Basic and Clinical Sciences (BCSE) Practice Exam

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What is the primary physiological change in the blood that leads to chronic mountain sickness?

  1. Decreased red blood cell count

  2. Increased hematocrit

  3. Decreased blood pressure

  4. Increased plasma volume

The correct answer is: Increased hematocrit

Chronic mountain sickness, also known as Monge's disease, is primarily characterized by an increase in hematocrit, which refers to the proportion of blood volume that is occupied by red blood cells. This condition often occurs in individuals who reside at high altitudes for extended periods. As a response to the lower oxygen levels available at high elevations, the body compensates by producing more red blood cells to enhance its oxygen-carrying capacity. This process is stimulated by increased levels of erythropoietin, a hormone produced by the kidneys. The increase in hematocrit can lead to a hyperviscous state of the blood, causing complications such as increased blood pressure and a higher risk of thromboembolic events. Individuals with chronic mountain sickness may experience symptoms such as headaches, fatigue, and shortness of breath due to the effects of this elevated hematocrit. In contrast, decreased red blood cell count would not contribute to chronic mountain sickness; rather, it would result in decreased oxygen-carrying capacity. Decreased blood pressure is not a feature of this condition, as the increased hematocrit typically leads to elevated rather than decreased blood pressure. Additionally, increased plasma volume does not directly relate to chronic mountain sickness, as the primary