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Multiplexed ventilator using existing equipment

This topic has been archived, and won't accept reply postings.
 freeflyer 21 Mar 2020

I've come across a technique for attaching up to four patients to one ventilator; clearly not standard practice, but better than sending three people home to die. I have few skills that I can use to assess its practicality, but it looks well worth considering to me. I've attempted to post the information on gov.uk where it calls for companies to help with ventilators.

I know there are people on here with a variety of medical and technical skills. Does it look feasible?

https://www.youtube.com/watch?v=uClq978oohY&

 Dr.S at work 21 Mar 2020
In reply to freeflyer:

I've only skipped through the Vid, and I'm sure the caveats are stated in there but:

risk of cross contamination

risk of misconnection of cobbled together componenet set

Each patients lungs are different, and it would be desirable to tailor ventilation to the patient - varying PEEP levels etc, also at different stages of the disease might want to have patients having the ability to trigger breathes and thats confusing for the little computor with 4 attached! Also will need to have multiple monitors to assess resp Fn

Of course in extremis....

(vet anaesthesia rather than quack, but know the broad picture)

In reply to freeflyer:

Mate - you watch some weird sh*t on youtube! But beyond that, you think with doctors like that around, we might be okay. She seems super sensible. I presume in Italy someone must have been trying the same kind of things by now? The way this doctor explains it, it seems quite obvious.

 Dr.S at work 21 Mar 2020
In reply to TobyA:

Hi Toby - certainly I've seen a FB post from italian colleagues linking to something being manufactured in Italy to do the same thing - making the tubing to be less prone to misconnection errors is the easy bit - working out the lung mechanics of connecting 4 patients is harder.

 elsewhere 21 Mar 2020
In reply to Dr.S at work:

> (vet anaesthesia rather than quack, but know the broad picture)

Get this man/woman into hospital! It's only a change from n to n+1 species.

Just don't give the patient a sugar cube.

 wercat 21 Mar 2020
In reply to elsewhere:

trying this did not end well in Royston Vasey if anyone remembers the "special weekend" in the guest house

Post edited at 11:54
 Deleted bagger 21 Mar 2020
In reply to Dr.S at work:

Unless you had closed circuit suction, suctioning one patient would be, er.......interesting.

In reply to freeflyer:

I read today that a Spanish team have produced a design for 3d printing ventilators, which they intend to release publically.

 Dr.S at work 21 Mar 2020
In reply to john arran:

As you can imagine, quite a few folk are doing similar things.

 Dr.S at work 21 Mar 2020
In reply to Deleted bagger:

Ha! Yes, lot of fun - maybe you just get 4 airway caths hooked up to the suction unit at the same time, 4 crack ITU nurses, 3,2,1,Go!

 Dr.S at work 21 Mar 2020
In reply to wercat:

I think most things did not end well in Royston Vasey - but you cant really blame Mr Chinery - he was cursed by the Monkeys nuts after all!

 Nicola 21 Mar 2020
In reply to freeflyer:

The Institute for Physics and Engineering in Medicine have opened their online community to non members. Your input on discussion re ventilators would be welcome, I’m sure. https://www.ipem.ac.uk/ConferencesEvents/ForthcomingConferences.aspx

 freeflyer 21 Mar 2020
In reply to Nicola:

Thanks, I've emailed them!

In reply to freeflyer:

I do wish people (in general) would stop banging on about the 1 vent for 4 + people thing. Ventilator number is NOT the limiting factor yet, or likely to be anytime soon. Experienced staff (fit and well staff who are not burnt out) is the main limitation, along with inadequate quarantining allowing rampant community spread. Most reasonably sized hospitals can probably drum up a couple of hundred ventilators easily enough.

OP, thanks for posting but please anyone reading this thread - don't go talking about this as a workable thing to your mates.

It WILL NOT WORK in people. It does work in simulation models where you are ventilating bags.

The issue with people is they come in all sorts of shapes and sizes; the coronavirus has variable effects on the lungs. This means, in effect, four different sets of balloons of varying size and stiffness.

So as the ventilator pushes air, it will follow the path of least resistance. The patient with the best lungs will explode, and the one with the stiffest lungs will get nothing. I'm only partially joking here. You can neither volume control nor pressure control effectively, and the volume assured pressure regulated (or vice versa) software algorithms can't function when more than one set of lungs is involved. 

So, nice thoughts and 10/10 for lateral thinking, but unusable. Sorry.

B

(Consultant respiratory physician)

 Nicola 22 Mar 2020
In reply to ben b:

Let’s channel the energy people are showing towards contributing to fighting this virus. https://www.linkedin.com/posts/impacting-business-by-design-ibbd_covid19-testing-device-activity-6646420738737750016-DM6b

In reply to Nicola:

Very happy to see lots of energy going in to solutions - it’s just this isn’t one of them. For everyone, staying at home (not mixing with others) is the biggest thing you can do to help. 

b

In reply to ben b:

> Very happy to see lots of energy going in to solutions - it’s just this isn’t one of them. For everyone, staying at home (not mixing with others) is the biggest thing you can do to help. 

> b

My wife (NHS staff) said the exact same thing about the ventilators. They just don't have the staff. 

Please, just stay at home. 

 Nicola 22 Mar 2020
In reply to ben b:

Telling people to stay at home isn’t working. People are heading to the hills in their masses. Human nature is often to be helpful. Let’s motivate people to use their time (at home, in isolation) for positive good. Using the forums that are being setup to generate solutions to problems. Those who aren’t key workers can use their creativity and intellect to contribute. Let’s innovate. Let’s create. Let’s encourage discussion so that facts are identified from all the fake science being shared on social media. 

Ok, sorry for the rant. Not meant at anyone in particular. I’ll get back in my box now.  

