%0 Journal Article %A Sandrah Eckel %A Noa Molshatzki %A Edward Rappaport %A Rima Habre %A William Linn %A Kiros Berhane %A Yue Zhang %A Frank Gilliland %T Factors associated with implausible estimates of alveolar nitric oxide concentration %D 2014 %J European Respiratory Journal %P P4203 %V 44 %N Suppl 58 %X INTRODUCTION: The fractional concentration of exhaled nitric oxide (FeNO) is a biomarker of airway inflammation, typically measured at a 50 ml/s flow rate (FeNO50). FeNO measured at multiple flow rates can be used to non-invasively estimate the concentration of NO in the distal alveolar region (CANO). Regardless of estimation method, researchers consistently have problems estimating CANO for some study subjects. Non-physiologic negative CANO estimates are often set to 0 or excluded.AIMS: To identify factors associated with implausible estimates of CANO.METHODS: In March-June 2010, multiple flow FeNO was assessed in 1507 schoolchildren, ages 12-15, from the Southern California Children's Health Study using 3 EcoMedics analyzers (CLD88-SP with DeNOx). CANO was estimated using 3 methods. An estimate of CANO was “problematic” if negative or 0 (for constrained methods). Associations between an indicator of problematic CANO and testing factors/patient characteristics were evaluated using logistic regression.RESULTS: 131 children (8.7%) had problematic CANO for ≥ 1 method and 77 children (5.1%) had problematic CANO for all methods. While problematic CANO was associated with avoidable testing factors (e.g., 1 analyzer with known zero instability) there were also robust associations with: body mass index (odds ratio (OR) of 2.2 per 10 kg/m2 increase, 95% CI: 1.2, 3.9), level of FeNO50 (OR of 1.3 per 10 ppb increase, 95% CI: 1.2, 1.45), and the slope of the 3-second “plateau” of NO concentration versus time at 300 ml/s.CONCLUSIONS: Exclusion of subjects with negative CANO may induce selection bias. The study of problematic CANO may aid the development of guidelines for multiple flow FeNO assessment. %U