TABLE 2.

CHARACTERISTICS OF VENTILATION DEFECT TYPES

Type of Hypointense Region	Ventilation Pattern That Elicits	Resistant to TLC Breath	Size of Defect	Location	Slices	Signal Intensity	Found in Naive Mice?
Type 1: persistent defect	Normal and low tidal volume	Yes	1.4% ± 0.3%	All lobes	Ventral	Background	No
Type 2: atelectatic defect	Low tidal volume	No	4.7% ± 1.9%	All lobes; greatest in left lung and cranial lobe	All	Background	No
Type 3: dorsal lucency	Normal and low tidal volume	Yes	2.0% ± 0.3%	Dorsal medial lobe and left lung; midline	Dorsal	Higher	Yes

Persistent defects are found predominantly with normal tidal volume (200 μL) ventilation throughout the lung. Atelectatic defects are larger and are seen primarily during low tidal volume (150 μL) ventilation. Dorsal lucencies are evident in the most dorsal slices of all animals regardless of treatment, generally at a midline location. Defect size was determined as the percentage of total lung area comprised of ventilation defect area, as described in Materials and Methods. Values under “Size of Defect” are means ± SEM.