On Wednesday, STAT News published an
influential story asking whether ventilators are being overused for Covid-19 patients. The United States is
facing a dire shortage of ventilators for coronavirus patients. In that context,
a complex debate within critical care medicine has become a matter of urgent
public interest. How many ventilators are needed is already a politicized issue:
Donald Trump and his son-in-law and adviser Jared Kushner have opined, seemingly
baselessly, that New York doesn’t need as many ventilators as Governor Andrew
Cuomo and his experts predict. “If ventilators are actually not the best
solution to this problem we’re wasting a whole bunch of time and effort,” tweeted journalist Dave Dayen, author of The
American Prospect’s Covid-19 blog, Unsanitized, in response to the STAT story. “Do Ventilators Help?” asked National Review.
The “yes ventilators” versus “no ventilators” frame is an overly simplistic take on a complex debate within critical care medicine. Some doctors think that a subset of Covid-19 patients would do better if they went on a respirator later, or not at all. That’s a far cry from saying that ventilators are “not the best solution” or that efforts to increase the ventilator supply are a waste of time. The debate over when to intubate, however, also has tricky ethical dimensions.
One pressing issue is whether ventilators will be allocated on a top-down basis by hospitals, hospital systems, or public officials—or whether bedside physicians will retain control over these decisions. The argument for top-down allocation is that it increases fairness and allocates resources more rationally. The Holy Grail is to find a list of objective criteria that predict who is most likely to benefit from a ventilator. But Dr. Lisa Moreno, president-elect of the American Academy of Emergency Medicine, who treats patients with severe Covid-19 at her hospital in New Orleans, told me that we simply don’t know enough about this new virus to reduce these decisions to algorithms. The fact that someone is young, thin, and healthy doesn’t necessarily mean they’re a better candidate than someone who’s older, obese, or suffering from a preexisting condition like diabetes. This disease affects people so differently that someone who looks good “on paper” may not be the strongest candidate for ventilator support.
When deciding whether to put a Covid-19 patient on a ventilator, Moreno says she takes into account various factors, including how well they’re breathing and how clearly they’re thinking (an indication of whether their brain is getting enough oxygen). “This has nothing to do with their age and even, in some cases, not necessarily to do with their underlying condition,” Moreno said.
Early in the pandemic, frontline health care providers in China argued that rapidly deteriorating patients should be intubated if their oxygen saturation levels fell below 93 percent and less invasive measures couldn’t bring these saturation levels back up. However, as the pandemic progressed, it became clear that many patients with severe Covid-19 remained functional and comfortable (at least by the standards of critically ill people) with oxygen saturation levels much lower than 93 percent. Now some doctors are rethinking the 93 percent threshold. Maybe some patients are better off sticking to less invasive ventilation methods that can’t push their oxygen saturation levels quite as high, but which can spare them the trauma that mechanical ventilation inflicts on their lungs.
“The interesting thing that we’re seeing with Covid is that patients still seem to be able to get carbon dioxide out,” Moreno said. “And we’re seeing, because people are not retaining carbon dioxide, that they are much more comfortable at lower oxygen levels.”
Most patients start getting distressed when the oxygen saturation of their blood falls to 88 percent, Moreno explained. All over the world, doctors are seeing coronavirus patients tolerating oxygen saturations as low as 80 percent, she said, with some places reporting patients tolerating oxygen saturation of 60 percent or lower. But it’s excess carbon dioxide, not low oxygen, that triggers our desire to breathe and makes us uncomfortable when we can’t expel it. And with Covid-19, the two don’t seem to be as closely linked as doctors might expect. “Because of that we are looking at different ways of treating these patients and a different timetable of intubating them,” Moreno said.
The standard of care for Covid-19 pneumonia is based on protocols developed to treat acute respiratory distress syndrome, or ARDS, a devastating lung disorder that can be triggered by sepsis, trauma, or pneumonia. In a recent editorial in Intensive Care Medicine, Luciano Gattinoni of the Medical University of Göttingen and colleagues noted that Covid-19 pneumonia patients differ from classic ARDS patients in key respects. Specifically, Covid-19 patients may have dangerously low levels of oxygen in their blood despite their lungs expanding almost normally under pressure, a state known as high pulmonary compliance. Compliance is a measure of how readily lung tissue expands under pressure. The less compliant the lungs, the harder it is to breathe. ARDS patients tend to have stiff lungs that are very difficult to inflate.
Gattinoni observed that Covid-19 patients could be divided into two categories: Type L, for low elastance (i.e., flexible, easy to expand) lungs with low lung weight, and Type H, high elastance (i.e., stiff) lungs, with high lung weight.
These two subtypes require different treatments, he argues. Type L patients, with their relatively easy-to-expand lungs, may particularly benefit from noninvasive methods to increase the amount of oxygen in their blood, such as oxygen delivered by high-flow nasal cannula, or a face mask connected to a machine that eases the work of breathing. Ideally, these patients can avoid a ventilator altogether, but if they do need a vent, Gattinoni and his colleagues observed that they did better on low-pressure settings because these were less likely to damage their lungs. Even Type L patients may ultimately need a ventilator, particularly if their breathing gets so labored that they’re at risk of injuring their lungs.
By contrast, Type H Covid-19 patients look more like typical ARDS sufferers. About 20 to 30 percent of Gattinoni’s patients were Type H. These patients seem to benefit from more traditional ARDS treatment protocols, including ventilation at higher pressure, which is needed to overcome the stiffness of their lungs. Patients who start out as Type L may progress to Type H as their disease worsens.
