Postoperative artificial ventilation by using an endotracheal tube may cause a pulmonary infection. A possibly necessary permanent sedation and relaxation may result in an additional danger for the patient. The principle of the "iron lung" represents an alternative to endotracheal artificial respiration, which applies especially to endangered patients who are under postoperative artificial respiration. After an abdominal operation five patients have been extubated and artificially respirated by using the "iron lung" principle while not being able to breath by themselves. The degree of the sedation was monitored both intraoperatively and postoperatively using an automatic EEG classification. The performance spectrum of the respiratory curve enabled very early detection of the onset of spontaneous respiration.