Estimation of the transfer coefficients of oxygen and carbon monoxide in the boundary of human and chicken red blood cells by a microphotometric method.

The reaction rates of O2 and CO with the human and chicken red blood cell (RBC) were measured by using a microphotometric apparatus. In the experiments on the human RBC, a small amount of RBCs were put in an air-tight reaction cuvette. Gas mixtures containing various concentrations of O2 and CO were sequentially injected into the cuvette and the change in O2 and CO saturation of hemoglobin was measured from the change in transmission of the RBCs at 402 and 416.5 nm. The reaction rate of CO with RBCs was significantly influenced by photodissociation of carboxyhemoglobin (COHb). To eliminate this, a short-pass filter (400 to 435 nm) and a sector (100 Hz) were used. By comparing the measured reaction rates of O2 and CO with the theoretical rates obtained from the numerical solutions of the partial differential equations of the diffusions of O2 and CO, the transfer coefficients of O2 and CO (eta O2 and eta CO) in the RBC boundary, including the RBC membrane and water layer around the RBC, were estimated. Both the values showed good agreement, ranging from 0.3 to 2.5 x 10(-6) cm.sec-1.Torr-1. Furthermore, the chorioallantoic capillary of chicken embryo was used for the measurements of the reaction rates of O2 and CO with RBC through the capillary membrane. The reaction rates of O2 and CO in the chorioallantoic capillary were slower than those obtained in the human RBC. By comparing the measured reaction rates and the numerical solutions, the eta O2 and eta CO in the boundary, including the capillary membrane, plasma, and RBC membrane, were estimated. These two values ranged from 0.1 to 0.4 x 10(-6) cm.sec-1.Torr-1 and showed good agreement. These results suggest that the diffusion rates for O2 and CO across the capillary and RBC membrane are similar.