Oct. 4 (UPI) -- President Donald Trump made a "surprise" visit to supporters outside Walter Reed National Military Medical Center on Sunday, hours after doctors said Sunday the president could be discharged as early as Monday despite acknowledging his blood oxygen levels dropped twice since Friday.
Trump wore a cloth mask while sitting in the back seat and waving as the motorcade drove by supporters near the hospital in Maryland.
"President Trump took a short, last-minute motorcade ride to wave to his supporters outside and has now returned to the Presidential Suite inside Walter Reed," White Hosue Deputy Press Secretary Judd Deere said in a statement.
Secret Service agents riding in the car wore N95 masks, protective eyewear and protective gowns.
The president hinted at the appearance in a video shared to his Twitter account on Sunday evening, in which he said he was able to meet "soldiers and first responders" at Walter Reed, but did not elaborate on the nature of those meetings.
"I also think we're going to pay a little surprise to some of the great patriots that we have out on the street," he said.
In the video, Trump also said that he was "getting great reports from the doctors" and that he has "learned a lot about COVID" since arriving at the hospital.
"I learned it by really going to school. This is the real school. This isn't the 'let's read the book' school and I get it. And I understand it. And it's a very interesting thing. I'm gonna be letting you know about it. In the meantime, we love the USA and we love what's happening," said Trump.
During a morning briefing, doctors treating Trump following his positive COVID-19 test late Thursday said the president has "continued to improve" and responded to treatment after he was transported to Walter Reed on Friday.
"If he continues to look and feel as well as he does today, our hope is that we can plan for a discharge as early as tomorrow to the White House where he can continue his treatment course," said Dr. Brian Garibaldi of Johns Hopkins University.
White House physician Dr. Sean Conley also said that doctors will begin discharge plans if "everything continues to go well."
The president, and first lady Melania Trump, tested positive for and doctors aid he had experienced symptoms including a mild cough, nasal congestion and fatigue beginning Thursday, but that those conditions have since improved.
As of Saturday, Conley said Trump had been fever free for more than 24 hours and had been walking around and tending to work.
Mark Meadows, the White House chief of staff, told Fox News on Saturday night that Trump's oxygen levels fell rapidly on Friday.
Conley, after previously declining to state whether Trump had been administered oxygen since the start of his treatment, said Sunday the president had two episodes of falling oxygen saturation levels and was administered supplemental oxygen Friday at the White House despite saying Trump was "fairly adamant" he did not need it.
Trump received the steroid dexamethasone to the president in response to his two drops in oxygen saturation, with Garibaldi saying the first dose was administered on Saturday.
The National Institutes of Health recommends only giving dexamethasone to Covid-19 patients who need oxygen, including those on ventilators, saying patients with severe Covid-19 can develop a systemic [all-of-body] inflammatory response that can lead to lung injury and multisystem organ dysfunction."
He also received two doses of the antiviral drug remdesivir that was authorized for emergency use in May for treating hospitalized patients with the coronavirus.
Conley said he did not initially disclose that Trump had received supplemental oxygen "to reflect the upbeat attitude of the team."
In a video shared to his Twitter account Saturday night Trump said he "wasn't feeling so well" when he arrived at Walter Reed but assured he would "be back soon" to finish his re-election campaign.
Trump's assistant Nicholas Luna tested positive for COVID-19, CNN reported Sunday. Luna was described as one of the president's "body men" tasked with accompanying him throughout the day and night.
He joins about a dozen people linked to events attended by Trump at the White House over the past week who have also tested positive for the coronavirus.