| 摘要 |
A method and apparatus for determining the level of hematocrit in blood passing through a blood circuit is disclosed. The method involves repeatedly providing infrared light to the blood in cuvettes (7a, b), measuring the amount reflected, and using the amount measured to calculate the hematocrit level of the blood according to one of two formulas. In one embodiment, the light is at the isobestic wavelength of oxy- and deoxyhemoglobin, and is measured at a single distance from the source. In another embodiment, light at two infrared wavelengths is repeatedly provided and measured, the two wavelengths (usually 810 and 830 mm) being symmetrically disposed about the isobestic wavelength. The two measurements are used to approximate the amount of light reflected at the isobestic point, according to formulas provided, and the approximation is used in the calculation of hematocrit. Apparatus is also disclosed which utilizes LEDs (20, 22, 24) as the light sources, a photodiode (258) for detecting the amount of light, and fiber-optic channels (12, 14, 16, 18) in cables (5) for transmitting it to the blood and from the blood to the photodiode (258). Software is utilized for the approximations and calculations. |
