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Ventilator Weaning — FRCA Final MCQ

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ModerateIntensive Care MedicineVentilator WeaningFRCA Final

A 72-year-old man has received invasive ventilation for 14 days following oesophagectomy complicated by an anastomotic leak and sepsis. During one minute of unassisted breathing through a T-piece, his respiratory rate is 32 breaths min−1 and his mean tidal volume is 280 mL. Using the conventional RSBI threshold of 105 breaths min−1 L−1, which interpretation is most appropriate?

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Correct answer: E — The RSBI supports an increased risk of weaning failure

The correct answer is E. RSBI is calculated as respiratory frequency divided by tidal volume in litres: 32/0.28 = 114 breaths min−1 L−1. This exceeds the conventional threshold of 105 and therefore supports an increased risk of unsuccessful ventilator liberation. It does not by itself determine whether extubation will fail: contemporary pooled evidence shows only moderate sensitivity and poor specificity, so the result must be integrated with the complete spontaneous breathing trial, gas exchange, haemodynamic stability, consciousness, cough and secretion burden. A low RSBI would support, but not establish, readiness for extubation. An elevated RSBI neither mandates tracheostomy nor determines whether prophylactic non-invasive ventilation is indicated. Minute ventilation is unnecessary because respiratory rate and tidal volume are already supplied.

Reference: Trivedi V et al. The Usefulness of the Rapid Shallow Breathing Index in Predicting Successful Extubation: A Systematic Review and Meta-analysis. Chest. 2022;161:97–111. https://pubmed.ncbi.nlm.nih.gov/34181953/