RT Journal Article
SR Electronic
T1 Diagnostic Performance of Carbon Monoxide Testing by Pulse Oximetry in the Emergency Department
JF Respiratory Care
FD American Association for Respiratory Care
SP respcare.06365
DO 10.4187/respcare.06365
A1 Nuria Villalba
A1 Zachary T Osborn
A1 Pamela R Derickson
A1 Chelsea T Manning
A1 Robert R Herrington
A1 David A Kaminsky
A1 Kalev Freeman
YR 2019
UL http://rc.rcjournal.com/content/early/2019/04/30/respcare.06365.abstract
AB 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 (SpCO) 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 SpCO ≥ 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 SpCO for detection of CO toxicity, research technicians performed 3 SpCO readings within 5 min of the blood draw for laboratory measurement. A positive SpCO test was defined as any SpCO ≥ 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 –10.3% and 8.1%. 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, SpCO < 10% for all three measurements) in 17% of ED subjects with elevated HbCO ≥ 15%. Triage screening with pulse oximetry detected cases of elevated HbCO that were not suspected by the clinical provider.