Tricks of the trade : the 4-5-6 ; 7-8-9 rule

 

This is a “cute” way to remember SpO2 vs. PaO2.

When the spo2=40%, the pao2=70.

When the spo2=50%, the pao2=80.

When the spo2=60%, the pao2=90.

SpO2                 PaO2

40%                    70

50%                    80

60%                    90