Sunday, March 30, 2008

Another Video of Pandemic Ventilator Norman

Here is a picture with the Plexiglas cover installed, ready for the science fair. The jug of water that was used for a weight is now replaced with a can filled with 4.5 Kg of metal. This makes for a more compact weight. The computer monitor is used to display LabView which is running on a P3 computer under the table.

Norman Pandemic Ventilator Ready for the Science Fair

Last week I showed some pictures of “Norman”, and a video of the ventilator running.
(link here)

This week I have another video that shows the functioning ventilator with alarms enabled and also outputting a pressure wave to Labview on the computer. When you see the video, it again shows it running with a pressure of about 22 cm of water and a stroke volume of about 400 cc. The black bag that is inflating and deflating is a lung simulator, and the gauge that is turning is a spirometer. The patient line occluded and the loss of air pressure alarms are demonstrated by occluding the patient line and then the compressor line. The pressure signal from the pressure transducer is displayed on the computer monitor.

Norman has now run for many hours with no failure of the bag. This prototype shows that the pandemic ventilator design can meet the pressure and volume requirements for a ventilator and can also be equipped with safety alarms, remote monitoring and control.

Friday, March 21, 2008

Norman Running on Video

In the blog so far I have written about and shown two prototype pandemic ventilators that we are working on. They are “Vinnie” (link here), and “Max” (link here). Today I will present the third prototype. This prototype will be named “Norman” after Norman Burn. Norman Burn was the Chief Technician at the Department of Anesthesia at Newcastle. Norman Burn built many of the very first positive pressure ventilators. Some of his “home made” ventilators were used during the polio epidemic in Britain in 1947. (link here)

A high school student at Forest Heights Collegiate in Kitchener Ontario is building “Norman”. It will be entered in the Waterloo Wellington Science and Engineering Fair to be held on April 1 2008.

Picture Here

Norman Pandemic Ventilator

Rockwell Allen Bradley Micrologix 1500

Ventilator Compressor

Jug of Water on the Bellows Plate

“Norman” is built from readily available components that can easily be obtained or re-purposed from other uses during a pandemic. It was constructed using the original design (link here) and is similar to “Max”, but with a few changes and improvements.
  • The bellows is a vertical slider instead of a hinged bellows. The slider is constructed from Bosch struts (link here) and plastic panels. It is an innovative design that does not jam, yet is easily constructed and forgiving of slightly out of tolerance assembly.
  • It uses an integral compressor so that it does not need to rely on pressurized air being available, but only electricity.
  • It has a pressure transducer instead of a manometer. A restrictor valve has been added in the “to patient” line, so that the inspiration time can be adjusted.
  • The bellows bag is a 2-liter PVC peritoneal dialysis bag. This is a very strong bag and has run many hours with no breakdown or apparent wear.
  • The PLC is an Allen Bradley Micrologix 1500.

Here is a video of Norman running.

You can see that there is a jug of water on the bellows plate. Adjusting the amount of water in the jug on the bellows plate controls the maximum pressure generated by the bellows. The Checkmate pressure gauge behind the ventilator shows the maximum pressure is about 22 cm water. The Boeringer spirometer is recording a tidal volume of about 400 cc and a minute volume of about 7 liters.

Saturday, March 15, 2008

Dr John Hick Interviewed by the Star Tribune

"But when we get hit hard with a bad outbreak, people are going to be saying, 'Why didn't you prepare for this?' And there won't be any good answers."
Dr. John Hick

You may have noticed that media coverage of the shortage of ventilators that will happen in the next pandemic has reduced somewhat recently. The coverage peaked about 2 years ago and has been slowly dropping in frequency. This week there were two stories, one in the Wall Street Journal (link here) and also a very interesting article in the Star Tribune of Minneapolis St Paul Minnesota. Warren Wolf of the Star Tribune interviewed Dr. John Hick of Hennepin County Medical Center about the recent shortage of ventilators in Minnesota hospital intensive care units. (link here)

Dr. John Hick is very prominent in the pandemic flu planning literature. He is the medical director for an emergency-preparedness compact of Minnesota hospitals. He has been involved with many planning committees and has authored several articles dealing with the expected scarcity of key medical supplies including ventilators in a pandemic. He is also frequently referenced in other major articles on this subject. He is clearly one of the leading thinkers on this issue. He is one of the authors in a document I recently reviewed entitled Mass Medical Care with Scarce Resources: A Community Planning Guide. (link here)

Dr. Hick, as you can expect, is usually somewhat more restrained in his comments in his major written articles. In fact, I have even criticized him previously for not pushing hard enough, or looking at enough options. In this interview however, he is a little more open. I was very impressed with his comments and will be re-quoting several of them here.

