Effects of smoking on respiratory capacity and control

The purpose of this study was to provide information concerning the possible early effects of smoking on measures of respiratory capacity and control in young adult female smokers vs. nonsmokers. In particular, maximum performance test results ( vital capacity and maximum phonation time) and measures of air pressures and airflows during voiceless, stop-plosive productions were analysed. Subjects were 45 female nonsmokers and 30 female smokers ( total n=75) between the ages of 18-30 years. For the purposes of this study, a smoker was defined as any subject who, at the time of this study, had smoked at least two cigarettes per day for at least 1 year. All of the subjects in the nonsmoker category were those who, at the time of this study, did not smoke and who had not smoked for at least 5 years prior to the study. Vital capacity measures were conducted using a handheld digital spirometer, while maximum phonation productions and voiceless, stop-plosive pressures and flows were recorded and measured using the Aerophone II Model 6800 (Kay Elemetrics Corp., Lincoln Park, NJ). Results showed significantly lower vital capacities and maximum phonation times in smokers vs. nonsmokers. The maximum phonation time task was also produced with significantly higher mean airflow rates in smokers than nonsmokers. In addition, the smokers were observed to produce significantly greater peak and mean pressures during the voiceless stop-plosive task than the nonsmokers. A weak, but significant correlation was observed between the number of days the subject had smoked and the mean pressure produced during the voiceless, stop-plosive task. The findings of reduced respiratory capacity and control in smokers may be associated with factors such as increased bronchial reactivity secondary to exposure to cigarette smoke and/or mild airway obstruction, increased airflow secondary to increased glottal gap size during phonation, and increased vocal fold mass and/or inefficiency in vocal fold closure. The findings of this study indicate that decrements in respiratory capacity and control may occur even in relatively young smokers who have only been smoking for a comparatively short time