Blood flow dynamics

Ongoing work is devoted to the accurate description of the origin and spread of excitation from the natural pacemaker to the rest of the heart. Computations of ventricular pressure development are being extended to account for blood flow dynamics in adjacent blood vessels. The thorax... 

ICG can be used to detect blood-flow dynamics. In the brain the absorption ehange after an ICG bolus shows differenees in superfieial and deeper blood vessels [327, 328, 329], and may be useful to indieate oeelusion of vessels and areas of inereased sboke risk. ICG dynamics have also been used for breast tumor iden-tifieation. Tumors usually have increased blood eontent, an inereased number of blood vessels, and inereased leakage of dye from the vessels into the tissue. Even with ICG injeetion, however, the contrast between tumour tissue and healthy tissue remains low. Moreover, the dwell time of ICG in the tissue is only about 10 minutes so that short aequisition times are required. 

The study on influence of Acanthopanax senticosus saponin on blood flow dynamics of isolated working heart showed the saponin had calcium channel blockade action dose-dependently. At concentration of SO, 100 and 200 u g/ml, the saponin reduced the myocardial contractility immediately, after washing out, the action disappeared[38]. 

Fig. 25. An example of Doppler color flow mapping, a real-time ultrasound technique that displays the dynamics of blood flow in color along with static tissue information in black and white. The image shows the record of a leaky mitral valve during systole.

Cenic A, Nabavi DG, Craen RA, Gelb AW, Lee TY. Dynamic CT measurement of cerebral blood flow a validation study. Am J Neuroradiol 1999 20 63-73. 

Rempp KA, Brix G, Wenz F, Becker CR, Guckel F, Lorenz WJ. Quantification of regional cerebral blood flow and volume with dynamic susceptibility contrast-enhanced MR imaging. Radiology 1994 193 637-641. 

Shen Q, Ren H, Fisher M, Bouley J, Duong TQ. Dynamic tracking of acute ischemic tissue fates using improved unsupervised isodata analysis of high-resolution quantitative perfusion and diffusion data. J Cereb Blood Flow Metab. 2004 24 887-897. 

The diameter and length of obstructing lesions and the influence of pressure drop across an area of stenosis also affect coronary blood flow and function of the collateral circulation. Dynamic coronary obstruction can occur in normal vessels and vessels with stenosis in which vasomotion or... 

The physiological changes and other aspects in the elderly makes this even more complicated. Example of this is decreased stomach acidity decreased motility decreased blood-flow to liver and gastrointestinal tract changed pharmacokinetics and -dynamics polypharmacy swallowing problems bad nutritional status and lack of documentation. 

It should be realized that although the principles outlined here are correct, the system is dynamic, not static. Molecules that are absorbed across the gastric or intestinal mucosa are removed constantly by blood flow thus, simple reversible equilibrium across the membrane does not occur until the agent is distributed throughout the body... 

Renal function Measurement of effects on urine excretion in saline loaded rats Renal dynamics Measurement of renal blood flow, GFR and clearance... 

The intestinal permeability may be determined from the rate of drug appearance in mesenteric blood (i.e. dM/dt) at steady state, using Eq. 2.12. Estimating the term C[ en will again depend on the flow dynamics of the model chosen. The most commonly used experimental procedure is the single-pass perfusion (i.e. parallel tube model) and the luminal concentration can be estimated using the logarithmic mean of inlet and outlet concentrations (i.e. ). 

Considering the spatial geometry of cerebral capillaries and capillary blood flow, a number of dynamic models of the blood-brain barrier have been developed, in which endothelial cells are cultured inside a permeable tube, the outer surface of which is coated with astrocytes. Supply of the cells with nutrients and artificial blood flow are maintained by using a peristaltic pump system [112, 113]. 

K. Yoshida, M. Furuse, A. Izawa, N. lizima, H. Kuchiwaki and S. Inao, Dynamics of cerebral blood flow and metabolism in patients with cranioplasty as evaluated by Xe CT and P magnetic resonance spectroscopy. J. Neurol. Neurosurg. Psychiatry, 1996,61, 166-171. 

As biological systems are dynamic, the concentration gradient will normally be maintained and an equilibrium will not be reached. Thus, the concentration on the inside of the membrane will be continuously decreasing as a result of ionization (see below), metabolism (see chap. 4), and removal by distribution into other compartments such as via blood flow (Fig. 3.4). It follows from Fick s Law that because A the surface area is an important term in the equation, the surface area of the site of exposure will have a major effect on the absorption of chemicals. 

Radionuclide Imaging Procedures. Brain tumors can be detected by external counting of radionuclides, a procedure introduced into general clinical use in the late 1950s. A significant advance in brain tumor imaging was the introduction of the gamma camera, which permitted more rapid studies with multiple views, as well as dynamic cerebral blood flow assessment. 

Substances that undergo bioconcentration are hydrophobic and lipophilic, and therefore tend to undergo transfer from water media to fish lipid tissue. The simplest model of bioconcentration views the phenomenon on the basis of the physical properties of the contaminant and does not account for physiologic variables (such as variable blood flow) or metabolism of the substance. Such a simple model forms the basis of the hydrophobicity model of bioconcentration, in which bioconcentration is regarded from the viewpoint of a dynamic equilibrium between the substance dissolved in aqueous solution and the same substance dissolved in lipid tissue. 

In a comparison of thrombolysis and angioplasty, reinfarction after thrombolysis (6.3% compared with angioplasty 1.6%) worsens the patient s outcome (20). The improved outcome here was driven by a reduction in the rate of reinfarction. If coronary blood flow by cine frame count improved in the culprit artery, the flow also improved in the nonculprit arteries (19). This suggests that the active inflammatory infiltrate is a dynamic phenomenon. 

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