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'Pandemic ventilator' could offer solution in potential 'worst case' scenario

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Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#101

Post by Medicalidiot »

mrfusion wrote: post #95
baxtr wrote: post #54

Earlier quoted context omitted.

At this stage it is totally unclear if Chloroquine will work. Unfortunately. Because, all the work published so far has not been produced through double-blind studies in randomized trials.

My god man, totally unclear? I bet you could find five or more recent peer reviewed studies on it working quite well. You realize most science isn’t double blind, right? I’ll grant you thats it a gold standard for long term drug use but saying “totally unclear it will work” is absurd. And we still do useful work relying on simple correlations, r values, peer review. We have all that now supporting some of these drugs…

>You realize most science isn’t double blind, right?

That's nice, but most science isn't reproducible at scale. We need to do a drug trial for SARS-CoV-2 because we need to 1)establish efficacy and 2) establish safety for this drug in this disease. There are a significant amount of adverse drug effects in individual infectious diseases. Jarisch–Herxheimer reaction when treating syphilis, epstein-Barr mononucleosis and penicillin; Reye syndrome with Aspirin and influenza. The list is long here. We want the most vetted research possible because even if the chance of death is less than half a percent, half a percent of what seems like is going to be over a million is going to be in the tens of thousands here.

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#102

Post by jariel »

war1025 wrote: post #41
pmoleri wrote: post #33

Earlier quoted context omitted.

Interesting, so a little improvement there may lead to less ICU beds and sorter overall time at the hospital. Wonder if that's possible.

My understanding is that's the hope for Chloroquine and the other drugs being rolled out en-masse this week. They have shown enough promise by various limited trials that we are rolling them out nation-wide to see if they actually do help reduce the severity of the virus. If they do, then less hospitalization, and less ICU / ventilator needs. If Chloroquine doesn't end up working, basically we need to find something…

" The only scalable way around that is to find a treatment that significantly lowers the need for hospitalization."

This isn't quite true.

Taiwan, Singapore and S. Korea have not 'shut-down' their economy, and they have tamed the problem.

Massive and widespread testing, assertive isolation and tracking of individuals who test positive can work on some level.

Combined with some other things like maybe keeping 'big gatherings' or 'social gatherings down', requiring people to wear masks on trains, busses, airplanes - we may be able to reasonably suppress Corona without a medical discovery.

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#103

Post by toolbox »

mdturnerphys wrote: post #66
enchiridion wrote: post #55

Earlier quoted context omitted.

This is a really off the wall idea that might actually work. Can anybody get this idea some lift? Definitely a way for Boeing to get some desperately needed good PR.

I'll ping my friend who's been at Boeing for 25 years about it in the morning. Anyone know an MD who could review the idea?

Hello! I'm just a medical student myself, but here's my take on this:

Your lungs operate on the principle of differential pressure. During normal breathing, hen the pressure inside your lungs becomes less than that of the surrounding atmosphere, air rushes in to normalize and fill it until they are again equal pressures. Gradually increasing or decreasing the pressure of the atmosphere around you (as on a plane or while diving) does not change the physical difficulty of breathing. It may slightly alter the diffusion coefficients of gasses passing through the membranes in your lungs, but this effect is mild at the pressures you could attain in an aircraft hull (and toxic at higher pressures! [0]).

For this reason, you'll notice in images of people in iron lungs, their heads are outside of the device. This allows those who cannot create negative pressure (due to damaged or paralyzed diaphragms or ribcage muscles) to follow a different path. The pressure outside of their chest becomes lower than that experienced in their lungs, forcing an expansion; in order to breath out, the pressure in the chamber is increased. In an aircraft hull a person's lungs/trachea/mouth would be exposed to the same pressure as their chests.

This of course does bring up the very valid question: What happened to all of the iron lungs after the decline of Polio?

