Background. The aim of our study was to assess the efficacy and safety of automated weaning from mechanical ventilation after off-pump coronary artery bypass grafting (OPCAB).
Methods: Forty adult patients aged 62 (56 – 68) yrs. after elective OPCAB were enrolled into a prospective randomized study. The informed consent was obtained from each patient in the preoperative period. For respiratory support in ICU we used a G-5 ventilator (Hamilton Medical, Switzerland) . Patients were randomized into two groups: automated weaning (n=20), using Adaptive Support Ventilation (ASV)-Intellivent mode with quick wean option; and physician-directed weaning (n=20), using conventional Synchronized Intermittent Mandatory Ventilation (SIMV) + Pressure Support (PS) mode. The inspiratory pressure, respiratory rate and inspired oxygen fraction (FiO2) were adjusted to maintain tidal volume 6-8 mL/kg of predicted body weight, EtCO2 35-40 mm Hg, and SpO2≥94%, respectively.  In the SIMV+PS group, every 30 minutes we  decreased inspiratory pressure by 2-4 cm H2O and mandatory respiratory rate by 2-4 bpm. In both groups, patients were extubated immediately after successful spontaneous breathing trial (SBT). Data are presented as median (25th–75th percentiles) and analyzed using Mann-Whitney U-test or χ2-test where appropriate. 
Results: Main demographic and preoperative characteristics of the patients, as well as hemodynamics and gas exchange during the study, did not differ between two groups. The average time until tracheal extubation in the automated weaning group was 191 (151 – 231) min vs. 196 (115-308) min in the physician-directed weaning group (p=0.9). Realization of the automated weaning protocol required change in respiratory settings only in one patient vs. 6 adjustments per patient in the physician-directed weaning group. The episodes of deviations from the safe ventilation zone were registered in 12 patients receiving ASV-Intellivent and in 18 patients with SIMV + PS (p=0.035). The FiO2 during SBT was significantly lower in the automated weaning group: 30 (30-35) % vs. 40 (40-45) % in the physician-directed weaning group (p< 0.01). All patients were successfully weaned from ventilator and survived Day 28 of the study. 
Conclusion: Automated weaning from mechanical ventilation after OPCAB is safe, reduces the load on medical staff and does not prolong the duration of ventilation.

Automated versus physician-directed weaning from mechanical ventilation after off-pump coronary artery bypass grafting