Exhaled nitric oxide in smokers and former smokers with chronic obstructive pulmonary disease

Background: Measurement of fractional exhaled nitric oxide (FeNO) is a useful technique for detection of eosinophilic airway inflammation and assessment of efficiency of corticosteroid treatment in patents with respiratory disease. Generally studies agree that measurement of FeNO is a useful non-invasive biomarker in patients with chronic obstructive pulmonary disease (COPD), however, there are reports that do not confirm such a relationship between FeNO and COPD. Aim of the study: The main objective of this study was to investigate FeNO levels in Polish patients with COPD compared to healthy controls. As a secondary objective, we assessed the influence of smoking on FeNO levels in healthy patients, and patients with COPD. Material and methods: FeNO concentration was measured using an electrochemical analyzer in healthy non-smokers (n=21), healthy smokers (n=25), and former smokers with COPD (n=30) and smokers with COPD (n=38). General characteristics, hematological variables and serum biochemical parameters were also obtained and analyzed using the Kruskal-Wallis test. Results: FeNO measurement revealed significantly reduced NO levels in healthy smokers compared to healthy non-smokers, former smokers with COPD and smokers with COPD (median [range]: 14 [6–17] vs. 21 [15–29], 25 [15–53], and 19 [11–32] ppb, respectively, p<0.001). Moreover, we found increased FeNO levels in ex-smokers with COPD compared with smokers with COPD (p<0.05). No associations between FeNO and other analyzed parameters were found. Conclusions: Levels of FeNO, measured by with an electrochemical analyzer, were elevated among patients with COPD compared to healthy non-smoking controls. Moreover, our study confirms that smoking results in a reduction in FeNO concentration in both healthy patients and patients with COPD.