National Physical Therapy Examination (NPTE) Practice Exam

What structure is compressed when a pregnant patient develops hypotension after lying supine for a period?

1. Inferior gluteal artery

2. Inferior vena cava

3. Abdominal aorta

4. Bilateral common iliac arteries

The correct answer is: Inferior vena cava

In the scenario described, the structure that gets compressed when a pregnant patient lies supine for an extended time is the inferior vena cava. This phenomenon is commonly referred to as supine hypotensive syndrome, which occurs due to the weight of the gravid uterus exerting pressure on the inferior vena cava when a pregnant woman is lying flat on her back. The inferior vena cava's role is to carry deoxygenated blood from the lower parts of the body back to the heart. When this vessel is compressed, it can lead to a decrease in venous return to the heart, resulting in lowered cardiac output and subsequent hypotension. This is particularly a concern during the later stages of pregnancy when the uterus is larger and heavier. While other structures, such as the inferior gluteal artery, abdominal aorta, and bilateral common iliac arteries, may be in proximity, they are not primarily responsible for the hypotensive effect in this lying position. The inferior gluteal artery primarily supplies blood to the gluteal muscles, and the abdominal aorta and iliac arteries handle major blood flow distribution but do not directly suffer from the same level of compression as the inferior vena cava in this context. Hence, the compression of the inferior vena cava is the direct cause