[theturingnerd]

(physician here) Vents can be quite tricky to get right; primarily because as disease progression continues on many things change. We are always trying to balance the deleterious effects of the intervention (in this case, the vent) with the goals of care.

What most people don't know is that vents cause a lot of injuries on their own. (See ARDS). Hypoxemic respiratory failure is serious stuff, and it's almost always not the only insult we're dealing with. So, it's about balance.

In the feedback loop is a lot of things. Certainly, oxygen saturation is a core measure, but we are also thinking about things like hypercapnia (and acidosis); overall perfusion status (blood circulation); infection management; etc.

Gas exchange is important, but there are a lot of things that have to go right for the lungs to take oxygen in, get it into the right transport, and get carbon dioxide back out. You can over-optimize for any of those at the expense of the other (see: hypercapnia).

In short, it's complex and there isn't a solid formula that will work for every patient. It's actually the subject of a lot of debate on details (some of it quite passionate in our Critical care / pulmonology community). This is why we call it PRACTICING medicine ;)

[djsumdog]

What do you think are the risks of cross contamination in this setup (let's say, just for 2 people sharing one unit)? She mentions how, in a situation where you'd have to use this, they'd have the same infection. What if they have different secondary infections or different types of pneumonia?

The example of the Vegas disaster is different because they were all gunshot victims; they were healthy, but wounded. I hope we would never need to see if these would be effective.

[markmichalski]

MD here. There is an inhalation and exhalation tube for each patient; the exhalation tubes would be in continuity using the described configuration. However, at least for part of the transmission route, viral particles would have to move against flow. So there is likely some cross-contamination.

All that being said in the situation where this is deployed I think it would be a risk most providers would take.

[gdubs]

I can't even figure out what my HVAC vents do, or how not to mess up my entire heating and cooling situation – so I leave them alone.

Utter respect for you and all the other medical professionals who are having to adapt and deal with this unfolding situation. Many thanks for what you do.

[lee]

I've got a really naive/dumb question for you.

Could you use a CPAP machine as a poor man's ventilator? Would it be better than nothing?

There's definitely a ton of CPAP machines out there.

[etrevino]

A doctor asked me that-- a fact I found disturbing, because shouldn't he know-- so I did some research. And I found out that the machine would spread the virus everywhere with the outgassing (I'm not sure if that's the right term).

[fifteenforty]

There are way too many different brands and types of CPAP machine for anyone to make any sort of sensible comment here. They aren’t all the same. Some of them do have a backup rate that could be used to mandatory mechanical ventilation, but that can’t be readily altered at the bedside in the models I have used. The use-case is radically different to the ICU.

[forkexec]

IANAMDOMP. After respiratory therapists, it seems like perfusionists will be stretched thin too because there are so few of them globally. I would predict lots of ECMOs and long waiting lists for lung transplants in the next few months, but also lots of poor outcomes for COVID patients with preexisting cardiopulmonary issues. I just hope young and middle-aged people take it seriously and don't avoidably waste healthcare resources through irresponsible behavior.

[bitexploder]

Thanks for this explanation.