A High Frequency Oscillatory Ventilator Design For Use in Pandemics

This is a continuation of some of the ideas I expressed in a previous post on HFOV design. You can see it here: http://panvent.blogspot.com/2009/08/crisis-is-near-now.html

Some of the news items I have been reading say that there will be a particular shortage of high frequency oscillatory ventilators. Many ICU units do not have any or may only have one. This type of ventilator is required to care for patients with the most damaged lungs. Here is a little more information on a design for an HFOV. This is very preliminary. It surely needs more work. Someone would have to to build and test a prototype to determine if it is feasable.


What is HFOV?

An HFOV (High Frequency Oscillatory Ventilator) is an advanced ventilator design that is sometimes used in ARDS (Acute Respiratory Distress Syndrome) patients when a conventional ventilator will no longer provide adequate ventilation. Using a HFOV is considered a “lung sparing” technique.

When using conventional ventilators, the ventilation levels can be increased by increasing the percentage of oxygen fed to the ventilator, increasing the stroke volume, or increasing the rate or frequency. Other measures to improve ventilation can be increased PEEP (Positive Expiratory End Pressure) levels, reversed I/E (Inspiration/Expiration) ratios, methods to increase the average airway pressure, or even PLV (Partial Liquid Ventilation) has been tried, where a perflourocarbon solution (perfluorooctyl bromide) is put into the lungs to reduce lung damage without reducing oxygen transfer. ECMO (Extra Corporeal Membrane Oxygenation) is another method that can prevent damage to lungs by the use of high pressures and oxygen levels in conventional ventilation.

The HFOV can maintain a fairly high mean airway pressure, resulting in better ventilation without causing as much lung damage. With the high rates required for HFOV, each breath is less than the dead space in the lungs. There are various mechanisms that explain how it works (http://priory.com/cmol/hfov.htm), but it does work quite effectively. The breathing mechanism is similar to a dog panting at a high rate.


How HFOV Works

To make a HFOV work, you need to have a system that maintains a set average airway pressure and then have another device that oscillates this column of air at a desired rate, amplitude and I/E ratio. That’s the fundamentals of what it does.

Now to optimize this design you need to have a gas management system that controls the oxygen level, temperature, humidity and inlet pressure and flows to the HFOV device. We do not have to worry about designing these parts. They are all standardized respiratory equipment that is also used on conventional ventilators.

Other design considerations are that the air flow goes through the tubing in such a way as to optimize gas exchange, and we will also need other alarms to warn us of low or high pressures, improper rates and loss of supply gas. We may also want additional alarm systems that warn us of equipment failure modes. The tubing should be relatively non-compliant and the system should have minimal dead space.











Fig 1. HFOV design from IEEE Transactions on Biomedical Engineering
this link.

This design would be based mostly on the diagram in Fig 1. The controls and operator interface could be modeled to be similar to the 3100B from Sensormedics. The 3100B is the most commonly used HFOV for adults. Many RTs are already trained in its operation. By making the controls and alarms similar to the 3100B, it could be more easily deployed in a pandemic situation.

This is how the device in Fig 1 works:

• A filtered, humidified air/oxygen mixture is fed into the feed tube near the ET (Endo Tracheal) tube. The flow rate is monitored and controlled by the mass flow meter
• It travels down the tube towards the oscillator unit and exits via the servo controlled restriction valve.
• The pressure sensor is that thing on the tube between the inlet and outlet ports. The electronics control system will receive this pressure signal and adjust the servo controlled restriction valve so that the average airway pressure is equal to the desired set point.
• The pneumotach is not really required for operation. They have to do measurements for their study. Vacuum is not really required either, as average airway pressures will always be positive.
• The oscillator is that plunger looking thing on the right hand side. It looks and works like a speaker in the 3100B but is really a special purpose built device. They call it the driver.
• The plunger moves in and out at the desired rate, wave shape and amplitude as determined by the driver circuitry and the operator settings.
• Now, you can see, that column of air is going to push and pull air in and out of the ET, which goes into the lungs. When the air comes out of the ET, the fresh bias flow gas will flush it away and out toward the servo controlled restriction valve. Fresh bias air is pushed into the lungs when the plunger moves toward the ET tube.
• The oscillations of the plunger will change the instantaneous pressure in the tube positive and negative with respect to the average pressure.
• The position feedback device improves the performance of the oscillator circuit and can also be used as a part of a safety system
  

Parts And Controls

I will group parts into 3 general categories.

