Capnothorax: Diagnosis

Capnothorax is a type of pneumothorax where carbon dioxide occupies space in the pleural cavity preventing full inflation of the lung. Capnothorax is suspected in the setting of abdominal laparoscopic surgery when CO₂ is used for insufflation and the procedure involves manipulation of the diaphragm as in esophageal surgery. In most cases of pneumothorax, etCO₂ gradually decreases as the relative shunt created by the air in the pleural space prevents alveoli expansion and gas exchange. In a capnothorax, however, etCO₂ gradually increases as carbon dioxide in the pleural space is absorbed and exchanged. Other diagnostic clues include absent or decreased breath sounds on the side of the pneumothorax, increasing etCO₂ despite compensatory increases in minute ventilation, gradually increasing mean airway pressure, decreasing oxygen saturation, and chest Xray showing pneumothorax. When capnothorax is suspected, pneumoperitoneum should be released and 100% FiO₂ administered until oxygen saturation recovers. Chest Xray can confirm the diagnosis and thoracentesis should be pursued in cases of large pneumothorax or pneumothorax unresponsive to conservative management.