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Thursday, March 5, 2020

How lethal is Covid-19 and will additional ventilators really help?

I wanted to do a little number crunching based on publicly available information and some limited analysis (as much as anyone can make) assuming that there are still many unknowns with this disease strain and how things will actually play out.

Did you notice?  They never seem to actually say how many people will die on the news. They just give percentages with strange acronyms and say that it is either much worse than the seasonal flu or not nearly as bad as the seasonal flu.

A lot of this information  I used was obtained from the published academic paper titled:
Potential Intensive Care unit Ventilator Demand/Capacity Mismatch due to Novel Swine-Origin H1N1 in Canada

If you want to see it for yourself.  It is open access and located at:
DOI 10.1155/2009/808209 
Most of the stats pertaining to this pandemic are gleaned from various news sources I have read.

This particular academic paper was written in the wake of the 2009 H1N1 (swine flu) pandemic that thankfully turned out to be extremely mild.  I remember when things looked bad then, everyone said that we were so foolish not to have foreseen such a problem with ventilator shortages but (trust them) it would all be fixed later.  I am not really sure how many emergency ventilators have actually been made available since then.  It seems to be secret and is not published data.  Even the writers of this paper could not get exact confirmed numbers.  I will use the estimated number from this paper for my calculations.  These numbers are from Canada, but I will assume the percentages are similar in other advanced western nations such as the USA.  They might actually be better elsewhere or they could be worse.

Now this paper makes some assumptions for a flu pandemic that are not the same as the COVID-19 we have now.  They assume that there will be a vaccine, which is not the case now.  They assume a need for ventilators in a bad flu pandemic at a rate of 0.4% of the population.  The numbers I have seen for COVID-19 are about 4%.  (10 times more)  The paper assumes different attack rates of up to 40%.  The numbers I have seen for COVID-19 based on Wuhan experience are from 30% to 70%.  This apparently is much worse than even the most lethal scenario they imagined.

Anyway, the paper says there are about 8.7 mechanically ventilated beds per 100,000 population.  this would work out to roughly 3000 for Canada, so you extrapolate to about 30,000 for the USA.

Now I keep hearing that the published numbers from WHO for death rates are almost certainly too high because of the way the COVID-19 stats are collected.  So let's de-rate them and assume that only 1% of sick people need a ventilator instead of 4% and also assume the minimum published attack rate of 30%.  I have to assume some length of time the pandemic is active, so I will also assume a 100-day pandemic and that each patient needs on average 10 days of ventilation.  This would mean each ventilator could be used 10 times.  I am also assuming an even distribution.  Now the real distribution will actually have a bell-shaped curve and so that would actually make things worse than my numbers due to higher peak demand.  So I think this calculation could be actually considered a too overly conservative estimate if anything.

An attack rate of 30% in a population of 330 million means that 100 million will get sick  If you assume that only 1% will need ventilators and you could actually save everyone that got a ventilator, that would mean that 1 million people would die if they had no access to a ventilator.  If absolutely nobody else in a hospital needed a ventilator at this time other than pandemic patients, the existing 30,000 ventilators could potentially save 300,000 of the 1 million.  Since there are other needs for those ventilators as well, the real number saved will actually be less than that.  Still, that is more than 700,000 excess deaths. Most of the dead will be older persons, so that means a great many of us will lose our parents and grandparents to this pandemic.

Now, no matter how many ventilators are physically available, you still need space, staff, and supplies.  I think space is the smallest problem and I will leave that to others to contemplate.  Some of the supplies could be disinfected, sterilized and reused if say a government or president declared a national emergency that suspended liability risks for such a life-saving measure.

Others say that most of the hospital staff will be off sick so this plan can not work.  That makes no sense at all.  Assuming a 30% attack rate over 10 cycles, at any given time, 95% of staff would not be sick from the pandemic.  If a good testing program was initiated, the ones that actually do get sick could return to work as soon as they are cleared.  Also, most people under age 60 do not get really sick. (Infectious and needing isolation, but not debilitatingly sick.)

So if it does get this bad, does it even make sense to make extra ventilators available?  Well, you can assume that a hospital could treat somewhere between 2 to 3 times the number of patients than their normal rate if they really had to.  They would rearrange and streamline priorities and recruit additional help from retired staff, cancel vacations, use EMS and students and other allied health people they could train for support roles.

Assuming this best case of 3 times normal capacity, you could use an additional 60,000 ventilators.  That is a big job for someone to make that many in such a short time if they do not have them in stock, and nobody seems to be talking about how much reserve they really have.  Too bad nobody had thought of this 10 years ago when we still had time.  (Oh, maybe someone did.)   If all of this worked out you could save 600,000 lives.

On a side note.   Just suppose that someone had reliable information to suspect a terrorist organization had really good plans to kill 600,000 people in your country and that there was a significant possibility this could happen in the next 10 years, how much money would we spend to prevent it?

If someone from any political stripe had had the guts and foresight to buy 60,000 ventilators in the last 10 years, we would be a lot better off.  Even at a full list price of $30,000 per ventilator that is 1.8 billion dollars.  It sounds like a lot but it is less than $6 per person.  That last calculation is probably the most thought-provoking one on this whole page.

Click on the word Comments below 



6 comments:

  1. So surely we can design an open source version.. that would use 3D printed and laser cut parts.. using arduinos or similar.. I can help with some of the design/manufacture of some of the components.. we just need something to start with

    ReplyDelete
  2. Replies
    1. I am working on this project right now at this site, with the help of many engineers.
      https://app.jogl.io/project/121
      You can join there. On Monday they will determine which projects to support and coordinate.

      Delete
  3. positive pressure ventilators have to be more precise then negative pressure ventilators. how quickly can we build an old wooden iron lung?

    ReplyDelete
  4. Thanks, Yes That will work. Not useful for people with COVID symptoms but can be used for other people in the hospital that will be triaged and competing for remaining ventilators. This is what you mean. https://www.youtube.com/watch?v=pvrUQCMa3a8 It is the same principle, Called a Cuirass ventilator. Uses much less space. Issues with CO2 retention in these patients though.

    Cuirass Ventilator the DIY way
    I made a proof of concept of a negative pressure Curiass ventilator. The principle is to lower the pressure over the chest to make you breath in, then you breath out naturally, with a bit of help from the wetsuit squeezing you. I used a 12 litre box and a 12v airbed fan - using the deflate port to create negative pressure. The fan is powered by ...
    www.youtube.com

    I am talking to this guy

    ReplyDelete
  5. I agree with the negative pressure Cuirass approach. Negative pressure is how we are built to breath. I am looking at his as a DIY project for personal emergency use. Why do you not feel that this is viable for COVID-19? A proper protective mask on the patient would reduce their spreading the virus. Additionally if you add a valve and use the pressure side of your pump you end up with a Biphasic Cuirass Ventilator. There is research showing excellent performance as compared to pressure ventilators as well as some key benefits like clearing phlegm easily. When I looked back at the iron lungs and the history I found the Popular Mechanix article and prints for the wooden lung. This BCV seems like an excellent field expedient hack. It could be rock stupid with a manual bellows to start and everything else is a plus..

    ReplyDelete

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