The Pulse Oximetry Gap in Carbon Monoxide Intoxication

Robert G. Buckley, Stephen E. Aks, James L. Eshom, Robert Rydman, Jeffrey Schaider, Phillip Shayne

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77 Scopus citations


See related editorial, "Should the Pressure Be Off or On in the Use of Oxygen in the Treatment of Carbon Monoxide-Poisoned Patients?". Study objective: Pulse oximetry has been reported to be falsely elevated in the presence of carbon monoxide (CO). However, the degree to which pulse oximetry overestimates measured oxyhemoglobin saturation (O2 Hb) has not been investigated in patients with CO exposure. This study quantifies the effect of CO on pulse oximetry and O2 Hb in a series of patients with elevated carboxyhemoglobin (COHb) levels. Methods: A prospective case series of 25 pulse oximetry measurements, with concurrent arterial blood gas sampling, were obtained on 16 adults with CO exposure. Results: COHb levels (mean, 16.1%; SD, 11.6%; range, 2.2% to 44%) did not significantly correlate with pulse oximetry saturation (mean, 97.7%; SD, 1.5%; range 96% to 100%) (r =.45; P =.1 [NS]). Compared with COHb, a pulse oximetry gap (mean, 17.5%; SD, 1.5%; range, 2.3% to 42%), defined as pulse oximetry saturation minus O2 Hb, yielded a linear regression model: pulse oximetry gap=1.82+0.94×COHb (SEM=0.07; F=204; R 2 =.90; P<.0001). Conclusion: Oxygen saturation as measured by pulse oximetry failed to decrease to less than 96% despite COHb levels as high as 44%. Regression between the pulse oximetry gap and COHb suggests that pulse oximetry overestimates O2 Hb by the amount of COHb present. Pulse oximetry is unreliable in estimating O2 Hb saturation in CO-exposed patients and should be interpreted with caution when used to estimate oxygen saturation in smokers. [Buckley RG, Aks SE, Eshom JL, Rhydman R, Schaider J, Shayne P: The pulse oximetry gap in carbon monoxide intoxication. Ann Emerg Med August 1994;24:252-255.].

Original languageEnglish (US)
Pages (from-to)252-255
Number of pages4
JournalAnnals of Emergency Medicine
Issue number2
StatePublished - Aug 1994

ASJC Scopus subject areas

  • Emergency Medicine


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