A patient with severe COPD (FEV1 30% predicted) is scheduled for right hemicolectomy. Which ventilation strategy is MOST appropriate to minimise dynamic hyperinflation during mechanical ventilation?
- A High respiratory rate with short inspiratory time to maximise minute ventilation
- B Low respiratory rate (8–10/min), large tidal volume, and prolonged expiratory time
- C Low respiratory rate (8–10/min), normal tidal volume (6–8 mL/kg IBW), and prolonged I:E ratio of 1:3 to 1:4 ✓
- D High PEEP of 10–12 cmH2O to splint airways open and prevent collapse
Correct answer: C. Low respiratory rate (8–10/min), normal tidal volume (6–8 mL/kg IBW), and prolonged I:E ratio of 1:3 to 1:4
Explanation
COPD patients have airflow obstruction and prolonged time constants; high respiratory rates or short expiratory times lead to gas trapping (dynamic hyperinflation) and auto-PEEP. The optimal strategy is a slow rate (8–10/min), physiological tidal volume (6–8 mL/kg IBW), and an extended I:E ratio of at least 1:3 to allow adequate exhalation. High intrinsic PEEP from external PEEP addition can worsen hyperinflation; modest extrinsic PEEP up to 50–75% of auto-PEEP may be used to balance threshold load, not 10–12 cmH2O.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
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