Hospitals across the country are filled with a curious sight these days: patients lying on their bellies.

Patients almost always lie on their backs, a position that helps nurses tend to them and allows them to look around if they’re awake. But for many patients, the coronavirus crisis is literally flipping the script.

The surprisingly low-tech concept called proning can improve breathing in patients stricken by the respiratory distress that is the hallmark of the virus, doctors have found. It draws from basic principles of physiology and gravity. Lying on one’s stomach helps open airways in lungs that have become compressed by the fluid and inflammation unleashed by the coronavirus infection.

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When patients are on their backs, “the heart is now sitting on top of the lungs and compressing it even more,” said Dr. Michelle Ng Gong, chief of the divisions of critical care and pulmonary medicine at Albert Einstein College of Medicine and the Montefiore Health System in the Bronx, New York. “The rib cage cannot move in the usual way because it’s now up against the bed.”

But, she said, “When you flip the patient onto the belly, now the back of the lungs can start to open,” allowing more air sacs to function, she said.

In addition, a larger share of the lungs is in the back of the body than the front, meaning that patients on their stomachs don’t have to support as much lung weight.


Before the coronavirus pandemic, proning had been used for some very ill patients on ventilators but not nearly as frequently as it is being tried now. That’s partly because turning heavily sedated patients onto their bellies is a labor-intensive maneuver, previously done with medical teams of as many as eight people who must carefully avoid dislodging a patient’s breathing tube or intravenous lines.

With the coronavirus producing an avalanche of patients with malfunctioning lungs, hospitals have been employing the maneuver not only for intubated and sedated patients but also for nonintubated patients who are having serious breathing trouble. In ICUs, doctors are asking patients to turn onto their stomachs in hopes that the position will keep them from needing ventilators. In emergency rooms and regular hospital floors, doctors are trying tummy time with some patients whose condition is not as dire, on the theory that it might help them recover faster.

Past experience has found that in ventilated patients with acute respiratory distress syndrome, or ARDS — a condition that many seriously ill COVID-19 patients develop — proning for many consecutive hours a day improves the medical outcome that matters most: survival.

“There’s a lot of evidence that it actually decreases mortality, and there are not a lot of things that actually do,” said Dr. C. Corey Hardin, a pulmonary and critical care physician at Massachusetts General Hospital.

There’s a lot of evidence that it [proning] actually decreases mortality, and there are not a lot of things that actually do.” — Dr. C. Corey Hardin, Massachusetts General Hospital.

In many patients with ARDS, only some of the air sacs are collapsed, so while pressure supplied by a ventilator can open those air sacs, too much pressure can overinflate air sacs that aren’t collapsed, Hardin said. Proning allows the ventilator pressure to be set at a minimum, meaning that the flattened air sacs are reinflated, but there’s “no danger of overinflating somewhere else,” he said.

A 2013 study convinced many experts in the field of the advantages of proning patients on ventilators. It found that intubated patients with ARDS who were flipped onto their bellies for stretches of 16 hours were twice as likely to survive as patients who spent the entire time on their backs. The prone group also had fewer cardiac arrests than the supine group.


Subsequent studies found similar benefits. Still, before the pandemic, the technique was being used for only about 15% of intubated ARDS patients, Gong said.

One reason for the wariness was the potential risk involved in flipping patients over. “Some of these patients who have very low oxygen in their blood, a simple act of just turning them to their side even, not even to their belly, can cause their oxygen level to drop,” Gong said.

“It’s a bit like going into battle,” she said. “The ability to turn these patients safely without dislodging a tube, without something accidentally falling out, without a patient going into cardiac arrest, that takes team coordination.”

Recently, she said, a coronavirus patient’s breathing tube fell out, and the team had to hurriedly flip the patient back over so the tube could be reinserted. But, Hardin said, most complications can be avoided with training and experience.

