We all know that COVID-19 is stressing our health system to the limit. One of the most important machines in this battle is the ventilator. Vents are critical for patients experiencing the worst symptoms of respiratory distress from the virus. Most of the numbers predict that hospitals won’t have enough ventilators to keep up with the needs during the height of the pandemic.
Now anyone with a walkman or iPod can tell you what they do when there is one music device and two people who want to listen: Plug in a Y-connector. Wouldn’t it be great if you could do the same thing with a medical ventilator? It turns out you can – – with some important caveats.
Way back in 2006, [Greg Neyman, MD and Charlene Babcock, MD] connected four simulated patients to a single ventilator. Ventilators connect to a patient with two tubes – an inflow and an exhaust. Using common parts available in just about any hospital, the doctors installed “T-tube” splitters on the inflow and exhaust tubes. They tested this with lung simulators and found that the system worked.
There were some important considerations though. The patients must be medically paralyzed, and have similar lung capacity — you couldn’t mix an adult and a child. The tubing length for each patient needs to be the same as well. The suggestion is to place the patients in a star pattern with the ventilator at the center of the star.
[Dr. Charlene Babcock] explains the whole setup in the video after the break.
Interestingly enough, this technique went from feasibility study to reality during the Las Vegas shooting a few years ago. There were more patients than ventilators, so emergency room doctors employed the technique to keep patients alive while equipment was brought in from outside hospitals. It worked — saving lives on that dark day.
The video and technique remind us of Apollo 13 and the CO2 scrubber modifications. Whatever it takes to keep people alive. We’ve already started looking into open source ventilators, but it’s good to see that medical professionals have been working on this problem for years.
59 thoughts on “Saving 4 Patients With Just 1 Ventilator”
I guess you can mix different lung capacies by adding a valve just before each patient.
The problem is that the system is forcing a measured volume of air into the lungs of the patient. When 1 patient has significantly lower lung capacity, this means the resistance to getting air in is likely to be significantly different. This means that one person could get too much volume and/or pressure, while the other doesn’t get anything. There must be at least some balance
+10 This nurse spells out the problem exactly as you stated – https://www.youtube.com/watch?v=pc9RV-5iK04
‘The problem is that the system is forcing a measured volume of air into the lungs of the patient.’
You are referring to volume-controlled ventilation, which is outdated and should be avoided. The most common ventilation mode is pressure-controlled ventilation, which means the ventilator forces oxygenated air until a preset pressure (minimum= PEEP; maximum usually set at 30mmHg) is reached.
This can easily be done with a simple bmp sensor and micro connected to a servo operated flap,
If using VCV couldn’t just the diameter or length of the hose be the variable? The smaller patients use larger or longer hoses to compensate for the volume in their circuit. Half the lung capacity, twice the hose.
PEEP is positive end expiratory pressure
I really disagree. Volume controlled ventilation is not out dated. There is a place for it. There is also a place for pressure control ventilation. It all depends on the patients needs. Given to the wrong patient pressure control ventilation cause put the patient in ARDS.
ok, this is not the ideal situation. but the question is: even with an inadequate volume, will the patient benefit? Would it be better to be without ventilatory support?
With electricity we solve that by placing equal resistances in series with each device that are large enough so as to make the difference between the resistance of the actual loads a negligible percentage.
Could not the same method apply here? I suppose with so much resistance you might need a bigger pump. This might be more an idea for making new, multi-user ventilators than it is to stretch out the use of the ones we have. That might not be a bad thing to do though if occasional pandemics are the new norm.
if your supply is a fixed-voltage regulator and all your consumers have consistent linear voltage-dependent behavior (i.e., resistive load), that’s pretty easy, right? but if the supply’s regulation and the demand’s response are more complicated, resonant and/or non-linear, then you’ve got a more difficult problem. you know, like if your supply is controlled by PID. more like impedance-matching than straightforward resistor balancing.
just expanding the electrical analogy, i think.
I bet this is going to save lives.
who needs FDA approval anymore if it seems to work.
In a war zone no one needs FDA
It isn’t a war zone.
How many patients can you save with a leaf blower?
I’m not good in medical speak, but I understand enginurding stuff. I understand 25cm of water pressure.
Leaf blowers and vacuum cleaners can also blow and suck. Industrial screw compressors do so on a much grander scale, a few of them would be enough for a whole hospital. This also centralises conditioning of the air which makes it a lot easier, and for non fda approved ad hoc systems you probably want to assign some people to constantly monitor the system, which is also much easier on a big scale.
Over pressure can be turned into under pressure with a venturi pump.
But as I wrote before, if this is a serious need at the moment, then get some doctors who know what they need, together with a few engineers who know how to build industrial stuff.
It’s not so much just about supplying air at a certain pressure, it’s about delivering a precisely metered volume of warm, moist, sterile air at a controlled flow rate. And then extracting that air at a controlled flow rate.
The fan is the easy bit.
That depends on how many people read the Darwin Award.