The Star Tribune article is about a recent shortage of ventilators in Minnesota hospital intensive care units that had many hospitals renting extra ventilators and had several hospitals directing patients with respiratory problems elsewhere for care. Dr Hick was asked about the “crisis” and said he did not think it was a real crisis but that it was a little too close for comfort.

He then linked the temporary shortage of ventilators they experienced to the real problem he perceives. "Even if we hit a temporary local crisis, we can deal with that. What worries me -- what keeps me awake sometimes -- is what will we do when we get a regional or national pandemic? That's going to happen. It's just a question of when and how bad.”

He then says the shortage will cause unnecessary deaths. "The truth is, in a major crisis like a pandemic we may be forced to triage patients because we just won't have the hardware, and some will die.” He said a major disaster or flu outbreak could "tip us over the balance and people would die for lack of ventilators."

The article then says; Hick has urged state officials to stockpile ventilators, "but in a year when we're cutting health care spending, buying ventilators at $50,000 each in case of emergency is kind of a hard sell.”

Hick concludes with, “This is a scary situation and it ought to make people nervous, We got through last week and we can do it again -- we probably will. But when we get hit hard with a bad outbreak, people are going to be saying, 'Why didn't you prepare for this?' And there won't be any good answers."

Thank you Dr. Hick. For telling it like it is.

Saturday, March 8, 2008

Review of - Positive-Pressure Ventilation Equipment for Mass Casualty Respiratory Failure

Today I will review the document “Positive-Pressure Ventilation Equipment for Mass Casualty Respiratory Failure”. This is available for free as html or PDF at
The authors are: Lewis Rubinson, Richard D. Branson, Nicki Pesik, and Daniel Talmor

This document discusses the need for additional ventilators for a mass casualty event including an influenza pandemic. They discuss the need to stockpile additional ventilators for such an emergency. They also acknowledge that it would be very expensive to stockpile and maintain enough full-featured ventilators to be adequately prepared for such an event, so they discuss how positive pressure ventilators (PPVs) with fewer alarms and capabilities could also be used to supplement the existing stocks in time of emergency.

In my opinion, this is a very well researched and prepared article. Many of the issues documented in this article have in fact shaped the aims of the Pandemic Ventilator Project as well. It deals at length with the advantages and disadvantages of various types of ventilators for use in mass casualty respiratory failure. The emergency ventilators we are designing at the Pandemic Ventilator Project are not meant to compete with or replace regular commercial ventilators, but are meant as a backup in case authorities do not stockpile adequate numbers ahead of time.

The use of improvised ventilator equipment during the polio epidemic in Copenhagen in 1952 is discussed. They had only 4 devices available, but had to ventilate as many as 70 persons at a time. They designed and built a number of devices that were manually operated by medical students and saved many lives that would otherwise have been lost. This is a great example that innovative ideas, methods and pragmatic thinking can be used in times of crisis to save lives.

(For additional information on the use of alternative ventilators in the Polio epidemic, see my previous post )

They then discuss how the use of PPVs requires highly trained and skilled health professionals, and that even in normal times, the number of skilled professionals and equipment is sometimes in short supply. In addition to increasing the physical supply of PPVs, there will also have to be plans in place to be able to extend the capabilities of the health care professionals. There is a discussion of different ways to stretch the existing supply of ventilators. There are details of various disaster scenarios and how they will affect the need for PVPs.

They give a good overview of the logistics of ventilator stockpiling and airway management. Endotracheal intubation is preferred. There is a chart that details the various types of alternative Ventilators and their characteristics. The text provides a detailed analysis of the advantages and disadvantages of each type.

They then reiterate the expected shortage:
“Even with significant state and regional investments in PPV caches, there will likely be a shortage of available PPV equipment during a severe influenza pandemic. Standardized approaches to prioritize allocation of scarce resources such as ventilators must be considered for such events.”

They close with this ominous statement:
“Even though not enough PPVs could be stockpiled to ensure that each patient with ARF has a ventilator during a severe influenza pandemic, the additional capacity afforded by reasonably sized caches can help a significant number of patients survive. This additional PPV equipment must be purchased within the context of a rigorously developed strategy to provide a coordinated medical response to catastrophes. Without such equipment, many patients may die despite having survivable clinical conditions.”

The Pandemic Ventilator Project exists to supply a design for a ventilator that can be built from readily available components to fill that last shortfall. I wonder what the writers of this document think of the Pandemic Ventilator Project? I wonder if they are even aware of it? This document was written nine months before the Pandemic Ventilator Project was started. They cite the use of jury-rigged ventilators constructed during the polio epidemic in Copenhagen as an example of how lives can be saved by using alternative ventilators, but then they recommend that only FDA approved devices be used. In fairness, I do not see how any planner working under the existing liability framework can recommend anything other than an FDA approved device. It is only when an actual crisis arrives, when they are faced with triaging the available ventilators to do the greatest good for the greatest number of people that real alternative solutions can be considered.