Relying on pulse oximetry to avoid hypoxaemia and hyperoxia: A multicentre prospective cohort study in patients with circulatory failure

Abstract

Purpose: The purpose of this study was to assess the predictive performance of pulse oximetry (SpO₂) to rule out hypoxaemia and hyperoxia in critically ill patients.

Methods: SpO₂, arterial oxygenation (SaO₂), and arterial partial pressure of oxygen (PaO₂) were prospectively and simultaneously measured every 6 h during the first 24 h of intensive care unit admission in a multicentre cohort of critically ill patients suffering acute circulatory failure. Likelihood ratios associated with different cutoff values of SpO₂ to rule out hypoxaemia (SaO₂ < 90% or PaO₂ < 60 mmHg) or hyperoxia (SaO₂ > 95% or PaO₂ > 100 mmHg) and post-test probabilities were calculated. Mean bias between SpO₂ and SaO₂ and agreement interval were calculated. Area under the receiver operating characteristics associated with SpO₂ to predict different threshold values of SaO₂ and PaO₂ were calculated.

Results: Five hundred seventy-one patients (mean [standard deviation] Simplified Acute Physiology Score II: 58.7 [20.1]; mechanically ventilated 75.6%) with 2643 available SaO₂ and PaO₂ samples and corresponding 2643 SpO₂ values were analysed. Mean bias between SpO₂ and SaO₂ was 1.1%, and its agreement interval ranged from -8.2 to +11.1%. SpO₂ cutoff values of 88%, 90%, and 92% left the possibility that 8%-13% of patients had hypoxaemia. SpO₂ < 95% left the possibility that 31% of patients had hyperoxia. All calculated areas under the receiver operating characteristics showed a lower limit of their 95% confidence interval below 0.85 CONCLUSION: In this cohort of patients with circulatory failure, SpO₂ had poor discriminative ability to rule out hypoxaemia and hyperoxia. Overconfidence upon SpO₂ monitoring may be dangerous.

Keywords: Acute respiratory failure; Blood gas; Oxygen saturation; Oxygen therapy; Pulse oximetry.