Transient decrease of exhaled nitric oxide after acute exposure to passive smoke in healthy subjects

Nitric oxide (NO) is produced and detected in the exhalate from the respiratory tract where it plays important regulatory functions. Exhaled nitric oxide (eNO) concentrations are reduced in active cigarette smokers between cigarettes and in nonsmoking subjects during short-term exposure to environmental tobacco smoke. In this study, the authors evaluated eNO before and after an acute exposure to environmental tobacco smoke in healthy, nonsmoking subjects (n = 12). Baseline eNO levels were measured by chemiluminescence at baseline (1 hr before exposure), shortly after the end of exposure, and 10 and 30 min after the end of exposure. Mean room air NO concentration increased from 3 ppb to 4 ppm (range, 560 ppb-8.5 ppm) during the exposure period. Carboxyhemoglobin levels were assessed before and after the exposure with spectrophotometry. All subjects had decreased eNO with exposure to environmental tobacco smoke (mean +/- standard error of the mean: 16.65 +/- 1.35 ppb to 13.86 +/- 1.33 ppb; p < .001). These concentrations remained significantly decreased at 10 min and recovered within 30 min. No modifications in airway resistance or increase in carboxyhemoglobin levels were observed. Exposure to environmental tobacco smoke transiently--but consistently--decreased eNO concentration in healthy, nonsmoking subjects, suggesting that second-hand smoke can directly affect NO in the airway environment.