Final answer:
Air in the pericardial sac is referred to as pneumopericardium, which is different from cardiac tamponade that involves the accumulation of fluid.
Step-by-step explanation:
Air in the pericardial sac is known as pneumopericardium. This condition occurs when there is the presence of air within the pericardial cavity, which surrounds the heart. Disorders of the heart like cardiac tamponade involve fluid, usually blood, accumulating within the pericardial cavity. This excess fluid places pressure on the heart, restricting its ability to fill properly with blood during the relaxation phase between contractions, and can be life-threatening if left untreated, leading to decreased cardiac output and potential death. However, pneumopericardium specifically refers to air, rather than fluid, within the pericardial space. The pericardium, or pericardial sac, consists of the fibrous pericardium and the serous pericardium, which includes both the parietal and visceral layers. The pericardial cavity is the space between the layers of the serous pericardium that contains a small amount of lubricating fluid.