Volume and density changes of biological fluids with temperature

Area of Science:

• Biophysics
• Fluid Dynamics
• Materials Science

Background:

• Accurate measurement of biological fluid properties is crucial for understanding physiological processes.
• The coefficient of thermal expansion (beta) describes how volume changes with temperature, a key physical property of fluids.
• Previous studies have limited data on the thermal expansion of human blood components across a physiological temperature range.

Purpose of the Study:

• To precisely measure the mass density and calculate the coefficient of thermal expansion (beta) of human blood, plasma, plasma ultrafiltrate, and erythrocyte concentrate.
• To investigate the temperature and density dependence of beta in these biological fluids.
• To compare the thermal expansion properties of intracellular and extracellular fluids.

Main Methods:

• Employed the mechanical oscillator technique for high-precision mass density measurements (10⁻⁵ g/ml).
• Conducted measurements across a temperature range of 4 to 48°C with high temperature accuracy (±1 × 10⁻² K).
• Calculated the coefficient of thermal expansion (beta) from density and temperature data.

Main Results:

• Beta increases with temperature in all investigated fluid samples, with the rate of increase diminishing at higher temperatures.
• Below 40°C, beta increases with fluid density; above 40°C, beta is independent of density.
• Intracellular fluid exhibits approximately twice the beta of extracellular fluid at low temperatures (4-10°C), becoming equal at ≥40°C.

Conclusions:

• The mechanical oscillator technique is suitable for precise beta calculations in small biological fluid volumes.
• Thermal expansion of blood components is temperature and density-dependent, with distinct intracellular and extracellular fluid behaviors.
• Findings provide essential physical data for biomedical research and applications involving human blood fluids.