Measurement of pulmonary edema in patients with acute respiratory distress syndrome

Objective: We measured pulmonary edema by thermal indocyanine green-dye double-dilution technique and quantitative computed tomography (CT) in patients with acute respiratory distress syndrome and compared the two techniques. Design and Setting: Prospective human study in a university hospital. Patients: Fourteen mechanically ventilated patients with acute respiratory distress syndrome (nine primary; nine with intubation <7 days). Interventions: All patients underwent a spiral CT of the thorax. We measured pulmonary thermal volume (PTV) and its components, extravascular lung water and pulmonary blood volume, with an integrated fiberoptic monitoring system (COLD Z-021). Measurements and Results: PTV was tightly correlated with lung weight (LW) measured by CT (PTV=0.6875 * LW(CT)+292.77; correlation coefficient=0.91; p<.0001; bias -11 +/- 8%). Neither etiology of acute respiratory distress syndrome (primary vs. secondary) nor days of intubation affected the accuracy of thermal dye dilution in comparison with CT. There was no correlation between the extravascular lung water (12.3 +/- 3.4 mL/kg) and CT distribution of lung tissue compartments. Extravascular lung water and pulmonary blood volume showed good reproducibility in 32 pairs of thermal dye dilution measurements. Conclusions: Measurements of lung edema by thermal indocyanine green-dye double-dilution method show good correlation with those by quantitative computed tomography and good reproducibility in patients with acute respiratory distress syndrome.