In 2020 we talk about the Internet of Things (IoT): the widespread intercommunication of devices which in the past were just things. Now they have become sensing, internetworked things. This is an opportunity.

Openness = Confidence

However, to achieve this modularity, parts and modules must be open. You cannot have confidence in replacing a part if you cannot see inside it. Sight is here used as a metaphor for being able to understand, examine, and test the part. You cannot have confidence in that which you cannot verify, and you cannot verify what you cannot examine.

Hot Swap is the Ultimate Resilience

The ultimate resilience is the ability to do a “hot swap” of components while the machine is in operation. This may seem unattainable, but in fact the proliferation of AmbuBag designs which do not specify the precise bag very clearly show it is possible, even a necessary design goal, in the current crisis.


In this article we argue why the global open-source community should adopt a modular approach to the development of specialized emergency equipment such as medical ventilators, defining four mottoes to encapsulate this approach (“Modularity = Resilience”, “Parallel = Fast,” “Softening = Versatility”, and “Openness = Confidence”). A follow-on article, Modular Design of Pandemic Ventilators, that will be maintained as an open-source living document, provides more practical detail of how the open-source community could effectively adopt a modular approach to design and development in emergency scenarios, in particular that of ventilator design to address the COVID-19 pandemic. We encourage your suggestions made within that document.

Public Invention

Public Invention is a US 501(c)3 public charity that has been working full-time on the COVID-19 ventilator crisis since March 15th. A small donation would make us feel appreciated.



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Robert L. Read

Robert L. Read


Public Inventor. Founder of Public Invention. Co-founder of @18F. Presidential Innovation Fellow. Agilist. PhD Comp. Sci. Amateur mathematician.