Gamma scintigraphic imaging of lung microvascular permeability in adult respiratory distress syndrome

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Abstract
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 the In 113m-labeled transferrin and Tc 99m-labeled erythrocytes. The LMVP index (LMVPI) (90/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 < .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 LMVP increased significantly (p < .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). In indirect late ARDS induced by pancreatitis (group C), the LMVP was elevated in both lungs (right LMVPI 10.5 .+-. 4.4, left LMVPI 9.2 .+-. 2.7%/h) at onset of ARDS. The sequences of LMVP distribution and degree are different in both ARDS groups, indicating a different sequence of mechanisms causing ARDS due to direct and indirect injury.