Accuracy of Multiple Pulse Oximeters in Stable Critically Ill Patients

An accurate S_pO value is critical in order to optimally titrate oxygen delivery to patients and to follow oxygenation guidelines. Limited prospective data exist on real-world performance of pulse oximeters in critically ill patients. The objective of this study was to assess accuracy and bias of the S_pO values measured by several oximeters in hospitalized subjects.

We included stable adults in the ICU with an arterial catheter in place. Main exclusion criteria were poor S_pO signal and S_pO > 96%. In each subject, we simultaneously evaluated 4 oximeters: Nonin (Plymouth, Minnesota) embedded in the FreeO₂ device (OxyNov, Québec City, Québec, Canada), Masimo (Radical-7, Masimo, Irvine, California), Philips (FAST, Philips, Amsterdam, the Netherlands), and Nellcor (N-600, Medtronic, Minneapolis, Minnesota). Arterial blood gases were drawn and simultaneously each oximeters' S_pO values were collected. S_pO values were compared to the reference (arterial oxygen saturation [S_aO ] value) to determine bias and accuracy. The ability for oximeters to detect hypoxemia and the impact of oximeters on oxygen titration were evaluated.

We included 193 subjects (153 male, mean age 66 y) in whom 211 sets of measurements were performed. The skin pigmentation evaluated by Fitzpatrick scale showed 96.2% of subjects were light skin (types 1 and 2). One oximeter overestimated S_aO (Philips, +0.9%), whereas the 3 others underestimated S_aO (Nonin -3.1%, Nellcor -0.3%, Masimo -0.2%). S_aO was underestimated with Nonin oximeter in 91.3% of the cases, whereas it was overestimated in 55.2% of the cases with Philips oximeter. Moderate hypoxemia (S_aO 86-90% or P_aO 55-60 mm Hg) was detected in 92, 33, 42, and 11% of the cases with Nonin, Nellcor, Masimo, and Philips, respectively.

We found significant bias and moderate accuracy between the tested oximeters and the arterial blood gases in the studied population. These discrepancies may have important clinical impact on the detection of hypoxemia and management of oxygen therapy.