Turbulent blood flow

In the case where the blood flow is turbulent, we can use the concept of enhancement factor for the case of liquid-phase mass transfer with a chemical reaction (Section 6.5). Thus, 

The value of the liquid phase mass transfer coefficient can be obtained from the experimental data for physical absorption of oxygen into blood saturated with oxygen, or estimated from the data with the same apparatus for physical oxygen absorption into water or a reference liquid or solution with known physical properties. Mass transfer coefficients for liquids flowing through or across tubes or hollow fibers can usually be correlated by equations, such as Equation 6.26a for 

Ihe overall coefficient of oxygen transfer based on the blood phase K-g (cm s ), neglecting the gas phase resistance, is given as 

The flux of oxygen transfer per unit membrane area /q (molorcm min cm ) is given by 

As the overall driving potentials (C - C) as well as (p-p ) vary over the membrane surface, some appropriate mean driving potential (C - C), or p should be used in calculating the total rate of oxygen transfer /q (mol or cm min ). Thus, 

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Murmurs are auditory vibrations heard on auscultation, and they occur because of turbulent blood flow within the heart chambers or through the valves. They are classified by timing and duration within the cardiac cycle (systolic, diastolic, and continuous), location, intensity, shape (configuration or pattern), pitch (frequency), quality, and radiation (Table 11-3). 

Anatomic alterations of the heart resulting in turbulent blood flow and endocarditis... 

The endothelial surface of the heart is damaged. This injury occurs with turbulent blood flow associated with the valvular lesions previously described. 

Bruit—An abnormal and often harsh sound heard over a blood vessel, usually an artery, on examination with a stethoscope caused by turbulent blood flow. 

Most types of structural heart disease resulting in turbulence of blood flow will increase the risk for IE. Some of the most important risk factors include / Presence of a prosthetic valve (highest risk)... 

Hypercoagulable states, in turn, have been traditionally associated with venous thrombosis. Consequently, attention has been paid to alterations of the hemostatic balance. Although this is a systemic variable, focality is favored due to the contribution of decreased blood flow, as confirmed by the preferential development of venous thrombi at the level of valves, an area of stasis where low-velocity flow is moderately turbulent. 

The role of nitric oxide in maintaining laminar blood flow. A sudden vasoconstriction in one branch of a vascular bed will cause an immediate increase in the upstream pressure that could cause turbulent flow. The myogenic constriction of the upstream branches responding to the turbulent flow will be counterbalanced by increased synthesis of nitric oxide, shown as a radial gradiant, due to shear stress on endothelium. 

Hollow-fiber (capillary)-type membrane oxygenators are the most widely used today, and comprise two main types (i) those where blood flow occurs inside the capillaries and (ii) those where there is a cross-flow of blood outside the capillaries. Although in the first type the blood flow is always laminar, the second type has been used more extensively in recent times, as the mass transfer coefficients are higher due to blood turbulence outside capillaries and hence the membrane area can be smaller. Figure 15.3 shows an example of the cross-flow type membrane oxygenator, with a built-in heat exchanger for controlling the blood temperature. 

Bleeding oesophageal varices may be triggered by three pathogenetic mechanisms (7.) critical pressure increase in the varices, especially when it is sudden (= explosion hypothesis), (2.) occurrence of flow turbulences with bidirectional blood flow in the varices (= circulation hypothesis), and (5.) inflammatory lesion at the varix surface with the formation of thin spots (= erosion hypothesis). 

Blood flow Slow rate of flow Turbulent flow Fast rate of flow Laminar flow... 

Most persons with IE have risk factors, such as preexisting cardiac valvular abnormalities. Many types of structural heart disease result in turbulence of blood flow that increases the risk for IE. 

For both CRVO and BRVO the pathophysiology includes the formation of thrombosis within the venule, typically at the crossing point of an arteriole and venule in the case of BRVO, and at or just posterior to the lamina cribrosa in the case of CRVO. In both instances the compartment syndrome model has been proposed whereby the vein is partially compressed by the adjacent arteriole artery within a restricted space. This can lead to turbulence of blood flow, and secondary development of thrombosis. Surgical decompression of the vein or the surrounding structures has been proposed as a therapeutic procedure for both disorders. 

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