Pulmonary barotrauma is defined as an extra-alveolar gas from lung damage secondary to changes in intrathoracic pressure. Pneumothorax, pneumoperitoneum, pneumomediastinum and subcutaneous emphysema developed due to complete occlusion of the expiratory tube of the scavenging system. During controlled endotracheal ventilation of the lungs of a 22 year old woman undergoing thyroidectomy increased airway pressure about 50 mbar on the airway pressure gauge approximately 8 minutes after starting ventilator was detected. Vital signs were stable. Subcutaneous emphysema around the neck, face and both shoulders were observed. The expiratory tubing was found to be trapped and competely obstructed between the upper and lower parts of the ventilator. The operation was cancelled and chest x-ray was taken in the operating room, which showed about 15% pneumothorax on the right chest, subcutaneous emphysema and pneumomediastinum. The follow up chest x-ray was taken in postanesthesia care unit and pneumoperitoneum was also detected on the right upper side of the abdomen. The signs of rupture of the abdominal viscus were not noted. She recovered uneventfully with insufflation of 100% oxygen and discharged 3 days later with complete spontaneous resorption of the pneumothorax.