Thx @airwaycam for the @nytimes article. My wife died a month ago, exactly the same way you describe: "silent hypoxia" for a week, no symptoms but cough. Then severe pneumonia, lungs full of blood clogs, and lastly pulmonary embolism. 5 days before, a chest xray showed nothing.

Less than 85 during all those days in the pulse oxim, watching movies, even breathing normal. As low as 62 when we called for an ambulance. Fully conscious and oriented, capable of speaking full sentences.