Engineers would definitely come in handy.
really just build ventilators. watch this series on what ventilators need to do https://www.youtube.com/watch?v=iP_jN1qAPtI . centrifugal blower, pressure sensor, displacement pump ( eg automotive cvboots on an offset wheel) pressure sensor, arduino, 02 regulator & irrigation solenoid if we wanna get fancy … get onto it guys … if you have italy’s experience your grandma wont get a ventilator because a younger person needs it
Sadly we won’t have enough ventilators. And some of the data in recent lancet article suggests once you are on a ventilator, your chance of survival is less than 10%. Hopefully I’m wrong.. only real hope is dramatically reducing spread…
the PB 840 Vent used in the video is a pretty old machine but an absolute work horse. and about as simple as they come pitty we just replaced and disposed of a bunch of them – 3 months ago we could have had double the amount of ventilators.
Hospitals may need to learn from this pandemic the importance of keeping older equipment, including ventilators, in ready storage. You never know what might happen.
No, this is the USA: the space is needed for the accounts receivable department.
Keeping old stuff around in a hospital is an invitation to disaster. Before long, there will be nobody trained to operate the machines. Components will fail. The old X-ray machine will fall out of calibration and fry patients. Plastics in an artificial kidney will degrade and poison the patient. And so forth, and so on.
That’s what I was thinking a lot of complex equipment may not store well, without regular maintenance and testing to insure i it fit for duty. Not like saving a bunch of old hand tool after the apocalypse. More like and old car will need some reconditioning to be road safe after years of storage. Some components can die of old age deterioration before they are worn out.
This is something the NHS, especially, sorely needs right now!
We’ve got hardly any ventilators in this country. There are a lot of companies that have offered to help with manufacturing more, but this idea could make things even more effective.
Kinda weird/funny that the Puritan Bennet brand was spun off by Tyco as part of a company named — get this — Covidien. It recently got bought by Medtronic, so that Covidien company name isn’t used any more.
AFAIU, they used the technique on trauma patients, similar patients (height & weight) will roughly have the same pulmonary compliance (dv/dp). That assertion is not true for patients suffering from ARDS, which is the worst pulmonary condition covid patients will experience. A preset inspiratory pressure will lead to different tidal volume in each patient that may lead to volutrauma if tidal volume is not monitored for each patient, which it is not in this setup… Not even talking about volume controlled ventilation.
What about an adjustable relief valve? A relief valve base on a ball and a spring, the spring should be adjusted to the patient lung capacity. In fact you might need two of these to prevent pressure loss in the other tube. Place two valves per tube.
The commodity part used in cheap turbo conversions is a radiator cap for a blow off valve. But I don’t suppose those are available in fractional PSI. Could do something like a water trap using pressure of water to lift, but you’d need some anti backflow, don’t know if a marble in a syringe body would do it.
This has been kicking round in my brain the last day or so…. Expedient 20cm H20 (or lower) relief valve, 1 balloon, (generic blow up party balloon) 1 710ml powerade or other tall sports drink bottle… drill/poke multiple holes in the base of the bottle, such that you can blow through it freely, could just cut the whole base out but it will make the bottle more floppy and will splash if knocked. Cut the “globe” off the balloon, giving you about a 5cm long piece of the neck. With the lid off, dangle the neck inside the bottle, pull the rubber ring apart and ease over the screw threads of the bottle neck. Add a few dots of food grade lubrication to the cap threads and carefully screw the lid on over the balloon, taking care not to snag and score the balloon. Attach nipple on bottle lid to hosing with whatever measures you have at hand, hose clamps, stretch tubing, cable ties pulled very tight. invert bottle and tape to upright. Fill with saline, mark bottle, glue/fasten ruler on it, or sewing measure for reference. Test.. valve should blow when water pressure exceeded, should not allow backflow. May work best with a cm or two over the balloon neck length, so probably 5cm/H2O minimum. May work at zero but without a bit of pressure on the balloon neck could suck backwards. Probably has annoying raspberry sounds when doing that, so built in audio alert LOL.
Needs more testing, needs monitored regularly, probably best to tee an empty upright bottle right underneath it, for a water trap in case high negative pressure inverts the balloon valve.
Yes it’s rough and ready might be better than nothing in Darfur or somewhere or when the crap hitting the fan is spread around up to neck level.
Possible alternatives to balloon are fingers from gloves. Other bottles than sport drink bottles may be used if they are tall enough, more rigid than generic PET bottles (Usually the more complex shaped juice or name brand trademark shape cola bottles etc) but then you’ll need to drill the cap for a nipple. Other methods for forming nipple may be to use similar bottle cut in half with cap screwed on, heat small spot in center of cap and blow, or push a pen or pencil into it.
As a former scuba diver seems like we could print some parts and convert a 2nd stage regulator to a ventilator. Just food for thought
A scuba diver would know that the demand valve (“regulator”) *requires* the lungs the pull negative pressure on it to open and supply air. By design, it CAN’T provide air at pressure above ambient, which is what (generally) a ventilator does.
