President Trump’s doctors offered rosy assessments of his condition on Sunday, but the few medical details they disclosed — including his fluctuating oxygen levels and a decision to begin treatment with a steroid drug — suggested to many infectious disease experts that he is suffering a more severe case of Covid-19 than the physicians acknowledged.
In photos and videos released by the White House, there is hardly any sign that Mr. Trump is sick. But at a news conference at the Walter Reed National Military Medical Center in Bethesda, Md., Mr. Trump’s doctors said his oxygen levels had dropped to a level that can indicate that a patient’s lungs are compromised. The symptom is seen in many patients with severe Covid-19.
The president’s medical team also said that he had been prescribed dexamethasone on Saturday. The drug is a steroid used to head off an immune system overreaction that kills many Covid-19 patients.
The drug is reserved for those with severe illness, because it has not been shown to benefit those with milder forms of the disease and may even be risky.
Because of the incomplete picture offered by the president’s doctors, it was not clear whether they had given him dexamethasone too quickly, or whether the president was far sicker than has been publicly acknowledged, experts in infectious disease and emergency medicine said on Sunday.
“The dexamethasone is the most mystifying of the drugs we’re seeing him being given at this point,” said Dr. Thomas McGinn, physician-in-chief at Northwell Health, the largest health care provider in New York State. The drug is normally not used unless the patient’s condition seems to be deteriorating, he added.
“Suddenly, they’re throwing the kitchen sink at him,” Dr. McGinn said. “It raises the question: Is he sicker than we’re hearing, or are they being overly aggressive because he is the president, in a way that could be potentially harmful?”
Dr. Esther Choo, a professor of emergency medicine at Oregon Health & Science University in Portland, said of the doctors’ statements on Sunday: “This is no longer aspirationally positive. And it’s much more than just an ‘abundance of caution’ kind of thing.”
Some experts raised an additional possibility: that the president is directing his own care, and demanding intense treatment despite risks he may not fully understand. The pattern even has a name: V.I.P. syndrome, which describes prominent figures who receive poor medical care because doctors are too zealous in treating them — or defer too readily to their instructions.
“You think you’re helping,” said Dr. Céline Gounder, a clinical assistant professor of medicine and infectious diseases at the N.Y.U. Grossman School of Medicine. “But this is really a data-free zone, and you just don’t know that.”
Still, based on the doctors’ account, Mr. Trump’s symptoms appear to have rapidly progressed since he announced early Friday morning that he had tested positive for the coronavirus.
Mr. Trump had a “high fever” on Friday, and there were two occasions when his blood oxygen levels dropped, his doctors said — on Friday and again on Saturday. The president’s oxygen saturation level was 93 percent at one point, his doctors said, below the 95 percent that is considered the lower limit of the normal range.
Many medical experts consider patients to have severe Covid-19 if their oxygen levels drop below 94 percent. The physicians said Mr. Trump had received supplemental oxygen at the White House on Friday; they were not clear about whether it had been administered again on Saturday, or whether his blood oxygen levels had fallen below 90 at some point.
On Friday, Mr. Trump was given an infusion of an experimental antibody cocktail that is being tested in Covid-19 patients by the drugmaker Regeneron. Mr. Trump is also receiving a five-day course of remdesivir, another experimental drug that is used in hospitalized patients and has been granted emergency authorization by the Food and Drug Administration.
Regeneron’s antibody cocktail is being tested in patients early in the course of the infection, because the treatment fights the virus itself and may prevent it from spreading throughout the body.
Remdesivir is also an antiviral and is already commonly used with dexamethasone, which tamps down the body’s immune response and is given later in the illness, when some patients’ immune systems go into overdrive and attack their vital organs.
On Sunday, the doctors said that Mr. Trump was in good spirits and that he was walking on his own and not complaining of shortness of breath.
“If he continues to look and feel as well as he does today, our hope is to plan for a discharge as early as tomorrow to the White House, where he can continue his treatment,” one of his doctors, Dr. Brian Garibaldi, said at the briefing on Sunday.
But several medical experts said that the decision to prescribe dexamethasone to Mr. Trump did not align with that optimistic scenario.
A large study of dexamethasone in Britain found that the drug helped those who had been sick for more than a week, reducing deaths by one-third among patients on mechanical ventilators and by one-fifth among patients receiving supplemental oxygen by other means.
