According to this author, red blood cells (RBCs) are biconcave to allow easier bending. The standard explanation in biology for higher surface area to volume ratios is that it improves reaction rates. When a RBC squeezes through narrow veins I imagine that it gets deformed. Considering that a RBC's function is to exchange oxygen in narrow capillaries, I was wondering whether it is appropriate to reason that the biconcave shape promotes gas exchange. So what is the SA:V of a biconcave RBC and by how much does the SA:V change depending on where in the body the RBC is traveling?