Pulse Oximeter: What It Measures, How It Works, and How to Read It
FL400 Fingertip Pulse Oximeter - Blood Oxygen Monitor (Blue) - with Case, FDA 510(K) cleared
What's a Pulse Oximeter, and Do I Really Need One at Home? - The New York Times
Pulse Oximetry > Fact Sheets > Yale Medicine
Amazon.com: Fingertip Pulse Oximeter Blood Oxygen Saturation Monitor Pulse Ox, Heart Rate and Fast Spo2 Reading Oxygen Meter with OLED Screen Included Lanyard and 2 X AAA Batteries : Health & Household