A Proposal for an Open Source Design to Assemble Ventilators to Meet
Pandemic Surge Demand

Clarence Graansma

Abstract:
In a predicted pandemic influenza outbreak, it is expected that there
will be a severe shortage of ventilators.  Ventilators are expensive
to buy and maintain, so government organizations are stockpiling only
a minimal reserve. Manual type ventilators will not be adequate for
many cases. The solution to this problem may an open source design for
an automated ventilator that will be adequate for the perceived need,
and can be built from parts that will be available in sufficient
quantities during a pandemic.  A community of developers must design,
and test a ventilator, and make the design freely available for
individuals and healthcare organizations to build their own units in a
pandemic crisis.

Background:
It is expected that in a pandemic influenza outbreak the number of
people requiring a ventilator will be much greater than the number of
ventilators that are available in hospitals. There are approximately
105,000 mechanical ventilators and 60,000 intensive care unit (ICU)
beds in the United States.  This is only 1 ventilator for every 2600
people and 1 ICU bed for every 4500 individuals. In an avian flu
pandemic, it is estimated that 30% of individuals will become
symptomatic and up to 50% will require ventilatory support. Using more
conservative estimates, data from the H1N1 pandemic flu of 1918
suggested that 2% of people required ventilatory support. If the same
is true for H5N1 (although less than what is currently estimated), a
city of 1 million people will have 300,000 affected individuals and
6000 of whom will require a ventilator  .

Based on these numbers, a city of 1 million people would have 385
ventilators in its hospitals.  Since 80% to 100% of the stock of
existing ventilators is typically already being used in the ICU
units , this leaves at most only 77 ventilators available at any given
time.  Triage methods will be used to remove some of the people
already on ventilators in order to give to people requiring
ventilatory support due to the pandemic.   Now it is possible that the
impact of the pandemic may be considerably less than the 1918 event
due to the use of vaccines and anti-viral medications.  Let us assume
again a very good response to medications, and we reduce the number of
people requiring ventilatory support by 50%.  The expected patient
load would now be 3000.  Pandemics do not always strike all at once,
but may come in several waves such as the 1918 pandemic .  The same
ventilator could be used sequentially 2 or 3 times in each wave to
treat pandemic victims in perhaps 3 subsequent waves.  This means that
each ventilator could now be used to treat 6 to 9 people.  Assume we
made up to 200 ventilators available via triage by removing existing
chronic and elderly patients from ventilatory support and then used
each of these ventilators to save 8 people from the pandemic. This
would save 1600 of our 3000 patients.

It is obvious that even strict triage and with conservative
assumptions of severity, we will be short of ventilators.  Even if we
had an unlimited supply of ventilators, we will not save everyone.
Many will die even with a ventilator and good critical care.  If the
availability of ventilators were not the issue, the limiting factor
then would be how far we can extend our critical care support system.
Physicians, intensive care nurses and respiratory therapists will also
be affected by the pandemic and their ability to respond may be
reduced.  There are also issues of availability of other supplies.  A
reasonable assumption of the limits of support extension would be
between a factor of 2 to maybe 3. This means our city of 1 million
would need to have available between 385 to 770 additional
ventilators.  Now these ventilators need not have every possible alarm
and treatment option, but they must have enough automation so that
nurses and respiratory therapists  (RTs) can run them without constant
intervention.

Some hospitals and organizations are stockpiling manual ventilators
for such an emergency.  These are either bag type manually operated
ventilators, or pressure driven transport type ventilators with no
alarm systems .  These have the advantage of low cost, disposability
and no maintenance. These devices require extensive supervision by
qualified personnel, however and will not be adequate in this
situation.  They may be useful if appropriate automation and alarm
systems could be fitted.  To buy enough full function ventilators to
fulfill the need is too expensive for hospitals to consider.  Even if
the government were to pay for enough ventilators to supply the entire
country, there would not be enough centralized manufacturing
capability to supply the product when it is needed.  Neyman and
Irvin   have published an innovative method to put up to 4 patients on
a single ventilator.  This system requires further testing and would
not have very good monitoring ability.