 Deleted bagger 22 Mar 2020
In reply to Stuart (aka brt):

Mornin' all, ahead of the government getting its emergency powers bill passed I've been accepted back on the nursing professional register. Crap!!!!! Back I go.😷

 lorentz 22 Mar 2020
In reply to wercat:

> trying this did not end well in Royston Vasey if anyone remembers the "special weekend" in the guest house

The dom with the switch carks it... 😁 Darkest of the dark comedy. Brilliant! 

 mik82 22 Mar 2020
In reply to Nicola:

People will need to be forced to stay at home.

Once people are on ventilators with all their lung membranes damaged and leaking fluid it's too late - their risk of death is going to be in the order of 40% and if they survive, they will take months-years to recover, if at all.

Discussion about innovation is great, but the innovations that are needed are a vaccine and/or an effective anti-viral medication. There are plenty of simple designs for ventilators that could be mass produced, but what's the point when there'll be no-one to staff them anyway, and so may survivors are going to have horrible lives, chronically breathless. Better they don't end up in that situation in the first place.

Post edited at 17:46
 Dr.S at work 22 Mar 2020
In reply to mik82:

amen to that

In reply to freeflyer:

This won't help but I'd love to corrupt this thread title to something a little more adult let's just say.....

It would be pulled though so I won't bother..

 Nicola 23 Mar 2020
In reply to mik82:

In these difficult times, I will politely agree to disagree without further argument from me.  

In reply to ben b:

Hi Ben,

If you do read this I hope that means you're getting a bit of a break from your work!

I thought your post was fascinating and it sort of closed the issue for me - if you in your job couldn't see how it would work, then who could? I've been getting into the bad habit of reading the New York Times before I go to bed - bad habit because it seems to be generally terrifying at the moment - and read an article last night that said:

"With ventilators in short supply, NewYork-Presbyterian Hospital, one of the city’s largest systems, has begun using one machine to help multiple patients at a time, a virtually unheard-of move, a spokeswoman said."

https://www.nytimes.com/2020/03/25/nyregion/nyc-coronavirus-hospitals.html

Do you think they've been forced to try something like this video shows? I do remember that the doctor in the video said a colleague had done it in Las Vegas after their hospital had taken lots of casualties from the mass shooting there last year (?).

Sorry - I'm not trying to make any point at all, well beyond maybe this is showing what a desperate position some NYC hospitals have been put in.

Best wishes to you at what must be a very difficult time.

In reply to TobyA:

Thanks TobyA - enjoying an afternoon off -  but in isolation from the family, which is the harder bit.

I think the machines shown are older, but show a couple of different modes of ventilation - one is in APRV mode, which is  a pressure release vent which holds air in the lungs for a longer period and then lets it out briefly. These can't be used in spontaneously breathing patients and need drug-induced sedation and paralysis to work.

The machines that are being used on more than one patient are, as far as I can tell, CPAP machines - these are a pretty basic in what they can do. CPAP machines are also used for obstructive sleep apnoea, they just blow at pretty much a constant pressure without any variation to match patient breathing patterns. They only work in patients who are spontaneously breathing. You could, in an emergency, run two patients on one - I suspect if you dialled up +10 on the machine only one of them would get +10 though (the other probably gets more, I think the number would be the minimum achieved in either patient). But in NY that may be all that is available at times. The other trouble with CPAP is that the majority of home CPAP machines use vented masks - these probably spray virus laden moist air into the room out of the mask vents, which is clearly suboptimal - at least until such times as everyone has coronavirus at which point it's only important in reducing viral load exposure to medical staff  rather than infecting other patients. 

Basically, the US in particular is at or near healthcare meltdown in multiple areas - I think in the UK that PPE and well staff to care for the patients are still more pressing than the number of ventilators at the moment and hopefully over the next week or two, by which time we may have more ventilator capacity anyway.

Hope that makes sense 

b

 Flinticus 29 Mar 2020
In reply to ben b:

Thanks for taking time out to reply. Its great to hear from someone who knows.

Sorry to hear who must self-isolate fron your family.  Take care and, as they say in the US, thanks for your service 

 Dr.S at work 29 Mar 2020
In reply to ben b:

On the multiplexed thing ASA (Thats American Society of Anaesthesiologists, not the advertising guys...) have come out pretty clearly:

"Even in ideal circumstances, ventilating a single patient with ARDS and nonhomogenous lung disease is difficult and is associated with a 40%‐60% mortality rate. Attempting to ventilate multiple patients with COVID‐19, given the issues described here, could lead to poor outcomes and high mortality rates for all patients cohorted. In accordance with the exceedingly difficult, but not uncommon, triage decisions often made in medical crises, it is better to purpose the ventilator to the patient most likely to benefit than fail to prevent, or even cause, the demise of multiple patients."

 Aly 30 Mar 2020
In reply to Dr.S at work:

Whilst I’m skeptical that lack of ventilators rather than ICU staff/experience will be the limiting factor it might be something we need to do.  There’s an interesting article on EMCrit here regarding that statement with references to a few of the setups people have been trialing.  Pressure-control will be key (as volume-control modes would have fairly major risks) which, with appropriate one-way valves and peep valves could be made to work (although I’m certainly not an expert).

https://emcrit.org/pulmcrit/pulmcrit-wee-why-the-sccm-aarc-asa-apsf-aacn-chest-joint-statement-on-split-ventilators-is-wrong/

In reply to Aly:

Interesting - thanks for the link. But the more compliant lungs still get more expansion per cmH2O of pressure - I think PCV can only work if there is some way of managing the flow down an individual's circuit to reduce hyperinflation and barotrauma +/- pneumothorax risk. Which puts us back at the one vent per patient again.


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