IEEE Robotics & Automation Magazine - March 2021 - 102

The COVID-19 Pandemic
COVID-19, caused by the novel human coronavirus, is a
severe acute respiratory disease that has wreaked havoc
on global public health, with more than 84 million confirmed cases and 1.83 million deaths worldwide as of the
beginning of 2021 [1]. As of this writing, there have been
23 million confirmed cases in the United States alone,
with more than 380,000 lives lost [1].
Patients presenting with COVID-19 can develop severe
acute respiratory distress syndrome (ARDS) [2], [3], which is
characterized by low respiratory compliance and a life-threatening impairment of pulmonary gas exchange [4], [5]. Approximately 20% of admitted COVID-19 patients require respiratory
assistance from a mechanical ventilator to achieve adequate oxygenation [6]. The resource-intensive therapeutic requirements
posed by COVID-19, coupled with the sudden and exorbitant
caseload onset, have overburdened health-care infrastructures
across the globe due to the dwindling supplies of the personal
protective equipment and devices (e.g., mechanical ventilators)
necessary to protect frontline workers and to treat patients with
the disease [7]. The insufficient access to clinically approved
ventilation systems has forced physicians to make particularly
difficult triage decisions, including the modification or even discontinuation of care for patients for whom the outcome is bleak,
in an effort to free up ventilators for those with more favorable
prognoses [8].
Ventilator Shortages Galvanize
Grassroots Innovation
Recognizing these critical supply shortfalls, many communities
across the globe have banded together to bootstrap ad hoc solutions in an effort to bridge the supply gap. These efforts range
from breweries and alcohol distilleries bottling hand sanitizer
instead of beer and whiskey [9] to large automotive companies
(General Motors [10], Tesla [11]) and aerospace companies
(Virgin Orbit [12], SpaceX [13], NASA [14]) retrofitting and
retooling entire factories to mass manufacture mechanical ventilators and requisite components at scale. A particularly inspiring
example of grassroots ingenuity in the fight against COVID-19
comes from the engineering and " maker " communities, who
have mobilized to develop custom, open source designs for
mechanical ventilators that can be rapidly manufactured with
fairly simple processes and easily sourced components. These
concepts range from mechatronic systems designed to compress
clinically approved bag-valve masks (Ambu bags) at digitally
programmable rates [15]-[17] to pneumatic systems that deliver
ventilation directly through digitally controlled valves [18] to
hybrid systems that use a pressurized chamber to compress an
Ambu bag [19]. To list all of the open source designs would
require a separate article in itself, so we encourage the reader to
consult Pearce's review [20] for a more complete picture of the
open source ventilator landscape.
In this article, we describe the work done by a team of
engineers, roboticists, and clinicians from Vanderbilt University, beginning in late March 2020, to develop an easily
reproducible mechanical ventilator out of core components
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that can be sourced locally, inexpensively, and en masse. We
detail the three-week process that took us from initial napkin sketches to a validated prototype and associated regulatory submission, and we provide design details and
experimental validation results that demonstrate the therapeutic efficacy of the proposed design. This process resulted
in an open source design that is set apart from other solutions by its manufacturing simplicity and reliance on components that are either readily available locally or ubiquitous
enough that they could be sourced quickly, even in the face
of pandemic-induced shortages and supply chain disruptions. As a supplement to this archival publication, all of the
design files, parts lists, software, and testing results are made
freely available in supporting information documents, with
the idea that the design can be rapidly built locally, wherever
it is needed in the world, by anyone with basic woodworking, soldering, and programming skills.
The Vanderbilt Open Source Ventilator
The Vanderbilt Open Source Ventilator (VOV) is a volumecontrolled, intubation-style ventilator (see Figure 1). We took
this device from a napkin sketch to a prototype in three
weeks. After a successful animal study, doctors deemed this
device able to save a life. Over the following three weeks, we
manufactured 100 units and submitted documentation to the
U.S. Food and Drug Administration (FDA) for Emergency
Use Authorization (EUA) clearance. Throughout this whirlwind process, we undertook multiple design iterations,
informed by continuous clinical input, literature review, and
experimental testing, enabling us to converge on a design that
is low cost, easily manufactured, and potentially life-saving.
Our device implements a simple, inexpensive design; it is
largely constructed from plywood, and we did away with
expensive, specialized dc/stepper motors and optical encoders. Instead, we relied on widely available windshield wiper
motors and a simple reciprocating transmission design based
around a Scotch yoke mechanism (SYM) and drawer glides.
The purpose of the device is to mechanically compress an
Ambu bag-a widely available medical device that is normally squeezed by hand to provide ventilation for patients while
transporting them to the hospital or while they are within the
hospital and having difficulty breathing on their own. By
leveraging medical Ambu bags and requisite ventilator/endotracheal (ET) tubing, the VOV is directly compatible with
many standard oxygenation and humidification sources. The
only components that come into contact with the patient's airway are clinically approved and disposable or otherwise subject to rigorous reprocessing protocols. We added
Arduino-based control electronics that, when combined with
mechanical inputs, enable physicians to set the volume of air
delivered per breath [tidal volume (TV)], the respiratory rate
in breaths per minute (BPM), the amount of the breathing
duty cycle devoted to inspiration versus expiration (the I/E
ratio), and the pressure thresholds at which alarms will sound
during operation [designed in accordance with International
Standards Organization (ISO) 60601]. Experimental
IEEE Robotics & Automation Magazine - March 2021

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