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Obstructive shock occurs when there is a physical obstruction in the circulatory system that prevents blood from flowing effectively. Each of the other options listed—tension pneumothorax, cardiac tamponade, and pulmonary embolism—are all conditions that interfere with normal blood flow and can lead to obstructive shock due to their mechanical impacts on the heart or major blood vessels.

Tension pneumothorax involves air trapped in the pleural space, which can compress the heart and great vessels, leading to decreased venous return and impaired cardiac output. Cardiac tamponade occurs when fluid accumulates in the pericardial space, also restricting the heart's ability to fill and thus effectively pump blood. Pulmonary embolism refers to a blockage in the pulmonary arteries, usually due to a blood clot, which obstructs blood flow to the lungs and can reduce oxygenation and circulatory efficiency.

In contrast, septic shock is a form of distributive shock caused by an overwhelming infection that leads to systemic vasodilation and increased capillary permeability, resulting in an inadequate blood supply to the body’s tissues despite a normal or increased cardiac output. It does not involve a physical obstruction like the others and is driven by a different mechanism—therefore, it