Figure 4.

Blood carboxyhemoglobin concentration over weeks of the study during progressive yield reduction of cigarettes (weeks 1–6) and after return to usual cigarettes or quitting (weeks 7–10). Yields in the boxes refer to FTC machine-determined nicotine yield. Solid line includes all subjects; dashed line excluded two quitters at week 10. Points, mean for 20 subjects; bars, SE. * P < 0.05 compared to viral brand.