Which of the following organs is most vulnerable to blast pressure changes?

The lungs are particularly vulnerable to blast pressure changes due to their air-filled structure. Unlike solid organs, the lungs contain air, which can be compressed and displaced during a blast event. This rapid change in pressure can cause barotrauma, leading to damage within the lung tissue, including ruptured alveoli and pneumothorax (collapsed lung). Inhalation of foreign objects and subsequent pulmonary complications can also occur due to the force of the blast.

The heart, brain, and liver, while important organs, are typically more protected from direct blast pressure due to their anatomical positions within the body and the solid nature of their tissues. The lungs' vulnerability makes them the most affected organ in scenarios involving explosive devices or other pressure-changing phenomena.