Blood flow model for noninvasive diagnostics

An artificial blood flow model (BFM) based on the human circulatory system was developed to allow a controlled variation of the blood parameter as total haemoglobin concentration (ctHb), oxyhaemoglobin (O₂Hb) and carboxyhaemoglobin (COHb). For this reason the optical properties of the blood were observed by online spectrometer measurements. The purpose was to observe the absorption, transmission and scattering properties of human whole blood in a wavelength range from 400 to 1700 nm. All the noninvasive measurements of the whole blood transmission-spectra were compared with sample results obtained by a Blood Gas Analyzer (BGA) to validate the results. For all measurements donor erythrocyte concentrates were used. The concentration of haemoglobin was changed by adding fixed amounts of blood plasma to the erythrocyte concentrate. Blood circulation and predetermined oxygen state were adjusted with an extra-corporal circulation unit. The blood was gently stirred and kept flowing through the blood tubes and the specially designed cuvettes (for spectrometric measurements). Oxygen saturation and COHb were adjusted by a continuous flow of N2, N2-CO- and N2-O2-mixture through a hollow fiber membrane oxygenator. The blood temperature was kept constant at 37°C via a tube heating mechanism and a separate water circulation through the Oxygenator. In the future the blood flow model can be used for testing newly developed optical prototype devices.