skip to main content

Mapleson A breathing system — FRCA Primary MCQ

Instant feedback + full explanation. One question, done properly.

HardPhysics and Clinical MeasurementMapleson A breathing systemFRCA Primary

A spontaneously breathing patient is anaesthetised using a Mapleson A system. Fresh gas flow is reduced and capnography begins to show rebreathing. Which statement is correct regarding this system?

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

Reveal the answer and explanation

Correct answer: E — It is efficient during spontaneous ventilation

The Mapleson A system is efficient for spontaneous ventilation because fresh gas flow can flush alveolar gas away from the patient end during expiration. It is inefficient during controlled ventilation because the expiratory valve position promotes rebreathing unless high flows are used. It does not use soda lime. The system has a reservoir bag and an expiratory valve near the machine end.

Reference: Dorsch and Dorsch Understanding Anesthesia Equipment; Primary FRCA physics texts