It is a mystery that has left doctors questioning the basic tenets of biology: Covid-19 patients who are talking and apparently not in distress, but who have oxygen levels low enough to typically cause unconsciousness or even death.
The phenomenon, known by some as “happy hypoxia” (some prefer the term “silent”) is raising questions about exactly how the virus attacks the lungs and whether there could be more effective ways of treating such patients.
A healthy person would be expected to have an oxygen saturation of at least 95%. But doctors are reporting patients attending A&E with oxygen percentage levels in the 80s or 70s, with some drastic cases below 50%.
“It’s intriguing to see so many people coming in, quite how hypoxic they are,” said Dr Jonathan Bannard-Smith, a consultant in critical care and anaesthesia at Manchester Royal Infirmary. “We’re seeing oxygen saturations that are very low and they’re unaware of that. We wouldn’t usually see this phenomenon in influenza or community-acquired pneumonia. It’s very much more profound and an example of very abnormal physiology going on before our eyes.”
Dr Mike Charlesworth, an anaesthetist at Wythenshawe hospital in Manchester, said that while other lung conditions could cause severe hypoxia, these patients would normally appear extremely ill. “With pneumonia or a pulmonary embolism they wouldn’t be sat up in bed talking to you,” he said. “We just don’t understand it. We don’t know if it’s causing organ damage that we’re not able to detect. We don’t understand if the body’s compensating.”