Deceptive simplicity: Systemic oxygen delivery and pulse oximetry

Abstract

Pulse oximetry is often perceived to be a measure of the adequacy of oxygen delivery. It is, however, only a measure of oxygen bound to haemoglobin. Systemic oxygen delivery is principally determined by cardiac output, haemoglobin concentration and haemoglobin saturation. Changes to both cardiac output and haemoglobin concentration will significantly alter oxygen delivery without changing oxygen saturation. This article will describe the components of systemic oxygen delivery and the physiologic limitation of pulse oximetry and caution against over-interpretation of oximetry in the care of newborns.

Oxygen therapy in neonatal care

“…These devices are noninvasive, do not need recalibrating and are relatively easy to use but they can vary in their performance (Johnson et al, 2011), have limitations (Collins and Andersen, 2007) and are frequently misunderstood (Popovich et al, 2004). Oximeters monitor the level of oxygen bound to haemoglobin rather than systemic oxygen delivery which depends on cardiac output, Hb concentration and Hb saturation (Collins and Andersen, 2007).…”