A linear relation between the compressibility and density of blood

Area of Science:

• Biophysics
• Cardiovascular Physiology

Background:

• Blood is a complex fluid mixture.
• Understanding blood's physical properties is crucial for physiological and medical applications.

Purpose of the Study:

• To deduce and experimentally verify a linear relationship between blood compressibility and density.
• To determine if this relationship is independent of hematocrit, plasma protein, and hemoglobin concentrations.

Main Methods:

• Theoretical deduction based on blood as a mixture of ultrafiltrate and protein concentrate.
• Experimental verification using porcine and canine blood in an extracorporeal circuit with varying hematocrit and plasma protein concentrations.
• Measurement of blood density and ultrasound velocity to calculate compressibility.

Main Results:

• A linear relationship between blood compressibility and density was deduced and experimentally confirmed with a correlation coefficient of 0.9978.
• The derived linear relation's intercept and slope were found to be independent of hematocrit, plasma protein, and hemoglobin concentrations.
• The established linear relation accurately fits existing sound velocity data for human, horse, and porcine blood.

Conclusions:

• A fundamental linear relationship exists between blood compressibility and density.
• This relationship is robust across varying blood compositions and species.
• The findings provide a simplified model for predicting blood compressibility from density measurements.