Relationship between Exhaled Nitric Oxide and Exposure to Low-Level Environmental Tobacco Smoke in Children with Asthma on Inhaled Corticosteroids

Abstract

Objectives. The relationship between exhaled nitric oxide (FeNO) and asthma severity or control is inconsistent. Active smoking lowers FeNO, but the relationship between passive smoking and FeNO is less clear. Children may be exposed to low-level environmental tobacco smoke (ETS) or thirdhand smoke, even if parents avoid smoking in the presence of their children. Our hypothesis was that FeNO is lower in children with asthma exposed to low-level ETS when compared with those who are not exposed. Methods. Children with stable asthma, 8–18 years of age, on low- or medium-dose inhaled corticosteroids (ICS) were enrolled. Spirometry, Asthma Control Questionnaire (ACQ), FeNO, exhaled breath condensate pH (EBC pH), and EBC ammonia were compared between children with and without ETS exposure as determined by urinary cotinine. Results. Thirty-three subjects were enrolled, of which 10 (30%) had urinary cotinine levels ≥1 ng/ml. There were no significant differences between the two groups in age, sex, BMI percentile, atopy status, FEV₁, EBC pH, or EBC ammonia. Median ACQ was 0.29 (IQR: 0.22–0.57) for those with cotinine levels <1 ng/ml and 0.64 (IQR: 0.57–1.1) for those with cotinine levels of ≥1 ng/ml, p = .02. Median FeNO (ppb) was 23.9 (IQR: 15.2–34.5) for unexposed subjects and 9.6 (IQR: 5.1–15.8) for exposed subjects, p = .008. Conclusions: Children with asthma on low to medium doses of ICS and recent low-level ETS exposure have lower FeNO levels when compared with non-ETS-exposed subjects. Exposure to low-level ETS or thirdhand smoke may be an important variable to consider when interpreting FeNO as a biomarker for airway inflammation.

• Secondhand smoking
• passive smoking
• FeNO
• exhaled breath condensate
• airway inflammation
• cotinine
• biomarker

Acknowledgments

We thank Lance Parton, MD, and the staff at his laboratory for assistance and guidance in performing all ELISA-based assays. We also thank the technicians and staff of the Clinical Pathology Laboratory at Westchester Medical Center for processing the EBC for measurement of pH and ammonia.

Declaration of Interest

Supported by the Children’s Environmental Health Center of the Hudson Valley and the Maria Fareri Children’s Hospital Foundation. The authors declare no conflicts of interest.