Capnograph Phase III Slope — FRCA Primary MCQ

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ModeratePhysics & Clinical MeasurementCapnograph Phase III SlopeFRCA Primary

Phase III of the capnograph waveform has an increased slope in:

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Correct answer: E — V/Q mismatch or obstructive airways disease

Increased Phase III slope indicates V/Q mismatch or obstructive airways disease (COPD / asthma / bronchospasm) because lung units with different time constants empty at different rates producing gradually increasing CO2. A flat plateau indicates homogeneous ventilation.

Reference: Al-Shaikh Stacey 2019 Essentials of Anaesthetic Equipment