Micro Flows in the Cardiopulmonary System: A Surgical Perspective - Bioanalysis Advanced Materials Methods and Devices - page 68

Chapter 5
Micro Flows in the Cardiopulmonary System:
A Surgical Perspective

Vasilios A. Karagounis and Axel R. Pries

Abstract Micro-flows in different organs—i.e., the flow of blood through the
smallest vessels, the microcirculation—differ in a number of aspects from blood
flow in larger vessels. Most prominently, the vessels of the microcirculation exhibit
diameters which are comparable in diameter to the size of red blood cells. In
addition to these hemorheological differences, the vessels of the microcirculation
exhibit the largest fraction of the overall inner vessel surface which is covered by
the endothelium. This chapter focuses on the heart and the lung addressing phe-
nomena in the microcirculation, including the no reflow phenomenon, coronary
microvascular dysfunction in the heart and the hypoxic pulmonary vasoconstriction
in the lung.

5.1 The Heart

The blood flow is delivered to the heart through large epicardial conductance
vessels (1-3 mm in size) and then into the myocardium by penetrating arteries
leading a plexus of capillaries. The bulk of the resistance to coronary flow is in the
penetrating arterioles (140 down to 20 m in size). Because the heart is metaboli-

cally very active, there is a high density of capillaries such that there is approxi-
mately one capillary for every myocyte, with an intercapillary distance at rest of
approximately 17

m

m[ 22 ].

m

V.A. Karagounis ( * )
Cardiothoracic Vascular Surgery, PO Box 819, Panorama Thessaloniki 55236, Greece
e-mail: [e-mail]
A.R. Pries
Department of Physiology and CCR, Charit´ - Universit¨tsmedizin Berlin, Charit´,
Arnimallee 22, Berlin 14195, Germany
e-mail: [e-mail]