We describe the case of a 57-year-old man with severe refractory hypoxemia, despite receiving ventilation therapy with 100% oxygen, following a gunshot wound to his left chest. A limited CT scan of the chest with contrast raised the suspicion of an arteriovenous (AV) fistula. Contrast-enhanced transthoracic echocardiography confirmed the presence of a pulmonary AV fistula. Traumatic pulmonary AV fistula is a rare, but serious and life-threatening condition that should be suspected in patients with thoracic injuries with persistent unexplained hypoxemia. Contrast echocardiography is a relatively simple, inexpensive, and readily available bedside test that can be used to confirm this diagnosis.