How does the carbon dioxide get out of the bloodstream back into the lungsto be breathed out?

Carbon dioxide (CO2) is transported in the bloodstream mainly as bicarbonate ions (HCO3-) after being produced by cellular metabolism. When blood reaches the lungs, the bicarbonate ions are converted back to CO2 through a reaction involving hydrogen ions. The CO2 then diffuses from the blood into the alveoli of the lungs due to the concentration gradient and is expelled from the body when we exhale. This exchange is facilitated by the differences in partial pressures of CO2 in the blood and the alveolar air.