Pulse Oximeter: Give it the middle finger!

What finger is best to use for a pulse oximeter? Most likely you would answer the pointer finger. However, research indicates that the middle finger on the right hand results in the most accurate SpO2 measurement when using a finger pulse oximeter.

An research paper published on the US National Library of Medicine states "Higher perfusion in the middle finger seems reasonable to expect the highest and most accurate SpO2 value. According to the results of our study, we believe that the middle finger of the dominant hand has the highest and possibly the most accurate SpO2 measurements. The highest SpO2 value can be taken as the most accurate value that reflects the arterial oxygen saturation (SaO2). Because there may be contributing factors that can decrease the SpO2 recording measured by a pulse oximeter lower than SaO2, but there is no contributing factor that can increase the SpO2 recording higher than SaO2 (when a carbon monoxide poisoning like condition does not exist)." Source Material

From the research, the highest SpO2 measurement is the most accurate. You can not cause the reading to increase. However, other factors can results in a lower SpO2 reading; finger nail polish, fake nails, cold hands, poor circulation, bright lights and CO poisoning.

If your finger nail has nail polish coating it or you have on fake nails, then you can take a SpO2 reading by rotating the pulse oximeter 90 degrees on your finger. This will take a reading through the sides of your finger.

If you have poor circulation or cold hand, try to warms them up prior to taking a measurement. Rub your hands together or place them in a warm towel to increase blood flow through your fingers.

If you have CO poisoning, there's not much you can do, If you are a smoker, read our article about the effects of smoking on SpO2 levels. CLICK TO READ

Make sure to take readings from the same finger to establish a baseline and for consistency.