Focus on Shared Ventilation Is “Missing the Point”: Expert Roundtable

coronavirus ventilator
Specialists emphasized that although shared ventilation may be necessary in times of crisis, innovative alternatives should be used to avoid such extreme measures during the COVID-19 pandemic.

As cases of the coronavirus disease 2019 (COVID-19) continue to multiply globally, creative efforts to cope with dwindling medical supplies and equipment have intensified. With anticipated or actual ventilator shortages affecting many facilities, the concept of using 1 ventilator for more than 1 patient simultaneously has become an increasingly important topic. New York-Presbyterian Hospital in New York, New York has already begun to implement shared ventilation between 2 patients, for which they recently published a protocol that was approved by the New York State Department of Public Health.1,2

The limited studies conducted on the topic have used lung simulators or animals. In 2006, Greg Neyman, MD, now an emergency medicine physician at Robert Wood Johnson Barnabas Community Medical Center in Tom’s River, New Jersey, and Charlene Babcock, an emergency medicine physician at Ascension St. John Hospital in Detroit, Michigan, published a pilot study using human lung simulators to investigate the feasibility of shared ventilation among 4 patients. Their results indicated “significant potential for the expanded use of a single ventilator during cases of disaster surge involving multiple casualties with respiratory failure.”3

(On her YouTube channel, Dr Babcock has posted videos demonstrating and describing how shared ventilation would work, as well as a video detailing how to modify a BiPAP machine to function as a ventilator.)

In another simulation study published in 2012, Richard Branson, MS, RRT, professor of surgery emeritus at the University of Cincinnati in Ohio, and past chancellor of the Board of Regents of the Society of Critical Care Medicine (SCCM), and colleagues demonstrated several limitations and risks involved in this strategy, including substantial variation in tidal volume delivery.4

While recognizing that shared ventilation may represent the only option in extreme circumstances, many experts have generally cautioned against the practice, and multiple organizations including the Society of Critical Care Medicine (SCCM) and the American Association for Respiratory Care (AARC) issued a joint statement advising against its use.

In addition, innovative alternatives have begun to emerge that could ultimately obviate the need for such extreme measures. For example, a system developed by the New York University Tandon School of Engineering (the NYU Tandon AirMOD) consists of modifications that “not only turn CPAP [continuous positive airway pressure] and BiPAP [bilevel positive airway pressure] machines into oxygen-enrichment tools, they trap the virus in a patient’s breath with viral filters,” according to a recent press release.5

“Unlike other conversions, the NYU Tandon modifications assemble in minutes and exclusively use FDA-approved off-the-shelf components already in stock in hospitals…,” including “viral filters, oxygen enrichment adaptors, tee-connectors, and positive end-expiratory pressure (PEEP) valves.”5 The team has made the assembly instructions available for free for use by other facilities.6

The use of other noninvasive tools such as nasal cannula has also been reported by institutions including Emory University School of Medicine in Atlanta, Georgia and 2 hospitals in China.7

In a video that was initially broadcast on April 1st on the JAMA YouTube channel, Derek Angus MD, MPH, FRCP, distinguished professor and chair of critical care medicine at the University of Pittsburgh Medical Center in Pennsylvania, discussed the promise and limitations of such strategies. As he stated in the video, “There’s a lot of interest… about whether [noninvasive methods] are actually being underused, because we’re already getting reports that a significant number of patients are incredibly hypoxemic at first, but actually if you just support them for a day or so they may get through it. And young, otherwise healthy people may actually not even need to be intubated.”

Among other points, Dr Angus noted that one “problem with doing more aggressive CPAP or BiPAP is then — what happens if the person fails? So you start them on CPAP, you put them off somewhere where they’re maybe not under constant vigilance, and then if they start to get into trouble, it would be very concerning if you then missed an opportunity to intubate.” These approaches may be adequate for a specific subset of patients, however, especially considering the current circumstances. As such, an “issue to really get on top of is how safely we can use noninvasive ventilation.”

We further explored these issues and innovations in an interview with Dr Neyman and Dr Branson, as well as Jamie Garfield, MD, associate professor of thoracic medicine and surgery at the Lewis Katz School of Medicine at Temple University, and pulmonary/critical care attending physician at the Temple Lung Center in Philadelphia, Pennsylavnia.

