Grading of Respiratory Distress Syndrome

Stage 1
slight reticular (slight granular) decrease in transparency of the lung, no certain difference to normal findings.

Stage 2
Soft decrease in transparency with an aerobronchogram, which overlaps the heart (= always a sign of an alveolar lung reaction!)

Stage 3
like stage 2, but with gradual stronger decrease in transparency, as well as a blurry diaphragm and heart.

Stage 4
White lung: practically homogenic lung opacity

Synopsis of the changes in Stages I - IV.

source : http://www.kinderradiologie-online.de/radiology/20021110223558.shtml#a1