FRC Reduction Anaesthesia — FRCA Primary MCQ

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ModeratePhysiology - RespiratoryFRC Reduction AnaesthesiaFRCA Primary

During anaesthesia FRC is reduced by approximately:

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Correct answer: D — 15-20%

General anaesthesia reduces FRC by approximately 15-20% (approximately 400-500 mL) in adults. This occurs within minutes of induction regardless of whether the patient is breathing spontaneously or mechanically ventilated. Causes include: loss of diaphragm tone / cephalad displacement of diaphragm / change in chest wall mechanics / and absorption atelectasis with high FiO2.

Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist