A pressure-volume loop displayed on modern anaesthesia workstations shows a rightward shift of the inspiratory limb with decreased peak pressure but unchanged tidal volume. This finding is most consistent with which condition?
- A Increased airway resistance from bronchospasm
- B Endotracheal tube cuff leak causing volume loss
- C Improved lung compliance, e.g., after repositioning or lung recruitment ✓
- D Pneumothorax reducing tidal volume delivery
Correct answer: C. Improved lung compliance, e.g., after repositioning or lung recruitment
Explanation
On a P-V loop, lung compliance is reflected by the slope: steeper slope (same volume for less pressure) indicates improved compliance, while a flatter slope indicates stiffness. A rightward shift with maintained tidal volume but decreased peak inspiratory pressure means less pressure is needed to deliver the same volume — this is consistent with improved compliance (e.g., after successful alveolar recruitment, patient repositioning, or treatment of bronchospasm). Bronchospasm increases resistance (lengthened inspiratory limb) rather than changing the PV curve slope.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.