Chloride shift

Chloride shift (also known as the Hamburger phenomenon or lineas phenomenon, named after Hartog Jakob Hamburger) is a process which occurs in a cardiovascular system and refers to the exchange of bicarbonate (HCO3−) and chloride (Cl−) across the membrane of red blood cells (RBCs).

Consequently, chloride concentration is lower in systemic venous blood than in systemic arterial blood: high venous pCO2 leads to bicarbonate production in RBCs, which then leaves the RBC in exchange for chloride coming in.

This releases hydrogen ions from hemoglobin, increases free H+ concentration within RBCs, and shifts the equilibrium towards CO2 and water formation from bicarbonate.

Inward movement of bicarbonate via the Band 3 exchanger allows carbonic anhydrase to convert it to CO2 for expiration.

[4] Reaction (as it occurs in the pulmonary capillaries) Bicarbonate in the red blood cell (RBC) exchanging with chloride from plasma in the lungs.