In the described COPD patient with acute on chronic respiratory failure, which ventilator settings are most appropriate?

• A. VC CMV rate 8, VT 500 mL, FIO2 0.6, PEEP 5
• B. VC CMV rate 12, VT 400 mL, FIO2 0.4, PEEP 3
• C. AC CMV rate 12, VT 600 mL, FIO2 0.3, PEEP 0
• D. SIMV rate 10, VT 350 mL, FIO2 0.5, PEEP 4

Answer: (B)

In COPD with acute on chronic respiratory failure, the goal is to ventilate effectively while minimizing dynamic hyperinflation from air trapping. That means using a fixed, small tidal volume so the lungs don’t overdistend, and choosing a rate that preserves a long enough expiratory phase to avoid auto‑PEEP. A volume‑controlled approach with about 6 mL/kg tidal volume (roughly 400 mL for an average adult) and a rate around 12 breaths per minute provides sufficient ventilation without pushing exhalation too short. A modest PEEP, such as 3 cmH2O, helps recruit some alveoli and counter auto‑PEEP without markedly increasing hyperinflation. FiO2 around 0.4 keeps oxygenation adequate without exposing the patient to unnecessary high oxygen levels. The other options either use too large a tidal volume that worsens hyperinflation, omit PEEP, or employ modes that don’t guarantee stable ventilation in this setting, making the described configuration the most appropriate choice.