Altitude Training 1

Question

Vignette: A 23-year-old woman presents to her primary care physician for a routine checkup. The patient recently moved to Denver, Colorado, from Miami, Florida, and reports experiencing shortness of breath and fatigue. Physical examination is unremarkable. Blood tests reveal a higher than normal hematocrit level.

Question: What is the physiological response responsible for the increase in this patient's hematocrit level?

Choices

A. Increased erythropoiesis

B. Decreased erythropoiesis

C. Increased thrombopoiesis

D. Decreased thrombopoiesis

E. Increased leukopoiesis

Answer

A. Increased erythropoiesis

Explanation

The patient moved from Miami, which is at sea level, to Denver, which is approximately 5,280 feet above sea level. At higher altitudes, the partial pressure of oxygen is lower, meaning there is less oxygen available for the body to use. The body compensates for this by increasing the production of erythropoietin, a hormone secreted by the kidneys that stimulates the bone marrow to produce more red blood cells (erythropoiesis). This leads to an increase in hematocrit, which is the proportion of blood volume that is occupied by red blood cells. This physiological response helps to increase the oxygen-carrying capacity of the blood, compensating for the lower availability of oxygen in the air at higher altitudes. The other options listed, thrombopoiesis (platelet production) and leukopoiesis (white blood cell production), are not directly related to the body’s response to altitude change.