Passive smoke inhalation decreases exhaled nitric oxide in normal subjects

Environmental tobacco smoke (ETS) exposure is one of the commonest pollutan ts in modern society. Despite documented clinical adverse effects of ETS on the lungs, objective methods of assessing airway damage have been lacking. Exhaled nitric oxide (eNO) is a rapid, sensitive method of assessing airwa y inflammation, and could be useful in this regard. Active smoking decrease s eNO in normal subjects and eNO levels are low in habitual smokers, but th e effect of ETS exposure on eNO has not previously been examined. In a sing le-blinded, placebo-controlled cross-over study, we examined the effect of ETS, sham and active smoke inhalation on eNO in non-smoking normal voluntee rs. Subjects were exposed to smoke over a period of 1 hour in a separately ventilated chamber, and eNO was measured at baseline, 15, 30, 45 and 60 min utes. With sham inhalation (n = 15), eNO levels did not change significantl y from baseline, although a small decrease occurred. ETS exposure (n = 15) resulted in a rapid fall in eNO from mean (SE) 134 (29) ppb to 102 (22) ppb , or by 23.6% (p < 0.05), and remained low for 60 minutes. With active smok ing (n = 7), levels fell acutely from baseline within the same time interva l (71 [16] to 49 [11] ppb, or by 30.3%), and remained low. These changes we re significant compared with sham exposure for both ETS (p < 0.05) and acti ve smoke inhalation (p < .01). This suggests that eNO can be used for the i nvestigation of the mechanisms of cigarette-induced lung damage in the expe rimental setting, and may potentially be useful also for environmental asse ssment of ETS effects.