Diagnostic value of the gallium-67 pulmonary leak index in pulmonary edema.

UNLABELLED: We studied the value of a noninvasive, bedside, dual-radionuclide method (67Ga-circulating transferrin and 99mTc-red blood cells) to measure pulmonary microvascular permeability in efforts to discriminate between pulmonary edema due to adult respiratory distress syndrome (ARDS) and hydrostatic pulmonary edema (HPE).

METHODS: Patients had respiratory insufficiency and bilateral alveolar pulmonary edema on chest radiographs. All patients, except one, were mechanically ventilated. Patients, were divided into groups according to various sets of etiologic, hemodynamic and ventilatory factors. Group 1 (n = 8) had risk factors for HPE only. Group 2 (n = 5) had risk factors for both ARDS and HPE, such as a pulmonary capillary wedge pressure (PCWP) above 18 torr. Group 3 (n = 13) had risk factors for ARDS only and a PCWP below 18 torr. Patients were also classified on the basis of a lung injury score, using radiographic and ventilatory variables. Group 4 (n = 12) had a score below 2.5 and Group 5 (n = 14) above 2.5, arbitrarily defined as ARDS. Any radioactivity measurements over the lungs and in blood within 72 hr after admission were used to calculate the 1 hr pulmonary leak index as a measure of microvascular permeability (upper limit of normal 14.1 x 10(-3).min-1).

RESULTS: The PLI ( x 10(-3).min-1) was median 10.2 (range 4.4-16.2) in Group 1, 26.8 (14.2-31.9) in Group 2 and 32.3 (23.0-52.4) in Group 3 (p < 0.001). It was 13.3 (4.4-39.9) in Group 4 and 31.1 (14.2-52.4) in Group 5 (p < 0.01). Using the various definitions, the sensitivity of a supranormal pulmonary leak index for ARDS was 100% and the specificity varied between 46% and 75%. In receiver operating characteristic curves, the pulmonary leak index performed best when ARDS and HPE were defined on the basis of risk factors only, and performed better than hemodynamic and equally well as ventilatory variables in discriminating between edema types, if definitions of the latter were mainly based on hemodynamic and ventilatory variables, respectively.

CONCLUSION: The 67Ga pulmonary leak index is a useful tool to differentiate ARDS from HPE.