Lung Zone Classification Criteria
The chest was divided into 9 zones (Figure 2), based on a modification of previously established protocols5, 36 to approximate lobar anatomy of the lung and reflect our clinical workflow in intubated patients. Each zone was classified based on an overall impression from an area no larger than x. Classification of findings (Figure 3) could be accomplished without advanced computer technology37 or the need to freeze an image and count abnormalities.
Similar to a previous study15, each zone was classified as:
A = lung sliding, presence of A-lines, and lack of B-lines or consolidation
B1 = 1-3 B-lines present per intercostal space;
B3 = confluent B-lines occupying >50% of an intercostal space
B2 = quantity of B-lines between B1 and B3.
Areas of non-aerated lung >3cm in its axis perpendicular to pleura with dynamic air bronchograms and lack of compressive reason for aeration loss (e.g. pleural effusion, elevated diaphragm) were classified as non-atelectatic consolidation . Areas of non-aerated lung >3cm in its axis perpendicular to pleura with distinct features suggesting volume loss atelectasis such as a pleural effusion size consistent with volume of tissue-like lung, lack of dynamic air bronchograms, typical atelectatic distribution in the inferior, lateral tip of lung with a smooth re-aeration line, were classified asatelectasis . A combined classification ofatelectasis/consolidation was assigned when the area examined consisted of tissue-like density and the physician was unable to see discriminating features indicative of either specific entity. Zones with small, focal, <3cm areas of peripheral consolidation were classified as small consolidations. The pleural effusionclassification was added to each zone when present.