• Oscillator driver and driver circuit.
• Sensor, actuator and associated circuitry.
• Control and display system.
  
  

Oscillator Driver and Driver Circuit

For the oscillator driver we would want to use a big, high power subwoofer type speaker. It should be tough and able to handle high duty cycles and long periods of operation. It should have a metal cone to make it inflexible. We might have to glue a metal plate to the cone to make it more rigid. In order to reduce the dead space, we could make a mold of the front of the cone surface in resin or silicone with an air access hole drilled in the center to mate with the speaker cone assembly.

I am not certain how well a speaker will work though. There must be technical reasons why the designers of the 3100 use that design. Speakers, even subwoofers have a certain compliance and harmonic resonance built into them that is at a higher frequency than the rates we would need to use. It may require a large speaker using only a small portion of it's maximum designed excursion in order to minimize the effects on the output airflow pattern caused by the damping effects of the speaker cone suspension.

I am not sure if a position sensor is absolutely required, but something can be attached to the back of the cone if it is. Cooling may also be required. We could use lots of air and fans, or perhaps an active system using peltier devices.

The drive circuit would be a high output audio amplifier. I think it is best to use one designed for automotive use. These are generally more rugged, modular and can easily run on a 12 volt battery for electrical backup purposes.


Sensor, Actuator and Associated Circuitry

The sensor and circuitry would be similar to the one my son Jeff used in his ventilator design (Norman). It would convert the pressure pulse to a digital value encoded and sent on an RS232 port. We may wish it use more than one pressure sensor in order to provide redundancy for safety reasons. The pressure controller and alarm board would be a servo controlled valve and driver circuitry that operates by RS232. It could also house the audio alarm. This alarm would also engage and cause the valve to open if communications were lost. These circuits would have to be hand built unless there is a commercially available alternative.

Control and Display System

The control and display system would be a computer. It would probably be a PC and probably a laptop. A laptop has its own integral battery backup system. A program such as Labview can be run to show a display that looks similar to the control interface from the 3100B.

The instantaneous pressure readings received from the sensors could be integrated over time for display. The minimum and maximum pressures would be the peak recurring pressure extremes integrated over a short time interval. The average pressure would be integrated over a longer time period.

Operating parameters could be entered by selecting the appropriate box on the screen and entering the parameter via the keyboard. Alarms could also be displayed and color coded.

The computer would also output an audio signal to the speaker amplifier. This wave shape is normally a square wave pulse produced by a pulse circuit with variable duty cycle, frequency and amplitude in the 3100B. In our machine, we would have full control of the waveform via software. We could add pre-emphasis and custom wave shaping to the output to compensate for physical design shortcomings in the speaker and driver circuit or shortcomings in the housing and tube.
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Here are some resources if you want to learn more about HFOV.

Guidlines for the use of HFOV
http://priory.com/cmol/hfov.htm

HFOV guidelines from Stanford Hospital and Clinics
http://scalpel.stanford.edu/ICU/HFOV%20Guidelines.pdf

The use of HFOV in surgical patients.
http://www.surgicalcriticalcare.net/Guidelines/High%20frequency%20ventilation.pdf

Slide show of HFOV in the adult patient.
http://intranet.unchealthcare.org/hospitaldepartments/respiratorycare/practice-education-and-research/inservices-presentations/HFOV%20in%20the%20Adult%20Patient.pdf?searchterm=suction

University of Virginia experience with HFOV.
http://www.healthsystem.virginia.edu/internet/respiratory/Research/Retired/HFOVposter.pdf

