In this image from video, President Donald Trump waves as he drives past supporters gathered outside Walter Reed National Military Medical Center in Bethesda, Md., Sunday, Oct. 4, 2020. Trump was admitted to the hospital after contracting COVID-19. (AP Photo/Carlos Vargas)

BETHESDA, Md. — President Donald Trump declared, “I get it,” in a video Sunday evening before briefly leaving the hospital to salute supporters from his motorcade in a move raising new questions about his understanding of the coronavirus, which has killed more than 209,000 Americans.

Hours earlier, the president’s medical team reported that his blood oxygen level dropped suddenly twice in recent days after Trump announced that he tested positive early Friday. The doctors also said his health is improving and that he could be discharged as early as Monday.

“It’s been a very interesting journey. I learned a lot about COVID,” Trump said, standing in his hospital room in a video posted on social media.

He added, “I get it, and I understand it.”

At least one medical professional inside Walter Reed National Military Medical Center, where Trump has been hospitalized since Friday evening, questioned whether Trump had really learned anything about the virus that has swept through Republican leadership.

“Every single person in the vehicle during that completely unnecessary presidential ‘drive-by’ just now has to be quarantined for 14 days. They might get sick. They may die. For political theater. Commanded by Trump to put their lives at risk for theater. This is insanity,” Dr. James P. Phillips, an attending physician at Walter Reed, tweeted.

Trump’s doctors revealed Sunday that they gave the president a steroid treatment typically only recommended for the very sick. But they sidestepped questions about exactly when Trump’s blood oxygen dropped — an episode they neglected to mention in multiple statements the day before — or whether lung scans showed any damage.

It was the second straight day of obfuscation from a White House already suffering from a credibility crisis. It raised questions about whether the doctors treating the president were sharing accurate, timely information with the American public about his condition.

Pressed about conflicting information he and the White House released on Saturday, Navy Cmdr. Dr. Sean Conley acknowledged that he had tried to present a rosy description of the president’s condition.

“I was trying to reflect the upbeat attitude of the team, that the president, that his course of illness has had. Didn’t want to give any information that might steer the course of illness in another direction,” Conley said. “And in doing so, came off like we’re trying to hide something, which wasn’t necessarily true. The fact of the matter is that he’s doing really well.”

The briefing outside the Walter Reed National Military Medical Center lasted just 10 minutes.

Medical experts said Conley’s revelations raised new questions about how ill the president was and are hard to square with the doctor’s upbeat assessment and talk of a discharge.

Blood oxygen saturation is a key health marker for COVID-19 patients. A normal reading is between 95 and 100. Conley said the president had a “high fever” and a blood oxygen level below 94% on Friday and during “another episode” on Saturday.

He was evasive about the timing of Trump oxygen drops.and asked whether Trump’s level had dropped below 90%, into concerning territory. But he revealed that Trump was given a dose of the steroid dexamethasone in response. At the time of the briefing, Trump’s blood oxygen level was 98% — within normal rage, Trump’s medical team said.

Asked about Conley’s lack of transparency, White House aide Alyssa Farah suggested doctors were speaking as much to the president as to the American public, “when you’re treating a patient, you want to project confidence, you want to lift their spirits and that was the intent.”

Trump was back on social media Sunday. First he shared a video of flag-waving supporters outside the hospital, many of them not wearing face masks to prevent spread of the virus.

Trump’s Democratic challenger, Joe Biden, pulled his attack ads off the air during Trump’s hospitalization. Biden was at home in Wilmington, Delaware, on Sunday with no plans for in-person campaigning or other public appearances. Having already tested negative, he is expected to release the results of a new coronavirus test later in the day. His campaign has pledged to disclose those results and all other future test results for the 77-year-old candidate.

More than 209,000 Americans have been killed by the virus, by far the highest number of confirmed fatalities in the word. In all, nearly 7.4 million people have been infected in the United States, and few have access to the kind of around-the-clock attention and experimental treatments as Trump.

Trump’s treatment with the steroid dexamethasone is in addition to the single dose he was given Friday of an experimental drug from Regeneron Pharmaceuticals Inc. that supplies antibodies to help the immune system fight the virus. Trump on Friday also began a five-day course of remdesivir, a Gilead Sciences drug currently used for moderately and severely ill patients.

The drugs work in different ways — the antibodies help the immune system rid the body of virus, and remdesivir curbs the virus’ ability to multiply. Garibaldi, a specialist in pulmonary critical care, said the president was not showing any side effects of the drugs “that we can tell.”

Several White House officials this weekend expressed frustration with the way level of transparency and public disclosure since the president announced his diagnosis early Friday. Most of that frustration appears to be directed at Trump, with aides believing that he has restricted what Conley can say or that Conley has tried to appease the president.

Story by Jill Colvin, Steve Peoples and Zeke Miller. Associated Press writers Lauran Neergaard and Jonathan Lemire in Washington, and Bill Barrow in Wilmington, Del., and Marilynn Marchione in Milwaukee contributed to this report.