Migration of air into the aorta is rare. We report a rare case of a patient in whom a penetrating aortic injury caused by broken ribs, led to the migration of air into the aorta from a pneumothorax.
A tree fell on the back of a 77-year-old male when he was cutting down trees. When emergency technicians (EMTs) reached him, he was in a state of cardiopulmonary arrest. The initial rhythm was asystole. Tracheal intubation, the insertion of a chest drain into the left thorax and the infusion of fluid and adrenaline were performed by the EMTs and an emergency physician. After his transfer to Shizuoka Hospital, Juntendo University, a monitor revealed that he remained asystolic in a state of cardiopulmonary arrest. The findings of a blood gas analysis (FiO2 1.0) on arrival were pH: 6.671, PCO2: 44.6 mmHg, PO2: 48.7 mmHg, HCO3−: 4.9 mmol/l, base excess: -26.1 mmol/l and hemoglobin: 1.9 g/dl. Additional right thoracostomy was performed but a return of spontaneous circulation was not obtained. A postmortem computed tomographic (CT) pan scan performed 90 minutes after the patient’s collapse revealed systemic air embolism, multiple rib fractures with a penetrating injury to the aorta, lung contusion, pneumohemothorax, pneumomediastinum, air in the aorta and a lumbar fracture (Figure 1). The cause of death was unstable circulation due to massive hemorrhage from an aortic injury and air embolism, and respiratory failure due to lung contusion and pneumohemothorax.
The main causes of migration of air into the aorta are iatrogenic, these include cardiac or aortic surgery, arterial endovascular management or transthoracic lung biopsy [1-5]. In rare cases, the suicidal connection of a peripheral venous catheter with oxygen gas has resulted in the migration of air into aorta . In patients with decompression sickness, CT can demonstrate intra-arterial gas . In the present case, a massive amount of air ventilated with positive pressure in a patient with pneumothorax, entered the site of a penetrating injury of the aorta (caused by rib fractures), which resulted in the aorta being filled with air. To the best of our knowledge, this is the first case to describe the introduction of air into the aorta by such a mechanism. The air in the aorta may have been the result of a massive hemorrhage and the introduction of air after the death of the patient as a result of no circulation and the presence of a hole in the aorta. However, distinguishing premortem from postmortem phenomena is difficult. Lung trauma involving laceration of air passages, lung parenchyma, and blood vessels may result in direct communication of these structures. Systemic air or gas embolism occurs when air or gas enters the pulmonary venous system as a result of a positive gradient caused by a low pulmonary venous pressure. Dedouit et al.  showed that a small amount of air in the ascending aorta due to a paradoxical embolism through patent foramen ovale or across the pulmonary capillary bed created tension pneumothorax. The present case also had lung contusion, and the gas in the aorta may have been produced by the paradoxical embolism. However, the amount of gas in the aorta in our case was massive, and we noted no gas at all in the left side of the heart. These findings therefore make it unlikely that the gas was produced by a paradoxical embolism.
This unique case adds one more cause to the list of documented etiologies of air in the aorta. The induction of microbubbles by arterial endovascular management, which can be detected by ultrasound, can be asymptomatic . However, in one report, the detection of the air in the aorta by radiological studies indicated systemic air embolization, which tended to be associated with a poor outcome, similar to that which was observed in our case .
In the present case, a massive amount of air ventilated with positive pressure in a patient with pneumothorax, entered the site of a penetrating injury of the aorta (caused by rib fractures), which resulted in the aorta being filled with air. This unique case adds one more cause to the list of documented etiologies of air in the aorta.