Effect of diameter variability along a microvessel segment on pressure drop

Area of Science:

• Physiology
• Biophysics
• Microcirculation Research

Background:

• Microcirculatory studies typically use a single average diameter for blood vessels.
• This simplification is used for calculating microvascular hemodynamic variables like pressure drop.
• The assumption of constant vessel diameter's validity and consequences require examination.

Purpose of the Study:

• To investigate the impact of axial variations in blood vessel diameter on pressure drop calculations.
• To assess the validity of assuming a constant vessel diameter in microcirculation.
• To analyze these effects in both individual capillaries and a microvascular network model.

Main Methods:

• Measured vessel diameters at intervals along individual capillaries in hamster cremaster muscle.
• Calculated the ratio of pressure drop using actual vs. average diameters (delta P/delta Po).
• Employed a mathematical network model of blood flow in rat mesenteric microvessels to simulate diameter variations.

Main Results:

• Standard deviation of diameter increased with average diameter; coefficient of variation (CV) was higher in smaller vessels.
• In single vessels, delta P/delta Po ranged from 1.05 to 3.0 and correlated with CV.
• Network model simulations showed delta P/delta Po values ranging from 0.01 to 100 when diameter variations were included.

Conclusions:

• Axial variations in microvessel diameter significantly affect pressure drop calculations.
• The assumption of constant vessel diameter can lead to substantial inaccuracies in hemodynamic analysis.
• These findings highlight the importance of considering in vivo diameter variations for accurate microvascular research.