ARDS and HFOV from Express Healthcare.
http://www.expresshealthcare.in/criticare2009/criticarefrontiers200912.shtml

Ventilation article from Answers.com.
http://www.answers.com/topic/mechanical-ventilation

Wickipedia Article about HFOV (please improve this)
http://en.wikipedia.org/wiki/High_frequency_ventilation

Spec sheet for the 3100B
http://www.viasyshealthcare.com/prod_serv/downloads/062_3100B_Spec_Sheet.pdf

Picture of a 3100 HFOV
http://commons.wikimedia.org/wiki/File:HFOV_3100A.jpg

Competency exam for 3100B operators.
http://www.viasyshc.com/smc/Reference/Critical_Care/Exams/3100BExam.pdf

Video showing operation of the 3100B
http://www.youtube.com/watch?v=jLroOPoPlig

Video showing initial operator calibration of the tubing set for the 3100B
http://www.youtube.com/watch?v=O2TaDyzxQAY

HFOV design is Coming Soon

If you are looking for my ideas on using a dialysis machine to do ECMO treatments you should visit my previous post here: http://panvent.blogspot.com/2009/09/using-dialysis-machine-to-do-ecmo.html

A lot of people have been looking at my ECMO post, and I have now had somefeedback on it. I am in the process of making contacts with local people to see if they will look at my idea and discuss its merits and drawbacks. I am not sure what the best strategy is to pursue this, through the Pandemic Ventilator Project or by other means.

Another idea I am working on is to produce a design for an HFOV (High Frequency Oscillatory Ventilator) using readily available components. See here: http://panvent.blogspot.com/2009/08/crisis-is-near-now.html .
I visited an ICU and saw one in operation. I talked to an RT about how it works and how they manage the device (thanks, Sue). I have also obtained some technical details and specifications for existing designs. I have a few days free this weekend and I hope to work on this idea a little more. Hopefully I can have some more info on the blog for Sunday night.

Here I reprint an excellent article I read on Propublica.org. The original is available at:
http://www.propublica.org/article/flu-nightmare-officials-ponder-disconnecting-ventilators-from-some-pat-923
This article is one of the most comprehensive, balanced and well written pieces I have read so far on the subject of ventilator shortages in the H1N1 pandemic. I hope that it is widely read by the public, as well as planning and “deciding” individuals.



Flu Nightmare: In Severe Pandemic, Officials Ponder Disconnecting Ventilators From Some Patients
by Sheri Fink, ProPublica, September 23, 2009 6:15 pm EDT















With scant public input, state and federal officials are pushing ahead with plans that -- during a severe flu outbreak -- would deny use of scarce ventilators by some patients to assure they would be available for patients judged to benefit the most from them.

The plans have been drawn up to give doctors specific guidelines for extreme circumstances, and they include procedures under which patients who weren’t improving would be removed from life support with or without permission of their families.

The plans are designed to go into effect if the U.S. were struck by a severe flu pandemic comparable to the 1918 outbreak that killed an estimated 50 million people worldwide. State and federal health officials have concluded that such a pandemic would sicken far more people needing ventilators than could be treated by the available supplies.

Many of the draft guidelines, including those drawn up by the Veterans Health Administration, are based in part on a draft plan New York officials posted on a state web site two years ago and subsequently published in an academic journal. The New York protocol, which is still being finalized, also calls for hospitals to withhold ventilators from patients with serious chronic conditions such as kidney failure, cancers that have spread and have a poor prognosis, or "severe, irreversible neurological" conditions that are likely to be deadly.

New York officials are studying possible legal grounds under which the governor could suspend a state law that bars doctors from removing patients from life support without the express consent of the patient or his or her authorized health agent.

State and federal officials involved with drafting the plans say they have been disquieted by this summer’s uproar over whether Medicare should pay for end-of-life consultations with families. They acknowledged that the measures under discussion go far beyond anything the public understands about how hospitals might handle a severe pandemic.