Doesn’t a ventilator assist the patient with both inhalation and exhalation? If so while pressure control is important, so is volume control.
Sorry a nurse is not a doctor, is not an engineer of medical devices. Does anyone here understand these devices must meet stringent standards so as to not cause fires, death, or damage? Ventilator-a-day is getting very old.
So your saying a doctor is smarter than a nurse? Give me a break on your ignorance. A doctor is nothing more than a person with a very good memory. Being a doctor does NOT mean you are smart. All it means is that your able to remember allot of crap. Smarts, is a whole other story. 99% of all medical doctors dont invent jack crap. They just diagnose, treat and prescribe medication. Anyone, who read the same books they read can do the same dam thing.
They are simply a person who takes symptoms and pulls from memory what to do next. Now, if you knew anything about the medical industry you would know that its the nurses that know what to do most of the time far better than the doctor.
You are aware she *is* an emergency room doctor, right? Being female in a medical profession doesn’t mean she’s a nurse.
She well-qualified her demonstration, clearly stating this is off-label, it has not been studied in humans, no studies of cross-contamination, etc. She also said it has been successfully used on humans during the Las Vegas shooting tragedy, when a former student of hers remembered reading her study on this and was able to use this to save lives despite the shortage of ventilators during the emergency.
She saves lives, so I’ll take her “old ventilator-a-day” over your unfounded complaints.
This guy approves, is that a Doctory enough Doctor for you?
She’s a MD, not a nurse. On top of that this was successfully used on people after the Las Vegas shooting
I agree. Everyone thinks its so easy to just make a ventilator. If it was and they were cheap then hospitals would have an abundance. But they dont because they want to atretch out vents life expectancy as long as possible to save money ( not lives). Those old out dated and 90% obsolete PB 840 vents are in many hospitals. Cant even get parts for. So if everyone thinks auto mfg can make them then Wow!!?? Hell i sometimes cant get a part for days/weeks for a repair. And almost all vents are built in europe. Cant see them giving ok to build there vents at fords. But if happens then it will help for future maybe. Big difference in a fault if car dont start versus fault in a lung overpressured. I really hope something somehow can happen tho to help the situation. If all the rt minds and timing happen would be Awesome!!!!
I was looking at hacking together a ventilator from CPAP machines (Google Arduino blog CPAP ventilator) — but turns out they are prescription regulated. Ugh. We need open source medical hardware!
they are prescription regulated for a reason…if you don’t know what you’re doing, you can easily kill the patient.
Someone with experience on another post was saying CPAPs may be required as they are. Possibly for the type of patient that they might ventilate as a precaution when they have plenty of ventilators free.
The ‘it isn’t certified’ people need to stop, we get that safety trials, board reviews, peer reviews, field trials haven’t been done on things being suggested, but you know what ? People don’t care if it saves their life.
Would you tell someone not to tourniquet your bleeding arm if they used their belt vs a medically purposed device if it meant you would bleed to death ? Of course not, both are tools and I know a respirator is more complicated but still it is just parts put together to perform a function. YOU do not have to use what is made, that is YOUR choice, just stop trying to decide for other people.
Excuse us your Highness, those who don’t fulfill your demands. ;)
Good grif; open source will not eliminate the need for a doctor to prescribe a CPAP for a patient, so the medical insurance will pay for it..CPAP is for patients that can breath on their own, CPAP, isn’t for patients experiencing respiratory failure. open source hardware sounds great. Do have the jack to buy out all intellectual property and patents, the release as open hardware to release as open hardware/FOSS? Open doesn’t eliminate the manufactures to meet stringent standards.
, beyond the ventilator issue even patients dealing with Covid-19, should isolated from other Covid-19 patients; so recovering patients are still exposed the virus, Here in US the situation, can get very bad very quickly. I don’t stew about it, but I don’t ignore the facts those show leadership failed us.
These ventilator companies need to describe and offer parts/best practices for their ventilators to accomplish this. Can we really afford to wait and hope more units are coming?
Different size hoses for the different size patients. The smaller patients in the group should use larger or longer hoses which would compensate for the extra volume in their particular circuit.
Respiratory therapist are well equipped with knowledge and clinical practice on how ventilators work and how to use them in different modes. Using PCV (pressure control ventilation) will be ideal, because you can apply lung protective strategies and avoid the problems created with VCV (Volumen Control Ventilation). We have used one ventilator to ventilate 2, 3 or 4 patients at the same time in our lab. Of course, this is an extreme measure, and certain criteria will need to be in place as to avoid cross contamination,etc., but if it saves lives. Amen
Does anyone know what happens to the air that is exhaled in a ventilator? Is it just exhausted in the room or decontaminated in the existing systems? I cant seem to find any info on that..
Every schematic I’ve seen of the air path in a ventilator includes a HEPA filter on the exhaust (i.e., the return line from the patient).
Nice video demonstrations
I would like to know what about the settings
Is it usual for single use or double for 2 patient
And 4 times for 4 patient…
Tidal volume, peep, pressure
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