Table 3.

Histological scoring of fixed lung tissue

	Groups
	Air (n = 12)	E-cig (n = 11)	3R4F (n = 13)	P Value (Kruskal-Wallis)
Inflammation
Acute	0.0 ± 0.0	0.09 ± 0.09	0.15 ± 0.10	0.805
Chronic	1.33 ± 0.26	1.09 ± 0.16	1.62 ± 0.27	0.462
Emphysematous changes (air space enlargement)	0.0 ± 0.0	0.18 ± 0.12	1.00 ± 0.28*§	0.019
Alveolar macrophages	1.3 ± 0.3	1.0 ± 0.0	1.6 ± 0.2	0.132
Pigmented macrophages	0.0 ± 0.0	0.0 ± 0.0	1.69 ± 0.26*§	0.0002
Smooth muscle hyperplasia (main stem bronchus)	0.08 ± 0.08	0.27 ± 0.14	0.62 ± 0.24	0.251
Fibrosis	0.0 ± 0.0	0.0 ± 0.0	0.08 ± 0.08	0.931

Values are means ± SE. Scoring criteria are as follows: 0 = none, 1 = minimal, 2 = mild, 3 = moderate, and 4 = marked. Boldface indicates statistical significance.

^*P < 0.05 vs. air and

^§P < 0.05 vs. E-cig.