By every indication, state and federal officials expect to weather this year’s flu season without having to ration ventilators. That assumes that the H1N1 virus will not mutate into a more serious killer, the vaccines against it and the other seasonal flus will continue to prove effective, and any dramatic surges in the number of patients in need of ventilators will occur in different parts of the U.S. at different times.

In recent months, New York officials have met three times with physicians, respiratory therapists and administrators to rehearse how their plan might play out in hospitals in a severe epidemic. In one of those “tabletop exercises,” participants suggested that the names of triage officers charged with making life and death choices among patients at each hospital should be kept secret. The secrecy would be needed, participants said in interviews, to avoid pressure and blame from colleagues caring for patients who were selected to be taken off life support.

When they posted their plan on the web in coordination with a video conference in 2007, New York officials promised to solicit public input. Since then, they have consulted with medical and legal professionals and other experts, but few members of the general public, and the plan has remained unchanged. They declined to make the comments they have gathered immediately available for review, and those comments are not published on the Health Department's Web site [1].

In the initial proposal, officials called public review “an important component in fulfilling the ethical obligation to promote transparency and just guidelines.”

The academic publication of the plan envisaged the use of focus groups to solicit comment from “a range of community members, including parents, older adults, people with disabilities, and communities of color.” Those have not been held.

Beth Roxland, the current executive director of the New York State Task Force on Life and the Law, said the ethicists included in the state's planning process focused largely on vulnerable populations. "Even if we didn’t have direct input from vulnerable populations," she said, "their interests have been well accounted for." Roxland said that public comment solicited when the ventilator plan was posted on the Health Department Web site was "sparse."

Dr. Guthrie Birkhead, Deputy Commissioner of the Office of Public Health for New York State said he wondered whether it was possible to get the public to accept the plans. "In the absence of an extreme emergency, I don’t know. How do you even engage them to explain it to them?"

Even so, other states, hospital systems and the Veterans Health Administration—which has 153 medical centers across all states -- have drafted protocols that are based in part on New York’s plan. The inclusion and exclusion criteria for access to ventilators, however, are different. For example, under the current drafts, a patient on dialysis would be considered for a ventilator in a VA hospital in New York during a severe pandemic, but not in another New York hospital that followed the State’s plan, which excludes dialysis patients. The VA’s exclusion criteria are looser because the patient population it is charged with serving is typically older and sicker than in other acute care hospitals. Different states, reflecting different values, have also established different criteria for who gets access to lifesaving resources.

The Institute of Medicine, an independent national advisory body, is expected to release a report on Thursday morning, at the request of the U.S. Department of Health and Human Services, that will recommend broad guidelines to help guide planners crafting altered standards of care in emergencies. At an open meeting held to inform the report on Sept. 1, participants described successful public exercises related to allocating scarce resources in Utah and in a Centers for Disease Control and Prevention study conducted in Seattle.

Questions about how hospitals would handle massive demand for life support equipment arose when New York state health department officials ran exercises based on a scenarios involving H5N1 avian influenza.

“They kept running out of ventilators,” said Dr. Tia Powell, director of the Montefiore-Einstein Center for Bioethics and former executive director of the New York State Task Force on Life and the Law, which was asked to address the problem. “They immediately recognized this is the worst thing we’ve ever imagined. What on earth are we going to do?”

Officials calculated that 18,000 additional New Yorkers would require ventilators in the peak week of a flu outbreak as deadly as the 1918 pandemic. Only a thousand machines would be available, the officials estimated. The state’s acute care hospitals in 2005 had about 6000 ventilators, 85% of which were normally in use. A moderately severe pandemic would have resulted in a shortfall of 1256 ventilators, health officials found.

In 2006, New York planners convened a group of experts in disaster medicine, bioethics and public policy to come up with a response. After months of discussion, the group produced the system for allocating ventilators. They first recommended a number of ways that hospitals could stretch supply, for example by cancelling all elective surgeries during a severe pandemic. The state has also since purchased and stockpiled 1700 Pulmonetic Systems LTV 1200 ventilators (Cardinal Health Inc., NYSE) -- enough to deal with a moderate pandemic but not one of 1918 scale.

