The sequence of lung microvascular permeability (LMVP) changes in early direct posttraumatic and late indirect pancreatitis-induced adult respiratory distress syndrome (ARDS) was studied and compared with that of a control group, as well as non-ARDS ICU patients. A computerized large field of view gamma camera was used to measure LMVP simultaneously over both lungs by In 113m-labeled transferrin and Tc 99m-labeled erythrocytes. The LMVP index (LMVPI) (%/h) was used to quantify LMVP in the dynamic scintigraphic measurement. In the control group the LMVPI was 2.6 +/- 2.8%/h for the right and 2.0 +/- 2.8%/h for the left lung. Similar values were found in mechanically ventilated ICU patients without ARDS (group A) on admission (right LMVPI 3.2 +/- 2.6, left LMVPI 2.6 +/- 2.7%/h) and 4 days later (right LMVPI 3.9 +/- 2.6, left LMVPI 2.3 +/- 1.8%/h). Interestingly, the initial evaluation of patients with direct early posttraumatic ARDS (lung contusion) (group B) showed significantly (p less than .01) elevated LMVP for the contused side (LMVPI 10.8 +/- 5.1%/h), but normal values for the nontraumatized lung (LMVPI 3.9 +/- 3.4%/h), whereas 4 days later the LMVP increased significantly (p less than .05) on the primarily healthy side (LMVPI 8.0 +/- 5.0%/h) while remaining elevated for the traumatized lung (LMVPI 10.9 +/- 6.0%/h).(ABSTRACT TRUNCATED AT 250 WORDS)