TRANSFERRIN CONCENTRATIONS IN SERUM AND LOWER RESPIRATORY-TRACT FLUIDOF MECHANICALLY VENTILATED PATIENTS WITH COPD OR ARDS

Transferrin serves as the primary iron transport protein in serum, but it also is present in the lower respiratory tract where it has antiox idant and antibacterial properties. Prior studies indicate that patien ts with respiratory failure (RF) due to ARDS have increased concentrat ions of transferrin in the lower respiratory tract, which is attribute d to increased lung vascular permeability. It is unclear whether mecha nical ventilation contributes to increased lung transferrin content in patients with ARDS, although mechanical ventilation may increase lung microvascular permeability. To assess whether mechanical ventilation in patients with RF due to causes other than ARDS is also associated w ith increased respiratory tract concentrations of transferrin, we comp ared transferrin concentrations in serum and lung lavage fluid obtaine d from 12 mechanically ventilated patients with RF attributable to COP D, 6 patients with ARDS, and 15 healthy volunteers. Serum transferrin concentrations in patients with RF due to COPD were variable, but mean concentrations were similar to those in control subjects (336 +/- 58 vs 307 +/- 9 [SE] mg/dL), whereas serum transferrin concentrations wer e decreased in patients with ARDS (182 +/- 68 mg/dL; p<0.05). Compared with control subjects, lavage fluid recovered from patients with RF d ue to COPD contained significantly decreased concentrations of transfe rrin (1.56 +/- 0.24 vs 4.27 +/- 0.44 mu g/mL; p<0.001), whereas transf errin concentrations in lavage fluid recovered from patients with ARDS were increased (15.72 +/- 2.01 mu g/mL; p<0.001). Transferrin concent rations of lavage fluid also were decreased in COPD patients when norm alized for lavage fluid protein content (4.35 +/- 0.72 vs 19.96 +/- 3. 13 mu g/mg in control subjects, p<0.001). These data indicate that mec hanical ventilation of patients with COPD is associated with decreased lung transferrin concentrations, in contrast to an increased transfer rin concentration found in patients with ARDS. Decreased transferrin c oncentrations in the lower respiratory tract may decrease defenses aga inst oxidant injury and bacterial infection in patients with RF due to COPD.