As the coronavirus disease 2019 (COVID-19) pandemic continues to develop across the United States and the world, guidance for critical care specialists is essential.

A joint statement issued by the Society of Critical Care Medicine (SCCM), American Association for Respiratory Care (AARC), American Society of Anesthesiologists (ASA), Anesthesia Patient Safety Foundation (APSF), American Association of Critical‐Care Nurses (AACN), and American College of Chest Physicians (CHEST) has advised against the use of 1 ventilator for multiple patients.

We reached out to Richard Branson, MS, RRT, professor of surgery emeritus at the University of Cincinnati in Ohio, and past chancellor of the SCCM, to learn more about the potential consequences of using a single ventilator for multiple patients.

Can you speak to the joint statement that SCCM has released, warning against sharing mechanical ventilators?

The conventional view is that is there is 1 ventilator and 1 patient, and that when using a single ventilator a clinician can determine how much flow volume and pressure goes to the patient, which are all important, not only for efficacy but for safety.

When you start to split what the ventilator delivers to more than 1 patient, it can be dangerous. No ventilator should ever be split between 4 patients — that should never be attempted in my opinion. There is no value in 4 patients to 1 ventilator. It’s just too dangerous. But let’s just say for the sake of argument you have 2 patients on the same ventilator, owing to a crisis.

When gas is delivered to the patient, a clinician usually sets the volume or pressure which is monitored by the ventilator. When 2 patients are on the same ventilator, the caregiver can determine the pressure and the volume that leaves the machine, but you have no idea how much goes to each [individual] patient. The distribution of ventilation between patients is not equal.  So one could have a situation where the patient who is the sickest (stiffest lung) gets the least gas, and the other patient whose lung is more compliant gets the most gas. In such a situation, neither patient is ventilated optimally.

Can you speak to the infection risk that that may occur when sharing a ventilator?

Even if a filter is installed in line, which is a solution that has been proposed, there are 2 things that can happen. In cases where 2 patients are attached to a single ventilator, the patients need to be paralyzed, which has its own list of untoward complications. For example, if one of the patients tries to breathe, they can actually draw gas from the other patient’s circuit. Let’s assume that both of these patients have the same COVID-19 virus [infection] — we still would not know what other infections they may have. And whatever they are, the patients are going to be sharing them in pretty short order.

Another issue to take into account is that when the circuits are joined, it has been proposed that the lungs from both patients do not fill at the same speed due to differences in compliance. In this case, an equilibrium may be reached, and the gas may circulate from one patient to the other. This phenomenon is referred to as pendelluft (ie, ‘air swinging back and forth freely’ in German). Usually, pendelluft refers to the movement of gas between the lung segments of the same patient.

How does COVID-19-related acute respiratory distress syndrome (ARDS) further complicate ventilator sharing?

The lung in this particular illness tends to have a very difficult job transferring oxygen into the blood, so the patients have severe hypoxemia. The lung compliance of patients with COVID-19 is low, but not as low as we often see with other patients with ARDS. With COVID-19, the disease progresses rapidly: when patients get sick and need to go on a ventilator, they generally develop severe respiratory failure pretty quickly.

So that the only way the multiplexing [the concept of sharing one ventilator between 2 or more patients] can possibly be achieved with a modicum of safety is for the 2 patients to have very similar lung mechanics, which is unlikely. In cases where 2 patients hooked to the same ventilator have similar lung mechanics, this may no longer be the case 6 hours later or the next day.

There is no way of determining the lung mechanics of each patient individually, as with typical ventilator monitoring, the values indicated are the average of the 2 patients, not those of each individual patient. Additional arterial blood gases would need to be performed, which means that a healthcare professional needs to be in the patients’ room, drawing blood from an infected patient. In addition, this procedure is more invasive. There is no upside to multiplexing of ventilation under normal circumstances.

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Could you potentially see a place for multiplexing ventilators in a situation where a clinician finds themselves without available ventilators? Do the risks outweigh the benefits?

Two patients on a ventilator instead of 1 patient is inherently more risky and dangerous. You lose the safety afforded you by alarms and monitoring. The problem is, I don’t think people appreciate the nuances here and how the changes in the patient’s condition impacts how the ventilator distributes its volume and pressure. This is not a plumbing problem, it’s a physiologic problem.

A clinician may be faced with 2 patients with COVID-19 in need of ventilation. The physician may able to save both of their lives by sharing the ventilator, but what happens if both end up dying because neither one of them is getting optimal treatment? But if you are out of ventilators and deny a patient access to a ventilator then 1 patient faces certain mortality while the other might be saved I realize this is an ethical conundrum for medical ethicists, not me, but ventilating more than 1 patient is not as simple as it seems.

What would you recommend as best practice for triaging patients when ventilators are limited? What should clinicians consider first?

The first thing clinicians should do is triage the patients to the device. There are some ventilators that are used in the intensive care unit (ICU) every day that cost $50,000 that do everything. Those should be used for the very sickest patients that clinicians are caring for.

Almost all hospitals have portable ventilators for transport, floor use, or a long-term care unit or facility. Sometimes these long term care facilities are built into the hospital, sometimes they are near the hospital. Those devices can be used on the patients who are not as sick.

There is a limit to triaging, as some devices, such as the ones that are used by paramedics, are not adequate for the ventilation of really sick people. A certain level of sophistication and operational performance is required. Ventilators can be borrowed from laboratories and universities, all of which are functional and could be used.

I think that the one site that keeps getting overlooked is every operating room in a hospital. Each operating room has an anesthesia workstation that includes a ventilator, a physiologic monitor, a capnograph, and an oximeter. It is like an ICU on wheels. Clinicians could make the decision to either care for the patients in the operating room or to wheel those devices into the recovery room or a larger room and use them to ventilate patients with COVID-19. These are all options I think are important to weigh long before ever considering the multiplexing option.

How are you faring as a clinician during this time? We are getting a lot of feedback that the front line healthcare workers are overwhelmed. We know that is happening in New York City; is it starting to affect other cities?

It is not affecting us yet. People feel strapped because of the preparation and concern but I do not think anybody is feeling what New York is feeling. And then behind New York is Seattle and a few other places, but again, they all know it is coming. The one thing I would say is: I know we all want to talk about ventilators, but if there are not nurses and respiratory therapists and pharmacists and physicians to care for the patients, we could have all the ventilators in the world and it would not make a difference.

I have friends in New York and northern New Jersey who say staff are getting sick. The Boston Globe recently reported there are 100 healthcare workers in Boston who have tested positive. So the staff is every bit if not more important than the ventilators because if you have a bunch of fancy ventilators and nobody knows how to use them properly, then the device itself is rendered useless.