Exhaled nitric oxide after beta(2)-agonist inhalation and spirometry in asthma

Exhaled nitric oxide (ENO) is used increasingly as a surrogate marker of ai rway inflammation in research protocols that may incorporate standard effic acy measures such as spirometry before and after bronchodilator, which coul d affect ENO measurements. In seven healthy volunteers and 11 mild asthmati c subjects, we measured ENO before and serially for 1 h after spirometry. O n two additional days in the subjects with asthma, we reexamined the effect of spirometry as before, followed by the serial measurement of ENO for 1 h after two puffs of salbutamol (100 mu g/puff) by metered-dose inhaler or m atching placebo. As early as 1 min after spirometry, ENO fell by 13% and 10 % in the normal and asthmatic subjects, respectively. In both groups, ENO r eturned to baseline over 1 h. In the asthmatic subjects, salbutamol caused a significant mean increase of the order of 10 parts per billion in ENO (p < 0.001) for 1 h as compared with placebo inhaler. We conclude that spirome try and beta(2)-agonist may perturb ENO values and recommend that studies c ontrol for these factors.