The article considers the impact of the diffusion capacity of the lungs to process oxygen transfer from the gas phase of the alveoli into the blood capillaries of the lungs. The main transport of oxygen in the blood takes place in a bound state with the hemoglobin of red blood cells. Therefore, the diffusion capacity of the lungs to transport gases other than diffusion through tissue affects the rate of reaction of oxygen with hemoglobin and red blood cell membrane permeability. The dependence of the reaction rate of oxygen on hemoglobin oxygen tension is analyzed using various literary sources. Using a mathematical model of the lungs and experimental data taken from the literature the rate of oxygen reaction with hemoglobin was evaluated. Numerical results when compared with the experimental data showed a good result.