Effect of inhaled ozone on exhaled nitric oxide, pulmonary function, and induced sputum in normal and asthmatic subjects

Background-Nitric oxide (NO) may have a role in the pathophysiology of tiss ue injury in response to inhaled ozone in animals. Methods-A double blind, randomised, placebo controlled, crossover study was undertaken to investigate the effects of inhaled ozone in 10 normal and 10 atopic asthmatic volunteers. Subjects were exposed to 200 ppb ozone or cle an air for four hours with intermittent exercise, followed by hourly measur ement of spirometric parameters and exhaled NO for four hours. Nasal NO and methacholine reactivity were measured and exhaled breath condensate and in duced sputum samples were collected four and 24 hours after exposure. Results-Exposure to ozone caused a fall in forced expiratory volume in one second (FEV,) of 7% in normal subjects (p<0.05) and 9% in asthmatic subject s (p<0.005). There was a 39% increase in sputum neutrophils at four hours i n normal subjects (p<0.05) and a 35% increase at four hours in asthmatic su bjects, remaining high at 24 hours (p<0.005 and p<0.05, respectively). Ther e were no differences between normal and asthmatic subjects. There were no changes in methacholine reactivity, exhaled or nasal NO, nitrite levels in exhaled breath condensate, or sputum supernatant concentrations of interleu kin 8, tumour necrosis factor a, or granulocyte-macrophage colony stimulati ng factor in either group. Conclusions-Exposure to 200 ppb ozone leads to a neutrophil inflammatory re sponse in normal and asthmatic subjects but no changes in exhaled NO or nit rite levels.