• Eric Boccio, Justin Belsky, Sandra Lopez, Brian Kohen, and James Bonz.
• Department of Emergency Medicine, Memorial Healthcare System, Hollywood, Florida. Electronic address: eboccio@mhs.net.
• J Emerg Med. 2024 Aug 6.

BackgroundPreoxygenation is intended to extend the duration of apnea until desaturation occurs. End-tidal oxygen (ETO2) is the standard for measuring preoxygenation, however, peripheral capillary oxygen saturation (SpO2) is used more commonly within the emergency department.ObjectiveThe primary aim was to determine whether patients were optimally preoxygenated as measured by ETO2 vs. SpO2 during rapid sequence intubation. Secondary aims investigated changes in these measurements before and after intubation and whether patient characteristics influenced the likelihood of preoxygenation success as measured by each of the modalities.MethodsA multicenter, prospective observational study of a convenience sample of patients undergoing rapid sequence intubation was performed. ETO2 and SpO2 were recorded at the cessation of preoxygenation (T1) and intubation completion (T2). Optimal preoxygenation was defined by an observed ETO2 level ≥ 90% and SpO2 level equal to 100% at T1.ResultsThirty patients were intubated and included in the analysis. Median ETO2 and SpO2 at T1 were 90.5% (interquartile range 86-93%) and 100% (interquartile range 97-100%), respectively. Preoxygenation success rates as measured by ETO2 and SpO2 were 56.7% and 53.3%, respectively (p = 0.431). The mean (SD) decrease in ETO2 during the intubation attempt was larger and more variable than that for SpO2 (25.8% [22.5%] vs. 2.1% [3.3%]; p < 0.001). Patient age, sex, and body mass index were not associated with likelihood of preoxygenation success for either modality.ConclusionsPreoxygenation success was similar when measured by strict ETO2 and SpO2 criteria. ETO2 is more sensitive to periods of apnea than SpO2 and may serve as an early indicator of an imminent desaturation event.Copyright © 2024 Elsevier Inc. All rights reserved.

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