Final answer:
The condition in which lung tissue progressively collapses due to the accumulation of air in the thorax is called tension pneumothorax, a serious medical emergency that differs from simple pneumothorax by the significant pressure it places on the heart and major blood vessels.
Step-by-step explanation:
A progressive collapsing of lung tissue due to accumulation of air in the thorax is known as tension pneumothorax. The accumulation of air in the pleural space causing a tension pneumothorax not only collapses the lung but also puts pressure on the heart and major blood vessels, which can lead to life-threatening consequences. Unlike the more simple pneumothorax, which involves a small amount of air leakage and might not always be severe, a tension pneumothorax creates a situation where each breath increases the amount of trapped air and can quickly become an emergency requiring immediate medical attention.
The options provided in the question refer to different thoracic or pulmonary conditions: A. simple pneumothorax involves air in the pleural space but without significant shift or pressure on mediastinal structures. B. Hemothorax is the accumulation of blood in the pleural space. C. Pulmonary embolism is the blockage of a pulmonary artery by a blood clot. D. Tension pneumothorax is a type of pneumothorax where the air trapped in the chest increases pressure on the lungs and other thoracic structures. Hence, the correct answer is D. tension pneumothorax.