[0] https://en.wikipedia.org/wiki/Nitrogen_narcosis

EDIT: Oh I realize I didn't fully discuss the possibility of using a plane as a hyperbaric chamber [1]. The constraints around this concept also rule it somewhere outside of what I would consider feasible. Aircraft typically use bottled oxygen (I believe the 737M does) or a chemical generator, neither of which can produce continuous oxygen or fill the entire plane with it to high levels [2]. If you were able to outfit patients with individual tanks (which would also have to accommodate for increased pressure), the gains seem mild at best compared to 100% O2 in a hospital setting. Fick's Law for the membranes in your lungs is roughly

Rate of diffusion = (Area * Solubility of gas * concentration gradient) / (membrane thickness * sqrt(molecular weight of solute))

The factor that increasing pressure would modify is the solubility of the gas, which according to Henry's Law [4] is directly proportional to pressure. At absolute best (100% O2 on the plane at 2atm), you could expect to get 2x improvement in blood oxygen saturation. Unfortunately I don't believe the breathing issues that are being described can be overcome by this strategy. It's an incredibly creative concept though!

[1] https://en.wikipedia.org/wiki/Hyperbaric_medicine

[2] https://en.wikipedia.org/wiki/Emergency_oxygen_system

[3] https://clinicalgate.com/gas-exchange-between-air-and-blood-...

[4] https://en.wikipedia.org/wiki/Henry%27s_law

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#104

Post by mattkrause »

mrfusion wrote: post #95
baxtr wrote: post #54

Earlier quoted context omitted.

At this stage it is totally unclear if Chloroquine will work. Unfortunately. Because, all the work published so far has not been produced through double-blind studies in randomized trials.

My god man, totally unclear? I bet you could find five or more recent peer reviewed studies on it working quite well. You realize most science isn’t double blind, right? I’ll grant you thats it a gold standard for long term drug use but saying “totally unclear it will work” is absurd. And we still do useful work relying on simple correlations, r values, peer review. We have all that now supporting some of these drugs…

I'll take that bet.

Here's a recent review: https://www.sciencedirect.com/science/article/pii/S088394412...

They find hundreds of relevant-sounding papers, registered trials, and guidelines, but almost no data beyond one in vitro study to back it up. That one study is promising--and it'll be great to see what the trials show--but the road from "works in a dish" to "drugs for all" is a long, bumpy one at the best of times.

We need to do this right so that if it works, we know that it works, and if it doesn't, we can make informed decisions to do something else.

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#105

Post by dathinab »

Fargren wrote: post #98
vermilingua wrote: post #92

Earlier quoted context omitted.

If this is true, the death toll of Covid-19 is going to be a lot worse than currently indicated, is that right? The complications of ventilators and whatever lasting damage is caused by the disease itself; will be killing a significant portion of the recovered population, will it not?

Most mortality estimates and forecasts include only deaths directly attributable to the virus. There are many indirect deaths that will be caused by it. Long term lung damage is one of the ways this will happen, probably among the most delayed. Many more deaths will happen because hospitals that are operating at capacity won't have the resources to prevent other deaths that they normally stop, or will have to stop no…

Actually Italy counts everyone who dies who has COVID19 as a COVID19 death. This does not include future death by long term after effects but it includes more then what e.g. was included in China, which is part of why the death rate is so much higher in Italy (the other part is in average people are much older in Italy then China).

Also put that in context with the fact that Italy reported that the majority of death is with people which have preexisting conditions/other illnesses.

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#106

Post by dorfsmay »

dschuler wrote: post #51
totalZero wrote: post #45

Earlier quoted context omitted.

It's too bad we can't put sick people in an airplane, put oxygen masks on them, shut the door, and pressurize the cabin. Like a hospital, but at the airport.

Very creative idea, I wouldn’t have thought of that. So standard pressure at sea level is 29.92inHg, a 737 MAX can sustain 39k ft altitude indefinitely I suppose, where the exterior air pressure would be 7.66inHg. The cabin is normally pressurized to the equivalent of 8k ft, giving 26.63inHg. The fuselage could withstand a pressure differential of 26.63inHg - 7.66inHg = 18.97inHg (at least, possibly more). That’s 63%…

What create the air pressure in an airplane? Is it external air speed? Or compression from the engines?

