Which statement best describes the consequence of polycythemia seen in COPD?

Which statement best describes the consequence of polycythemia seen in COPD?

• A. It reduces risk of thrombotic events
• B. It results from chronic hypoxia and increases blood viscosity, leading to complications
• C. It improves oxygen delivery by increasing red blood cell mass
• D. It has no impact on exercise tolerance

Answer: (B)

In COPD, chronic low oxygen levels stimulate the body to produce more red blood cells, a response known as secondary polycythemia. This increases the red cell mass and hematocrit, which makes the blood thicker or more viscous. The higher viscosity slows blood flow, raises the workload on the heart, and increases the risk of clotting and vascular complications such as thrombosis, stroke, and pulmonary hypertension. While having more red blood cells can improve oxygen-carrying capacity to some extent, the downsides of increased viscosity often outweigh this benefit, and tissue oxygen delivery can actually be impaired rather than improved. This explains why the consequence described is an increase in blood viscosity with associated complications, rather than a reduced thrombotic risk, no impact on exercise tolerance, or a straightforward improvement in oxygen delivery.