Exhaled Nitric Oxide and Hydrogen Peroxide Concentrations in Asthmatic Smokers

Abstract

Background: Cigarette smoking is associated with decreased nitric oxide (NO) production and increased oxidative stress in the airways. Exhaled NO levels are not higher in asthmatic smokers than in healthy non-smokers, and the value of exhaled NO for diagnosing asthma in smokers has been questioned. Objectives: To compare exhaled NO concentrations between healthy and steroid-naive and steroid-treated asthmatic smokers and non-smokers. To also assess the acute effect of cigarette smoking on exhaled NO and hydrogen peroxide (H₂O₂) levels in asthmatic smokers. Methods: Exhaled NO was measured by chemiluminescence and exhaled H₂O₂ spectrophotometrically. In 7 steroid-naive asthmatic smokers exhaled NO and H₂O₂ was measured both before and 15 min after smoking one cigarette. Data are given as median (range). Results: Exhaled NO level was significantly higher in steroid-naive asthmatic smokers than in healthy smokers [7.7 (3.4–32.5) ppb vs. 3.2 (2.0–7.2) ppb, p < 0.001]. Exhaled NO values were lower in smokers than in non-smokers both in healthy subjects and in steroid-naive asthmatic patients. Steroid-treated asthmatic smokers had a tendency for lower exhaled NO values [5.4 (1.7–12.0) ppb] compared to steroid-naive asthmatic smokers. Cigarette smoking caused an acute increase in exhaled H₂O₂ concentrations together with a decrease in exhaled NO concentration. Conclusions: Our data suggest that an elevation in exhaled NO concentration is associated with asthma in smokers. This difference may be useful for diagnosing the disease in smokers, but its clinical value needs further evaluation. Acute increase in exhaled H₂O₂ concentrations suggests that smoking increases the oxidative stress in the asthmatic airways.