  Contemporary paradigm of vascular hemodynamics considers normal blood flow to
be pulsatile laminar flow. Transition to turbulence can cause diseases such as
atherosclerosis or brain aneurysms. Recently, we demonstrated the existence of
turbulence in experimental models of brain aneurysm; in the aneurysm sac as
well as in the main artery. Thus, we were intrigued to explore if such a
long-standing assumption of the laminarity of blood flow could be challenged.
We have used methods and tools from chaos theory, hydrodynamic stability theory
and turbulence physics to explore the existence of turbulence in normal
vascular blood flow. We used Womersley exact solution of the Navier-Stokes
equation with the HaeMed database of physiologic blood flow measurements, to
offer reproducible evidence for our findings, as well as evidence from Doppler
ultrasound measurements from healthy volunteers. The tools we used to
investigate the properties of blood turbulence are well established in the
fields of chaos theory, hydrodynamic stability and turbulence dynamics. We
show, evidently, that blood flow is inherently chaotic and turbulent and not
laminar. We propose a paradigm shift in the theory of vascular hemodynamics
which requires rethinking the hemodynamic-biologic links governing physiologic
and pathologic processes.