“There’s certainly a lot of anxiety about that when you talk about rolling out something if you haven’t done it a lot,” he said. But “once you’ve done it a couple of times, people are like, ‘Oh wow, this isn’t that big of a deal.’ ”

To limit medical staff exposure to infected patients during the pandemic, hospitals have been proning patients with much smaller teams, often just three or four people.

Proned patients must periodically be turned onto their backs again, called supinating, because that position is better for some nursing tasks and because too much uninterrupted time facedown can cause the equivalent of bedsores on the face. Ventilated patients are typically proned for 16 hours, but at Mass General, Hardin said, some are proned for 24 or 48 hours.


“Some of these patients will lose the benefits once we supinate them, and then we have to prone them again,” Gong said. “So some of these patients we’re supinating, proning, supinating, proning, and it can go on for days.”

Susan Zhang, 56, of Long Island, New York, was proned each of the seven days she was sedated and on a ventilator in April in Montefiore’s neuroscience intensive care unit.

At first, Zhang needed 85% oxygen from the ventilator, but that level decreased almost daily and was down to 35% on the seventh day, according to her husband, Dr. William Liang, an internist, who created a handwritten flow chart of his wife’s daily medical status.

“They proned her the whole day, then let her rest a little bit, and then proned her in the evening,” he said. Zhang also received some medications, so it’s impossible to say how much the proning helped, but Liang believes it contributed to “a very nice progression.”

In a telephone interview from a hospital recovery room earlier this month, Zhang, who was receiving nasal oxygen, said in a voice still weak from the intubation that she was grateful to the hospital for “saving my life.” She is now recuperating in a rehabilitation hospital.

The benefits for intubated patients have prompted hospitals to examine whether proning can help prevent the need to put patients on ventilators. A clinical trial at Rush University Medical Center in Chicago is studying whether ICU patients lying on their stomachs are less likely to be intubated than those who remain on their backs.


“People are saying go ahead and prone them, but we need to find out if that is truly something that stands out in terms of mortality benefit or ICU length of stay or mechanical ventilation need or ventilation length,” said Dr. Sara Hanif Mirza, an assistant professor of pulmonary and critical care medicine at Rush, one of the trial leaders.

Equally important is understanding whether proning can have negative effects for such patients, said David Vines, another trial leader and an associate professor at Rush’s College of Health Sciences. He said that sometimes it’s better to intubate severely ill patients early, depending on how much their lungs can benefit from resting while a machine breathes for them.

If by proning them, “we may just be delaying them and they wind up getting intubated anyways, we worry about that because those people can end up having worse outcomes,” he said. “We would be concerned if there’s a mortality difference because we didn’t act fast enough.”

One of Vines’ recent patients was an older man in the ICU on nasal oxygen. “I went ahead and told him to prone, but I just delayed his intubation 24 to 36 hours, and he ended up being intubated anyway,” Vines said.

Because of such concerns, Vines said the trial will evaluate patients soon after they prone themselves, and “if we don’t see improvement in an hour, we should intubate you.”


Another issue is that some patients, because of factors like weight or age, find lying on their stomachs uncomfortable or difficult, which can affect results. Some hospitals are using mattresses designed with cutouts for pregnant women’s bodies to make patients more comfortable.

Proning may have helped Leticia Espinoza, 50, of Elmwood Park, Illinois, who went to Rush’s emergency room in late March. After several days of fever and chills, her breathing problems became so serious that she was transferred to the ICU, where, Mirza said, it seemed likely she would need intubation.

“They asked me to lay down on the bed with my belly down,” Espinoza said in a recent interview. “It was not really comfortable. It’s an unusual position for me. I did it because I wanted to improve.”

Espinoza, a participant in the clinical trial, managed to spend about 20 hours each day on her stomach, with interruptions only to use the bathroom, eat or turn briefly on her side when she needed a break. She ended up avoiding a ventilator, her oxygen needs steadily decreased, and after three days she was moved out of the ICU. Soon afterward, she went home.