Smoking topography: reliability and validity in dependent smokers.

Data from two studies were analyzed to determine whether smoking through the mouthpiece of a topography unit yields consistent measures over time and to verify that smoking through a mouthpiece results in a similar degree of smoke exposure as conventional smoking. In both studies, subjects smoked their usual brand of cigarette ad libitum. In study A, subjects (n=7) smoked through a mouthpiece on 4 separate experimental days. In study B, subjects (n=10) smoked on 2 separate days: Once conventionally and once through a mouthpiece. In both studies, exhaled carbon monoxide (CO) and physiological effects (heart rate and blood pressure) were measured before and after smoking. In study B, plasma nicotine concentrations also were measured. In study A, puff volume, puff duration, interpuff interval, and maximum puff velocity averaged 30.8 ml,.9 s, 19.9 s, and 44.6 ml/s, respectively. Intraclass correlation coefficients computed for puff volume (0.66), puff duration (0.75), and maximum puff velocity (0.68) indicated that these measures showed good reliability. In study B, smoking through the mouthpiece yielded similar topographical (time to smoke and number of puffs per cigarette) measures as conventional smoking. Also similar were changes in biochemical values: Plasma nicotine (18.5 ng/ml vs. 25.5 ng/ml), exhaled CO (4.6 ppm vs. 5.1 ppm), and heart rate (8.6 beats/min vs. 7.4 beats/min) for conventional and topography mouthpiece smoking conditions, respectively. Topography measures did not differ significantly between the two studies. Overall, the data from these two small-sample studies suggest that smoking topography provides a valid and reliable index of conventional smoking and an indirect measure of smoke exposure.