Auto-PEEP and dynamic hyperinflation in COPD patients during controlled mechanical ventilation and high frequency jet ventilation

We investigated the levels of auto-PEEP and dynamic hyperinflation during high frequency jet ventilation (HFJV) and controlled mechanical ventilation (CMV) in six patients with chronic obstructive pulmonary disease within the first 36h of acute exacerbation. The comparative evaluation was performed at similar conditions of gas exchange in HFJV and CMV: PaO₂ 77.6±11 mmHg vs 80.8±12 mmHg; PaCO₂ 46.8±2.5 mmHg vs 47±2.8 mmHg; pH 7.38 vs 7.38. In this situation, the values of auto-PEEP and dynamic hyperinflation, expressed as Δ over the apneic functional residual capacity (FRC) did not differ: (auto-PEEP_HFJV 8.9±3.8 cmH₂O; auto-PEEP_CMV 8.8±4.7 cmH₂O; ΔFRC_HFJV 0.56±0.191; ΔFRC_CMV 0.54±0.2l). This result suggests that, with a suitable machine setting and similar gas exchanges, HFJV produces the same level of auto-PEEP and dynamic hyperinflation as CMV in patients with chronic obstructive pulmonary disease.