An increase in blood viscosity will cause an increase in peripheral resistance.

An increase in blood viscosity will cause an increase in peripheral resistance.

• A. True
• B. False
• C. Not determinable
• D. Depends on other factors

Answer: (A)

An increase in viscosity raises the friction the blood experiences as it moves, increasing resistance to flow. By Poiseuille’s law, resistance to laminar flow in a vessel is proportional to viscosity (and the vessel length) and inversely proportional to the fourth power of radius. With the radius and length held constant, higher viscosity directly increases resistance. Clinically, thicker blood (higher viscosity) makes it harder for the heart to push blood through, raising peripheral resistance. So the statement is true.

An increase in viscosity raises the friction the blood experiences as it moves, increasing resistance to flow. By Poiseuille’s law, resistance to laminar flow in a vessel is proportional to viscosity (and the vessel length) and inversely proportional to the fourth power of radius. With the radius and length held constant, higher viscosity directly increases resistance. Clinically, thicker blood (higher viscosity) makes it harder for the heart to push blood through, raising peripheral resistance. So the statement is true.