How can I convert SpO2 to PaO2?

PaO2 is a measurement of the partial pressure of oxygen in arterial blood and requires an arterial blood gas (ABG). In many settings an ABG may not be practical or feasible, and thus the established mathematical relationship between SpO2 and PaO2 can be used. There is a distinct relationship between PaO2 and SpO2 which is illustrated by the Oxygen Dissociation Curve (see image). This relationship can be altered by many factors (e.g. temperature, FDG, pH) but generally follows the classic “S-shape” graph with PaO2 on the x axis and oxygen saturation on the y axis. This online calculator can be used to convert SpO2 to PaO2.

References: Lifebox Pulse Oximetry Learning Module; Oxygen Calculator Website

Keywords: PaO2, oxygen dissociation curve, conversion