Sunday, January 27, 2008

Everything Old is New Again

Workshop Built Ventilators

I return to something I mentioned in an earlier post about homemade (wooden) iron lungs described in a 1950s Popular Mechanics article. the link under the picture will take you to a site that posts the original complete assembly plans.

Intended only for emergency use until a commercial respirator could be obtained, this “wooden lung” was designed by engineers and built by a volunteer group under the supervision of Dr. Gerald M. Cline, Dr. Homer O. Dolley, and Sister Celine of the medical staff of St. Joseph’s Hospital, Bloomington, Illinois. On completion, the unit was put into immediate use in emergency treatment of eight-year-old Rudy Landheer, a victim of polio in the epidemic of 1949. The original unit did emergency service for 12 hours until a conventional iron lung could be obtained.


I will also talk about some of the earliest positive pressure ventilators built in Great Britain and home made iron lungs used in the United States.

The British ventilators were built in Newcastle for anesthesia and also the polio epidemic in the late 1940s and 1950s. These ventilators were built by the inventive Newcastle professor of Anesthesia Edgar Pask, his chief technician Norman Burn and his staff of highly able technicians using war surplus parts.

This is the Newcastle ventilator. (Known as a respirator at the time.) Just as we named our ventilator “Vinnie”, they named the ventilator they designed and built. They named theirs “Mother”.

"Mother"

The electric motor was controlled by mercury switches. A spinning disc allowed speed variation, and a camshaft moved four small bellows up and down to provide the ventilation.

After the success of their first ventilator design they wanted to design another that could be easily and cheaply and quickly constructed by any able technician. They were building these ventilators to save lives in the polio epidemic. There simply were not enough “iron lungs” available in Britain to deal with this epidemic. There were about 1000, but many of these were already in use. There were 1000 cases of polio in 1946 in England and Wales, but this increased to 9000 by 1947. The use of a ventilator could reduce the death rate of those polio victims that were afflicted with respiratory paralysis from 90% to 30%.

One version of a cheap and easy to build ventilator was the Bang ventilator of 1953. This design was shared with others and similar units were built elsewhere.

The Newcastle "Bang" ventilator

The “Bang “ ventilator design worked well, but it required frequent adjustment and maintenance. The mercury switches it used were important for anesthesia, but were not required for polio patients. They could also be difficult to obtain.

They then built two prototype "polio ventilators" out of materials that were readily available in any workshop. The “blow” side of a domestic vacuum cleaner powered these ventilators. Up to 10 ventilators could be powered from one Hoover.

Two Polio Ventilators

These ventilators were made of plywood and perspex. The one on the left, used a magnet to operate its main valve. Inflation pressure was varied by adding weights onto the hinged flap on top much as we do with our design. There were no electronic controls and alarms. Cycling was controlled by regulating the leak out of the plastic bag under the flap. When the bag emptied, the magnet lowered and opened the main valve, allowing inspiration until the bag had filled enough to again lift the magnet from the valve, which would then shut until the bag was empty again

The device on the right used the "flick over" rocker from a light switch as a main switch which opened and closed a piece of tubing to allow gas flow. Inflation pressure was varied by altering tension in springs rather than by using weights, while controlled gas leak was still used to control cycling.

Both these devices split the inlet air, from the vacuum cleaner, to both the patient and the control bag. The expansion of the bag triggered the main valve that stopped the flow of air and allowed expiration.

The inspiratory and expiratory phases of the wooden polio ventilator

Above is a more functional diagram of one of the “Polio” ventilators. These devices seem incredibly crude by today’s standards. Even with the most basic of control systems and electrical valves, a far more sophisticated and reliable system can be constructed today. The people that designed and built these early ventilators were very inventive, brave and capable. They saw the need for ventilators during the polio epidemic and did whatever was required, in order to supply them. Although these units seem crude, they, and others like them saved many lives that would have been lost.

These early ventilators were followed by many more, for both adults and infants. "Home made" ventilators of all shapes and sizes were used for another thirty years at the Royal Victoria Infirmary.




In America, the polio epidemic also caused a large demand for ventilators. There was more demand than could be supplied by the existing stock of "iron lung" negative pressure ventilators.

An Iron Lung ward filled with polio patients. 1953
Rancho Los Amigos Hospital, Downey California

During the height of the polio epidemic years, the iron lung became such a crucial part of treatment that Philip Drinker and Edgar L. Roy offered instructions for building a makeshift emergency ventilator for cases of life-threatening paralysis. Although this emergency version of an iron lung was only intended for use until a board-approved version arrived, it was functional enough to save lives.

Image of an emergency ventilator, from the article by Drinker and Roy.

In contrast to the original, professionally crafted iron lung of 1929, Drinker and Roy employed common household and conveniently available hardware store materials in their emergency respirator. The materials included a car inner tube for a rubber collar, a common vacuum pump to provide pressure, a six-inch square piece of double-thick glass, a piece of sole leather to serve as the valve, a glass U-tube with colored water to show pressure, and several pieces of spruce wood. Drinker and Roy provided detailed construction plans and clearly indicated that it was an emergency respirator that could only accommodate small children and was not meant to replace the standard-size iron lung. Nonetheless, they fully supported its use in emergency situations

Assembly diagram




You can see these and more at :

The Brian Welsh Memorial Museum of Anaesthesia



Thursday, January 17, 2008

Larry Brilliant on Bird Flu

Here is a video on Bird Flu from Larry Brilliant.
It is about 55 minutes long.

