Initial Synchronized Intermittent Mandatory Ventilation Versus Assist/Control Ventilation in Treatment of Moderate Acute Respiratory Distress Syndrome: A Prospective Randomized Controlled Trial

Background: Assist/control (A/C) ventilation may induce delirium in patients with acute respiratory distress syndrome (ARDS). We conducted a trial to determine whether initial synchronized intermittent mandatory ventilation with pressure support (SIMV + PS) could improve clinical outcomes in these patients.Methods: Intubated patients with moderate ARDS were enrolled and we compared SIMV + PS with A/C. Identical sedation, analgesia and ventilation strategies were performed. The co-primary outcomes were early (<= 72 h) partial pressure of arterial oxygen to fraction of inspired oxygen (PaO2/FiO(2)) and incidence of delirium. The secondary outcomes were all-cause in-hospital mortality, dosages of analgesics and sedatives, incidence of patient-ventilator asynchrony, and duration of mechanical ventilation and hospital stay.Results: We screened 2,684 patients and 40 patients were enrolled in our study. In SIMV + PS, early (<= 72 h) PaO2/FiO(2) was greater improved than that at baseline and that in A/C (P<0.05) with lower positive end-expiratory pressure (PEEP) (8.7 +/- 3.0 vs. 10.3 +/- 3.2, P<0.001) and FiO(2) (58%+/- 18% vs. 67%+/- 19%, P<0.001). We found more SIMV + PS success (defined as SIMV + PS successfully applied without switching to A/C) (100.0% vs. 16.7%, P<0.001), less male (46.3% vs. 85.7%, P=0.015) and pulmonary etiology of ARDS (53.8% vs. 92.9%, P=0.015), and lower PEEP (9.1 +/- 3.1 vs. 10.3 +/- 3.3, P=0.004) and FiO(2) (58%+/- 19% vs. 71%+/- 19%, P<0.001) in survival patients. However, there were no significant differences in incidence of delirium and mortality, dosages of analgesics and sedatives, incidence of patient-ventilator asynchrony, duration of mechanical ventilation and hospital stay (P>0.05).Conclusions: In patients with moderate ARDS, SIMV + PS can safely and effectively improve oxygenation, but does not decrease mortality, incidence of delirium and patient-ventilator asynchrony, dosages of analgesics and sedatives, and duration of mechanical ventilation and hospital stay.