Trump's doctors say the president is getting better. But they also started him on a steroid usually reserved for patients with 'severe and critical COVID-19'

• White House physician Sean Conley announced Sunday that President Trump was feeling better. Conley said he hoped the president could return to the White House by Monday.
• But Trump's doctors have chosen to give him dexamethasone, a corticosteroid, after the president required supplemental oxygen on Friday and Saturday.
• According to the World Health Organization, dexamethasone should only be given to patients with “severe and critical COVID-19."
• Steroids are given "to the sickest patients" to reduce a patient's risk of death when on a ventilator, one expert told Business Insider.

White House physicians told reporters that President Trump was feeling better on Sunday morning and that they hoped he could be discharged on Monday.

But Trump's doctor, Sean Conley, also said that the president had been treated Saturday with dexamethasone, a corticosteroid that, according to the World Health Organization, is only for patients with "severe and critical COVID-19."

Research suggests dexamethasone reduces risk of death in such patients, who require supplemental oxygen and ventilators to breathe. But the benefits of such a steroid come at a cost: they blunt the immune system's response, which means it takes longer for the body to clear the virus.

Dr. Panagis Galiatsatos, a pulmonary physician at Johns Hopkins Bayview Medical Center, said he's seen steroids work well for critically ill people, but that they're by no means curative.

"You're giving them to the sickest patients," Galiatsatos told Business Insider. "And when I say they work well, it just keeps them from dying. It doesn't mean it got them off the ventilator faster."

Dexamethasone is for patients about to be put 'on a breathing machine'

While this latest addition to Trump's treatment plan may seem counter to the "upbeat attitude" Conley said Trump and his team were trying to maintain, the president's physician revealed startling new details about Trump's condition on Sunday that could explain why steroids are on the table.

Trump needed supplemental oxygen at least once for an hour on Friday at the White House, and possibly again in the hospital Saturday.

Conley said Trump's blood oxygen levels momentarily dipped below 94% on Friday, and then to 93% on Saturday. Blood-oxygen readings can help flag serious cases even before a person has developed severe symptoms like shortness of breath. They can also signal to patients when it's time to go to the hospital, or to physicians when it's time to consider certain treatments like dexamethasone.

"If [Trump is] telling me he's much more short of breath where his work of breathing is bad and I'm looking at the pulse oximeter and his oxygen is low, I'm pulling the trigger for the steroid at that moment because I'm about to put him on a breathing machine," Galiatsatos said of how he might approach the situation.

Indeed, the National Institutes of Health stipulated that a 10-day course of the steroid is only recommended for patients who need a ventilator or extra oxygen, and specifically recommended against dexamethasone as a treatment for patients that don't need assistance breathing.

Even at 93%, Trump's blood oxygen levels don't meet the WHO's criterion for dexamethasone treatment: the organization defines "severe" COVID-19 patients as those with blood oxygen levels lower than 90%.

But according to Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security, there's nothing abnormal about the president's treatment given what we know about his illness.

"Dexamethasone is what we use on anybody requiring supplemental oxygen," Adalja told Business Insider, adding: "It's standard even if it's a transient need for oxygen."

Steroids blunt the immune system's response to the virus

The steroid isn't the only drug Trump is getting.

He's taking remdesivir, an FDA-emergency authorized drug proven to speed patient recovery, and an experimental antibody cocktail from drug company Regeneron that's been shown to improve symptoms in non-hospitalized patients.

Adalja said there's nothing "particularly right or wrong" about Trump's doctors prescribing him that Regeneron cocktail, just that there's not enough evidence to show it's effective yet.

Throwing a steroid into the mix may suppress the benefits of that antibody cocktail, which tries to mimic the body's natural immune system to fight off the virus. Steroids, in turn, are used to stop our immune system from reacting too aggressively. Sometimes, during the later stage of the COVID-19 illness, the immune system will start attacking the body instead of the virus, an event known as a "cytokine storm."

"If he gets steroids, whatever that antibody was is gone now," Galiatsatos said. "You're trying to just stop that chaos of an immune response."

Aria Bendix contributed reporting to this story.