a: Pulmonary Surfactant Protein B in Current, Former, Never Smokers Levels of pulmonary surfactant protein B (SP-B) across never, former, and current smokers. Lower and upper borders of box indicate 10th and 90th percentile, respectively. Horizontal bar indicates median, and whiskers 5th and 95th percentiles. Median SP-B levels were markedly higher among current vs. never smokers (7.83ng/mL vs. 1.64ng/mL; P<0.0001).
b: Pulmonary Surfactant Protein B in Current Smokers by Pack Years Levels of pulmonary surfactant protein B (SP-B) in current smokers by quartiles of pack-years smoked. Lower and upper borders of box indicate 10th and 90th percentile, respectively. Horizontal bar indicates median, and whiskers 5th and 95th percentiles.
c: Pulmonary Surfactant Protein B in Current Smokers by Smoking Frequency Levels of Pulmonary surfactant protein B (SP-B) in current smokers who smoked intermittently or everyday in the past 30 days. Lower and upper borders of box indicate 10th and 90th percentile, respectively. Horizontal bar indicates median, and whiskers 5th and 95th percentiles.