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CO2 IR Wavelength — FRCA Primary MCQ

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ModeratePhysics & Clinical MeasurementCO2 IR WavelengthFRCA Primary

Capnography uses infrared absorption at approximately which wavelength to measure CO2?

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Correct answer: C — 4260 nm (4.26 μm)

CO2 absorbs infrared radiation at approximately 4.26 μm (4260 nm). Nitrous oxide absorbs at 4.5 μm causing potential cross-interference (collision broadening) requiring correction. Oxygen is not measured by IR absorption as it is not an IR-absorbing gas (it uses paramagnetic or fuel cell analysers).

Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment