Detecting lung injury in patients with pulmonary edema

Objective: Current entry rules for clinical trials of acute lung injury (ALI) depend on clinical criteria and arterial blood gas measurements. The objective of this study was to determine whether estimates of pulmonary vascular permeability could be used to more accurately identify patients with ALI for this purpose. Design and setting: Cross-sectional study in a university hosptial in a large metropolitan city. Patients and participants: 21 patients with noncardiogenic pulmonary edema, 7 patients with hydrostatic forms of pulmonary edema, and 10 healthy volunteers. Interventions: Positron emission tomographic (PET) imaging with ⁶⁸Ga-labeled transferrin, or γ-camera scintigraphy (γ-S) with ^99mTc-labeled albumin. All patients were studied within 24 h of onset, and all were selected exclusively on the basis of radiographic, not clinical, criteria. PET estimates of PTCER were used as a "gold standard." Measurements and results: Radioactivity data were analyzed to compute the pulmonary transcapillary escape rate (PTCER) and the normalized slope index. PTCER by γ-S was more strongly correlated to PTCER_PET than normalized slope index by γ-S. Although PTCER_γ was significantly correlated with PaO₂/FIO₂, it did not distinguish patients with noncardiogenic pulmonary edema from those with hydrostatic pulmonary edema. Conclusions: These data cast doubt on whether the γ-S method can be used as a screening tool in clinical trials of ALI.