What are your thoughts on the feasibility of using 1 ventilator for multiple patients, including in the COVID-19 pandemic? What are the potential limitations and risks associated with this approach? 

Dr Neyman: I was never able to get it to animal models, but other researchers were able to re-perform the research in sheep.8 That article was responded to by this paper.9

When I started the research, the initial idea was for use in healthy lungs, such as in a botulism outbreak or attack, or a mass casualty incident. In fact, this use was mentioned in the numerous after-action reports from the medical response to the 2017 Las Vegas concert shooting,10 where Kevin Menes, MD recalled my research and hooked up 2 patients to a single ventilator when they were running low.

When chatter on a Facebook group began to unearth this research, I maintained that it would be problematic to deploy in COVID-19 because, unlike trauma or botulism, COVID-19 affects the lungs themselves. So, a problem develops with fluid dynamics, as 1 patient whose lungs are deteriorating faster than a ventilator partner’s lungs will start to increase his pressure, and then divert air away from one’s own branch of the circuit. This will mean that the deteriorating patient will end up getting less and less oxygen, while the other patients on the circuit get higher pressures infused into their lungs, which could cause a secondary lung injury.

In order to deploy such a setup in patients where the lungs are the problem, ICU staff would need to monitor the air pressure inside the lungs of the 4 patients individually. Right now, that function is handled by the ventilator, but if 4 patients were placed on it, it would only be able to show the average pressure of all 4 patients.

Unless they were very closely monitored, such a setup could result in more harm than good. However, all of these concerns remain hypothetical as they have never been tested on lung disease patients.

I have made a video detailing my concerns, although it is geared more towards the lay public.

Dr Garfield: I think that to focus only on whether shared ventilation is doable is missing the point of preparing for this crisis. Adequately preparing means watching your colleagues who are ahead of you and trying to be equipped to deal with the surge to come.

What’s more important than the question about shared ventilation is trying to build and bring more ventilators into your institution and speaking to your colleagues in engineering about creative solutions, like turning your BiPAP machines and Ambu Bags® into ventilators. If you’re thinking about that question right now instead of how to get more ventilators, you’re missing the call. I don’t think it’s a fruitful conversation.

The various organizations released a joint statement advising against this practice because it cannot be done safely. I’m not saying you shouldn’t prepare for the possibility — it’s worth walking into your respiratory unit and considering what that would require — but it should be the absolute last resort.

It’s difficult enough to ventilate someone in ARDS [acute respiratory distress syndrome], so there’s no reason to ventilate not 1 but 2 patients with ARDS on the same machine. I don’t see a role for this approach in ARDS or acute COVID-19 patients.

Shared ventilation has been explored with some success with victims of massive trauma, like in the Las Vegas shooting, but the patients were otherwise healthy with normal lungs. That’s a totally different scenario because they could find groupings that were similar: patients of roughly the same height and weight and with normal lung mechanics and compliance.

If you really run out of ventilators and there is no other option, patients you might consider for this would be trauma patients. In that case, you would talk to your trauma colleagues and ask if it would be possible to combine 2 of their patients. Of course, that’s very ethically complicated.

Each institution really needs to prepare with their bioethicist and legal team to determine how to allocate ventilators; this needs to be very systematic. At Temple, we are very carefully working on a ventilator allocation protocol that utilizes allocation scores based on factors such as severity of illness and likelihood of recovery.

Dr Branson: The use of a single ventilator for 2 patients should be reserved for extreme circumstances after other single ventilator options are exhausted. Our research in the laboratory with a lung model shows that there are limitations and safety issues which must be considered. The gas delivered to the lungs is not controlled — the patient with the sickest lungs get the least volume and the patient with the better lungs gets more volume, perhaps too much. 

A major limitation is that it is difficult to monitor what volume each patient is getting without a device for each patient. The use of 2 patients on the same ventilator increases the risk. One major concern is that a catastrophe in one patient — pneumothorax or plugged [endotracheal] tube — results in a potentially dangerous situation for the other patient. Filters and one-way valves in the circuit can be used to reduce the risk for contamination.

