The limits of agreement are the mean difference ± 2SD. Stratified analyses were performed to investigate contributions of lactate, hypoxemia (as

estimated by a SaO2 <90%), bacteremia, pH, hemoglobin, and the requirement of vasoactive drugs to the relationship of SpO2 and SaO2. Normally or near-normally distributed variables were reported as means with standard deviations (SD) and non-normally distributed variables as medians with inter-quartile ranges (IQR). Means were compared using the appropriate Student's t test. A P-value of ≤ 0.05 was considered statistically significant. Given the exploratory nature of the analysis, no Inhibitors,research,lifescience,medical correction for multiple analyses was made. Results Ninety patients had simultaneous arterial blood gases and oxygen saturation values recorded. Upon review, 2 results were deemed to be venous samples and were excluded from the analysis. The remaining 88 simultaneous readings were analyzed to determine the bias and limits of agreement. Patient characteristics are reported in Table ​Table1.1. None of the patients Inhibitors,research,lifescience,medical had any recorded history of smoke inhalation or carbon monoxide exposure. Table 1 Summary of patient characteristics. The mean ± SD for SpO2 was 93.9% ± 4.8% and the mean for SaO2 was 90.2% ± 9.7%. Bland Altman analysis indicated a bias of 2.75% and limits of agreement -3.4% and

8.9% (Figure ​(SCH 900776 research buy Figure1).1). The effects Inhibitors,research,lifescience,medical of hypoxemia (SaO2 <90), lactate (>2 mmol/L and >4 mmol/L), acidosis (pH < 7.35), anemia (below median and quartile hemoglobins), bacteremia (positive cultures from ED draw), and Inhibitors,research,lifescience,medical requirement for vasoactive drugs on bias and limits of agreement

are shown in Table ​Table2.2. The mean differences (SpO2 – SaO2) in hypoxemic patients was 4.92% and in non-hypoxemic patients was 1.89% (p < 0.004). All 28 patients with SpO2 values ≥ 98% had SaO2 values > 90%. Of the 31 patients with SpO2 values ranging from 94-97%, 3 (9.7%) had SaO2 values < 90%. Eleven (50%) of the 22 patients with SpO2 values from 90-93% have SaO2 Inhibitors,research,lifescience,medical values < 90%. Accuracy of SpO2 was not demonstrated to be affected the by acidoisis, hyperlactatementa, anemia, or vasoactive drug use in this cohort. However, these variables markedly decreased precision (Table ​(Table22). Figure 1 Bland-Altman plot for bias and limits of agreement. Table 2 Pulse oximeter bias (mean SpO2 – SaO2) (%) in different subgroups of patients. Bias was higher in those who experienced ICU mortality but this did not reach statistical significance (3.9% vs. 2.5%, p = 0.28). There was no significant association between bias and admitting APACHE II score. Discussion There is little data on the accuracy of pulse oximetry in critically ill ED patients. Studies in both the ED and the ICU have produced mixed results and were comprised of mostly small and heterogenous patient populations that did not include sepsis.