The story began in early March. With COVID-19 bearing down upon us, it became clear that we could run out of ventilators. This sparked interest in the concept of splitting ventilators between several patients. Some articles and videos were circulated on twitter describing how this could be done. These mostly described splitting a ventilator set in volume control mode.
Upon seeing this, two things were apparent to me:
- Splitting a ventilator in volume control mode would be a disaster. This could lead to all sorts of dangerous interactions between the patients. There are many ways to turn a ventilator into an assault weapon, and this is one of them. At risk of being pedantic, I would not ever consider splitting ventilators in a volume control mode.
- Using pressure-cycled ventilation with continuous mandatory ventilation could overcome most of these problems. This might allow splitting the ventilator in a reasonably safe manner (not perfect, but not an assault weapon either).
I described the fundamental concepts of how this might be done here. Subsequently Drs. Mergeay and Pinson led a team in Belgium to develop this idea much, much further. Almost simultaneously with Dr. Pinson’s report, the team at Columbia Presbyterian in NYC released a detailed protocol for split ventilation and began using it.
At nearly the same time that Dr. Pinson’s and Columbia’s reports surfaced, a joint statement from multiple professional societies was released admonishing us against splitting a ventilator. This is a unique statement which seems to have been derived via spontaneous generation:
- It contains no actual evidence.
- It lacks any defined methodology.
- It lists no authors.
- It cannot legitimately claim to be a “guideline,” so instead it's labelled a “joint statement.”
The statement seems to be directed primarily towards the concept of splitting ventilators in a volume cycled mode (which, as described above, is indeed an idea that would not work). As such, the statement is already obsolete. Based on the work done by the Belgian team & the Columbia protocol, many of the concerns listed in the joint statement are now demonstrably incorrect. Some examples include the following:
#1) Joint statement says: “Attempting to ventilate multiple patients would likely require arranging the patients in a spokelike fashion around the ventilator as a central hub… Spacing the patients farther apart would likely result in hypercarbia.”
- One of the concerns commonly raised with split ventilation is that the tubing would increase the amount of dead space. However, one-way valves could prevent patients from re-breathing exhaled gas. With the use of one-way valves, it shouldn’t matter how long the tubes are between the patient and the ventilator.
#2) Joint statement says: “Spontaneously breathing by a single patient sensed by the ventilator would set the respiratory frequency for all the other patients.”
- Any sane approach to split ventilation would be designed to avoid this. This could be managed by “locking out” the ventilator trigger (reducing trigger sensitivity so that patients would not trigger the ventilator – effectively achieving a controlled mandatory ventilation mode). Additionally, patients would need to be rendered passive on the ventilator (either using paralytic or high-dose respirolytic sedation).
#3) Joint statement says: “Patients may also share gas between circuits in the absence of one-way valves”
- Yep, that’s why modern protocols for doing this involve one-way valves.
#4) Joint statement says: “Volumes would go to the most compliant lung segments.”
- Yep, that’s why you need to set the ventilator in a pressure cycled mode.
#5) Joint statement says: “Positive end-expiratory pressure, which is of critical importance in these patients, would be impossible to manage.”
- There is some truth to this, but not necessarily much. Patients with obstructive lung disease could develop AutoPEEP – and this couldn’t be managed on an individual basis. However, most patients with COVID don’t have airway obstruction and don’t develop AutoPEEP.
#6) Joint statement says: “Alarm monitoring and management would not be feasible.”
- Again, a bit of truth here, but this is an overstatement. Please see the Columbia Protocol part G on how to set ventilator alarms. This isn’t perfect, but it’s not flying blind.
#7) Joint statement says that in the event of a cardiac arrest, if a patient were disconnected from the ventilator this “would alter breath delivery dynamics to all of the other patients.”
- Not in a pressure-cycled mode. As long as the tubing to the patient was clamped, ventilation of other patients attached to the ventilator wouldn’t be changed.
#8) Joint statement says “The greatest risks occur with sudden deterioration of a single patient (e.g. pneumothorax, kinked endotracheal tube), with the balance of ventilation distributed to the other patients.”
- Again, this problem exists only with a volume-cycled mode. Using a pressure-cycled mode, if one patient deteriorated that wouldn’t affect the other patients attached to the ventilator.
So, overall, the Joint Statement is a laundry list of reasons why split ventilation could be dangerous if done poorly. However, there are solutions to many of these problems. It doesn’t appear that the authors of the statement anticipated the ingenuity of the teams in Belgium and Columbia at avoiding these issues.
The safety and efficacy of split ventilation remains an intensely controversial issue. Further evidence is required to answer this, possibly in the form of outcomes from actual case series at various hospitals. At this point, it is premature for anyone to claim to know the answer with certainty.
In this context, the Joint Statement represents a classic over-reach by professional societies which seek to infantilize front-line clinicians. The statement might be right, but it might also be disastrously wrong. In the absence of any solid evidence, this opinion statement writ large does little more than stymie innovation and expose well-intentioned physicians to excess liability.
more on split ventilation
- Splitting ventilators (PulmCrit)
- Columbia Presbyterian protocol for splitting ventilators here.
- More advanced and granular exploration about how to hook everything up here.
