Bariatric Surgery Ventilation — FRCA Final MCQ

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ModerateGeneral AnaesthesiaBariatric Surgery VentilationFRCA Final

A 60-year-old man who is 154 cm tall and weighs 100 kg (BMI 42 kg/m²) has severe obstructive sleep apnoea and is undergoing laparoscopic sleeve gastrectomy. As part of an intraoperative lung-protective ventilation strategy, which initial tidal volume target is most appropriate?

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Correct answer: A — 6–8 mL/kg predicted body weight

The correct answer is A. Lung size correlates principally with sex and height, not excess adipose mass, so tidal volume in obesity should be calculated from predicted (ideal) body weight. At 154 cm, this man's predicted body weight is approximately 51.5 kg, giving an initial tidal volume of about 310–410 mL. Using actual weight would deliver 600–800 mL with option D and 1000–1200 mL with option B, risking excessive strain and volutrauma. Option C remains unnecessarily high despite using the correct weight scalar. Option E is below the usual initial protective range in a patient without established ARDS and could promote hypercapnia or atelectasis. Severe OSA increases perioperative respiratory risk but does not change the basis for tidal-volume calculation. PEEP should be individualised; fixed high PEEP and routine recruitment manoeuvres are not universally indicated.

Reference: Royal College of Anaesthetists and British Journal of Anaesthesia, RCoA and BJA Webinar – Perioperative pulmonary complications, ventilation Q&A, 2021. https://www.rcoa.ac.uk/rcoa-bja-webinar-perioperative-pulmonary-complications