Happy hypoxia, or silent hypoxia, is a phenomenon in which patients with catastrophically low oxygen levels appear comfortable and even capable of speech despite their serious condition. As the Covid-19 outbreak continues to rage on, there have been increasing reports from medical professionals of patients presenting with this strange juxtaposition of symptoms and pathology, revealing just another way in which this deadly disease causes confusion that can slow its diagnosis. The phenomenon is described in an article published in the British Journal of Anaethesia, which explains that while its occurrence is anecdotal, happy hypoxia appears to be emerging as a common clinical pattern for Covid-19.
Oxygen saturation is a measure of how much oxygen is being carried in your blood and for a healthy person this would be expected to be around 95 percent or above. Reports from A&E doctors have described patients in emergency centers who are seemingly stable but when tested are found to have oxygen saturation levels in the 80s or 70s, and even in extreme scenarios as low as 50 percent.
At levels in the 80s, 70s, or below, patients would usually be expected to be in some notable distress and certainly not sitting up in bed talking comfortably. It’s not uncommon for illnesses such as pneumonia to cause an oxygen saturation level of below 90 percent, and this condition is usually considered grounds for hospitalization due to the seriousness of the possible outcomes, which can range from confusion to shock and death.
In an interview with the Guardian, Dr Jonathan Bannard-Smith – a consultant in critical care and anesthesia at the Manchester Royal Infirmary – said: “It’s intriguing to see so many people coming in, quite how hypoxic they are. 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.”
The exact mechanism through which these patients are able to compensate for their low oxygen levels isn’t known, but one possible explanation is that the illness is blocking the body’s ability to detect increasing carbon dioxide levels. Usually, a reduction in oxygen triggers the body to take steps to return the balance, such as increased breathing and rest, but for some reason this physiological response isn’t happening in some Covid-19 patients. The phenomenon poses a danger to patients and an obstacle to physicians in addressing the severity of their symptoms before it's too late, as swift treatment of hypoxia is needed in order to achieve a positive outcome for the patient.