I understand that something must match, but why should one liter of air match one liter of blood??
I think the explanation with busses and passengers is particularly poor (but very commonly accepted). In expired alveolar air there is about 14% O2 (140 ml pr L), while in blood that has just passed the alveolar wall there is 100% saturation (no seats left). This means that there is nowhere close to a match between passengers (molecules of O2) and busses (Hb molecules), there is a lot more O2 molecules.
So, can anyone explain the stoichiometry behind a V/Q of one.