The best replacement for po2 is pao2.

The best alternatives to po2 are rated as following:
★★★★★  pao2
★★★★  pco2
★★★  spo2
★★  sao2
★★  o2 saturation
★★  o2 sat
★  saturation
★  pulse ox
★  fo2
  po2
  oxygen saturation

Your alternative for po2 is not listed? Suggest!
Speaking about po2, one probably shouldn't forget about normal saturation.

Other search terms related to po2 and their ratings are:
★★★★★ normal saturation
You have in mind a companion for po2 and it is not yet here? Propose!



Google Trends

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