Equations of Brown et al for Estimating PaO2 from the SpO2

Patient selection: mechanically-ventilated patient in the ICU

Models:

(1) linear

(2) log-linear

(3) nonlinear

PO2 by linear model =

= (FIO2) * (((SpO2) / (FIO2)) - 64) / 0.84

PO2 by log-linear model =

= (FIO2) * 10^((0.78 * (LOG10((SpO2) / (FIO2)))) + 0.48)

PO2 by nonlinear model=

= A + B

A =

= ((11700/C) + SQRT(125000 + ((11700/C)^2)))^0.3333

B =

= ((11700/C) - SQRT(125000 + ((11700/C)^2)))^0.3333

C =

= (1 / (SpO2)) - 1

The nonlinear equation was used to generate a lookup table for PaO2 from SpO2.