In the FDA website https://www.fda.gov/medical-devices/saf ... %20values. the accuracy is discussed for FDA approved oximeters.
There are a couple of learning points here:FDA-cleared prescription pulse oximeters are required to have a minimum average (mean) accuracy that is demonstrated by desaturation studies done on healthy patients. This testing compares the pulse oximeter saturation readings to arterial blood gas saturation readings for values between 70-100%. The typical accuracy (reported as Accuracy Root Mean Square or Arms) of recently FDA-cleared pulse oximeters is within 2 to 3% of arterial blood gas values. This generally means that during testing, about 66% of SpO2 values were within 2 or 3% of blood gas values and about 95% of SpO2 values were within 4 to 6% of blood gas values, respectively.
However, real-world accuracy may differ from accuracy in the lab setting. While reported accuracy is an average of all patients in the test sample, there are individual variations among patients. The SpO2 reading should always be considered an estimate of oxygen saturation. For example, if an FDA-cleared pulse oximeter reads 90%, then the true oxygen saturation in the blood is generally between 86-94%. Pulse oximeter accuracy is highest at saturations of 90-100%, intermediate at 80-90%, and lowest below 80%. Due to accuracy limitations at the individual level, SpO2 provides more utility for trends over time instead of absolute thresholds. Additionally, the FDA only reviews the accuracy of prescription use oximeters, not OTC oximeters meant for general wellness or sporting/aviation purposes. (bold emphasis added by FDA)
(1) it is implied that the oximeter readings of an oximeter under test/review are averaged then compared with a laboratory-based arterial blood gas determination for purposes of the analysis.
(2) Clearly states that the acceptable range is 8% (plus 4% or minus 4%) from the blood gas value.
(3) The FDA only reviews (tests?) oximeters that are for prescription-use. (sounds like they will not review/evaluate OTC oximeters.