Guidelines from the World Health Organization recommend that the drug only be given to patients with “severe and critical Covid-19.” The National Institutes of Health has issued similar guidance, specifying that the drug is recommended only for people who require a mechanical ventilator to help them breathe, or who need supplemental oxygen.
“When I think about people needing dexamethasone, I think about people who are escalating their condition, who are heading closer to I.C.U. level than to home,” said Dr. Rochelle Walensky, chief of the division of infectious disease at Massachusetts General Hospital and a professor at Harvard Medical School.
Using multiple drugs at once could have an impact on their effectiveness, and it increases the risk of harmful drug interactions, said Dr. McGinn.
“You’re giving remdesivir, you’re giving dexamethasone, and you’re giving monoclonal antibodies,” he said, referring to the experimental treatment by Regeneron. “No one’s ever done that, not to mention famotidine and some zinc and a mix of cocktails, or whatever else he’s on.”
Uncertainty over the president’s condition stemmed at least in part from earlier mixed signals from the president’s physicians. On Sunday, the team acknowledged delivering an overly positive description of the president’s illness on Saturday.
“I didn’t want to give any information that might steer the course of illness in another direction, and in doing so, you know, it came off that we were trying to hide something, which wasn’t necessarily true,” Dr. Sean P. Conley, the White House physician, said to reporters on Sunday.
Dr. Rajesh Gandhi, an infectious diseases physician at Massachusetts General Hospital and a member of the panel that developed Covid-19 treatment guidelines for the N.I.H, said, “What would be very helpful to know is how much oxygen did the president need and for how long.”
The president’s physicians also have not described in detail the results of imaging scans of Mr. Trump’s lungs, or of blood tests indicating whether he is at risk for blood clots, a common complication in Covid-19 disease.
Mr. Trump is moderately obese, a condition that is usually accompanied by at least mild or moderate hypertension and mild to moderate diabetes, Dr. McGinn noted. The president’s high blood pressure is said to be under control, and he is not known to have Type 2 diabetes. Still, studies have identified the conditions as critical predictors of severe Covid-19 disease.
If Mr. Trump’s illness has significantly progressed, then dexamethasone and remdesivir are appropriate, several doctors said.
“He got the therapies that anybody going into any good hospital in the United States would receive today,” said Dr. Carlos del Rio, a professor of medicine at Emory University in Atlanta.
But the doctors also raised the possibility they might discharge the president as early as Monday, shortly after starting him on the steroid therapy, perplexing some experts.
“If you start somebody on steroids because their oxygen saturations are dropping, then that is the time to be vigilant and to be monitoring somebody more closely,” said Dr. Sam Parnia, an associate professor of critical care medicine at N.Y.U. Langone who has seen many Covid-19 patients.
“If there was a concern that certain things were not available at the White House when his oxygen was a little higher, it probably makes sense to be vigilant now,” Dr. Parnia said.
The fact that Mr. Trump is walking on his own, and that he delivered video statements in which he was able to complete sentences without gasping for breath, was seen as a positive sign by several experts.
Nevertheless, many sick Covid-19 patients appear to be doing well even when their lung function is poor, a condition doctors have nicknamed “happy hypoxia.”
“Of course, we like to see that he is feeling good, but it doesn’t put him in a category that’s essentially mild Covid,” Dr. Choo said.
Steroids may also give a false impression of the patient’s state. The drugs are also known to affect mood, causing euphoria or a general happiness. Steroids can also disrupt sleep, leading to insomnia, irritability or depression.
In some cases they may cause psychiatric effects, leading to feelings of grandiosity and mania, or even delirium and psychosis.
“The thing about steroids is they can have psychiatric side effects at almost any dose,” said Dr. J. Michael Bostwick, a psychiatrist with the Mayo Clinic who authored a paper on the subject.
While steroids are used widely in medicine without much concern about psychotropic effects, “it is necessary to notice if the use of these drugs causes changes in mood or thinking or sleep,” Dr. Bostwick said.
During the first week of Covid-19, the course of disease is unpredictable, Dr. Parnia said. It is never clear whether the illness will progress or plateau. “It can go north, or it can go south,” he said.
Any patient who has experienced low oxygen levels, or hypoxemia, must be closely watched, said Dr. Michelle Prickett, a pulmonary and critical care specialist at Northwestern Memorial Hospital in Chicago.
“It’s hard to feel confident early that things are going to turn around, especially in the presence of hypoxemia early on,” she said.
Denise Grady, Maggie Haberman and Sheryl Stolberg contributed reporting.