Exhaled nitric oxide following repeated spirometry or repeated plethysmography in healthy individuals

Subjects with asthma have higher concentrations of exhaled nitric oxide (NO ) than normal individuals. It has been demonstrated that in asthmatics, rep eated FVC maneuvers reduce NO. Although the cause of this phenomenon is not known, it has been hypothesized that deep breaths associated with FVC mane uvers reduce exhaled NO by affecting neural sources of NO, possibly via a m echanism related to the pathobiology of asthma. To establish whether FVC ma neuvers influence NO concentrations in normal individuals, we measured exha led NO at baseline values and after FVC maneuvers performed every 15 min fo r 1 h in subjects without asthma. To investigate the role of deep breaths i n reducing exhaled NO, we compared these results with concentrations of exh aled NO after plethysmography. Repeated FVC maneuvers over 60 min produced a decrease in NO concentrations in mixed expired gas (FENO; 24.6 +/- 5.1% d ecrease for FENO, p < 0.01 versus baseline). In contrast to the results aft er spirometry, repeated specific airway conductance (sGaw) maneuvers do not have a significant effect on FENO (p = 0.16). These results, which demonst rate that in nonasthmatic subjects FVC maneuvers-but not panting maneuvers- -produce fall in NO, suggest that the mechanism responsible for the reducti on in exhaled NO after FVC maneuvers is related to volume history of the lu ng rather than the pathobiology of asthma.