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LMA Displacement During Surgery — FRCA Final MCQ

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ModerateAirway ManagementLMA Displacement During SurgeryFRCA Final

A 42-year-old man (ASA I) is anaesthetised for elective knee arthroscopy with an LMA. During the procedure the surgeon needs to position the leg in extreme flexion. The capnograph suddenly shows a decrease in ETCO2 from 4.5 to 1.8 kPa with loss of the normal waveform shape. SpO2 begins to fall. The most likely cause is:

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: E — Circuit disconnection

Sudden decrease in ETCO2 with loss of normal waveform shape during a procedure with significant patient repositioning most likely indicates LMA displacement. The extreme leg flexion can cause the patient's body to shift on the table, displacing the LMA from its optimal position and creating a leak or obstruction. The waveform changes (decreased amplitude, irregular shape) are characteristic of a partially displaced SAD rather than complete disconnection (which would show zero ETCO2). Management: hold the surgical leg position, check LMA position, jaw thrust, and reinsert or reposition the LMA.

Reference: RCOA – 2023 – Airway management; AAGBI – 2019 – Supraglottic airway devices