Blood flow

An interesting problem in hemorheology is to calculate the volume fraction of erythrocytes (hematocrit) that is optimal for transporting a maximum amount of oxygen. If the hematocrit is too low, too few erythrocytes are present to transport oxygen. If it is too high, the blood is very viscous and cannot flow quickly, so that oxygen supply to the tissues is again reduced. (Stark & Schuster, 2012)

Hematocrit	Oxygen
10%	57%
40%	100%
60%	86%
90%	25%

We thank BruceBlaus (Wikimedia Commons) for blood cell images,
licensed under the Creative Commons Attribution 3.0 Unported license.

References:

Sitina M, Stark H & Schuster S (2024) Optimal hematocrit theory: a review. Journal of Applied Physiology 137:3, 494-509. DOI:10.1152/japplphysiol.00034.2024 / ISSN:8750-7587

Sitina M, Stark H & Schuster S (2021) Calculating the optimal hematocrit under the constraint of constant cardiac power. Sci Rep 11: 3925. DOI:10.1038/s41598-021-83427-2 / EISSN:2045-2322

Schuster S, Stark H (2014) What can we learn from Einstein and Arrhenius about the optimal flow of our blood? BBA General Subjects 1840 (1): 271-276. DOI:10.1016/j.bbagen.2013.08.026 / ISSN:0304-4165

Stark H, Schuster S (2012) Reply to Böning, Maassen, and Pries. Journal of Applied Physiology 113: 1169–1169. DOI:10.1152/japplphysiol.01012.2012 / ISSN:8750-7587

Stark H, Schuster S (2012) Comparison of various approaches to calculating the optimal hematocrit in vertebrates. Journal of Applied Physiology 113: 355-367. DOI:10.1152/japplphysiol.00369.2012 / ISSN:8750-7587