Larry Brilliant is an M.D., M.P.H. board-certified in preventive medicine and public health, and a former associate professor of Epidemiology and International Health Planning at the University of Michigan. After studying religion in a Himalayan monastery, he joined WHO in 1973 as a medical officer and helped manage the WHO smallpox eradication program in South Asia. He was a staff member of the WHO Global Commission to Certify Smallpox Eradicated and served as the last WHO medical officer to visit Iran in search of hidden smallpox.
More Info on Larry
What more can I add, the name says it all.

Larry has a very balanced look at the whole issue of bird flu and pandemics. He says that Pandemics are a low probability high impact issue. The probability is low in any given year but over a longer term approaches certainty. He has a very interesting take on people who are worried about catastrophe and people who want to ignore the issue. He calls them "Chicken Little" and "Ostriches" (both birds).





Here is another article he has written.

Monday, January 7, 2008

Some Short Pandemic Info Videos from Youtube

Any Community That Fails to Prepare

U.S. Secretary of Health and Human Services Michael Leavitt comments on the need for all communities to prepare for pandemic in this excerpt from his interview with Charlie Rose that aired on Feb. 14, 2007.



How Does a Pandemic Start?

Dr. Gregory Poland, founder and head of The Vaccine Research Group at the Mayo Clinic discusses how pandemics start and why H5N1 is on track to spark the next pandemic in this excerpt from the BBC Horizon show "Five Things You Need to Know About Pandemic."




Pandemics Happen


U.S. Secretary of Health and Human Services Michael Leavitt addresses the fact that pandemics have happened throughout history in this excerpt from his interview with Charlie Rose that aired on Feb. 14, 2007.



Pandemic Is Hard to Talk About
U.S. Secretary of Health and Human Services Michael Leavitt explains why pandemic is a difficult topic of discussion in this excerpt from his interview with Charlie Rose that aired on Feb. 14, 2007.



Pandemic Preparation Is Good for Any Emergency

U.S. Secretary of Health and Human Services Michael Leavitt explains that preparations for pandemic will serve communities well in the event of other types of emergencies in this excerpt from his interview with Charlie Rose that aired on Feb. 14, 2007.




Preparation Saves Lives

U.S. Secretary of Health and Human Services Michael Leavitt comments on the the fact that pandemics are unlike any other disaster known to humankind in this excerpt from his interview with Charlie Rose that aired on Feb. 14, 2007.



Two Key Pandemic Differences

U.S. Secretary of Health and Human Services Michael Leavitt discusses the two key differences between pandemic and other natural disasters in this excerpt from his interview with Charlie Rose that aired on Feb. 14, 2007.



Why Kids Are at Most Risk During Pandemic

Dr. Gregory Poland, founder and head of The Vaccine Research Group at the Mayo Clinic discusses why children are at the most risk of infection and death during a pandemic in this excerpt from the BBC Horizon show "Five Things You Need to Know About Pandemic."

Sunday, January 6, 2008

The Ventilator is a Lifeboat

The Pandemic Ventilator Project is an effort to try to supply enough ventilators to fill the needs in a pandemic. The original prototype, which you can see elsewhere on this blog is a very basic unit that can be constructed of commonly available materials. It is not a sophisticated design, but with more refinement may be able to provide a very basic level of support.

Lately we have been working on a second prototype. This one we call Vinnie. If you look at my original proposal I had hoped that we might eventually have a more capable unit to offer as well. It looks as if Vinnie may be that more capable unit. We have gone over what we believe is possible to achieve with Vinnie and compared it to the AARC guidelines for mass casualty care, and we hope we can meet these specifications.

The original unit is designed to be built with commonly available components that are expected to be available even with the economic and transportation disruptions that may occur in a pandemic. In order to achieve a design that could encompass the AARC guidelines however, we needed to have more design flexibility. Many of the components in Vinnie are still commonly available components, but some key control components are not commonly available and may have to be custom made. We have made every effort to keep these custom components at as low a cost as possible. Due to this change, it would be required to stockpile some components ahead of time to ensure availability.

Now about the lifeboat story and how it relates. In the early days of seagoing vessels, it was known that travel by ship was a dangerous activity that passengers did not always survive. There was often little that could be done to save the passengers if a ship sank even if they had enough lifeboats, because no one knew the ship had sank and so no one would go to rescue. Some ships had enough lifeboats and others did not. There was little regulation or enforcement. Many ships did not carry enough lifeboats because the owners thought they were ineffective, or the ship was so rugged it could not sink, or they were just too expensive to stockpile.

This changed after the Titanic sinking. After the Titanic sinking, ships were required to have adequate lifeboats and radio communication ability. The regulation changes were not made because no major sinking and loss of life had ever occurred before, but it was because it was then realized that technology had improved so much that it was possible to save a lot more lives than previously.

The Spanish flu of 1918 killed an estimated 50 million worldwide. There was not a whole lot that 1918 technology could do to save the victims. By mid century medical technology had improved considerably. The Asian flu of 1957 and the Hong Kong Flu of 1968 were mild compared to the 1918 pandemic so the loss of life was also much lower. Now with the H5N1 virus, we face the possibility of a severe pandemic similar to the 1918 one. This time however, there is much that modern medical technology can do to save lives. Knowledgeable tracking systems, quarantines and vaccine deployment may reduce the impact considerably. We also have a far greater capability to treat those that are infected.

One of the tools required to treat the infected is a ventilator. Unfortunately, many people say we do not need to have a very large stockpile of ventilators because they believe they would be ineffective, or the vaccines will be so good we will not need them, or they are just too expensive too stockpile.

Having a stockpile of ventilators is like having a lifeboat. Technology has changed. We can save the lives if we want to.


AARC Standard for Mass Casualty Ventilators
Lifeboat Standards