Tension pneumothorax with deep sulcus sign and mediastinal shift

A 24-year-old male motorcyclist is brought to the emergency department after a high-speed collision. He is tachycardic (HR 138), hypotensive (BP 82/54 mmHg), tachypneic (RR 36), with SpO2 82% on 15 L non-rebreather. Clinical examination reveals right-sided chest wall bruising, distended neck veins, tracheal deviation to the left, hyperresonant percussion, and absent breath sounds on the right. Supine chest radiograph shows a hyperlucent right hemithorax, abnormally deepened right costophrenic sulcus, and flattened right hemidiaphragm. The structure marked **D** in the diagram—contralateral mediastinal shift with tracheal deviation to the left—indicates which of the following pathophysiological consequences?