A 21-year-old, 70-kg male presents to the emergency department few hours after being in a vehicle accident in which he was thrown from the vehicle and hit his left side on a concrete surface. He complains of chest and back pain. On admission to the emergency department. He was awake, alert but cyanotic (Sp O2 92%) and dyspneic, moves all four extremities without restrictions, has no abdominal pain or bruising, and denies difficulty breathing. His vital signs on arrival are a temperature of 98.8°F, pulse of 154 beats/minute, blood pressure of 146/86 mmHg, and respiratory rate of 38 beats/minute. His FAST exam is negative. He has abrasions on his entire back, with contusions over the upper back and shoulders. Initial arterial blood gas analysis (ABGA) revealed the following results: pH 7.7, PaCO2 54.6 mmHg, PaO2 41.3 mmHg, and HCO3 - 19.2 mmol/L. The patient is transported to the radiology suite for a two-view chest radiograph. While in radiology, he begins vomiting and complains of difficulty breathing. On repeat examination, his oxygen saturations 69% on 4 liters oxygen by nasal cannula.

The patient's chest X-ray reveals bilateral pulmonary contusions encompassing 50% of each lung. He is immediately intubated, but his oxygen saturations fail to improve. Endotracheal bleeding was observed during intubation and mechanical ventilation was started. A chest computed tomography (CT) scan is obtained and reveals 70% bilateral pulmonary contusions without rib fractures, pneumothorax, or hemothorax.

Which of the following findings is pathognomonic in the diagnosis of this patient’s condition?