This is a Covid-19-related posting. Source was a doctor interviewed by CBS News at about 8:00 am today. He recommended that everyone take their oxygen levels daily. He added that Coronavirus patients “presenting” at ER’s often had blood oxygen levels half of normal, and he was surprised they could still walk around. So I ordered an oximeter, many choices online, family member says Costco doesn’t currently have them. He added that many CV patients don’t need ventilators, but if they let the disease progress untreated their oxygen levels are so low and CO2 levels so high that a ventilator is needed. My oximeter is weeks away but at least I’ll have one.