Effect of inspiratory synchronization during pressure-controlled ventilation on lung distension and inspiratory effort

Abstract

Background: In pressure-controlled (PC) ventilation, tidal volume (VT) and transpulmonary pressure (PL) result from the addition of ventilator pressure and the patient’s inspiratory effort. PC modes can be classified into fully, partially, and non-synchronized modes, and the degree of synchronization may result in different VT and PL despite identical ventilator settings. This study assessed the effects of three PC modes on VT, PL, inspiratory effort (esophageal pressure–time product, PTPes), and airway occlusion pressure, P0.1. We also assessed whether P0.1 can be used for evaluating patient effort. Methods: Prospective, randomized, crossover physiologic study performed in 14 spontaneously breathing mechanically ventilated patients recovering from acute respiratory failure (1 subsequently withdrew). PC modes were fully (PC-CMV), partially (PC-SIMV), and non-synchronized (PC-IMV using airway pressure release ventilation) and were applied randomly; driving pressure, inspiratory time, and set respiratory rate being similar for all modes. Airway, esophageal pressure, P0.1, airflow, gas exchange, and hemodynamics were recorded. Results: VT was significantly lower during PC-IMV as compared with PC-SIMV and PC-CMV (387 ± 105 vs 458 ± 134 vs 482 ± 108 mL, respectively; p < 0.05). Maximal PL was also significantly lower (13.3 ± 4.9 vs 15.3 ± 5.7 vs 15.5 ± 5.2 cmH2O, respectively; p < 0.05), but PTPes was significantly higher in PC-IMV (215.6 ± 154.3 vs 150.0 ± 102.4 vs 130.9 ± 101.8 cmH2O × s × min−1, respectively; p < 0.05), with no differences in gas exchange and hemodynamic variables. PTPes increased by more than 15% in 10 patients and by more than 50% in 5 patients. An increased P0.1 could identify high levels of PTPes. Conclusions: Non-synchronized PC mode lowers VT and PL in comparison with more synchronized modes in spontaneously breathing patients but can increase patient effort and may need specific adjustments. Clinical Trial Registration Clinicaltrial.gov # NCT02071277.