Required section · Section 5 of 6
Choose the measurement that answers the question
A second scenario has an unexpectedly normal SpO2 after a possible smoke exposure, while the clinical picture is discordant. A pulse oximeter estimate cannot rule out COHb because its two wavelengths do not distinguish COHb from oxyhemoglobin. A calculated blood-gas saturation can also appear normal when it assumes normal hemoglobin behavior. The bounded laboratory action is to review specimen and method context and obtain arterial blood gas testing with co-oximetry when fractions are needed.
Do not infer oxygen content from saturation alone. To assess CaO2, use hemoglobin plus saturation and PaO2; use co-oximetry to separate FO2Hb from functional sO2 when a dyshemoglobin question exists. COHb level does not reliably predict poisoning severity because timing, oxygen exposure, symptoms, and neurologic status matter. Clinical treatment decisions require clinical judgment.
Put the laboratory reasoning sequence in order, then use the checks to state what each method answers. The goal is a defensible result interpretation with method limits visible. Select co-oximetry for hemoglobin fractions, not as a substitute for understanding which saturation was reported.
Ordering exercise
Order the laboratory response to a saturation reading that does not fit the clinical picture.
1. Use co-oximetry when fractions are needed
Measure O2Hb, HHb, COHb, and MetHb from an arterial sample.
2. Communicate result and method limit
Release the result using local policy and make the relevant limitation visible.
3. Review collection and handling
Assess air exposure, heparin, delay, and other preanalytical concerns.
4. Identify method and saturation convention
Confirm whether the number is SpO2, calculated sO2, functional sO2, or FO2Hb.
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The module finishes after every required section is marked done and every check in those sections is correct.