If the latter, how does it work on airplanes with needless engines?

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#107

Post by raducu »

totalZero wrote: post #45
thornjm wrote: post #35

Earlier quoted context omitted.

Med student here - so I know some of the theory only. The most relevant "law" is Fick's Law of Diffusion ( https://d2jmvrsizmvf4x.cloudfront.net/CTU792sKR2evT2ezizQp_f... ). Doctors can increase diffusion by increasing the partial pressure of oxygen. In a diffuse infection a patient begins to lose both lung area (due to shunting) and the thickness of the diffusion barrier increases (due to inflammation). To help over…

It's too bad we can't put sick people in an airplane, put oxygen masks on them, shut the door, and pressurize the cabin. Like a hospital, but at the airport.

Aren't the lungs re-inflated because of the positive pressure differential?

If your whole body is inside, there is no pressure diferential to inflate your lungs.

Am I missing something?

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#108

Post by tcbawo »

jariel wrote: post #102
war1025 wrote: post #41

Earlier quoted context omitted.

My understanding is that's the hope for Chloroquine and the other drugs being rolled out en-masse this week. They have shown enough promise by various limited trials that we are rolling them out nation-wide to see if they actually do help reduce the severity of the virus. If they do, then less hospitalization, and less ICU / ventilator needs. If Chloroquine doesn't end up working, basically we need to find something…

" The only scalable way around that is to find a treatment that significantly lowers the need for hospitalization." This isn't quite true. Taiwan, Singapore and S. Korea have not 'shut-down' their economy, and they have tamed the problem. Massive and widespread testing, assertive isolation and tracking of individuals who test positive can work on some level. Combined with some other things like maybe keeping 'big gat…

Published literature suggests that surgical masks reduce the amount of escaped virus by 3x. If we can make enough masks, we need everyone to start wearing them. They should be handing them out at grocery stores!

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#109

Post by dschuler »

dorfsmay wrote: post #106
dschuler wrote: post #51

Earlier quoted context omitted.

Very creative idea, I wouldn’t have thought of that. So standard pressure at sea level is 29.92inHg, a 737 MAX can sustain 39k ft altitude indefinitely I suppose, where the exterior air pressure would be 7.66inHg. The cabin is normally pressurized to the equivalent of 8k ft, giving 26.63inHg. The fuselage could withstand a pressure differential of 26.63inHg - 7.66inHg = 18.97inHg (at least, possibly more). That’s 63%…

What create the air pressure in an airplane? Is it external air speed? Or compression from the engines? If the latter, how does it work on airplanes with needless engines?

I don't know much about it, but I think it's usually provided by pressurized bleed air from the engines.

There are cabin pressurization test carts for use on the ground, as well as start carts to provide bleed air for starting engines, and bleed air in turn can supply cabin pressurization in flight, although this probably requires some rigging on the ground.

Interestingly, they switched to electric compressors for the 787 [0] because those no longer provide bleed air from/to each engine to simplify the plumbing.

[0] https://aerosavvy.com/aircraft-pressurization/

Re: 'Pandemic ventilator' could offer solution in potential 'worst case' scenario

#110

Post by war1025 »

baxtr wrote: post #54
war1025 wrote: post #41

Earlier quoted context omitted.

My understanding is that's the hope for Chloroquine and the other drugs being rolled out en-masse this week. They have shown enough promise by various limited trials that we are rolling them out nation-wide to see if they actually do help reduce the severity of the virus. If they do, then less hospitalization, and less ICU / ventilator needs. If Chloroquine doesn't end up working, basically we need to find something…

At this stage it is totally unclear if Chloroquine will work. Unfortunately. Because, all the work published so far has not been produced through double-blind studies in randomized trials.

My understanding is that it's part of the official Chinese treatment regimen. That seems like good enough authority to me given they've been through the worst of it so far.
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