Severinghaus pH Method — FRCA Primary MCQ
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Correct answer: E — CO2 diffusing through a membrane and changing pH of a bicarbonate solution which is measured by a glass pH electrode
CO2 diffuses through a Teflon membrane into a sodium bicarbonate solution forming carbonic acid which changes pH. This pH change is detected by a glass pH electrode and is proportional to log PaCO2. The Clark electrode measures PaO2 by polarographic reduction.
Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment