A theoretical analysis of nonsteady-state oxygen transfer in layers of hemoglobin solution

The oxygenation of layers of hemoglobin solutions thick enough to ensure chemical equilibrium between oxygen and hemoglobin has been analyzed theoretically assuming simultaneous diffusion of oxygen and oxyhemoglobin. The dimensionless transfer equation was solved for the finite and semi-infinite situation, the parameters being 1) the ratio of bound to physically dissolved oxygen after equilibration (H), 2) the ratio of carrier-mediated to free oxygen flux at steady state (D), and 3) the dimensionless saturation curve (characterized by phi 50). A parametric analysis provided plots of the dimensionless oxygenation time against these three dimensionless parameters. In this way, from the oxygenation times plotted as a function of the reciprocal oxygen driving pressure in any particular hemoglobin solution, the values of the oxygen permeability (or, knowing oxygen solubility, of the oxygen diffusion coefficient) and of the hemoglobin diffusion coefficient can be derived simultaneousl

Use of a wedge cuvette in this layer photometry and its application to oximetry

A wedge cuvette was constructed by fixing 2 glass plates at a known angle with a spacer at one end. This resulted in a thin layer with thickness varying from 0 to 250 micrometer. By measuring the intensity of a beam of light through the thin layer as a function of distance along the wedge (and thus layer thickness), the absorption coefficient at the light wavelength used could be obtained without a separate measurement of I0, the reference light intensity. In addition, the difficult problem of determining accurate layer thickness as encoutered in conventional thin layer photometry has been avoided. Tests of the wedge cuvette method with Evans Blue and Malachite Green serial dilutions as well as with haemoglobin solutions at several oxygen saturations demonstrate that accuracy of the order of 1% can be obtained. Application of the wedge cuvette in experiments on oxygen uptake by layers of haemoglobin solution are discusse

Intermittent on line (vivo) measurement of pO/sub 2/, pCO/sub 2/, pH and K/sup +/ by means of automatic sampling of blood and automatic calibration of electrodes and amplifiers

ABGA (Automated Blood Gas Analyser) may be connected by sample catheter to either an artery or vein. At desired intervals ABGA draws a blood sample automatically and performs an analysis. The measuring part consists of a special cuvette with conventional electrodes. Before a blood sample is drawn the four signal amplifiers are calibrated automatically by means of two calibration solutions equilibrated with gas mixtures of known composition. After completion of the analysis the blood within the cuvette is rinsed away but the blood within the catheter is returned to the patient with the aid of a saline infusion. The measuring cycle time including calibration is 8 minutes; without calibration 3 minutes. Blood loss per cycle amounts to 2 cm/sup 3/. With electrical grounding the patient current is less than 1 mu

Myocardial perfusion distribution and coronary arterial pressure and flow signals:clinical relevance in relation to multiscale modeling, a review

\u3cp\u3eCoronary artery disease, CAD, is associated with both narrowing of the epicardial coronary arteries and microvascular disease, thereby limiting coronary flow and myocardial perfusion. CAD accounts for almost 2 million deaths within the European Union on an annual basis. In this paper, we review the physiological and pathophysiological processes underlying clinical decision making in coronary disease as well as the models for interpretation of the underlying physiological mechanisms. Presently, clinical decision making is based on non-invasive magnetic resonance imaging, MRI, of myocardial perfusion and invasive coronary hemodynamic measurements of coronary pressure and Doppler flow velocity signals obtained during catheterization. Within the euHeart project, several innovations have been developed and applied to improve diagnosis-based understanding of the underlying biophysical processes. Specifically, MRI perfusion data interpretation has been advanced by the gradientogram, a novel graphical representation of the spatiotemporal myocardial perfusion gradient. For hemodynamic data, functional indices of coronary stenosis severity that do not depend on maximal vasodilation are proposed and the Valsalva maneuver for indicating the extravascular resistance component of the coronary circulation has been introduced. Complementary to these advances, model innovation has been directed to the porous elastic model coupled to a one-dimensional model of the epicardial arteries. The importance of model development is related to the integration of information from different modalities, which in isolation often result in conflicting treatment recommendations.\u3c/p\u3