A randomized trial of automated versus conventional protocol-driven weaning from mechanical ventilation following coronary artery bypass surgery.
OBJECTIVE
The Siemens servo 300 A ventilator has an automode function that allows automated weaning of patients from mechanical ventilation. Spontaneous breathing triggers the ventilator. After two spontaneously triggered breaths, the ventilator automatically changes from mandatory mechanical ventilation to spontaneous ventilation. If spontaneous breathing or triggering does not occur, the Siemens servo 300 A ventilator changes from spontaneous ventilation back to mandatory mechanical ventilation. We compared the effects of automated versus conventional protocol-driven weaning on the time until extubation in patients undergoing coronary artery bypass graft (CABG) surgery. In addition, we studied the effects of the mode of weaning on hemodynamic and physiologic parameters.


METHODS
Twenty consecutive male patients without respiratory disease scheduled for CABG at the University Hospital of Regensburg were entered into the study. Patients were randomized to postoperative ventilation with the Siemens 300 A/automode ventilator (group A, n = 10) or with the Siemens 300 ventilator (group B, n = 10). All patients were weaned from ventilation according to a standardized protocol.


RESULTS
On average, patients in group A were younger and had lower pulmonary artery pressure (PAP) and higher cardiac output compared to patients in group B. However, patients in group A had longer ischemic and bypass times compared to patients in group B. Postoperative use of analgesia and sedation were similar in both groups. Time from tracheal intubation until extubation was 2 h shorter in patients assigned to automode ventilation compared to patients assigned to conventional ventilation (mean time group A 7.9 h, group B 10.0 h; p = 0.069). Peak airway pressure was reduced by 2 cm H2O at the beginning of spontaneous ventilation in group A compared to group B. After extubation, cardiac index showed a greater increase in patients assigned to group A compared to those in group B.


CONCLUSIONS
Automode ventilator weaning trended toward more rapid extubation than did conventional protocol-driven ventilation in conjunction with a standardized weaning protocol. Physiologic and hemodynamic factors were better in patients using automode ventilation compared to patients using conventional ventilation. Automode ventilation was well tolerated and did not induce significant adverse effects.
Hendrix
Holger
H
Division of Cardiothoracic Surgery, University Hospital of Regensburg, Germany. holger.hendrix@hotmail.com
Kaiser
Michael E
ME
Yusen
Roger D
RD
Merk
Johannes
J
D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000097:blood; D002985:Clinical Protocols; D001026:Coronary Artery Bypass; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D010865:Pilot Projects; D011182:Postoperative Care / Q000379:methods*; D012121:Respiration, Artificial / Q000379:methods; D015300:Ventilator Weaning / Q000379:methods*; D014797:Vital Capacity
D002245:Carbon Dioxide; D010100:Oxygen