Table 1. Histological score of lung damage.

Points	0	1	2	3	4
% of lung injury	0–20%	20–40%	40–60%	60–80%	80–100%
% of collapsed or irregular alveoli	0–20%	20–40%	40–60%	60–80%	80–100%
Hyperplasia of bronchial epithelial cells	None	Mild	Severe	Severe with important thickening	–
Metaplasia of Club cells	None	Mild	Severe	–	–
Plugs of mucus	Absence	Presence	–	–	–
Infiltration of inflammatory cells	Absence	Presence	–	–	–