I am quite amazed. For my first responder missions I use a Nellcor pulse oximeter which cost CHF 900 at the time. I maintain it is still slightly more accurate than both the Beuer PO30 and PO80. I tested them, but all devices were pretty much identical. Partly 1% deviation in the oxygen saturation. I think this deviation can be neglected. We take the pulse value as a guideline and count the pulse manually anyway. With the PO80, as with my big Nellcor, the pulse rate is indicated acoustically and you can set an alarm value for (pulse) (too slow & too fast) and a limit value for oxygen saturation yourself. The Beuer PO80 has replaced my large and bulky Nellcor.