Polycythemia would cause what changes to viscosity and flow?

Polycythemia would cause what changes to viscosity and flow?

• A. Increased viscosity and decreased flow
• B. Increased viscosity and increased flow
• C. No change in viscosity or flow
• D. Decreased viscosity and increased flow

Answer: (A)

Higher blood viscosity due to more red blood cells thickens the blood. When hematocrit rises, the plasma becomes more resistant to flow because there are more cells in the same volume, increasing the overall viscosity. In the circulation, flow through a vessel is inversely related to viscosity (with a given pressure difference, higher viscosity means more resistance and less flow). So polycythemia leads to increased viscosity and decreased flow. The other patterns (decreased viscosity with increased flow, or no change) don’t fit the way viscosity and flow are linked in hemodynamics.

Higher blood viscosity due to more red blood cells thickens the blood. When hematocrit rises, the plasma becomes more resistant to flow because there are more cells in the same volume, increasing the overall viscosity. In the circulation, flow through a vessel is inversely related to viscosity (with a given pressure difference, higher viscosity means more resistance and less flow). So polycythemia leads to increased viscosity and decreased flow. The other patterns (decreased viscosity with increased flow, or no change) don’t fit the way viscosity and flow are linked in hemodynamics.