Cardiac tamponade and tension pneumothorax can cause which type of shock?

• A. Hypovolemic shock
• B. Distributive shock
• C. Cardiogenic shock
• D. Obstructive shock

Answer: (D)

The main concept is obstructive shock, where the problem is external obstruction to blood flow, not a lack of volume or a failure of the heart muscle itself. In cardiac tamponade, fluid around the heart increases pericardial pressure and prevents the ventricles from filling properly, especially during diastole, which lowers preload and reduces stroke volume. In tension pneumothorax, air in the chest cavity raises intrathoracic pressure and shifts the mediastinum, compressing the heart and great vessels and again decreasing venous return to the heart. The result is a drop in cardiac output despite adequate or even normal heart muscle function.

This differs from hypovolemic shock, which is due to loss of circulating blood volume; distributive shock, which stems from widespread vasodilation and relative hypovolemia; and cardiogenic shock, which is a primary pump problem from myocardial failure.