As the venous blood passes through the lungs, the HCO3- and H+ are transformed by the RBC carbonic anhydrite back into CO2, which then diffuses into the alveolus and is exhaled by the mechanisms of alveolar ventilation.

• 当静脉血流经肺脏时，HCO3-和H+被红细胞中的碳酸酐酶转回成co2，co2再弥散进入肺泡，并经过肺泡通气机制排出体外。