These findings make some doctors wonder if Covid-19 is primarily a lung disease after all. Maybe the profound oxygen deficits are caused by something other than lung damage, at least early on.
Another important ethical question is whether early intubation reduces the risk of transmitting the virus to health care workers: It doesn’t matter how many ventilators we have if all the people who know how to run them are sick. In Italy, 20 percent of health care workers treating coronavirus patients became infected, and many have died. Intubation is by far the riskiest procedure for spreading Covid-19 from patient to health care provider, but once intubated and on a ventilator, the circulation of a patient’s breath occurs in a closed system, and thus infectious particles are less likely to spread. Some doctors argue that intubating patients early decreases the risk that the patient will spread Covid-19 virus while on a high-flow nasal cannula or continuous positive airway pressure machine. But at the same time, masks and cannulas can eliminate the need for some intubations. Since intubation is such a risky procedure for transmitting Covid-19, a protocol that results in fewer intubations might end up being the safer alternative. All of these staff protection arguments have added urgency because so many health care workers lack masks, gowns, and other personal protective equipment.
An additional argument for early intubation is that Covid-19 patients can deteriorate very quickly, and it’s better to intubate them a little earlier if they seem to be getting worse in order to avoid a rushed intubation later on, which is likely to be more dangerous to the staff and the patient. Many patients with Covid-19 have inflamed, swollen airways that make intubation especially challenging.
The term “early intubation,” however, is also somewhat vague. Intubation is a dramatic intervention that no physician performs lightly, even those who prefer to intubate earlier rather than later. “We don’t intubate and ventilate a patient who’s improving,” Moreno said. “The decision becomes: Am I going to intubate when they absolutely are going to die, or am I going to intubate a little bit earlier than that? In the hospital where I work, we are at this point intubating people a little bit earlier,” she continued. “If we intubate them before we have to do a crash intubation, we’re finding they do better, and we are getting a 50 percent extubation rate at this point in time.”
A 50 percent extubation rate—in other words, the ability to remove the breathing tube so the patient can breathe on their own again—is excellent for Covid-19 patients. An estimated 80 percent of ventilated Covid-19 patients in New York have died so far, according to officials.
Intubating Type L patients later, or not at all, would decrease demand for ventilators to some extent, but we don’t have hard data on what percentage of severe Covid-19 patients are Type L or what percentage of them could do without a ventilator.
Intubating fewer patients is likely preferable to some other options for stretching the ventilator supply, such as modifying ventilators to serve multiple patients—another ethical nightmare. “SUNY Downstate and one other New York hospital have already started splitting ventilators,” claimed Dr. Lorenzo Paladino, who helped the Federal Emergency Management Agency develop a vent-splitting protocol. On Tuesday, Cuomo admitted New York would be trying this “experimental procedure,” saying “at this point, we have no alternatives.”
The Society for Critical Care Medicine, however, has issued a strongly worded consensus statement against vent-splitting except as a short-term option of last resort, mainly because it decreases the ventilator’s efficacy for all patients involved. “It is better to purpose the ventilator to the patient most likely to benefit,” it argued, “than fail to prevent, or even cause, the demise of multiple patients.” Split ventilators, respiratory therapist and University of Cincinnati College of Medicine Professor Emeritus Richard Branson told me, have largely been used on an ad hoc basis and described in anecdotes to the media, rather than within the confines of controlled trials and peer-reviewed journals. Doctors, engineers, and backyard tinkerers are circulating YouTube videos on how to connect multiple patients to a single ventilator. Branson said many of these hacks are impractical, dangerous, and unmoored from basic principles of physics and physiology. A few serious researchers are also trying to crack the split-vent problem, but Branson doesn’t hold out much hope for them, either.
Splitting a ventilator between two patients runs up against the limitations of respiratory mechanics. How do you make sure that each patient gets an equal share of the breath? If one patient suffers a catastrophic complication, like a blocked tube or a collapsed lung, it will become a catastrophe for both patients. “When you go from one to two patients, you don’t just double the risk, it’s more exponential,” Branson explained. You can’t hook a second person up to the machine without significantly decreasing the first patient’s chances of survival.
Branson says it’s theoretically possible to mitigate some of these risks by modifying ventilators with valves and other spare parts, but having taught a lot of people to run ventilators in emergencies, he doesn’t consider these hacks to be a practical solution for unseasoned vent operators in a crisis. There was a shortage of trained respiratory therapists in the U.S. even before Covid-19, and now the shortage is much worse. “Mid-pandemic, people are critically ill, staff is stretched thin, everyone’s wearing suits that are hot and uncomfortable,” he said. “Now you’re going to modify the ventilator circuit with some parts you picked up at Home Depot?”
Covid-19 is a new virus, and doctors still have a lot to learn about how best to treat it. Most of what we think we know has been figured out on the fly, rather than proven by rigorous studies. Only time and careful research will tell if Gattinoni’s taxonomy of Covid-19 patients holds up in real life or if doctors can avoid significant numbers of intubations by boosting oxygen levels less invasively. Whatever experts decide, their research is not an excuse to wave off dire shortages of ventilators—which are occurring alongside shortages of almost all other crucial equipment—in a pandemic. These machines will play an important role in the management of Covid-19 for the foreseeable future.