Clinical signs concerning tension pneumothorax include tachycardia, hypotension, and tachypnea; absence of breath sounds on the affected side; neck vein distension; asymmetric chest movement; and tracheal deviation. Any patient who deteriorates under anesthesia while being mechanically ventilated and has wounds to the upper abdomen, lower neck, or ribs should be assumed to have a tension pneumothorax until proven otherwise.