Background: Adaptive support ventilation (ASV) is a microprocessor-controlled mode of mechanical ventilation that switches automatically from controlled ventilation to assisted ventilation and selects ventilatory settings according to measured lung mechanics.
Methods: In a randomized controlled trial, non-fast-track coronary artery bypass grafting patients' lungs were ventilated with ASV or pressure-controlled/pressure-support ventilation (control) to compare time until tracheal extubation, duration of controlled ventilation versus assisted ventilation, and ventilation characteristics.
Results: One hundred twenty-eight consecutive patients were randomized. ASV patients had their tracheas extubated after median 16.4 and interquartile range 12.5-20.8 hr, and control patients after 16.3 (13.7-19.3) hr, respectively (P = 0.97). The percentage of time patients were on assisted ventilation (expressed as the median percentage of total duration of ventilation) was 43% (28%-67%) in the ASV group and 52% (33%-75%) in the control group (P < 0.05). However, the number of switches from controlled to assisted ventilation was higher in the ASV group (43.0 [14.0-74.0]) than in the control group (4.0 [2.0-9.0]) (P < 0.001). In ASV patients, mean tidal volumes were significantly larger during controlled ventilation than in control patients (8.6 +/- 0.8 mL/kg predicted body weight vs 7.1 +/- 1.4 mL/kg predicted body weight; P = 0.05), and no differences in tidal volumes were found during assisted ventilation.
Conclusion: Weaning automation with ASV is feasible and safe in non-fast-track coronary artery bypass grafting patients. Time until tracheal extubation with ASV equals time until tracheal extubation with standard weaning and allows for frequent (automatic) switches between controlled and assisted ventilation.