Officials realized those two measures alone would not be enough to meet demand in a worst-case scenario. Ventilators were costly, required highly trained operators, and used oxygen, which could be limited in a disaster.

The group then drew up plans for rationing of ventilators. The goal, participants said, was to save as many lives as possible while adhering to an ethical framework. This represented a departure from the usual medical standard of care, which focuses on doing everything possible to save each individual life. Setting out guidelines in advance of a crisis was a way to avoid putting exhausted, stressed front line health professionals in the position of having to come up with criteria for making excruciating life and death decisions in the midst of a crisis, as many New Orleans health professionals had to do after Hurricane Katrina [2].

The group based its plans, in part, on a 2006 protocol developed by health officials in Ontario, Canada which relied on quantitative assessments of organ function to decide which patients would have preference for an intensive care unit bed. The tool, known as the Sequential Organ Failure Assessment (SOFA) score, is not designed to predict survival, and not validated for use in children, but the experts adopted it in light of the lack of an appropriate alternative triage system.

This summer, New York officials brought the state’s plan to groups from several New York hospitals for the tabletop exercises. They met behind closed doors to assess how hospitals might implement the proposed measures if the H1N1 pandemic turned unexpectedly severe this fall. In the fictional scenario, paramedics were ordered not to place breathing tubes into patients until physicians “can assess whether they meet the criteria to be placed on a ventilator.’’

Problems were immediately apparent. Dr. Kenneth Prager, a professor of medicine and director of clinical ethics at Columbia University Medical Center, was concerned about the lack of awareness of the plan among the larger public and the majority of the medical community. Societal input “is totally absent,” he said and called for more outreach to the public. “Maybe society will say, 'We don’t agree with your plan. You may think it’s ethically OK; we don’t.'"

The protocol, he said, would also place a great burden on clinicians charged with selecting which patients would be removed from life support. Physicians were concerned doctors involved in the legitimate and painful selection processes might be inappropriately construed as "death squads." “We facetiously dubbed them the ‘death squad’ or the ‘guys in the back room’,” Prager said. He envisioned family members breaking down and screaming when they found out their loved ones would be disconnected from ventilators. “It really is a nightmare.”

Even so, he felt that the plan – and its effort to save the greatest number of patients – was ethically appropriate. “If we don’t use triage, people will die who would have otherwise been saved,” he said, because a number of ventilators are “being used to prolong the dying process of patients with virtually no chance of surviving.”

Doctors at the exercises feared that they would be sued by angry patients if they followed the draft guidelines. “There’s absolutely no legal backing for physicians,” said Lauren Ferrante, a medical resident at Columbia University Medical Center. “Who’s to say we’re not going to get sued for malpractice?”

New York State law forbids doctors from removing living patients from ventilators or other life support except in cases where the patient has clearly stated such wishes, for example in a living will, or through his or her legal health care agent. Other sources of liability could come from federal and state anti-discrimination laws or claims of denial of due process.

New York officials said they were currently working out legal options for implementing the plans, such as gubernatorial emergency declarations or emergency legislation.

“You can take something today that’s not necessarily active and overnight flip the switch and make it into something that has those teeth in it,” said Dr. Powell, who served on the committee that drafted the plan.

Dr. Powell cautioned that it is critically important to maintain flexibility in the guidelines. Any rationing measures taken in a disaster must be calibrated to need and severity.

Guidelines can also promote investment in new technology, such as cheaper, easier to use ventilators, that would make rationing less likely. Already at least one company, St. Louis-based Allied Healthcare Products, is marketing a line of ventilators [3] specifically for use in disasters.

Some states, including Louisiana and Indiana, have adopted laws that immunize health professionals against civil lawsuits for their work in disasters. Other states, including Colorado, have drawn up a series of relevant executive orders that could be applied to address these issues.