Proposed solution:

reference design for a low cost, relatively reliable ventilator that
can be produced in a large quantity in a relatively short time from
commonly available materials that are not in short supply. The device
will not require every feature and ability of existing full function
ventilators, but must have the features required to properly care for
Acute Respiratory Distress Syndrome (ARDS) in a pandemic situation.
The device should be automated as much as possible as to enable the
existing RTs to care for a large number of patients. Also the design
of controls and alarms should be intuitive so that other persons can
be trained to help support the devices in use.  The components used to
build these devices must be components that will be available during a
pandemic.

The best way to engineer and distribute such a reference design would
probably be based on an open source model. Existing projects to
emulate and gain organizational insight could be the "One Laptop per
Child" project or the various open source software projects such as
the Mozilla Foundation or various Linux branches.  The non-profit
Architecture for Humanity (http://www.architectureforhumanity.org/) is
doing a similar thing for designs for housing to rebuild communities
in the wake of natural disasters.  We need to start a Pandemic
Ventilator Project now.

The ventilator must be able to be built from commonly available
components sourced from the industrial and instrumentation
marketplace.  The component specification should be standardized as
much as possible. For example a good specification would be "12V
solenoid actuated air valve with a minimum flow rate of 3 liters per
minute" rather than "ACME solenoid valve AS3506T." This will allow
substitution if required.

A centralized listing would be have to be established and maintained
of possible components that will satisfy the requirements and known
supply sources. The design should incorporate "fail-safe" design
techniques as much as possible.  In order to use "off the shelf"
components, the design will have to rely on an electronic control
system to enhance safety and usability instead of using innovative
pneumatic component designs. It will probably be either PLC based or
some type of dedicated PC control.

Testing criteria and minimum performance specifications will have to
be developed.
It is expected that alpha, beta and release candidate versions will be
released and then tested. There may be version upgrades based on
testing results. It may be beneficial to fork the project at some
point in order utilize differing design philosophies or to produce
devices tailored to certain requirements, such as simplicity of
operation, desired features or ease of assembly.

A community of developers will need to be established.  It is doubtful
that existing ventilator manufacturers will participate on a formal
level due to competitive and legal obstacles, however it is expected
that they may allow some of their engineering staff to participate on
their own as a humanitarian gesture.  It would be expected that
professional groups may encourage their members to support the
project.  It would be very helpful to obtain the support of university
engineering labs.  It is expected that the bulk of support would be
individuals from the medical, instrumentation and information
technology communities.

A legal framework will have to be established to protect contributors
to the project from legal liability of any misuse of the reference
design or any lawsuits from failure of a device.  Something like the
GPL will have to be used to control derivative use of the reference
design.  As it is unlikely that the design will be submitted for FDA
approval, there would have to be legislation enacted by governments in
a crises to permit use of any devices produced. Perhaps some draft
documentation to guide the government agencies at the time of a crisis
could be produced ahead of time.  Humanitarian groups may wish to use
the designs for third world relief projects.

A foundation may have to be established to support the project.  A
core group will have to be established to control and maintain the
direction of the project.  Training, servicing and operation
guidelines and materials must also be produced and maintained.  A
website for feedback, communication and software distribution will be
required. Perhaps Sourceforge could be used.

Mar 11 2007
www.panvent.blogspot.com
References for a proposal for open source

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2 CMAJ · November 21, 2006 · 175(11) | 1377
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Christian, Michael D. et al

3 Mass Critical Care with Scarce Resources: A Community Planning
Guide  AHRQ Publication No. 07-0001  Marc Roberts PHD et al

4 Taubenberger JK, Morens DM. 1918 influenza: the mother of all
pandemics. Emerg Infect Dis [serial on the Internet]. 2006 Jan [date
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6 A Single Ventilator for Multiple Simulated Patients to Meet Disaster
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Greg Neyman, MD, Charlene Babcock Irvin, MD
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