Patients with simple pneumopericardium due to blunt thoracic trauma occasionally progressed to tension pneumopericardium, although pneumopericardium is believed to be benign in general. A 65-year-old man had both arms caught in a grinding machine and his face struck hard at work. He was diagnosed with bilateral degloving injuries of both arms and mediastinal emphysema on computed tomography. He required transfer to an advanced emergency medical service center for treatment. Although he was hemodynamically stable then, the patient's condition deteriorated during transportation. The patient returned to the local hospital as cardiopulmonary resuscitation continued, repeat computed tomography was performed, which showed a substantial pneumopericardium and exacerbation of mediastinal and subcutaneous emphysema. After then, cardiopulmonary resuscitation was discontinued because there was no response. For the patient to be rescued in this situation, thoracotomy is required, although it should be reserved for patients with evidence of hemodynamic compromise attributable to cardiac tamponade.