Shortness of breath and chest pain can occur after exercise. Yellow discoloration of the skin may occur in some anemias. It all comes down to the transport of oxygen by the red blood cell. Air is a mixture of gases, each of which contributes a share of the total atmospheric pressure called its partial pressure. Partial pressures are important because they determine the rate of diffusion of a gas, and therefore strongly affect the rate of gas exchange between the blood and alveolar air.
Partial pressures change as a diver descends and ascends in the water column.
At the alveolus, the blood is said to unload carbon dioxide and load oxygen. The efficiency of both processes depends on the length of stay of an erythrocyte in an alveolar capillary, and how long it takes for oxygen and carbon dioxide to reach equilibrium in the capillary blood. The poisonous effect of carbon monoxide stems from its competition for the same binding site as oxygen. Hemoglobin unloads more oxygen into the tissues that need it most. NOAA Scuba Hematologic Disqualifications Hematological Sickle cell anemia should be disqualifying.