Inclusion Criteria:  Patients undergone minimal invasive off-pump coronary artery bypass graft (CABG), valvular surgery or combined procedures at Far Eastern Memorial Hospital, New Taipei City, Taiwan between January 1, 2020 and August 31, 2020. Age above 20 y/o  Exclusion Criteria:  Emergency surgery Postoperative mechanical ventilation more than 6 hours Extubated in the operating room