Specific aim: To test whether transfusion of leukoreduced red cells of lesser storage time (versus conventional storage time) reduces mild alterations in pulmonary function and immune activation in critically ill patients with mechanically ventilated lungs.

We propose to perform a prospective, randomized, double-blind clinical trial in critically ill patients whose lungs are mechanically ventilated, and who have orders to receive transfusion of at least one unit of packed red cells, comparing pulmonary function between patients randomly allocated to receive a unit of red cells stored for 5 days or less, with similar patients randomly allocated to receive a unit of red cells stored conventionally (median 21 days). We will test the hypothesis that transfusion of red cells of lesser storage age, (5 days or less) will produce the less changes of pulmonary function and immune activation than will transfusion of red cells of conventional storage age (median 21 days).

Specific aim: To test whether transfusion of leukoreduced red cells of lesser storage time (versus conventional storage time) reduces mild alterations in pulmonary function and immune activation in critically ill patients with mechanically ventilated lungs.

Inclusion Criteria:

• Patients, male or female, any race or ethnicity, age 18 years or older, in one of the seven adult critical care units of the Mayo Clinic, Rochester, with mechanically ventilated lungs, requiring elective transfusion of at least one unit of red cells

Exclusion Criteria:

• transfusion of any blood component within the previous 2 hours, emergency transfusion or hemodynamic instability defined by other than a stable dose of vasoactive medications.