An emergency doctor, Richard Levitan, reports in the NY Times his opinion that pulse oximetry can indicate an early warning of pneumonia.
His final paragraph is:
All patients who have tested positive for the coronavirus should have pulse oximetry monitoring for two weeks, the period during which Covid pneumonia typically develops. All persons with cough, fatigue and fevers should also have pulse oximeter monitoring even if they have not had virus testing, or even if their swab test was negative, because those tests are only about 70 percent accurate. A vast majority of Americans who have been exposed to the virus don’t know it.
His reasoning is that the pneumonia associated with COVID brings about "silent hypoxia". The patient does not seem or feel short of breath, but their o2 levels are very, very low. "Silent hypoxia progressing rapidly to respiratory failure explains cases of Covid-19 patients dying suddenly after not feeling short of breath.
Use your oximeter, folks!