TABLE 1.

Scoring grid for histopathologic examination of lung tissue

Parameter	Score	Interpretation
Inflammatory cells	0	No neutrophils, lymphocytes, or eosinophils in alveoli and lung tissue; normal amount of alveolar macrophages
	1	Slight increase in the number of any inflammatory cell population
	2	Recruitment of a large number of inflammatory cells
Hemorrhage	0	No erythrocytes in alveoli
	1	Few erythrocytes in alveoli
	2	Numerous erythrocytes
Edema	0	Absent
	1	Minimal swelling of alveolar walls
	2	Widespread swelling of tissue interstitium
Tissue injury	0	Absent
	1	Minimal modification in alveolar architecture
	2	Widespread disorganization of lung tissue, including injuries to organelles
Regeneration	0	Normal amount of type II pneumocytes and surfactant
	1	Slight increase in the number of type II pneumocytes and surfactant secretion
	2	Marked increase in type II pneumocytes and surfactant