The purpose of this study was to compare the intubation time using Smart Care, a knowledge-based system for automated weaning, with that of conventional physician-controlled weaning after off-pump coronary artery bypass (OPCAB) and to determine the efficacy of Smart Care. During 2004, 53 sequential patients were scheduled for isolated coronary artery bypass grafting without cardiopulmonary bypass. Patients were divided into two groups: the Smart Care group (n = 10) and the control group (n = 35). Eight patients requiring hemodialysis and patients undergoing the awake OPCAB method were excluded. The intubation times were 172.6 +/- 51.6 min in the Smart Care group compared with 342.0 +/- 239.0 min in the control group (P = 0.032). No specific complications occurred with this computer-driven expert weaning system. In conclusion, the Smart Care system reduced the duration of mechanical ventilation and the respiratory care workload. This system was effective in the care of patients without complications requiring mechanical ventilation after OPCAB.