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Is the only alternative to manufacture or purchase more ventilators, or are there any other potential creative solutions to address a ventilator shortage in a pandemic or other disaster situation?

Dr Neyman: A lot of people are collaborating on the site I also came across this video.

Dr Garfield: There are ways to engineer or modify a CPAP or BiPAP machine to perform as a ventilator. Engineers at Temple and other universities like the Massachusetts Institute of Technology are working to figure out ways to modify what we already have to serve this function.

An Ambu Bag is not the best alternative because we can’t be sure how much air is being delivered, but it certainly has some value in this setting. Engineers are working on an automated squeezing mechanism. I don’t know if it will turn out to be useful, but it may be a good interim measure for a couple of hours.11

You have to consider everything. For example, you might train in-house folks to service ventilators instead of sending them off to be serviced and having to wait weeks.

Dr Branson: There are a multitude of ventilators in the hospital: ICU ventilators, portable ventilators, anesthesia ventilators, ventilators from the strategic national stockpile, ventilators used for face mask ventilation, all are possibilities before considering the use of 2 patients on 1 ventilator. But the best solution to the need for more ventilators is to help existing manufacturers with their supply chain and manufacturing. I personally do not hold out much hope for many of the DIY projects that are floating around the internet.

What should be the focus of future research or other efforts in this area? 

Dr Garfield: The message I want to convey is that we knew a pandemic was possible, and had we really prepared for this, we would be much better off. Even just a few weeks of aggressive preparation before the first patient presented with COVID-19 at Temple was enormously helpful. So, research should focus on preparing for a pandemic so that  health systems, cities, and countries have the ability to quickly mobilize resources in situations like this.

Dr Branson: Of course, an ounce of prevention is worth a pound of cure. Social distancing, vaccines, and pharmacologic treatment [warrant continued investigation]. Ventilators are only supportive until the illness resolves. A system for sharing ventilators between areas minimally affected and those under duress would be helpful but logistically difficult. For instance, children’s hospitals have been minimally affected, and some of their ventilators could be shared with adult facilities.

The point I cannot [stress] enough is that, right now, PPE [personal protective equipment] and safety of the staff is far more important than ventilators — because without the staff, all the ventilators in the world will not be helpful.

For an in-depth interview with Dr Branson regarding the risks of shared ventilation, see “SCCM Former Chancellor of Board of Regents on Sharing Ventilators During COVID-19 Pandemic.”


1. Columbia University College of Physicians & Surgeons, New York-Presbyterian Hospital. Ventilator sharing protocol: dual-patient ventilation with a single mechanical ventilator for use during critical ventilator shortages. Published March 24, 2020. Accessed  April 13, 2020.

2. Siegel B. New York approves ventilator splitting, allowing hospitals to treat two patients with one machine. ABC News. March 26, 2020.

3. Neyman G, Irvin CB. A single ventilator for multiple simulated patients to meet disaster surge. Acad Emerg Med. 2006;13(11):1246-1249.

4. Branson RD, Blakeman TC, Robinson BR, Johannigman JA. Use of a single ventilator to support 4 patients: laboratory evaluation of a limited concept. Respir Care. 2012;57(3):399-403.

5.  American Association for the Advancement of Science — EurekaAlert! NYU Tandon School of Engineering develops CPAP alternative For mechanical ventilators.  April 9, 2020.

6. NYU Tandon School of Engineering. AirMOD: CPAP/BiPAP fluid circuit modification assembly manuals. Accessed  April 13, 2020. 

7. Begley S. With ventilators running out, doctors say the machines are overused for Covid-19. STAT. April 8, 2020. [WU1] [WU2] 

8. Paladino L, Silverberg M, Charchaflieh J, et al. Increasing ventilator surge capacity in disasters: ventilation of four adult-human-sized sheep on a single ventilator with a modified circuit. Resuscitation. 2008;77(1):121-126.

9. Branson RD, Rubinson L. One ventilator multiple patients —what the data really supports. Resuscitation. 2008;79(1):171-172; author reply 172-173.

10. Klauer KM. Emergency physician and victim share experiences from Las Vegas mass shooting. ACEP Now. February 11, 2018.11.  Chandler DL. MIT-based team works on rapid deployment of open-source, low-cost ventilator.MIT News. March 26, 2020.