Dr. Carl Schultz, a professor of emergency medicine at the University of California at Irvine and co-editor of the forthcoming textbook, Koenig and Schultz’s Disaster Medicine (Cambridge University Press), is one of the few open critics of the establishment of altered standards of care for disasters. He says the idea “has both monetary and regulatory attractiveness” to governments and companies because it relieves them of having to strive to provide better care. “The problem with lowering the standard of care is where do you stop? How low do you go? If you don’t want to put any more resources in disaster response, you keep lowering the standard.”
Federal officials disagree. “Our goal is always to provide the highest standard of care under the circumstances,” said RADM Ann Knebel , deputy director of preparedness and planning at the Office of the Assistant Secretary for Preparedness and Response, Department of Health and Human Services. “If you don’t plan, then you are less likely to be able to reuse, reallocate and maximize the resources at your disposal, because you have people who’ve never thought about how they’d respond to those circumstances.”

The Crisis is Near Now

A High Frequency Oscillatory Ventilator Design

Some of the news items I have been reading say that there will be a particular shortage of high frequency oscillatory ventilators. Many ICU units do not have any or may only have one. This type of ventilator is required to care for patients with the most damaged lungs.

I found a design for such a device in the IEEE transactions on Biomedical Engineering publication. Here is the drawing.















The link to the PDF is located at this link.
The PDF essentially gives instructions on how to build this ventilator.

This device is much more complex than the basic ventilators I have built, but it seems that it would possible to build such a ventilator from common valves, sensors and control systems substituting for some of the components that are listed. The diaphragm actuator for example could be a large bass (subwoofer) type speaker.

It would be great if someone could build one of these unists and get back to me about how feasible it is and how well it works in testing.

Next week an idea for using ECMO.
Don't know what ECMO is?
Have a look.
http://panvent.blogspot.com/2009/09/using-dialysis-machine-to-do-ecmo.html

Now My Rant
Many of the recent reports that I have read indicate that there is a high likelihood that the current H1N1 pandemic will result in very busy ICU units and shortages of ventilators this fall in Canada. Doctors that work in ICU units that have had to treat H1N1 patients with Acute Respiratory Distress Syndrome (ARDS) say that the patients may have to be on a ventilator for a longer time period than they have seen with patients that got lung function complications in normal seasonal flu.

Here is a link to one such news item from CP.
Intensive care units likely to be main battlegrounds in the war against H1N1
There have been many stories like it originating from hospitals in Canada, the US, India, Australia, UK, Brazil, etc.

When I first proposed the Pandemic Ventilator Project two years ago as a means to alleviate some of the needs for ventilators in a pandemic, I expected it might be used for the H5N1 Avian flu. It seemed like a good insurance plan for a pandemic that, if we were lucky, might not even happen. Things have changed a lot since then. Now it is H1N1, people have actualy died from it, and this pandemic might return stronger this fall and winter, killing even more people. The risk of ventilator shortages has gone from a remote possibility to more likely. A lot has changed in the last six months.

Unfortunately, something that has not changed is the development status of the Pandemic Ventilator Project. As I have said several times before, the project has largely reached the limits of what I can do on my own to develop it. I need people with more ideas, more technical knowledge, more clinical expertise and better management and organizational skills than I possess on my own to carry the project further than I have. It would be a shame if we reach the stage where we really could use a ventilator from he pandemic ventilator project, but no one worked on it beforehand to get it ready in time.

Canada to Buy Ventilators for the H1N1 Flu

I saw an article in the Globe and Mail Today. I posted a comment on the article. Here is my comment:

The potential shortage of ventilators has been an issue with ethicists and planners for a while now. Most feared for the pandemic was the H5N1 Avian flu. Some officials thought that stockpiling ventilators would be a waste of resources because the expected H5N1 pandemic would be so severe that there would not be enough hospital staff or supplies to run them anyway.