- Alternatives to vent splitting and the safest vent splitting methods in COVID-19 (EMCrit RACC with Scott Weingart and Marco Garrone.
- Should we put multiple COVID-19 patients on a single ventilator? Jack Iwashyna on LITFL
Opening image from YouTube video of Buddy Breathing.
- PulmCrit Wee – Loading infusion auto-titration (LIAT) for infused medications with intermediate half-lives - March 23, 2025
- PulmCrit Wee: Michelin Chest Syndrome - March 15, 2025
- PulmCrit: ADAPT and SCREEN trials are full of sound and fury, signifying little - December 13, 2024
Thank you for this post. I was a little stunned by the joint statement and I agree with pretty much everything you said, however I do have some concerns. How would you guarantee that patients with the most compliant lungs don’t receive excessive tidal volumes? The joint statement is right in that volumes *would* go to the most compliant lung segments, even on pressure control ventilation. I suppose you could pair patients with similar lung compliance, but not sure how practical this is considering the dynamic nature of lung compliance and the inability to accurately measure individual patient tidal volumes.… Read more »
Thank you for the update. I agree these new guidelines are misguided and that split ventilation may be a good choice for some facilities. However in my facility we have all private rooms that are separated significantly. I think manually bagged ventilation indefinitely like Governor Coumo is talking about is better. You can control essential components easily The respiratory rate,, oxygen concentration and peep Can al be easily adjusted for each individual. The size of the breath would be relatively consistent Monitoring with pulse ox and waveform capnography if available could fine tune the technique. This technique could be done… Read more »
Hi Dr. Farkas, thanks a lot for this article. We sincerely hope adding some simple components will increase the safety and control for each patient individually (hopefully only needed until another ventilator arrives!). Also, just to make it clear: I’m not the expert, the actual experts in our team are working very hard at hospital Geel, Belgium (Dr. Mergeay, Dr. Stiers, Dr. Janssen). I’m just helping these amazing medical doctors spread the word.
Well refuted. I am surprised that this statement was published. When discussing this with some of my RT colleagues I can sense a palpable and institutionally reinforced resistance to innovation. This seems to be driven by both a misunderstanding of the proposed technique, and fear of potential liability. At least here in the US, we all work in a modern medical system that has (for the most part) never had to “make do”. The last bullet in the joint statement is worth second consideration, for many reasons; “Finally, there are ethical issues. If the ventilator can be lifesaving for a… Read more »
Re: #4. There are a couple of teams, myself included, who are working on ways to solve this with simple 3d printed devices that allow you to correct for the high compliance lung by adding resistance in series with that patient. This means that they will receive their breath slower. You can calibrate it in such a way that by the end of the inspiration phase, you have roughly equal volumes delivered to each patient. Stay tuned.
I am interested in thoughts about 3D printing combination splitter and flow sensor. Seems that one of the biggest drawbacks to these schemes is a lack of individual patient feedback. Could measuring each patient tidal volume in the exhalation branch provide valuable feedback? Could this help insure the configuration was working right for each patient?
In order for individual patient flow sensor feedback to be processed by vent, there would need to be some input for processing this data on vent, and a fundamental re-programming of the vent to compute differential flow rates from different components (patients) on the vent air circuit. The use of a pressure-cycled, CMV mode on the vent suggested by Dr. Farkas would essentially do the same thing without significantly modifying the ventilator or use extra sensors. For sure it is a stopgap measure, with the idea to be used only until extra ventilators can be had, but reasonable sounding given… Read more »
Thank you so much for these articles. It’s like pulling teeth trying to get RCPs to think outside the box.
The one study published in AARC in 2012 was written by Rick Branson. It was a flawed technique they used. Volume! That is the sole study used to make their recommendation against splitting vents.
It’s pretty funny that Rick Branson helped write the Recent Columbia protocol for Splitting Vents. I’m ashamed of the AARC and all the others.
Anyway. Thank you so much.
This is an interesting idea, however I thong in our institution we’ll run out of personel and other resources before this is a problem. I do however see a couple of issues: Titration of 5-8 ml/kg? Titration after pH instead.? Will 2-4 patients on one ventilator cause strain on the turbine with risk of ventilator failure? Accodental disconnect will cause loss of PEEP in all patients, with possible 2-4 patients crashing simulaniously… Finding patients with simular fio2, PEEP, TV and rr will be logistically difficult, and what to do when one recovers and the orher one doesn’t? Is it better… Read more »
Has anyone tried splitting ventilators and using APRV? Any thoughts on this?
I think conceptually this makes sense…wouldn’t have to worry about trigger/synchrony between patients…..the concern would be patients with different time constants and dealing with differing levels of hypercarbia. Interested to hear other thoughts….
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I do agree that the joint statement was written in haste and is overreaching. One has to consider all the forces that can drive or hinder innovation. Hopefully this time of crisis allow us all to restructure the bureaucratic overhead of review.
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[…] resources I have been able to find both for and against.8.3.1. PulmCrit wee – Why the SCCM / AARC / ASA / APSF / AACN / CHEST joint statement on split ventilato…8.3.2. PulmCrit – Splitting ventilators to provide titrated […]