Real-time measurement of human blood flow with high temporal and spatial resolution

The examination of human microcirculation allows for monitoring important body conditions. To analyze the human microcirculation, the measurement of the blood flow in capillaries is a efficient method. This requires a high spatial resolution in the first instance. The cutaneous capillary microscopy is a noninvasive optical method, which makes the capillary shape visible in the microcirculation area of interest. A convenient area for observation is the nail fold of the fingers. The erythrocyte columns in these capillaries can be distinguished from their surroundings and from the the blood plasma. This paper presents a system, that determines the flow rate of the erythrocytes in the capillary at the nail fold according to the spatial filter principle. This measuring principle represents an interesting and powerful approach for the determination of the blood flow rate in the capillaries. In the practical use, the unavoidable finger movements of the patients inducing problems in the capillary measurements. This problem is solved by implementing a new fast movement correction. To this end the finger movements will computed and therewith the position of the points for measuring the erythrocyte velocity is corrected. This new system detects the path of a capillary and is able to issue velocity values of blood in the capillaries over a long time and with high temporal resolution.