With the comparatively mild H1N1 strain, some feel that existing resources will be adequate. The truth of the matter is that predicting the severity of a future pandemic is nearly impossible. It could be anywhere in between these extremes, and can change rapidly during the course of a pandemic as well. Many experts are concerned that with the very high numbers of infections happening with the H1N1 strain, that even a moderate increase in the severity of illness could cause widespread shortages of ventilators.

The Canadian and Ontario governments have not done very much up to this point of addressing the potential of a very deadly ventilator shortage. Governments in the US that have done the most to provide a creditable emergency supply have mostly focused on buying low cost, lower tech ventilators that can be operated by individuals with moderate training levels. The optimal number to purchase is between one and two times the current number of ventilators being used in ICU units.

I have a discussion of some of these issues in my blog at panvent.blogspot.com Pay special attention to an article I wrote more than 2 years ago comparing the government and Canadian Red Cross's inadequate response to the issue of AIDS contamination in the blood supply. http://panvent.blogspot.com/2007/02/trusting-in-pandemic-plans.html


I will be gone fishing for the next 2 weeks.

Possible Swine Flu Pandemic Brewing

It has been a while since I have posted. I have had other priorities and this project has been left on the back burner. The events of this week seem to have made the Pandemic Ventilator Project a priority once again.

For the sake of those that are visiting this blog for the first time I will summarize the goals of the Pandemic Ventilator project. I will then discuss the work that has been done to date. I will then relate the project to the current swine flu outbreak that could possibly become a worldwide pandemic requiring many ventilators, possibly more than are currently available.

In February of 2007, I became aware of concerns by the World Health Organization that a worldwide influenza pandemic was imminent. One of the problems that will almost certainly be encountered if there is even a moderately severe pandemic is a shortage of ventilators. I had the idea that using modern industrial control devices such as PLCs (Programmable Logic Controllers), readily available solenoid valves and other readily available components, a functioning emergency use ventilator could be constructed. I came up with an initial design that I published on this blog and invited others to improve on the design or come up with better, different designs.

The project has had some success but is not complete. So far three different prototypes have been built by two other persons, and myself but there has been limited testing done. There have also been projects started by students at Michigan Tech University and two different groups in India that have used some of the ideas presented here develop different ventilators for use in pandemics or third world situations. If you follow through the blog postings from the first one, you can see the development of the project. In addition to working on my ventilator design, I have also written postings that encourage greater participation by government agencies in increasing the stockpiles of ventilators set aside for pandemic use. There are also several postings defending the use of non-commercially made ventilators in emergency situations. These postings mainly chronicle the brave individuals that built home made ventilators during the last polio epidemic. There are also reviews of other publications and videos.

It is difficult to predict if this outbreak will develop into a worldwide pandemic that is bad enough to cause a severe shortage of ventilators. Two factors cause it to be hard to predict. One, it is difficult to get good information because government authorities want to control panic and reduce economic disruption, and two, the nature of outbreaks themselves is unpredictable.

So what do we know? First the people that are dying are not the typical elderly and very young. They are mainly healthy young and middle aged adults. The death rate seems fairly high, perhaps as great as 10%. Death rates early on in a pandemic however are very difficult to pin down, as we really do not know how many people were infected but in fact had very mild symptoms and were not counted. The virus is spreading to many geographical locations quickly. The WHO has already stated that it’s first line defense against pandemic outbreaks, which is containment, is no longer possible. The reason that there are no major travel restrictions imposed by governments is not that they think the threat is too minor, but that it is past the point where travel restrictions will help. What is still unknown is how severe it will eventually be, and how readily it will spread.

In the region that I live in, there are about 50 ventilator equipped ICU stations. The population served is about 500,000. If we had an pandemic that struck 10 percent of the population in each wave, and the virus was severe enough that 1 percent of those infected in each wave required a ventilator, then the number of ventilators required would be 500. Let us hope and pray that this pandemic is a very, very mild one.


Here is a link to a BBC News Link on Mexico Flu Experiences