Lung Hysteresis P-V Curve — FRCA Primary MCQ
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Correct answer: D — At a given pressure, volume is greater during deflation than inflation
The best answer is “At a given pressure, volume is greater during deflation than inflation”. Pulmonary hysteresis means that inflation and deflation do not follow the same pressure–volume path. The deflation limb lies above the inflation limb, so lung volume is greater during deflation at an equivalent pressure. Recruitment and derecruitment plus surface-tension behaviour contribute to the energy dissipated over each cycle.
Reference: Royal College of Anaesthetists, Primary FRCA Syllabus 2021: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf