Diagnostic Performance of Carbon Monoxide Testing by Pulse Oximetry in the Emergency Department

摘要

BACKGROUND: Carbon monoxide (CO) exposure causes roughly 40,000 emergency department (ED) visits annually and is commonly misdiagnosed. Whereas the standard method of carboxyhemoglobin (HbCO) measurement utilizes blood gas analysis, a noninvasive, FDA-cleared alternative exists. We evaluated the performance of pulse oximetry (S-pCO) for identification of CO exposure in ED patients. METHODS: We compared pulse oximetry to blood HbCO levels in a prospective observational study of adult and pediatric subjects recruited from the ED. Nurses screened a convenience sample of patients and referred those with S-pCO >= 10% to research staff. Researchers also approached individuals who presented with signs and symptoms of CO toxicity. We determined diagnostic performance with a Bland-Altman analysis and calculated sensitivity and specificity for detection of elevated HbCO at thresholds of >= 10% and >= 15%. To optimize the potential sensitivity of S(pCO )for detection of CO toxicity, research technicians performed 3 S pco readings within 5 min of the blood draw for laboratory measurement. A positive S-pCO test was defined as any S-pCO >= 10%. RESULTS: 42,000 patients were screened, 212 were evaluated, and 126 subjects were enrolled. Median HbCO level was 6% (range 1.6-21.9%). Limits of agreement were -103% and &1%. Of 23 individuals with elevated HbCO >= 10%, 13 were not suspected based on clinical assessment. Critically elevated HbCO was present in 6 individuals. Based on our a priori threshold of 10% for a positive test, pulse oximetry identified 14 of 23 subjects with HbCO >= 10%, with a sensitivity of 61% (95% CI 39-80%) and a specificity of 86% (95% CI 78-92%), and 5 of 6 subjects with HbCO >= 15%, with a sensitivity of 83% (95% CI 36-100%) and a specificity of 81% (95% CI 73-87%). CONCLUSIONS: Pulse oximetry underestimated HbCO and produced false negative results (ie, S-pCO = 15%. Triage screening with pulse oximetry detected cases of elevated HbCO that were not suspected by the clinical provider.