President Donald J. Trump’s blood oxygen level sank to a precariously low level after he announced that he had tested positive for the coronavirus last year, according to a new book by Mark Meadows, his former chief of staff.

The new details contradict Mr. Trump’s denials this year that his Covid bout was more dire than White House medical officials had acknowledged at the time…

On Friday, Oct. 2, 2020, hours after the president announced on Twitter that he had tested positive for the virus, he recorded a blood oxygen level of about 86 percent, Mr. Meadows wrote. That is roughly 10 points below what would be considered normal. Most healthy people have a blood oxygen level of about 95 to 98 percent, although some people may have lower normal readings.

Mr. Trump’s health had deteriorated so much that day that members of his medical team feared they would not be able to treat him adequately without immediate attention from hospital staff, Mr. Meadows wrote.