Hemoglobin (Hb) content is an important indicator for determining oxygen carrying capacity and anemia in clinical practice. Based on the content of hemoglobin, anemia patients can be screened. In addition, monitoring hemoglobin levels can understand the patient's blood loss situation and guide clinical transfusion management.

The spectral detection method has become a promising method due to its convenience, painlessness, non invasiveness, high-speed, high-precision, and multi-dimensional information principles. In non-invasive measurement of blood components using near-infrared spectroscopy, currently only blood oxygen monitoring is widely used in clinical practice. Monitoring blood oxygen plays a very important role in surgical anesthesia, medical monitoring, and research on exercise and sleep processes. Domestic and foreign scholars have conducted extensive research on blood oxygen detection, and there are various commercial blood oxygen monitoring products available. In the measurement of blood oxygen saturation spectrum, specific two wavelengths are usually selected for calculation to obtain the intermediate value of blood oxygen saturation coefficient. The value of blood oxygen saturation is calculated through empirical formula or fitting method.

In the visible near infrared band of 300-1500nm, the absorption coefficient curves of reduced hemoglobin (Hb), oxygenated hemoglobin (HbO2), and water (H2O) are shown in Figure 1. The difference in absorption coefficients between Hb and HbO2 is used to measure blood oxygen saturation using Lambert Beer's law. Usually, blood oxygen measurements are taken at the fingertips, earlobes, and other locations.

Blood oxygen spectroscopy measurement adopts in vivo fingertip transmission measurement. The collection device consists of four parts: light source, optical fiber, spectrometer, and computer, as shown in Figure 2. The light source adopts halogen lamps, and the optical fiber is a customized fiber bundle. The output end is arranged in a "one" shape to match the entrance slit of the spectrometer; The spectrometer adopts AvaSpec-HS1024x58TEC-USB2 and AvaSpec-NIR256-1.7TEC from Avantes, Netherlands, with built-in cooled back illuminated CCD detector array and cooled InGaAs detector array, with wavelength ranges of 200-1160nm and 1050-1700nm respectively. The spectrometer is connected to the computer through a USB cable.