A 44-year-old female was presented to our department with a 4-day history of shortness of breath and chest pain. The chest X-ray showed pneumothorax with completely collapsed left lung. Thoracentesis was performed. She complained of dyspnea and the oxygen saturation decreased to 74% after thoracentesis. The 2nd chest X-ray and computed tomography demonstrated a left-sided pulmonary edema. A 67-year-old man came to our department complaining of persistent cough. The chest X-ray showed pneumothorax with collapsed right middle and lower lobes. Thoracentesis was performed. He complained of dyspnea and the oxygen saturation decreased to 87% after thoracentesis. The 2nd chest X-ray and computed tomography demonstrated an expanded right upper lobe, but also pulmonary edema in the right middle and lower lobes. Those patients were treated with supplemental oxygen without endotracheal intubation. Their oxygen saturation stabilized within 12 hours. They were successfully treated with the sole administration of oxygen.