Assessment of carboxyhemoglobin content in the blood with high accuracy: wavelength range optimization for nonlinear curve fitting of optical spectra

The impact of carbon monoxide (CO) gas on the human organism is very dangerous. The affinity of CO to hemoglobin is considerably higher than that of oxygen. Thus, the interaction of CO with the blood results in a higher content of carboxyhemoglobin (HbCO) in red blood cells (RBCs) and correspondingly in tissue hypoxia. The disruption in the organism depends on the HbCO content in the blood. To assess any complications in the body at a given moment due to CO exposure and predict future consequences, it is necessary to measure the dynamics of hemoglobin derivative concentrations simultaneously. However, measuring HbCO and other derivatives in RBCs without hemolysis accurately is complicated due to the strong intercollinearity between the molar absorptivities of hemoglobin derivatives and superposition of absorption and scattering spectra. In the present study, to quantitatively assess the contents of the hemoglobin derivatives in the blood after exposure to CO, improved accuracy is achieved by optimizing the wavelength range used for the nonlinear curve fitting of optical spectra. Experimental spectra were measured in the wavelength range Δλ=500−700nm. For each experimental curve, it was established the value of optimal interval Δλopt for which the correlation coefficient between experimental data and corresponding points of the theoretical fitting curve was the maximum in the wavelength range Δλtyp=535−580nm, which contains the typical absorption peaks for HbO2, Hb, and HbCO. The concentrations obtained based on such fitting curves were considered to be highly accurate. The quantitative assessment enabled the determination of theHbCO nonlinear increase with the time of CO exposure in the in vitro experiment and the study of the dynamics of hemoglobin derivative transformations during blood incubation.