Fig. 2.

Changes in plasma nicotine. The increase in plasma nicotine levels was not different in chronic tobacco cigarette (TC) smokers (n = 31) after smoking 1 TC and in chronic electronic cigarette (EC) vapers (n = 22) after using the EC with nicotine (ECN). When EC vapers used the ECN, the increase in nicotine was significantly greater compared with the nicotine inhaler (NI, n = 19). When nonsmokers used the ECN (n = 41), the increase in plasma nicotine was not different compared with the NI (n = 17). Mean postexposure minus baseline differences were compared across TC, ECN, and NI using a crossover repeated-measure (mixed) analysis of variance model, and results are displayed as means ± SE.