Relationship of Effective Circulating Volume with Sublingual Red Blood Cell Velocity and Microvessel Pressure Difference: A Clinical Investigation and Computational Fluid Dynamics Modeling

Athanasios Chalkias; Michalis Xenos

doi:10.3390/jcm11164885

Relationship of Effective Circulating Volume with Sublingual Red Blood Cell Velocity and Microvessel Pressure Difference: A Clinical Investigation and Computational Fluid Dynamics Modeling

J Clin Med. 2022 Aug 20;11(16):4885. doi: 10.3390/jcm11164885.

Authors

Athanasios Chalkias^{1

2

3}, Michalis Xenos⁴

Affiliations

¹ Department of Anesthesiology, Faculty of Medicine, University of Thessaly, 41500 Larisa, Greece.
² Outcomes Research Consortium, Cleveland, OH 44195, USA.
³ Committee on Shock, Hellenic Society of Cardiopulmonary Resuscitation, 10434 Athens, Greece.
⁴ Section of Applied and Computational Mathematics, Department of Mathematics, University of Ioannina, 45110 Ioannina, Greece.

Abstract

The characteristics of physiologic hemodynamic coherence are not well-investigated. We examined the physiological relationship between circulating blood volume, sublingual microcirculatory perfusion, and tissue oxygenation in anesthetized individuals with steady-state physiology. We assessed the correlation of mean circulatory filling pressure analogue (Pmca) with sublingual microcirculatory perfusion and red blood cell (RBC) velocity using SDF+ imaging and a modified optical flow-based algorithm. We also reconstructed the 2D microvessels and applied computational fluid dynamics (CFD) to evaluate the correlation of Pmca and RBC velocity with the obtained pressure and velocity fields in microvessels from CFD (pressure difference, (Δp)). Twenty adults with a median age of 39.5 years (IQR 35.5−44.5) were included in the study. Sublingual velocity distributions were similar and followed a log-normal distribution. A constant Pmca value of 14 mmHg was observed in all individuals with sublingual RBC velocity 6−24 μm s−1, while a Pmca < 14 mmHg was observed in those with RBC velocity > 24 μm s−1. When Pmca ranged between 11 mmHg and 15 mmHg, Δp fluctuated between 0.02 Pa and 0.1 Pa. In conclusion, the intact regulatory mechanisms maintain a physiological coupling between systemic hemodynamics, sublingual microcirculatory perfusion, and tissue oxygenation when Pmca is 14 mmHg.

Keywords: anesthesia; cardiovascular dynamics; hemodynamic coherence; hemodynamics; microcirculation; oxygen transport; physiology; red blood cell velocity; tissue perfusion.

Grants and funding

This research received no external funding.