Assessing pulmonary capillary protein permeability noninvasively at the bedside to yield the pulmonary leak index (PLI) could help in determining the extent of tissue injury, as was previously described [18] [19] [20] . This radionuclide technique involves gallium-67-labelled transferrin ( 67 Gatransferrin) and technetium-99m-labelled red blood cells ( 99m Tc-RBCs). In bacterial pneumonia, for instance, the PLI is elevated and the increase above normal directly relates to the severity of pneumonia, expressed as the lung injury score (LIS) [19] . In patients with acute lung injury (ALI) or ARDS during the course of bacterial pneumonia, the PLI is uniformly and greatly elevated above normal (up to 14.1 × 10 -3 /min) when LIS is greater than 2.5; the PLI is also elevated in 80% of patients with mild injury and a LIS between 1.5 and 2.5 [19] . Hence, the technique is a direct measure of permeability and an indirect measure of capillary injury in the lungs. The PLI is also elevated in interstitial lung disease [21] .