Protocol for storing RBC units. A total of 6 pools of blood were produced, each from 3 donors to reduce variation. Pools were split so that 1 set was stored under standard conditions, 1 under hypoxic conditions, and a third under standard conditions for end-point rejuvenation. Color coding of units is consistent throughout the data figures: standard storage in black, hypoxic storage in red, biochemically rejuvenated units in blue. At the time points indicated, RBC units were sampled for measurements the day after.