Method of evaluation of process of red blood cell sedimentation based on photometry of droplet samples
The paper focuses on research aimed at creating and testing a new approach to evaluate the processes of aggregation and sedimentation of red blood cells for purpose of its use in clinical laboratory diagnostics. The proposed method is based on photometric analysis of blood sample formed as a sessile drop. The results of clinical approbation of this method are given in the paper. Analysis of the processes occurring in the sample in the form of sessile drop during the process of blood cells sedimentation is described. The results of experimental studies to evaluate the effect of the droplet sample focusing properties on light radiation transmittance are presented. It is shown that this method significantly reduces the sample volume and provides sufficiently high sensitivity to the studied processes.
A Prototype of Optical Blood Coagulometer
The paper presents the results of the evaluation of coagulation time of whole blood, obtained by the method of digital correlation of speckle patterns. The analysis of previously published papers and study results of plasma clotting time that we obtained showed that the method of correlation of digital speckle patterns has the prospect of using for determination of the clotting time of whole blood. The paper discusses the application features of the method of speckle pattern correlation for estimating the clotting time of whole blood, the design of the device for continuous monitoring of clotting time and the main medical and technical requirements for the device under development.
Role of Light Scattering in Spectrophotometric Measurements of Arteriovenous Oxygen Difference
The role of light scattering in the spectrophotometric measurement of arteriovenous oxygen difference (a ¿vO2) in whole blood was investigated. Optical absorbance of whole blood and corresponding hemoglobin solutions was measured to elucidate the contributions of true absorbance and "total scattering effects" to the total absorbance of whole blood. Twersky's radiation scattering theory, which provides a mathematical separation of absorbance and total scattering effects, was applied to the data. It is shown that, although the optical density of whole blood is a highly nonlinear function of hematocrit, the difference in optical density between venous and arterial blood is approximately a linear function of the arteriovenous difference in oxygen content. Furthermore, "total scattering effects" contribute significantly more than true absorbance to the total optical density of whole blood and hence to the actual spectrophotometric measurement of a ¿vO2. Twersky's equation fits the data remarkably well and thus provides a theoretical basis for whole blood measurements. The validity of whole blood spectrophotometric arteriovenous oxygen difference analyzers is thus demonstrated both empirically and theoretically.